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Studies on physiological responses to stimuli from physical factors are essential for understanding the dynamics of the microorganisms and higly important for the management of plant diseases. Besides, the development of an epidemiological model for pathogen populations requires studying their physiological responses to physical stimuli. The objective of this study was to evaluate the germination dynamics of spores from six isolates of Bipolaris bicolor under effects of light at 25 °C. Suspensions of 1.6 × 10 5 conidia mL - 1 from the B. bicolor isolates were inoculated onto Petri dishes containing agar-water culture medium and incubated in a BOD chamber under two physical conditions: (a) constant darkness and (b) constant light for five hours. The study was conducted in a completely randomized design, with a 6 × 2 factorial arrangement (six B. bicolor isolates and two physical conditions) and five replications. The length of the germ tube was measured hourly. The constant darkness resulted in higher mean germ tube growth for the pathogen; however, differences in the final germination percentage were found among the isolates. The isolate F-24-02 exhibited the highest germination adaptability to constant darkness, presenting the longest germ tube length., Competing Interests: Declarations. Competing interests: Authors have declared that no competing interests exist., (© 2024. The Author(s) under exclusive licence to Sociedade Brasileira de Microbiologia.)

Bioaerosols control techniques, especially ultraviolet germicidal irradiation (UVGI) are gaining attention due to increasing needs for controlling of health risk caused by airborne biocontaminants. The effectiveness of a full-scale in-duct UVGI air disinfection system was investigated. One bacterium, a wild type Escherichia coli, and three fungal spores, Penicillium aragonense, Rhodotorula glutinis, and Cladosporium sp., were selected as test organisms and their inactivation under different conditions representative of a real application in HVAC systems were investigated. The results demonstrated that inactivation of airborne E. coli by the UVGI system was extremely effective, with >99.5 % of the input E. coli inactivated at a residence time lower than 0.36 s in the disinfection section. Airborne fungal spores were less susceptible to UV irradiation than E. coli. Under same conditions, viable counts reduction of P. aragonense, R. glutinis, and Cladosporium sp. spores were 53 %, 63 % and 73 %, respectively. The effect of UV light intensity, air flowrate and relative humidity were analyzed separately. A simplified model based on redefinition of the parameters in the classical inactivation kinetic equation was used to simulate the inactivation of airborne contaminants in the in-duct system under different conditions. The results showed that the simplified model was adequate to estimate disinfection efficacy of different bioaerosols by the UVGI system which could be useful for system design. Overall, this study shows that such in-duct UVGI systems can provide significant control of bioaerosols., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The effect of UVC (254 nm) treatment on the mould-free shelf-life of par-baked wholemeal, rye and six-grain bread was examined. Currently, these breads are par-baked, wrapped in high-density polyethylene (HDPE)-foil and transported or stored at room temperature for a couple of days before being full-baked and sold/consumed. Generally, after five days, these breads show signs of mould spoilage. A shelf-life increase in one or more days would already offer immense economical and logistic benefits for the baker or retailer. In this study, the parameters fluence rate (irradiation intensity), fluence (UV dose), distance to the UV-lamp (DTL) and number of layers of a common wrapping HDPE-foil (20 µm) were diversified. The breads were subjected to a UVC treatment (0-2502 mJ/cm²), packed and stored at room temperature for a period of 15 days (21.5 ± 0.8 °C). Similar as for the breads, agar plates with mould spores of Aspergillus niger , Aspergillus montevidensis and Penicillium roqueforti were UVC treated (0-1664 mJ/cm²) and checked daily for visible mould growth during 15 days (25 °C). Aspergillus niger showed the strongest resistance towards UVC, a fluence of 800 mJ/cm² was needed to inhibit growth during 15 days of storage, whereas for P. roqueforti and A. montevidensis , respectively, UV levels of 291 and 133 mJ/cm² were found sufficient. Furthermore, the shelf-life of wholemeal, rye and six-grain bread can be prolonged from 5 to 6, 8 and 9 days, respectively, using 2502 mJ/cm². The effect of higher UVC dosage on shelf-life reached a maximal level and was strongly impacted by the wide spread on data of mould-free shelf-life. The main factors influencing the potential of UV decontamination were the rough bread surface, differences in DTL, the possibility of post-contamination and UV permeability of packaging materials., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Entomopathogenic fungi offer an ecologically sustainable and highly effective alternative to chemical pesticides for managing plant pests. However, the efficacy of mycoinsecticides in pest control suffers from environmental abiotic stresses, such as solar UV radiation and temperature fluctuations, which seriously hinder their practical application in the field. Herein, we discovered that the synthetic amphiphilic thermal-responsive polymers are able to significantly enhance the resistance of Metarhizium robertsii conidia against thermal and UV irradiation stresses. The thermosensitive polymers with extremely low cytotoxicity and good biocompatibility can be engineered onto the M. robertsii conidia surface by anchoring hydrophobic alkyl chains. Further investigations revealed that polymer supplementation remarkably augmented the capacity for penetration and the virulence of M. robertsii under heat and UV stresses. Notably, broad-spectrum entomopathogenic fungi can be protected by the polymers. The molecular mechanism was elucidated through exploring RNA sequencing and in vivo / vitro enzyme activity assays. This work provides a novel avenue for fortifying the resilience of entomopathogenic fungi, potentially advancing their practical application as biopesticides.

Fungal contamination poses a serious threat to public health and food safety because molds can grow under stressful conditions through melanin accumulation. Although ultraviolet (UV) irradiation is popular for inhibiting microorganisms, its effectiveness is limited by our insufficient knowledge about UV tolerance in melanin-accumulating molds. In this study, we first confirmed the protective effect of melanin by evaluating the UV sensitivity of young and mature spores. Additionally, we compared UV sensitivity between spores with accumulated melanin and spores prepared with melanin biosynthesis inhibitors. We found that mature spores were less UV-sensitive than young spores, and that reduced melanin accumulation by inhibitors led to reduced UV sensitivity. These results suggest that melanin protects cells against UV irradiation. To determine the most effective wavelength for inhibition, we evaluated the wavelength dependence of UV tolerance in a yeast (Rhodotorula mucilaginosa) and in molds (Aspergillus fumigatus, Cladosporium halotolerans, Cladosporium sphaerospermum, Aspergillus brasiliensis, Penicillium roqueforti, and Botrytis cinerea). We assessed UV tolerance using a UV-light emitting diode (LED) irradiation system with 13 wavelength-ranked LEDs between 250 and 365 nm, a krypton chlorine (KrCl) excimer lamp device, and a low pressure (LP) Hg lamp device. The inhibition of fungi peaked at around 270 nm, and most molds showed reduced UV sensitivity at shorter wavelengths as they accumulated pigment. Absorption spectra of the pigments showed greater absorption at shorter wavelengths, suggesting greater UV protection at these wavelengths. These results will assist in the development of fungal disinfection systems using UV, such as closed systems of air and water purification., (© 2024. The Author(s).)

Calonectria pseudonaviculata , responsible for boxwood blight, produces sticky conidia that pose a contamination risk in boxwood production via cross-contamination from tools, equipment, and other resources. This study evaluated UV-C light-emitting-diode (LED) irradiation (263 to 287 nm) as a disinfection method by examining its effectiveness in inactivating conidia and determining the UV-C sensitivity. Conidial suspensions were exposed to quantifiable UV-C doses under a dynamic stirring condition. Average volumetric intensity was quantified by accounting for UV gradients and UV dose was calculated as a product of average fluence rate (mW⋅cm -2 ) and exposure time (s). UV-C irradiation effectively inactivated the tested pathogen following log-linear + shoulder kinetics as identified by parameters of goodness of model fit (i.e., high R 2 and low root mean square error [RMSE] values). The model predicted the UV sensitivity of C. pseudonaviculata conidia as 46.6 mJ⋅cm -2 per log. A total of 2.04 log reductions of the population could be obtained by an exposure of 60 mJ⋅cm -2 of UV-C dose. The calculated decimal reduction dose (D 10 ) was 13.53 ± 0.98 mJ⋅cm -2 ( R 2 = 0.97, RMSE = 0.14), inactivation rate constant ( K max ) = 0.17 ± 0.01, and shoulder length = 33.06 ± 1.81 mJ⋅cm -2 . These findings indicate that UV-C irradiation could be a viable option for disinfecting tools, equipment, and possibly propagation cuttings in nurseries., Competing Interests: The author(s) declare no conflict of interest.

