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Thermal processing remains the major technology in food industry while it inevitably destructs sensory, nutrition and functional ingredients of food. In recent years, there has been a growing interest in non-thermal process. Spores are the dormant state of vegetative cells and have unique multilayers structure. A lot of research focused on the inactivation of spores due to its extremely resistance. This review focused on the inactivation effects and mechanisms of spores by non-thermal processing. High-pressure processing inactivated spores by two step pathways. First moderate high pressure induced the germination of spores, and the resistance decreased rapidly. Then the germinated spores inactivated as followed. Some non-thermal techniques such as ultrasound and ultraviolet radiation had synergistic effects and were usually applied as hurdle technologies.

Microorganisms efficiently colonize the external and internal surfaces of the animal body establishing mutually beneficial interactions and forming site- and individual-specific microbiota. The degradation of complex polysaccharides in the animal gut, the production of useful compounds, protection against pathogenic microorganisms and contribution to the development of an efficient immune system are the main beneficial effects of a balanced microbiota. A dysbiosis, an imbalanced composition of the microbiota, has been associated with a large number of diseases from gastro-intestinal or urogenital disorders to allergies, cardiovascular and autoimmune diseases and even to the onset of certain cancers. A growing body of evidence has indicated that probiotic treatments, aimed at maintaining or rebalancing the microbiota, are useful to treat/prevent those illnesses. Lactic Acid Bacteria and Bifidobacteria are the most common microbes used in probiotic preparations; however, other bacteria and yeast cells are also widely used in commercial products. Here we focus on the use of bacterial spore formers as probiotics. Spore formers have been marketed as probiotics for over 50 years and are now extensively used for the treatment of intestinal disorders and as dietary supplements in humans, as growth promoters and competitive exclusion agents in animals.

Bacterial sporulation is a conserved process utilized by members of Bacillus genus and Clostridium in response to stress such as nutrient or temperature. Sporulation initiation is triggered by stress signals perceived by bacterial cell that leads to shutdown of metabolic pathways of bacterial cells. The mechanism of sporulation involves a complex network that is regulated at various checkpoints to form the viable bacterial spore. Engulfment is one such check point that drives the required cellular rearrangement necessary for the spore assembly and is mediated by bacterial proteolytic machinery that involves association of various Clp ATPases and ClpP protease. The present study highlights the importance of degradation of an anti-sigma factor F, SpoIIAB by ClpCP proteolytic machinery playing a crucial role in culmination of engulfment process during the sporulation in Bacillus anthracis.

The ever-increasing applications of enzymes are limited by the relatively poor performance in harsh processing conditions. As a result, there are constant innovations in immobilization protocols for improving biocatalyst activity and stability. Bacterial spores are cheap to generate and highly resistant to environmental stress. The spore core is sheathed by an inner membrane, the germ cell wall, the cortex, outer membrane, spore coat and in some species the exosporium. The spore surface is anion-rich, hydrophobic and contains several reactive groups capable of interacting and stabilizing enzyme molecules through electrostatic forces, hydrophobic interactions and covalent bonding. The probiotic nature of spores obtained from non-toxic bacterial species makes them suitable carriers for the enzyme immobilization, especially food-grade enzymes or those intended for therapeutic use. Immobilization on spores is by direct adsorption, covalent attachment or surface display during the sporulation phase. Hindrances to the immobilization on spore matrix include the production rates, operational instability, and reduced catalytic properties due to conformational changes in enzyme. This paper reviews bacterial spore as a heterofunctional support matrix gives reasons why probiotic bacillus spores are better options and the diverse technologies adopted for spore-enzyme immobilization. It further suggests directions for future use and discusses the commercialization prospects.