Germicidal UV light (UV-C) has been shown to effectively suppress several plant pathogens as well as some arthropod pests. Recent reports describe the efficacy of nighttime applications of UV-C at doses from 100 to 200 J/m 2 in vineyards to reduce grape powdery mildew ( Erysiphe necator ). Our in vitro studies confirmed the efficacy of UV-C to inhibit germination of E. necator and Botrytis cinerea conidia, demonstrated a range of tolerances to UV-C within a collection of E. necator isolates, and showed growth stage-specific effects of UV-C on B. cinerea . Nighttime use of UV-C was evaluated at 48 to 96 J/m 2 in small plot trials (<1,000 vines) from 2020 to 2023. Once- or twice-weekly UV-C applications significantly reduced the incidence of foliar powdery mildew compared with non-UV-C-treated controls ( P < 0.02). Suppression of powdery mildew on fruit was less consistent, where once or twice weekly UV-C exposure reduced powdery mildew disease severity in 2020 ( P = 0.04), 2021 ( P = 0.02), and 2023 ( P = 0.003) but less so in 2022 ( P = 0.07). Bunch rot severity was not significantly reduced with UV-C treatment in any year of the study. Application of UV-C until the onset of fruit color change (veraison) also had a minimal effect on the fruit-soluble solids, pH, anthocyanins, or phenolics in harvested fruit at any UV-C dose or frequency ( P > 0.10). Suppression of powdery mildew by nighttime application of UV-C at lower doses in small plots suggests that such treatments merit further evaluation in larger-scale studies in Western Oregon., Competing Interests: The author(s) declare no conflict of interest.

Fungal contaminations of cereal grains are a profound food-safety and food-security concern worldwide, threatening consumers' and animals' health and causing enormous economic burdens. Because far-ultraviolet C (far-UVC) light at 222 nm has recently been shown to be human-safe, we investigated its efficacy as an alternative to thermal, chemical, and conventional 254 nm UVC anti-fungal treatments. Our microplasma-based far-UVC lamp system achieved a 5.21-log reduction in the conidia of Aspergillus flavus suspended in buffer with a dose of 1032.0 mJ/cm 2 , and a 5.11-log reduction of Fusarium graminearum conidia in suspension with a dose of 619.2 mJ/cm 2 . We further observed that far-UVC treatments could induce fungal-cell apoptosis, alter mitochondrial membrane potential, lead to the accumulation of intracellular reactive oxygen species, cause lipid peroxidation, and result in cell-membrane damage. The lamp system also exhibited a potent ability to inhibit the mycelial growth of both A. flavus and F. graminearum. On potato dextrose agar plates, such growth was completely inhibited after doses of 576.0 mJ/cm 2 and 460.8 mJ/cm 2 , respectively. To test our approach's efficacy at decontaminating actual cereal grains, we designed a cubical 3D treatment chamber fitted with six lamps. At a dose of 780.0 mJ/cm 2 on each side, the chamber achieved a 1.88-log reduction of A. flavus on dried yellow corn kernels and a 1.11-log reduction of F. graminearum on wheat grains, without significant moisture loss to either cereal type (p > 0.05). The treatment did not cause significant changes in the propensity of wheat grains to germinate in the week following treatment (p > 0.05). However, it increased the germination propensity of corn kernels by more than 71% in the same timeframe (p < 0.05). Collectively, our results demonstrate that 222 nm far-UVC radiation can effectively inactivate fungal growth in liquid, on solid surfaces, and on cereal grains. If scalable, its emergence as a safe, cost-effective alternative tool for reducing fungi-related post-harvest cereal losses could have important positive implications for the fight against world hunger and food insecurity., Competing Interests: Declaration of competing interest The authors declare the following competing financial interest(s): Professor Yi-Cheng Wang is concurrently collaborating with the co-founder and chief technology officer of Eden Park Illumination, Inc., Dr. Sung-Jin Park, on a Small Business Innovation Research project sponsored by the U.S. Department of Energy, which is unconnected to the present work. Dr. Park provided technical support with the far-UVC lamps used in the present work, but had no direct involvement in it, and placed no restrictions on any part of its study design; its data collection, analysis, or interpretation; or its publication., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Mold infestations in buildings pose significant challenges to human health, affecting both private residences and hospitals. While molds commonly trigger asthma and allergies in the immunocompetent, they can cause life-threatening diseases in the immunocompromised. Currently, there is an unmet need for new strategies to reduce or prevent mold infestations. Far-UVC technology can inactivate microorganisms while remaining safe for humans. This study investigates the inhibitory efficacy of far-UVC light at 222 nm on the growth of common mold-producing fungi, specifically Penicillium candidum, when delivered in low-dose on-off duty cycles, a configuration consistent with its use in real-world settings. The inhibitory effect of the low-dose duty cycles was assessed on growth induced by i) an adjacent spore-producing P. candidum donor and ii) P. candidum spores seeded directly onto agar plates. In both setups, the far-UVC light significantly inhibited both vertical and horizontal growth of P. candidum, even when the UV doses were below the Threshold Value Limit of 23 mJ/cm2. These results suggest that far-UVC light holds the potential to improve indoor air quality by reducing or preventing mold growth, also when people are present., Competing Interests: EHM is a full-time employee and CKH is a co-founder and an employee at UV Medico A/S. This does not alter our adherence to PLOS ONE policies on sharing data and materials. There are no patents, products in development, or marketed products associated with this research to declare., (Copyright: © 2024 Mogensen, Holm. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Nosema bombycis (Nb) is a pathogen causing pebrine in sericulture. Ultraviolet (UV) light exposure is a common physical disinfection method, but the mechanisms underlying UV-based disinfection have only been studied at the population level. In this study, changes in and germination of UV-irradiated spores were observed using Raman tweezers and phase-contrast imaging to evaluate the effects of UV radiation on Nb spores at the single-cell level. We found that irradiation caused the complete leakage of trehalose from individual spores. We also found that more spores leaked as the UV dose increased. There was no significant loss of intracellular biomacromolecules and no marked changes in the peaks associated with protein secondary structures. Low-dose radiation promoted spore germination and high-dose radiation decreased the germination rate, while the germination time did not undergo significant alterations. These results suggest that UV radiation disrupts the permeability of the inner membrane and alters the spore wall, thereby affecting the ability of the spore to sense and respond to extracellular stimuli, which further triggers germination and reduces or stops spore germination. This study provides new insights into the molecular mechanisms underlying conventional disinfection measures on microsporidian spores., (© 2023 American Society for Photobiology.)

Background: UV-B radiation represents a significant challenge for the widespread use of entomopathogenic fungi in pest management. This study focused on research of the asynchronous response between virulence and conidial viability against Ceratitis capitata adults using specific statistical models. Moreover, it was also investigated whether the observed differences in susceptibility to UV-B radiation in in vitro assays among three selected isolates of Beauveria bassiana were reflected in the above-mentioned asynchrony., Results: While the irradiation of the three isolates of B. bassiana was associated with a significant loss of conidial viability, their virulence was not significantly affected compared to nonirradiated treatments when exposed to 1200 mW m -2 for 6 h before or after the inoculation of C. capitata. In fact, the irradiation time needed to reduce the mortality to 50% compared to the controls was 34.69 h for EABb 10/225-Fil, 16.36 h for EABb 09/20-Fil, and 24.59 h for EABb 09/28-Fil. Meanwhile, the irradiation time necessary to reduce conidial viability to 50% was 9.89 h for EABb 10/225-Fil, 8.74 h for EABb 09/20-Fil, and 4.71 h for EABb 09/28-Fil., Conclusion: These results highlight the importance of modeling the response of entomopathogenic fungi virulence and conidial susceptibility when exposed to UV-B radiation for the selection of environmentally competent isolates, regardless of the results obtained in previous in vitro assays on conidial germination. This strategic approach is critical in overcoming the challenges posed by UV-B radiation and holds the key to realizing the full potential of entomopathogenic fungi in pest management. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry., (© 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.)

Aim: To evaluate the photodynamic mechanism of hypericin nanoencapsulated in P123 copolymer micelles against Microsporum canis in vitro . Material & methods: Antifungal susceptibility tests were performed, including the determination of the minimum fungicidal concentration and time-kill curve. Flow cytometry was used to evaluate the internalization of P123-Hyp in conidia and the activation of PDT type I and II mechanisms via the detection of reactive oxygen species (ROS), as well as to assess changes in the cell membrane using propidium iodide (PI) and cell morphology. Results: P123-Hyp-PDT exerted a fungistatic action on fungus, maintaining this action up to 24 h after exposure, corroborating the PS internalization results, which showed satisfactory uptake of P123-Hyp from a concentration of 3.125 μmol/l. Among the ROS studied, singlet oxygen was detected. Furthermore, the increased fluorescence intensity of PI in treated cells indicated necrotic cell death, while the size and granularity of the cells were also altered. Conclusion: Our results show, for the first time, a proposal for the mechanism of action of P123-Hyp-mediated PDT against M. canis , proving that it has a prolonged action on the fungus through activation of the type II photodynamic pathway, which resulted in disruption of the plasma membrane and cellular alterations.

Background: Solar ultraviolet (UV) irradiation is harmful to formulated conidia as active ingredients of fungal pesticides and hence restrains their field application in sunny days of summer, a season requiring frequent pest controls. This conflict makes it necessary to explore optimal strategies for the application of fungal pesticides to suppress pest populations but avoid solar UV damage during summer., Results: The conidia of Beauveria bassiana, a wide-spectrum fungal pesticide, were tolerable to UVB (major solar UV wavelengths) damage of ≤0.5 J cm -2 . The damage of this upper limit caused a loss of conidial viability and infectivity if not photoreactivated by light exposure after irradiation. Intriguingly, the light exposure resulted in a high photoreactivation rate of UVB-inactivated conidia and an insignificant or marginal difference in insecticidal activity between normal conidia and those photoreactivated. Modeling analysis of solar UVB intensity recorded hourly over the daylight of five sunny summer days from 5:00 am to 7:00 pm at 30° 17'57'' N and 120°5'7'' E revealed a variation of daily accumulated UVB dose from 2.07 to 2.78 J cm -2 , which was far beyond the upper limit. A more tolerable dose of ~0.2 J cm -2 appeared between 3:00 pm and 5:00 pm, and no harmful dose accumulated between 5:00 pm and 7:00 pm., Conclusion: Fungal UVB tolerance, fungal photoreactivation capability and the daily accumulation pattern of solar UV irradiation are based to propose an optional strategy for low-risk or non-risk application of fungal pesticides after 3:00 or 5:00 pm during summer. © 2022 Society of Chemical Industry., (© 2022 Society of Chemical Industry.)

White light during mycelial growth influences high conidial stress tolerance of the insect-pathogenic fungus Metarhizium robertsii, but little is known if low- or high-white light irradiances induce different stress tolerances. The fungus was grown either in the dark using two culture media: on minimal medium (Czapek medium without sucrose = MM) or on potato dextrose agar (PDA) or PDA medium under five different continuous white light irradiances. The stress tolerances of conidia produced on all treatments were evaluated by conidial germination on PDA supplemented with KCl for osmotic stress or on PDA supplemented with menadione for oxidative stress. Conidia produced on MM in the dark were more tolerant to osmotic and oxidative stress than conidia produced on PDA in the dark or under the light. For osmotic stress, growth under the lower to higher irradiances produced conidia with similar tolerances but more tolerant than conidia produced in the dark. For oxidative stress, conidia produced under the white light irradiances were generally more tolerant to menadione than conidia produced in the dark. Moreover, conidia produced in the dark germinated at the same speed when incubated in the dark or under lower irradiance treatment. However, at higher irradiance, conidial germination was delayed compared to germination in the dark, which germinated faster. Therefore, growth under light from low to high irradiances induces similar conidial higher stress tolerances; however, higher white light irradiances cause a delay in germination speed., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Aspergillus oryzae is a safe filamentous fungus widely used in the food, medicine, and feed industries, but there is currently not enough research on the light response of A. oryzae. In this study, 12 different light conditions were set and A. oryzae GDMCC 3.31 was continuously irradiated for 72 h to investigate the effect of light on mycelial growth and conidium production. Specifically, each light condition was the combination of one light wavelength (475, 520, or 630 nm) and one light intensity (20, 40, 60, or 80 μmol photon m -2 s -1 ). The results show that mycelium growth was inhibited significantly by green light (wavelength of 520 nm and intensities of 20 and 60 μmol photon m -2 s -1 ) and blue light (wavelength of 475 nm and intensity of 80 μmol photon m -2 s -1 ). The production of conidia was suppressed only by blue light (wavelength of 475 nm and intensities of 40, 60, and 80 μmol photon m -2 s -1 ), and those levels of inhibition increased when the intensity of blue light increased. When the strain was irradiated by blue light (80 μmol photon m -2 s -1 ), the number of conidia was 57.4% less than that of the darkness group. However, within our set range of light intensities, A. oryzae GDMCC 3.31 was insensitive to red light (wavelength of 630 nm) in terms of mycelium growth and conidium production. Moreover, interaction effects between light wavelength and intensity were found to exist in terms of colony diameter and the number of conidia. This research investigated the light response of A. oryzae, which may provide a new method to regulate mixed strains in fermented foods by light. IMPORTANCE Studies on the monochromatic light response of Aspergillus nidulans and Neurospora crassa have gone deep into the molecular mechanism. However, research methods for the light response of A. oryzae remain in the use of white light sources. In this study, we first demonstrated that A. oryzae GDMCC 3.31 was sensitive to light wavelength and intensity. We have observed that blue light inhibited its growth and sporulation and the inhibitory effect increased with intensity. This research not only adds new content to the study of the photoreaction of Aspergillus but also brings new possibilities for the use of light to regulate mixed strains and ultimately improve the flavor quality of fermented foods.

The aim of this work is to understand the inactivation efficiency of medium pressure mercury lamps, measured in terms of growth inhibition as well as cell death, damage and response, using three strains from three different Aspergillus species (A. fumigatus, A. niger and, A. terreus) spiked in filtered surface water. A complete characterization of the effect of the treatment on each strain of the fungal species was assessed considering spores' morphology, cell wall integrity and enzymatic activity, the formation of pyrimidine dimers in the DNA and proteome analysis. Results showed that, when subjected to medium pressure mercury lamps, A. niger is the most resistant to inactivation, that both A. fumigatus and A. niger suffer more morphological changes and present a higher number of damaged spores and A. terreus presented more dead spores. DNA damages detected in A. niger were able to be repaired to some extent, under both light and dark conditions. Finally, proteome analysis showed that the UV radiation treatment triggered different types of stress response, including cell wall reorganization and DNA repair in A. fumigatus and A. terreus, and oxidative stress responses like the increase in production of citric acid and itaconic acid in A. niger and A. terreus, respectively., (Copyright © 2021. Published by Elsevier B.V.)

Fungal polyketide synthases play important and differential roles in synthesizing secondary metabolites and regulating several cell events, including asexual development, environmental adaptation, and pathogenicity. This study shows the important functions of a highly reducing polyketide synthase, Pks11, in Beauveria bassiana, a filamentous fungal insect pathogen used worldwide for pest biocontrol. The deletion of pks11 led to severe defects in conidial yields on different media and a decrease of 36.27% in the mean thickness of conidial cell wall under normal conditions. Compared with the wild-type, Δpks11 showed higher tolerance to oxidation and increased sensitivity to high temperature during colony growth. Moreover, the lack of pks11 caused a decrease in conidial germination after exposure to UV radiation but did not affect the virulence of B. bassiana against Galleria mellonella larvae via typical cuticle infection. These findings concurred with the alteration in the transcript levels of some phenotype-related genes. These data suggested that pks11 played vital roles in the asexual development, cell wall integrity, and fungal responses to oxidation, high temperature, and UV irradiation of B. bassiana., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The aim of the present study was to analyze ten native Metarhizium spp. isolates as to their UV-B tolerances. Comparisons included: different fungal propagules (conidia, blastospores, or microsclerotia [MS]); conidia in aqueous suspensions or in 10% mineral oil-in-water emulsions; and conidia mixed with different types of soil. The UV-B effect was expressed as the germination of conidia or culturability of blastospores and MS relative to nongerminated propagules. Metarhizium anisopliae LCM S05 exhibited high tolerance as blastospores and/or MS, but not as conidia; LCM S10 and LCM S08 had positive results with MS or conidia but not blastospores. The formulations with 10% mineral oil did not always protect Metarhizium conidia against UV-B. Conidia of LCM S07, LCM S08, and LCM S10 exhibited the best results when in aqueous suspensions, 24 h after UV-B exposure. In general, conidia mixed with soil and exposed to UV-B yielded similar number of colony forming units as conidia from unexposed soil, regardless the soil type. It was not possible to predict which type of propagule would be the most UV-B tolerant for each fungal isolate; in conclusion, many formulations and propagule types should be investigated early in the development of new fungal biocontrol products., (© 2020 Wiley‐VCH GmbH.)

The present work aimed to evaluate and to model the influence of UV-C light treatments with different irradiances (6.5, 13, 21, and 36 W/m 2 ) on Aspergillus fischeri and Paecilomyces niveus ascospores inactivation in clarified apple juice. Approximately 5.0 and 6.0 log CFU/mL spores of P. niveus and A. fischeri, respectively, were suspended in 30 mL of clarified apple juice (pH 3.8, 12 ± 0.1°Brix) and exposed to UV-C light at different irradiances (as above) and exposure times (0 to 30 min). The first-order biphasic model was able to describe the experimental data with good statistical indices (RMSE = 0.296 and 0.308, R 2  = 0.96 and 0.98, for P. niveus and A. fischeri respectively). At the highest irradiance level tested (36 W/m 2 ), the UV-C light allowed the reduction of 5.7 and 4.2 log-cycles of A. fischeri and P. niveus ascospores, respectively, in approximately 10 min. P. niveus was the most UV-C resistant mould. The results showed that, to a defined UV-C fluence, a change in the level of either time or UV-C irradiance did not affect the effectiveness of UV-C light for A. fischeri and P. niveus inactivation. Thus, the modeling of the inactivation as a function of the UV-C fluence allowed the estimation of the primary model parameters with all experimental data and, consequently, no secondary models were needed. The model parameters were validated with experiments of variable UV-C fluences. Accordingly, experimental results allowed to conclude that UV-C treatment at the irradiances tested is a promising application for preventing A. fischeri and P. niveus spoilage of juices., (Copyright © 2020 Elsevier B.V. All rights reserved.)