Combinatorial application of different dye removal methods with specific features can lead to a novel and robust decolorizing system. In this study the bacterial spore laccase and TiO2 nanoparticles were co-entrapped to enhance dye degradation. The optimum entrapment conditions were achieved in the presence of alginate 2% (w/v) and Ca2+ (0.2M), Cu2+ (0.05M) and Zn2+ (0.25M) as matric polymer and counterions, respectively. Immobilized laccase showed a wide range of pH and temperature stability in comparison to the free spores. The entrapped degradation systems include single laccase, single TiO2, laccase + TiO2 (one-step remediation), TiO2/laccase (two-step remediation), and laccase/TiO2 (two-step remediation) that result to the 22%, 26% 45.6%, 47.6%, and 69.3% indigo carmine decolorization in 60 min. In the kinetic studies, the half-life of indigo carmine (25 mg/l) in the remediation processes containing laccase, TiO2, laccase + TiO2, TiO2/laccase, and laccase/TiO2 was calculated as 173, 138, 161, 115, and 57 min, respectively. The degradation products by co-entrapped system were not toxic against Sorghum vulgare. The results showed two-step decolorization by co-entrapped spore laccase and TiO2 nanoparticles, including the pretreatment of dye by laccase, and then, treatment by TiO2 has potential for degradation of indigo carmine.

Recent developments in preservation technologies allow for the delivery of food with nutritional value and superior taste. Of special interest are low-acid, shelf-stable foods in which the complete control or inactivation of bacterial endospores is the crucial step to ensure consumer safety. Relevant preservation methods can be classified into physicochemical or physical hurdles, and the latter can be subclassified into thermal and nonthermal processes. The underlying inactivation mechanisms for each of these physicochemical or physical processes impact different morphological or molecular structures essential for spore germination and integrity in the dormant state. This review provides an overview of distinct endospore defense mechanisms that affect emerging physical hurdles as well as which technologies address these mechanisms. The physical spore-inactivation technologies considered include thermal, dynamic, and isostatic high pressure and electromagnetic technologies, such as pulsed electric fields, UV light, cold atmospheric pressure plasma, and high- or low-energy electron beam.

Microbial number reduction in spices through various treatments represents a necessity considering possible changes which may occur during spices’ storage and application in food resulting in public health risk. The present study was conducted in order to examine the effects of sterilisation and microwave irradiation treatments on total mesophilic aerobic bacteria (TMAB) and bacterial spore content reduction in black pepper. Treatments applied were: sterilisation at 130 °C during 30, 60 and 90 min; and microwave irradiation at a power level of 600 W during 1.5, 3, and 5 min. Prolongation of the sterilisation treatment expressed positive influence on TMAB and bacterial spore reduction in black pepper. Compared to the sterilisation, microwave irradiation treatment exhibited better results in terms of black pepper decontamination. Maximal decontamination regarding TMAB and bacterial spore was achieved in black pepper samples treated with microwave irradiation during 3 min. The present results suggest that microwave irradiation could be applied in black pepper decontamination considering better effectiveness compared to the sterilisation treatment.

Sporeforming bacteria are responsible for the spoilage of several dairy products including fluid milk, cheese, and products manufactured using dried dairy powders as ingredients. Sporeforming bacteria represent a considerable challenge for the dairy industry because they primarily enter the dairy product continuum at the farm, survive processing hurdles, and subsequently grow in finished products. As such, strategies to reduce spoilage due to this group of bacterial contaminants have focused on understanding the effect of farm level factors on the presence of spores in bulk tank raw milk with the goal of reducing spore levels in raw milk, as well as understanding processing contributions to spore levels and outgrowth in finished products. The goal of the current study was to investigate sources of spores in the farm environment and survey farm management practices to identify variables using multimodel inference, a model averaging approach that eliminates the uncertainty of traditional model selection approaches, that affect the presence and levels of spores in bulk tank raw milk. To this end, environmental samples including feed, bedding, manure, soil, water, and so on, and bulk tank raw milk were collected twice from 17 upstate New York dairy farms over a 19-mo period and the presence and levels of various spore types (e.g., psychrotolerant, mesophilic, thermophilic, highly heat resistant thermophilic, specially thermoresistant thermophilic, and anaerobic butyric acid bacteria) were assessed. Manure had the highest level of spores for 4 out of 5 aerobic spore types with mean counts of 5.87, 5.22, 4.35, and 3.68 log cfu/g of mesophilic, thermophilic, highly heat resistant thermophilic, and specially thermoresistant thermophilic spores, respectively. In contrast, bulk tank raw milk had mean spore levels below 1 log cfu/mL across spore types. Multimodel inference was used to determine variables (i.e., management factors, environmental spore levels, and meteorological data from each sampling) that were important for presence or levels of each spore type in bulk tank raw milk. Analyses indicated that variables of importance for more than one spore type included the residual level of spores in milk from individual cows after thorough teat cleaning and forestripping, udder hygiene, clipping or flaming of udders, spore level in feed commodities, spore level in parlor air, how often bedding was topped up or changed, the use of recycled manure bedding, and the use of sawdust bedding. These results improve our understanding of how spores transfer from environmental sources into bulk tank raw milk and provide information that can be used to design intervention trials aimed at reducing spore levels in raw milk.