White-nose syndrome is a fungal disease responsible for the rapid decline of North American bat populations. This study addressed a novel method for inactivating Pseudogymnoascus destructans, the causative agent of WNS, using ultraviolet A (UVA) or B (UVB) radiation in combination with methoxsalen, a photosensitizer from the furanocoumarin family of compounds. Fungal spore suspensions were diluted in micromolar concentrations of methoxsalen (50-500 μM), then exposed to fixed doses of UVA radiation (500-5000 mJ/cm2), followed by plating on germination media. These plates were examined for two to four weeks for evidence of spore germination or inactivation, along with resultant growth or inhibition of P. destructans colonies. Pretreatment of fungal spores with low doses of methoxsalen resulted in a UVA dose-dependent inactivation of the P. destructans spores. All doses of methoxsalen paired with 500 mJ/cm2 of UVA led to an approximate two-log10 (~99%) reduction in spore viability, and when paired with 1000 mJ/cm2, a four-log10 or greater (>99.99%) reduction in spore viability was observed. Additionally, actively growing P. destructans colonies treated directly with methoxsalen and either UVA or UVB radiation demonstrated UV dose-dependent inhibition and termination of colony growth. This novel approach of using a photosensitizer in combination with UV radiation to control fungal growth may have broad, practical application in the future., Competing Interests: The authors have declared that no competing interests exist.

The purpose was to investigate the effect of daylight-intensity blue light on F. solani isolated from the cornea of patients with fungal keratitis. Spore suspensions of 5 F. solani strains (one standard strain and 4 clinical corneal isolates) were prepared in 6-well plates. Blue light groups were irradiated by a light-emitting diode (LED) device with a peak wavelength of 454 nm at 0.5 mW/cm 2 for 0 to 48 h, while the controls were maintained in darkness. Hyphal morphology in the 6-well plates was recorded at 0, 12, 24, 36, 48 h. One hundred microliters of spore suspensions of each strain at these five time points was transferred to SGA plates and cultured for 36 h at 29 °C; the number of colonies formed was counted as a measure of conidia quality and viability. Blue light has dual effects on F. solani. The hyphal length of F. solani exposed to blue light was significantly shorter than that of the control (P < 0.01), indicating that fungal growth was inhibited. Meanwhile, instead of reducing the viability of spores, blue light significantly enhanced the conidia quality and viability after at least 24 h irradiation. Daylight-intensity blue light exposure will inhibit the hyphal growth of F. solani but promote conidiation, which would be more harmful to fungal keratitis. Eliminating the influence of blue light for these patients should be taken into account.

We investigated the comparative susceptibility to heat and UV-B radiation of blastospores and aerial conidia of Metarhizium spp. (Metarhizium robertsii IP 146, Metarhizium anisopliae s.l. IP 363 and Metarhizium acridum ARSEF 324) and Beauveria bassiana s.l. (IP 361 and CG 307). Conidia and blastospores were produced in solid or liquid Adámek-modified medium, respectively, and then exposed to heat (45 ± 0.2 °C) in a range of 0 (control) to 360 min; the susceptibility of fungal propagules to heat exposures was assessed to express relative viability. Similarly, both propagules of each isolate were also exposed to a range of 0 (control) to 8.1 kJ m -2 under artificial UV-B radiation. Our results showed that fungal isolates, propagule types and exposure time or dose of the stressor source play critical roles in fungal survival challenged with UV-B and heat. Conidia of ARSEF 324, IP 363, IP 146 and IP 361 exposed to heat survived significantly longer than their blastospores, except for blastospores of CG 307. Conidia and blastospores of IP 146 and IP 363 were equally tolerant to UV-B radiation. We claim that blastospores of certain isolates may be promising candidates to control arthropod pests in regions where heat and UV-B are limiting environmental factors., Competing Interests: Declaration of competing interest The authors have declared no competing interests., (Copyright © 2020 British Mycological Society. Published by Elsevier Ltd. All rights reserved.)

Fungi sense light and utilize it as a source of environmental information to prepare against many stressful conditions in nature. In this study, Metarhizium robertsii was grown on: 1) potato dextrose agar medium (PDA) in the dark (control); 2) under nutritive stress in the dark; and 3) PDA under continuous (A) white light; (B) blue light lower irradiance = LI; (C) blue light higher irradiance = HI; (D) green light; and (E) red light. Conidia produced under these treatments were tested against osmotic stress and UV radiation. In addition, a suite of genes usually involved in different stress responses were selected to study their expression patterns. Conidia produced under nutritive stress in the dark were the most tolerant to both osmotic stress and UV radiation, and the majority of their stress- and virulence-related genes were up-regulated. For osmotic stress tolerance, conidia produced under white, blue LI, and blue HI lights were the second most tolerant, followed by conidia produced under green light. Conidia produced under red light were the least tolerant to osmotic stress and less tolerant than conidia produced on PDA medium in the dark. For UV tolerance, conidia produced under blue light LI were the second most tolerant to UV radiation, followed by the UV tolerances of conidia produced under white light. Conidia produced under blue HI, green, and red lights were the least UV tolerant and less tolerant than conidia produced in the dark. The superoxide dismutases (sod1 and sod2), photolyases (6-4phr and CPDphr), trehalose-phosphate synthase (tps), and protease (pr1) genes were highly up-regulated under white light condition, suggesting a potential role of these proteins in stress protection as well as virulence after fungal exposure to visible spectrum components., (Copyright © 2019 British Mycological Society. Published by Elsevier Ltd. All rights reserved.)

Fungi are versatile organisms which thrive in hostile environments, including the International Space Station (ISS). Several isolates of the human pathogen Aspergillus fumigatus have been found contaminating the ISS, an environment with increased exposure to UV radiation. Secondary metabolites (SMs) in spores, such as melanins, have been shown to protect spores from UV radiation in other fungi. To test the hypothesis that melanin and other known spore SMs provide UV protection to A. fumigatus isolates, we subjected SM spore mutants to UV-C radiation. We found that 1,8-dihydroxynaphthalene (DHN)-melanin mutants of two clinical A. fumigatus strains (Af293 and CEA17) but not an ISS-isolated strain (IF1SW-F4) were more sensitive to UV-C than their respective wild-type (WT) strains. Because DHN-melanin has been shown to shield A. fumigatus from the host immune system, we examined all DHN mutants for virulence in the zebrafish model of invasive aspergillosis. Following recent studies highlighting the pathogenic variability of different A. fumigatus isolates, we found DHN-melanin to be a virulence factor in CEA17 and IF1SW-F4 but not Af293. Three additional spore metabolites were examined in Af293, where fumiquinazoline also showed UV-C-protective properties, but two other spore metabolites, monomethylsulochrin and fumigaclavine, provided no UV-C-protective properties. Virulence tests of these three SM spore mutants indicated a slight increase in virulence of the monomethylsulochrin deletion strain. Taken together, this work suggests differential roles of specific spore metabolites across Aspergillus isolates and by types of environmental stress. IMPORTANCE Fungal spores contain secondary metabolites that can protect them from a multitude of abiotic and biotic stresses. Conidia (asexual spores) of the human pathogen Aspergillus fumigatus synthesize several metabolites, including melanin, which has been reported to be important for virulence in this species and to be protective against UV radiation in other fungi. Here, we investigate the role of melanin in diverse isolates of A. fumigatus and find variability in its ability to protect spores from UV-C radiation or impact virulence in a zebrafish model of invasive aspergillosis in two clinical strains and one ISS strain. Further, we assess the role of other spore metabolites in a clinical strain of A. fumigatus and identify fumiquinazoline as an additional UV-C-protective molecule but not a virulence determinant. The results show differential roles of secondary metabolites in spore protection dependent on the environmental stress and strain of A. fumigatus As protection from elevated levels of radiation is of paramount importance for future human outer space explorations, the discovery of small molecules with radiation-protective potential may result in developing novel safety measures for astronauts., (Copyright © 2020 Blachowicz et al.)