In line with the recent promotion of biocementation as an environmentally friendly ground improvement method, this study presents an investigation into microbially induced calcite precipitation (MICP) as a method of improving the engineering properties of soft clay. Bacillus pasteurii bacterium in vegetative cell and bacterial spore forms were used to induce MICP in clay specimens. Untreated and treated clay specimens were tested for their mechanical properties and microstructures through unconfined compression (UC) tests, free–free resonance (FFR) tests, X-ray diffraction (XRD) tests, and scanning electron microscopy with energy dispersive X-ray (SEM/EDX) tests. Results showed that both vegetative cells and bacterial spores can effectively enhance the strength and modulus of clays by inducing MICP to generate calcite crystals. Clays treated with vegetative cells exhibited earlier improvements in their strength than clays treated with bacterial spores due to earlier activity availability; however, the clays treated with bacterial spores exhibited greater strength improvements in the long term. Bacterial spores may also prove more convenient to use in geotechnical engineering practice.

International audience; Bacterial spores can cause significant problems such as food poisoning (like neurotoxin or emetic toxin) or serious illnesses (like anthrax or botulism). This dormant form of bacteria, made of several layers of barriers which provide extreme resistance to many abiotic stresses (radiation, temperature, pressure, etc.), are difficult to investigate in situ. To better understand the biological and chemical mechanisms involved and specific to spores resistance, the acquisition of environmental parameters is necessary. For that purpose, our research has been focused on the detection and analysis of a unique spore component, dipicolinic acid (DPA), used as the main in situ metabolite for sporulating bacteria detection. In its native form, DPA is only weakly fluorescent but after Ultraviolet irradiation at the wavelength of 254 nm (UVc), DPA photoproducts (DPAp) exhibit a remarkable fluorescence signal. These photoproducts are rarely identified and part of this study gives new insights offered by mass spectrometry (MS) in the determination of DPA photoproducts. Thanks to DPA assay techniques and fluorescence spectrometry, we highlighted the instability of photoproducts and introduced new assumptions on the effects of UVc on DPA. Studies in spectroscopy and microscopy allowed us to better understand these native probes in bacterial spores and will allow the implementation of a new method for studying the physico-chemical parameters of spore resistance.

American foulbrood (AFB) of Apis mellifera, caused by the bacterial spore former Paenibacillus larvae, is a notifiable disease in Italy and its spread is prevented by burning hives with clinical sy...

This paper introduces a new active material which responds to changes in environmental humidity. There has been growing interest in active materials which are able to respond to their environment, creating dynamic architectural systems without the need for energy input or complex systems of sensors and actuators. A subset of these materials are hygromorphs, which respond to changes in relative humidity (RH) and wetting through shape change. Here, we introduce a novel hygromorphic material in the context of architectural design, composed of multiple monolayers of microbial spores of Bacillus subtilis and latex sheets. Methods of fabrication and testing for this new material are described, showing that small actuators made from this material demonstrate rapid, reversible and repeatable deflection in response to changes in RH. It is demonstrated that the hygromorphic actuators are able to lift at least 150% of their own mass. Investigations are also extended to understanding this new biomaterial in terms of meaningful work.