Microorganisms sense environmental fluctuations in nutrients and light, coordinating their growth and development accordingly. Despite their critical roles in fungi, only a few G-protein coupled receptors (GPCRs) have been characterized. The Aspergillus nidulans genome encodes 86 putative GPCRs. Here, we characterise a carbon starvation-induced GPCR-mediated glucose sensing mechanism in A. nidulans. This includes two class V (gprH and gprI) and one class VII (gprM) GPCRs, which in response to glucose promote cAMP signalling, germination and hyphal growth, while negatively regulating sexual development in a light-dependent manner. We demonstrate that GprH regulates sexual development via influencing VeA activity, a key light-dependent regulator of fungal morphogenesis and secondary metabolism. We show that GprH and GprM are light-independent negative regulators of sterigmatocystin biosynthesis. Additionally, we reveal the epistatic interactions between the three GPCRs in regulating sexual development and sterigmatocystin production. In conclusion, GprH, GprM and GprI constitute a novel carbon starvation-induced glucose sensing mechanism that functions upstream of cAMP-PKA signalling to regulate fungal development and mycotoxin production., Competing Interests: The authors have declared that no competing interests exist

Different methods have been applied in controlling contamination of foods and feeds by the carcinogenic fungal toxin, aflatoxin, but nevertheless the problem remains pervasive in developing countries. Curcumin is a natural polyphenolic compound from the spice turmeric (Curcuma longa L.) that has been identified as an efficient photosensitiser for inactivation of Aspergillus flavus conidia. Curcumin mediated photoinactivation of A. flavus has revealed the potential of this technology to be an effective method for reducing population density of the aflatoxin-producing fungus in foods. This study demonstrates the influence of pH and temperature on efficiency of photoinactivation of the fungus and how treating spore-contaminated maize kernels affects aflatoxin production. The results show the efficiency of curcumin mediated photoinactivation of fungal conidia and hyphae were not affected by temperatures between 15 and 35 °C or pH range of 1.5-9.0. The production of aflatoxin B 1 was significantly lower (p < 0.05), with an average of 82.4 μg/kg as compared to up to 305.9 μg/kg observed in untreated maize kept under similar conditions. The results of this study indicate that curcumin mediated photosensitization can potentially be applied under simple environmental conditions to achieve significant reduction of post-harvest contamination of aflatoxin B 1 in maize., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Fungi are able to grow on diverse food products and contribute to food spoilage worldwide causing food loss. Consumers prefer freshly squeezed fruit juices, however, the shelf life of these juices is limited due to outgrowth of yeast and fungi. The shelf life of pulsed electric field (PEF) treated juice can be extended from 8 days up to a few weeks before spoilage by moulds becomes apparent. Conidia produced by three Penicillium ssp. (Penicillium expansum, Penicillium buchwaldii and Penicillium bialowiezense), previously isolated from spoiled PEF treated fruit juice and smoothie, were characterized for resistance towards selected mild physical processing techniques in orange juice and toward sanitizers on surfaces. The results show that Penicillium spp. conidia are susceptible to mild heat, high pressure pasteurization (HPP), PEF, cold atmospheric plasma (CAP), UV, and chemical sanitizers chlorine dioxide and hypochlorite albeit with different susceptibility. Treatment with mild heat, HPP, PEF, or chlorine dioxide reduced conidia by more than 5 log. For hypochlorite, UV, and CAP the reduction was between 1 and 3 log. Together, this study provides data for the development of intervention strategies to eliminate spoilage mould conidia in fruit juices., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The filamentous fungus Alternaria alternata is a common postharvest contaminant of food and feed, and some strains are plant pathogens. Many processes in A. alternata are triggered by light. Interestingly, blue light inhibits sporulation, and red light reverses the effect, suggesting interactions between light-sensing systems. The genome encodes a phytochrome (FphA), a white collar 1 (WC-1) orthologue (LreA), an opsin (NopA), and a cryptochrome (CryA) as putative photoreceptors. Here, we investigated the role of FphA and LreA and the interplay with the high-osmolarity glycerol (HOG) mitogen-activated protein (MAP) kinase pathway. We created loss-of function mutations for fphA , lreA , and hogA using CRISPR-Cas9 technology. Sporulation was reduced in all three mutant strains already in the dark, suggesting functions of the photoreceptors FphA and LreA independent of light perception. Germination of conidia was delayed in red, blue, green, and far-red light. We found that light induction of ccgA ( c lock- c ontrolled g ene in Neurospora crassa and light-induced gene in Aspergillus nidulans ) and the catalase gene catA depended on FphA, LreA, and HogA. Light induction of ferA (a putative ferrochelatase gene) and bliC ( bli-3, light regulated, unknown function) required LreA and HogA but not FphA. Blue- and green-light stimulation of alternariol formation depended on LreA. A lack of FphA or LreA led to enhanced resistance toward oxidative stress due to the upregulation of catalases and superoxide dismutases. Light activation of FphA resulted in increased phosphorylation and nuclear accumulation of HogA. Our results show that germination, sporulation, and secondary metabolism are light regulated in A. alternata with distinct and overlapping roles of blue- and red-light photosensors. IMPORTANCE Light controls many processes in filamentous fungi. The study of light regulation in a number of model organisms revealed an unexpected complexity. Although the molecular components for light sensing appear to be widely conserved in fungal genomes, the regulatory circuits and the sensitivity of certain species toward specific wavelengths seem different. In N. crassa , most light responses are triggered by blue light, whereas in A. nidulans , red light plays a dominant role. In Alternaria alternata , both blue and red light appear to be important. In A. alternata , photoreceptors control morphogenetic pathways, the homeostasis of reactive oxygen species, and the production of secondary metabolites. On the other hand, high-osmolarity sensing required FphA and LreA, indicating a sophisticated cross talk between light and stress signaling., (Copyright © 2019 Igbalajobi et al.)

Damp indoor environments contaminated with different mold species may contribute to the development and exacerbation of respiratory illnesses. Human bronchial epithelial BEAS-2B cells were exposed to X-ray treated spores and hyphal fragments from pure cultures of Aspergillus fumigatus , Penicillum chrysogenum , Aspergillus versicolor and Stachybotrys chartarum . Hyphal fragments of A. fumigatus and P. chrysogenum induced expression and release of the pro-inflammatory cytokine interleukin (IL)-6 and the chemokine IL-8, while none of the other hyphal preparations had effects. Hyphal fragments from A. fumigatus and P. chrysogenum also increased the expression of IL-1α, IL-1β and tumor necrosis factor (TNF)-α, but these cytokines were not released. X-ray treated spores had little or no inflammatory potential. Attenuating Toll-like receptor (TLR)-2 by blocking antibodies strongly reduced the A. fumigatus and P. chrysogenum hyphae-induced IL-6 and IL-8 release, whereas TLR4 antagonist treatment was without effects. Untreated A. fumigatus spores formed hyphae and triggered expression of pro-inflammatory genes with similarities to the effects of hyphal fragments. In conclusion, while X-ray treated spores induced no pro-inflammatory responses, hyphal fragments of A. fumigatus and P. chrysogenum enhanced a TLR2-dependent expression and release of IL-6 and IL-8.

UV-C irradiation is known to compromise germination of Blumeria graminis conidia and to reduce powdery mildew infestation. However, only scarce information is available on the effects of UV-C irradiation on B. graminis appressorium formation. Applying a Formvar® resin-based in vitro system allowed for analyzing B. graminis germination and appressorium formation in absence of plant defense. UV-C irradiation more strongly affected the differentiation of appressoria than conidial germination. In vivo and in vitro, a single dose of 100 J m -2 UV-C was sufficient to reduce germination to less than 20 % and decrease appressorium formation to values below 5 %. UV-C irradiation negatively affected pustule size and conidiation. White light-mediated photoreactivation was most effective immediately after UV-C irradiation, indicating that a prolonged phase of darkness after UV-C treatment increases the efficacy of B. graminis control. UV-C irradiation increased transcript levels of three putative B. graminis photolyase genes, while mere white light or blue light irradiation did not contribute to the transcriptional up-regulation. Thus, UV-C irradiation effectively controls B. graminis infestation and proliferation by restricting prepenetration processes. Nevertheless, photoreactivation plays an important role in UV-C-based powdery mildew control in crops and hence has to be considered for planning specific irradiation schedules., (Copyright © 2018 British Mycological Society. Published by Elsevier Ltd. All rights reserved.)

Fungal conidia serve as active ingredients of fungal insecticides but are sensitive to solar UV irradiation, which impairs double-stranded DNA (dsDNA) by inducing the production of cytotoxic cyclobutane pyrimidine dimers (CPDs) and (6-4)-pyrimidine-pyrimidine photoproducts (6-4PPs). This study aims to elucidate how CPD photolyase (Phr1) and 6-4PP photolyase (Phr2) repair DNA damage and photoreactivate UVB-inactivated cells in Beauveria bassiana , a main source of fungal insecticides. Both Phr1 and Phr2 are proven to exclusively localize in the fungal nuclei. Despite little influence on growth, conidiation, and virulence, singular deletions of phr1 and phr2 resulted in respective reductions of 38% and 19% in conidial tolerance to UVB irradiation, a sunlight component most harmful to formulated conidia. CPDs and 6-4PPs accumulated significantly more in the cells of Δ phr1 and Δ phr2 mutants than in those of a wild-type strain under lethal UVB irradiation and were largely or completely repaired by Phr1 in the Δ phr2 mutant and Phr2 in the Δ phr1 mutant after optimal 5-h exposure to visible light. Consequently, UVB-inactivated conidia of the Δ phr1 and Δ phr2 mutants were much less efficiently photoreactivated than were the wild-type counterparts. In contrast, overexpression of either phr1 or phr2 in the wild-type strain resulted in marked increases in both conidial UVB resistance and photoreactivation efficiency. These findings indicate essential roles of Phr1 and Phr2 in photoprotection of B. bassiana from UVB damage and unveil exploitable values of both photolyase genes for improved UVB resistance and application strategy of fungal insecticides. IMPORTANCE Protecting fungal cells from damage from solar UVB irradiation is critical for development and application of fungal insecticides but is mechanistically not understood in Beauveria bassiana , a classic insect pathogen. We unveil that two intranuclear photolyases, Phr1 and Phr2, play essential roles in repairing UVB-induced dsDNA lesions through respective decomposition of cytotoxic cyclobutane pyrimidine dimers and (6-4)-pyrimidine-pyrimidine photoproducts, hence reactivating UVB-inactivated cells effectively under visible light. Our findings shed light on the high potential of both photolyase genes for use in improving UVB resistance and application strategy of fungal insecticides., (Copyright © 2019 American Society for Microbiology.)

Background: Solar radiation is assumed to be a major factor limiting the efficacy of entomopathogenic fungi used as biocontrol agents in open field applications. We evaluated 12 natural UV-protective co-formulants for their effect on the survival of UV-exposed Beauveria bassiana spores on agar plates, colza leaf discs and in the field., Results: Colony-forming unit (CFU) counts of unformulated conidia on agar plates and leaf discs dropped to ≤ 50% after exposure to UV radiation. The highest UV protection was achieved with humic acid, which provided > 90% protection of UV-B-exposed conidia in laboratory experiments. In the field, 10% humic acid increased spore persistence up to 87% at 7 days after application. Sesame and colza oil also provided high UV protection in both assays (> 73% and > 70%, respectively)., Conclusions: This study shows that it is possible to increase the persistence of B. bassiana spores under exposure to UV radiation by formulation with natural UV-protective additives. UV protectants might, therefore, increase the efficacy of entomopathogenic fungi as biocontrol agents in open field applications. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry., (© 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.)

Fungal development and secondary metabolism are closely associated via the activities of the fungal NK-kB-type velvet regulators that are highly conserved in filamentous fungi. Here, we investigated the roles of the velvet genes in the aflatoxigenic fungus Aspergillus flavus. Distinct from other Aspergillus species, the A. flavus genome contains five velvet genes, veA, velB, velC, velD, and vosA. The deletion of velD blocks the production of aflatoxin B1, but does not affect the formation of sclerotia. Expression analyses revealed that vosA and velB mRNAs accumulated at high levels during the late phase of asexual development and in conidia. The absence of vosA or velB decreased the content of conidial trehalose and the tolerance of conidia to the thermal and UV stresses. In addition, double mutant analyses demonstrated that VosA and VelB play an inter-dependent role in trehalose biosynthesis and conidial stress tolerance. Together with the findings of previous studies, the results of the present study suggest that the velvet regulators play the conserved and vital role in sporogenesis, conidial trehalose biogenesis, stress tolerance, and aflatoxin biosynthesis in A. flavus.

The effect of light on the binding of Ca 2+ to mycelia and to cell walls isolated from aerial mycelia of three strains of Trichoderma spp. was studied. Two independent methods were used to measure the total Ca 2+ content in mycelia and the Ca 2+ bound to cell walls isolated from aerial mycelia. The results of these methods showed that the light-induced formation and maturation of conidia in Trichoderma spp. is accompanied by increased Ca 2+ deposition in mycelia and cell walls. Moreover, the cultivation of Trichoderma atroviride F-534 in the presence of 45 Ca 2+ under circadian illumination showed that radioactivity was exclusively localized in the light-induced conidial rings of aerial mycelia. The fluorescence microscopy of chlortetracycline-stained mycelia showed that the major fraction of Ca 2+ was accumulated in conidia and fructification structures, or some intracellular compartments in T. atroviride F-534 grown under circadian illumination, while only a limited amount of Ca 2+ was associated with hyphal surfaces. In addition, the study of 45 Ca 2+ binding to cell walls revealed that T. atroviride F-534 displays both increased 45 Ca 2+ binding capacity and elevated affinity to 45 Ca 2+ binding upon illumination. The results indicate that conidia formation and (or) maturation is associated with changes in Ca 2+ homeostasis.

This study verified the influence of different temperatures on P. insidiosum in vitro zoosporogenesis. P. insidiosum isolates (n = 26) were submitted to zoosporogenesis and incubated at 5°C, 15°C, 20°C and 37°C (1st stage). Grass fragments were evaluated under optical microscopy at 4, 8, and 24 hours of incubation. Afterward, all isolates were incubated at 37°C and assessed at the same periods of time (2nd stage). The development of hyphae, presence of vesicles, zoosporangia and zoospores were checked. Only the presence of short hyphae was observed at 5°C. At 15°C, the hyphae were either under development or elongated and two isolates produced zoospores. When the isolates were submitted to 20°C for 4 hours, the presence of long and mycelial hyphae, vesicles, zoosporangia and zoospores was observed, which also happened at the other periods evaluated. In the second stage, the isolates which were initially at 5°C and 15°C evidenced long developing hyphae with the presence of vesicles, zoosporangia, and zoospores within 4 hours of incubation, and these characteristics were kept at the other evaluated periods. The isolates kept at 37°C showed evident zoosporogenesis in the first 4 hours of evaluation. It was concluded that temperatures of 20°C and 37°C support P. insidiosum zoosporogenesis process. On the other hand, 5°C and 15°C temperatures do not kill the microorganism.

Bacterial and fungal spore contamination in different industries has a greater economic impact. Because of the remarkable resistance of spores to most physical and chemical microbicidal agents, their inactivation need special attention during sterilization processes. Heat and chemical sporicides are not always well suited for different sterilization/decontamination applications and carries inherent risks. In recent years, novel nonthermal agents including nonthermal plasmas are emerging as effective sporicides against a broad spectrum of bacterial and fungal spores. The present review discusses various aspects related to the inactivation of spores using nonthermal plasmas. Different types of both low pressure plasmas (e.g., capacitively coupled plasma and microwave plasma) and atmospheric pressure plasmas (e.g., dielectric barrier discharges, corona discharges, arc discharges, radio-frequency-driven plasma jet) have been successfully applied to destroy spores of economic significance. Plasma agents contributing to sporicidal activity and their mode of action in inactivation are discussed. In addition, information on factors that affect the sporicidal action of nonthermal plasmas is included.

Penicillium digitatum (Pers.:Fr.) Sacc. is the main fungus causing postharvest losses in citrus fruits. Previous work showed the potential of LED blue light (LBL) in controlling P. digitatum growth. Here, we have investigated whether LBL alters the ability of this fungus to infect citrus fruits. Before fruit infection, Petri plates inoculated with the same conidia concentration were held under darkness (control) or LBL (100 μmol m -2 s -1 ) for 8 d (continuous light), or were treated with the same LBL for 3 d and then shifted to darkness for 5 d (non-continuous light). Spores from cultures exposed to continuous light showed very low capacity to germinate (1.8% respect to control) but a high viability and a similar morphology and ability to infect the fruits than spores from control cultures. The number of spores produced in plates exposed to non-continuous light was slightly lower than in control plates, but they showed much lower viability and lower capacity to infect the fruits. This effect was more likely related to aberrant morphology of spores, which formed aggregates, than to its metabolic activity or its ability to produce ethylene that might contribute to destroy natural defense barriers from the fruit., (© 2018 The American Society of Photobiology.)

The isolate ARSEF 324 of Metarhizium acridum is very tolerant to UV-B radiation and heat, but the intrinsic traits behind the extreme tolerance of this isolate to both stress conditions have not been elucidated. Because trehalose and mannitol are documented stress reducers in fungi, we investigated the accumulation of these compounds in conidia of ARSEF 324 compared with the accumulation of these two compounds in conidia of M. robertsii (ARSEF 23 and ARSEF 2575), which are considerably more susceptible to UV-B radiation and heat than ARSEF 324. Conidia of ARSEF 324 produced on potato dextrose agar plus yeast extract accumulated two-fold more trehalose and mannitol than conidia of ARSEF 23 and ARSEF 2575 produced on the same medium. The high accumulation of trehalose and mannitol in conidia of ARSEF 324 suggests one mechanism that it uses to attain its high tolerance to UV-B radiation and heat., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Ultraviolet (UV) radiation is a key limiting factor for biological pest control with entomopathogenic fungi. While little is known about the impact of UV on Metarhizium anisopliae Metchnikoff (Sorokin) (Hypocreales: Clavicipitaceae) conidia in aquatic mosquito-breeding sites, this study determined the effect of UV-B on the viability and virulence of M. anisopliae sensu lato (s.l.) strain IP 46 in the laboratory against Aedes aegypti (L.) (Diptera: Culicidae) larvae. Conidia were treated in cups under defined water depths (0, 1, 2, and 3 cm) to six different UV-B doses (0, 0.657, 1.971, 3.942, 7.884, 11.826, or 15.768 kJ m-2) at 27 ± 2°C. The ability of treated conidia to germinate up to 24 h postexposure on PDAY + benomyl + chloramphenicol medium at 25 ± 1°C was adversely affected by higher doses of UV-B radiation regardless of the water depth. Germination, however, did not fall below 70% regardless of the test conditions. In fact, conidial virulence against second-instar larvae was not affected by either the water depth (F3,84 = 0.3, P = 0.85) or any tested levels of UV-B radiation (F6,21 ≤ 1.2, P ≥ 0.39) including those distinctly higher than might be expected for tropical sites. These findings strengthen previous observations that IP 46 has significant potential for use against A. aegypti larvae, even when exposed to elevated UV-B irradiance levels in the small breeding sites that are common for this important vector.

Aims: The effect of nutritional supplementation of two Metarhizium species with riboflavin (Rb) during production of conidia was evaluated on (i) conidial tolerance (based on germination) to UV-B radiation and on (ii) conidial expression following UV-B irradiation, of enzymes known to be active in photoreactivation, viz., photolyase (Phr), laccase (Lac) and polyketide synthase (Pks)., Methods and Results: Metarhizium acridum (ARSEF 324) and Metarhizium robertsii (ARSEF 2575) were grown either on (i) potato dextrose agar medium (PDA), (ii) PDA supplemented with 1% yeast extract (PDAY), (iii) PDA supplemented with Rb (PDA+Rb), or (iv) PDAY supplemented with Rb (PDAY+Rb). Resulting conidia were exposed to 866·7 mW m -2 of UV-B Quaite-weighted irradiance to total doses of 3·9 or 6·24 kJ m -2 . Some conidia also were exposed to 16 klux of white light (WL) after being irradiated, or not, with UV-B to investigate the role of possible photoreactivation. Relative germination of conidia produced on PDA+Rb (regardless Rb concentration) or on PDAY and exposed to UV-B was higher compared to conidia cultivated on PDA without Rb supplement, or to conidia suspended in Rb solution immediately prior to UV-B exposure. The expression of MaLac3 and MaPks2 for M. acridum, as well as MrPhr2, MrLac1, MrLac2 and MrLac3 for M. robertsii was higher when the isolates were cultivated on PDA+Rb and exposed to UV-B followed by exposure to WL, or exposed to WL only., Conclusions: Rb in culture medium increases the UV-B tolerance of M. robertsii and M. acridum conidia, and which may be related to increased expression of Phr, Lac and Pks genes in these conidia., Significance and Impact of the Study: The enhanced UV-B tolerance of Metarhizium spp. conidia produced on Rb-enriched media may improve the effectiveness of these fungi in biological control programs., (© 2018 The Society for Applied Microbiology.)

Recently, we had shown that conidia-derived growth of many dermatophytes can be inhibited by curcumin plus exposure to visible light. This method of photo inactivation should be developed further aiming for an option to stop mycelial growth in superficial tinea. Wells of microtitre plates were inoculated with either mycelial or conidial elements collected from 5 strains of Trichophyton rubrum. Then either micellar curcumin or curcumin dissolved with DMSO was added and after 20 min the wells were filled up with Sabouraud broth. Thereafter the assays were irradiated once with visible light (wave length 420 nm, 20 J/cm 2 ) and fungal growth was monitored photometrically. Identical effects were measured with conidia and mycelial elements of all 5 T. rubrum strains. Curcumin dissolved with DMSO plus irradiation had a marked dose-dependent inhibitory effect on fungal growth that was almost complete with 5.0 mg/L (P < .01) over a period of 9 days. In contrast, the same procedure with micellar curcumin had no inhibitory effect on growth obtained from conidia or mycelial elements. Mycelial elements of T. rubrum and its conidia are equally sensitive to photochemical inactivation with curcumin and the galenic compounding of curcumin is essential to achieve this photochemical effect., (© 2018 Blackwell Verlag GmbH.)

Onychomycoses are fungal infections of the fingernails or toenails having a prevalence of 3% among adults and accounts for 50% of nail infections. It is caused by dermatophytes, non-dermatophyte filamentous fungi, and yeasts. Compressions and microtraumas significantly contribute to onychomycosis. Laser and photodynamic therapies are being proposed to treat onychomycosis. Laser light (1064 nm) was used to treat onychomycosis in 156 affected toenails. Patients were clinically followed up for 9 months after treatment. Microbiological detection of fungal presence in lesions was accomplished. A total of 116 samples allowed the isolation of at least a fungus. Most of nails were affected in more than two thirds surface (some of them in the full surface). In 85% of cases, after 18 months of the onset of treatment, culture turned negative. After 3 months months, only five patients were completely symptom-free with negative culture. In 25 patients, only after 6 months, the absence of symptoms was achieved and the cultures negativized; in 29 patients, 9 months were required. No noticeable adverse effects were reported. This study reinforces previous works suggesting the applicability of laser therapies to treat toenail onychomycosis.

Background: Mung bean is a rich source of protein, carbohydrates and fiber content. It also exhibits a high level of antioxidant activity due to the presence of phenolic compounds. Aspergillus flavus and A. niger are the two major fungal strains associated with stored mung bean that lead to post-harvest losses of grains and also cause serious health risks to human beings. Thus there is a need to explore an economical decontamination method that can be used without affecting the biochemical parameters of grains., Results: It was observed that infrared (IR) treatment of mung bean surface up to 70 °C for 5 min at an intensity of 0.299 kW m -2 led to complete visible inhibition of fungal growth. Scanning electron microscopy revealed that surface irregularities and physical disruption of spores coat are the major reasons behind the inactivation of IR-treated fungal spores. It was also reported that IR treatment up to 70 °C for 5 min does not cause any negative impact on the biochemical and physical properties of mung bean., Conclusion: From the results of the present study, it was concluded that IR treatment at 70 °C for 5 min using an IR source having an intensity of 0.299 kW m -2 can be successfully used as a method of fungal decontamination. The fungal spore population was reduced (approximately 5.3 log 10 CFU g -1 reductions) without significantly altering the biochemical and physical properties of grains. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

In storage of modern museums, collections are packed and stored with acid-free paper-based materials for keeping safe and stable conditions. Direct contact of fungal contaminated packing and storing materials with the collections is concerned about expanding of infection in storage facilities. In this study, fungicidal effects of UV light irradiation on the materials such as archival board and Japanese tissue paper contaminated with Penicilliun commune and Chaetomium globosum were tested. The analyzed materials were divided into two groups; Group 1 was examined with 20 μl of spore suspensions of fungi (10 6 cfu/ml) ; and Group 2 was tested on Czapek- Dox agar medium modified without sugar and inoculated with 100 μl of the spore suspensions of fungi (10 6 cfu/ml) . Six doses of UV irradiation were examined on Group 1 and five doses on Group 2 in addition to control. The assessment was done by using 1) adenosine triphosphate (ATP) bioluminescence assay and double staining to determine the cell viability; 2) observation under light microscope to evaluate morphophysiological change of tested fungi (spores and hyphae) . Because of the thinness and high transparency of tissue paper, UV irradiations were highly efficient to fungicide its fungal contamination compared with archival board. In spite of the high resistance of C. globosum spores, the rate of growth was slow, and with a little amount of perithecia or fruiting bodies and a high amount of ycelium (which damaged rapidly through UV irradiation) . This may be due to a low relative humidity of the incubation environment. Minimum dosage of UV irradiation with fungicidal effectiveness against all fungal contamination was estimated as 118 J/cm 2 .

Controlled environment chamber experiments at Petri dish level were conducted to examine the wavelength and dose dependent efficacy of ultraviolet (UV) radiation, the recovery action potential of optical radiation applied concomitantly/subsequently to effective UV treatment, and the lapse time between UV treatment and subsequent exposure to recovery wavelength on germination efficiency of Oidium neolycopersici conidia. Conidia of eight- to nine-day-old colonies were dusted on water agar surface in Petri dishes and exposed to UV treatments (without lid). Immediately after UV treatments, Petri dishes were sealed and incubated in darkness or differing optical environments generated using seven different radiation sources (range 290nm to 780nm). Twenty-four hours after UV treatment, fifty conidia from each sample were assessed for germination. Compared to non-UV controls, <10% of the conidia germinated after 30s of exposure to 254nm or 283nm UV and subsequent dark incubation. Conidia germination was almost negligible if the exposure duration increased to 4min. Germination was about 60% with broad spectrum UV after 1min of exposure, and about 35% after 2 to 4min of exposure. There was no reduction of conidia germination with the exposure of ≤4min with 310nm. With the tested wavelength and dose ranges, germination recovery was effective in the 350nm to 500nm range. Germination efficiency of conidia treated with effective UV was significantly higher (>73%) if incubated subsequently in the 350nm to 500nm range (germination recovery). Furthermore, germination recovery depends on the characteristics of UV treatment (wavelength, and duration of exposure) and the lapse time between UV treatment and subsequent exposure to optical radiation in the recovery range. The findings of this study provide key criteria for wavelength selection, combination and application time in the optical radiation range, enabling improved design of optical based management strategies against powdery mildews., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Although meiosis in warm-blooded organisms takes place in a narrow temperature range, meiosis in many organisms occurs over a wide variety of temperatures. We analyzed the properties of meiosis in the yeast Saccharomyces cerevisiae in cells sporulated at 14°C, 30°C, or 37°C. Using comparative-genomic-hybridization microarrays, we examined the distribution of Spo11-generated meiosis-specific double-stranded DNA breaks throughout the genome. Although there were between 300 and 400 regions of the genome with high levels of recombination (hot spots) observed at each temperature, only about 20% of these hot spots were found to have occurred independently of the temperature. In S. cerevisiae , regions near the telomeres and centromeres tend to have low levels of meiotic recombination. This tendency was observed in cells sporulated at 14°C and 30°C, but not at 37°C. Thus, the temperature of sporulation in yeast affects some global property of chromosome structure relevant to meiotic recombination. Using single-nucleotide polymorphism (SNP)-specific whole-genome microarrays, we also examined crossovers and their associated gene conversion events as well as gene conversion events that were unassociated with crossovers in all four spores of tetrads obtained by sporulation of diploids at 14°C, 30°C, or 37°C. Although tetrads from cells sporulated at 30°C had slightly (20%) more crossovers than those derived from cells sporulated at the other two temperatures, spore viability was good at all three temperatures. Thus, despite temperature-induced variation in the genetic maps, yeast cells produce viable haploid products at a wide variety of sporulation temperatures. IMPORTANCE In the yeast Saccharomyces cerevisiae , recombination is usually studied in cells that undergo meiosis at 25°C or 30°C. In a genome-wide analysis, we showed that the locations of genomic regions with high and low levels of meiotic recombination (hot spots and cold spots, respectively) differed dramatically in cells sporulated at 14°C, 30°C, and 37°C. Thus, in yeast, and likely in other non-warm-blooded organisms, genetic maps are strongly affected by the environment., (Copyright © 2017 Zhang et al.)

The agent of apple scab disease (Venturia inaequalis) is the most common pathogen in apple cultivation. Its ascospores are released in spring, mainly during daylight hours and triggered by rain events. To investigate the causes of diurnal rhythm of ascospore dissemination of the apple scab fungus ascospore releases were examined continuously with spore traps in the orchard and with laboratory assays. One of the spore traps was illuminated at night with different light sources in each year during 2011-2015. The laboratory assays were performed with different light sources with varying wavelengths and intensities. In field and laboratory conditions only light including infrared radiation stimulated ascospore release, but not with light in the visible spectrum only. Artificial illumination during night was correlated with an increase of up to 46 % of ascospores released overnight in the field. We proved that infrared radiation induces V. inaequalis to release its spores. This is the first report in which spore discharge could be stimulated during night under field conditions., (Copyright © 2017 British Mycological Society. Published by Elsevier Ltd. All rights reserved.)

Antimicrobial photodynamic treatment (APDT) is a promising light based approach to control diseases caused by plant-pathogenic fungi. In the present study, we evaluated the effects of APDT with the phenothiazinium photosensitizer methylene blue (MB) under solar radiation on the germination and viability of conidia of the pathogenic fungus Colletotricum abscissum (former Colletotrichum acutatum sensu lato). Experiments were performed both on petals and leaves of sweet orange (Citrus sinensis) in different seasons and weather conditions. Conidial suspensions were deposited on the leaves and petals surface, treated with the PS (25 or 50μM) and exposed to solar radiation for only 30min. The effects of APDT on conidia were evaluated by counting the colony forming units recovered from leaves and petals and by direct evaluating conidial germination on the surface of these plant organs after the treatment. To better understand the mechanistic of conidial photodynamic inactivation, the effect of APDT on the permeability of the conidial plasma membrane was assessed using the fluorescent probe propidium iodide (PI) together with flow cytometry and fluorescence microscopy. APDT with MB and solar exposure killed C. abscissum conidia and prevented their germination on both leaves and petals of citrus. Reduction of conidial viability was up to three orders of magnitude and a complete photodynamic inactivation was achieved in some of the treatments. APDT damaged the conidial plasma membrane and increased its permeability to PI. No damage to sweet orange flowers or leaves was observed after APDT. The demonstration of the efficacy of APDT on the plant host represents a further step towards the use of the method for control phytopathogens in the field., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Recent studies have demonstrated the presence of Metarhizium species on the epigeal areas of weeds and woody plants in various Mediterranean ecosystems, and the question arises whether isolates from the phylloplane, which experiences greater exposure to environmental UV-B radiation than soil isolates do, could have better UV-B radiation tolerance. The in vitro response of 18 Metarhizium strains isolated from phylloplane and soil of several Mediterranean ecosystems to UV-B radiation and the in vitro and in vivo effects of UV-B radiation on the viability and virulence of a selected M. brunneum strain against C. capitata were determined. The conidial germination, culturability and colony growth of these strains exposed to 1200mWm -2 for 2, 4 or 6h were evaluated. Germination rates below 30% and poor conidia recovery rates were observed for all strains. However, no relationship between the Metarhizium species or isolation habitat and the effect of UV-B radiation was found. Strain EAMa 01/58-Su, which showed a high tolerance to UV-B inactivation in terms of relative germination, was subsequently selected to investigate the UV-B related effects on virulence toward C. capitata adults. In a series of bioassays, the virulence and viability was determined using pure dry conidia, which were irradiated with 1200mWm -2 for 6h prior or after adult flies were inoculated, which resulted in a significant 84.7-86.4% decrease in conidial viability but only a slightly significant reduction of virulence, with 100.0% and 91.4% adult mortality rates and 4.6 and 5.9days average survival time for the no UV-B and UV-B treatments, respectively. A second series of experiments was performed to determine whether the UV-B effects on strain EAMa 01/58-Su were dose- or exposure time-dependent. Adult flies were inoculated with five doses (1.0×10 4 -1.0×10 8 conidiaml -1 ) and then irradiated at 1200mWm -2 for 6h, and similar LC 50 values, 3.8×10 7 and 4.3×10 7 conidiaml -1 , were determined for the UV-B and no UV-B treatments, respectively. However, the LT 50 values for flies inoculated with 1.0×10 8 conidiaml -1 and with1.0×10 7 conidiaml -1 were 15.1% and 30.8% longer for UV-B treatments than no UV-B treatments, respectively. Next, adult flies were treated with 1.0×10 8 conidiaml -1 and then exposed to 1200mWm -2 for 0, 6, 12, 24, 36 and 48h, and the relationships among exposure time and conidia viability and fly mortality losses were determined. The exposure time for adult flies at 1200mWm -2 to achieve a 50% reduction in fly mortality was 47.2h, which was longer than that of 5.6h required for a 50% reduction in conidia viability. Our results show that the UV-B radiation significantly affected the virulence of EAMa 01/58-Su strain against C. capitata adults, with this effect being dependent on the exposure time but not related to fungal dosage., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The plant-pathogenic leotiomycete Botrytis cinerea is known for the strict regulation of its asexual differentiation programs by environmental light conditions. Sclerotia are formed in constant darkness; black/near-UV (NUV) light induces conidiation; and blue light represses both differentiation programs. Sensing of black/NUV light is attributed to proteins of the cryptochrome/photolyase family (CPF). To elucidate the molecular basis of the photoinduction of conidiation, we functionally characterized the two CPF proteins encoded in the genome of B. cinerea as putative positive-acting components. B. cinerea CRY1 (BcCRY1), a cyclobutane pyrimidine dimer (CPD) photolyase, acts as the major enzyme of light-driven DNA repair (photoreactivation) and has no obvious role in signaling. In contrast, BcCRY2, belonging to the cry-DASH proteins, is dispensable for photorepair but performs regulatory functions by repressing conidiation in white and especially black/NUV light. The transcription of bccry1 and bccry2 is induced by light in a White Collar complex (WCC)-dependent manner, but neither light nor the WCC is essential for the repression of conidiation through BcCRY2 when bccry2 is constitutively expressed. Further, BcCRY2 affects the transcript levels of both WCC-induced and WCC-repressed genes, suggesting a signaling function downstream of the WCC. Since both CPF proteins are dispensable for photoinduction by black/NUV light, the origin of this effect remains elusive and may be connected to a yet unknown UV-light-responsive system. IMPORTANCE Botrytis cinerea is an economically important plant pathogen that causes gray mold diseases in a wide variety of plant species, including high-value crops and ornamental flowers. The spread of disease in the field relies on the formation of conidia, a process that is regulated by different light qualities. While this feature has been known for a long time, we are just starting to understand the underlying molecular mechanisms. Conidiation in B. cinerea is induced by black/near-UV light, whose sensing is attributed to the action of cryptochrome/photolyase family (CPF) proteins. Here we report on the distinct functions of two CPF proteins in the photoresponse of B. cinerea While BcCRY1 acts as the major photolyase in photoprotection, BcCRY2 acts as a cryptochrome with a signaling function in regulating photomorphogenesis (repression of conidiation)., (Copyright © 2017 American Society for Microbiology.)