Bacterial spores are a major challenge in industrial decontamination processes owing to their extreme resistance. High-pressure (HP) of 150 MPa at 37°C can trigger the germination of spores, making them lose their extreme resistance. Once their resistance is lost, germinated spores can easily be inactivated by a mild decontamination step. The implementation of this gentle germination-inactivation strategy is hindered by the presence of a subpopulation of so-called high-pressure superdormant (HPSD) spores, which resist germination or germinate only very slowly in response to HP. It is essential to understand the properties of HPSD spores and the underlying causes of superdormancy to tackle superdormant spores and further develop germination-inactivation strategies involving HP. This study investigated factors influencing the prevalence of HPSD spores and successfully isolated them by combining buoyant density centrifugation and fluorescence-activated cell sorting, which allowed further characterisation of HPSD spores for the first time. The prevalence of HPSD spores was shown to be strongly dependent on the HP dwell time, with increasing treatment times reducing their prevalence. Spore mutants lacking major germinant receptors further showed a highly increased prevalence of HPSD spores; 93% of the spores remained dormant even after a prolonged HP dwell time of 40 min. In contrast to nutrient germination, sublethal heat treatment of 75°C for 30 min prior to pressure treatment did not induce spore activation and increase germination. The isolated HPSD spores did not show visible structural differences compared to the initial dormant spores when investigated with transmission electron microscopy. Re-sporulated HPSD spores showed similar germination capacity compared to the initial dormant spores, indicating that HPSD spores are most likely not genetically different from the rest of the population. Moreover, the majority of HPSD spores germinated when exposed a second time to the same germination treatment; however, the germination capacity was lower than that of the initial population. The fact that the majority of spores lost superdormancy when exposed a second time to the same trigger makes it unlikely that there is one factor that determines whether a spore germinates with a certain HP treatment or not. Instead, it seems possible that there are other reversible or cumulative causes. This study investigated the factors influencing spore HP superdormancy to improve the understanding of HPSD spores with regard to their stability, germination capacity, and potential underlying causes of spore HP superdormancy. This knowledge will contribute to the development of HP-based germination-inactivation strategies for gentle but effective spore control., International Journal of Food Microbiology, 343, ISSN:0168-1605, ISSN:1879-3460

Spore-forming bacteria are a great concern for fruit juice processors as they can resist the thermal pasteurization and the high hydrostatic pressure treatments that fruit juices receive during their processing, thus reducing their microbiological quality and safety. In this context, our objective was to evaluate the efficacy of Ultraviolet-C (UV-C) light at 254 nm on reducing bacterial spores of Alicyclobacillus acidoterrestris, Bacillus coagulans and Bacillus cereus at two stages of orange juice production. To simulate fruit disinfection before processing, the orange peel was artificially inoculated with each of the bacterial spores and submitted to UV-C light (97.8–100.1 W/m2) with treatment times between 3 s and 10 min. The obtained product, the orange juice, was also tested by exposing the artificially inoculated juice to UV-C light (100.9–107.9 W/m2) between 5 and 60 min. A three-minute treatment (18.0 kJ/m2) reduced spore numbers on orange peel around 2 log units, while more than 45 min (278.8 kJ/m2) were needed to achieve the same reduction in orange juice for all evaluated bacterial spores. As raw fruits are the main source of bacterial spores in fruit juices, reducing bacterial spores on fruit peels could help fruit juice processors to enhance the microbiological quality and safety of fruit juices.

Bacterial spore formers are used as probiotic supplements for use in animal feeds, as well as in approved medicines for human nutritional supplements over the last decade. But most of the probiotics commonly used are based on lactic acid bacteria, primarily Enterococcus sp. and that of Lactobacillus sp. Multiple Bacillus sp. are desirable for use as probiotic supplements because of their ability to produce spores. Their heat stability and tolerability to the gastric barrier make them advantageous as dietary supplements making them superior over other probiotic microorganisms and this application is now being sought. This chapter summarizes the current uses of Bacillus sp. as probiotics, their safety, possible mode of action, health benefits, as well as their commercial applications.

The germination kinetics of Bacillus subtilis, Bacillus cereus, and Bacillus megaterium spores were comprehensively studied using nutrients, dodecylamine, exogenous dipicolinic acid (DPA), and the nonthermal technology of High Pressure Processing (HPP) as germinants at water activities aw = 0.995–0.698 and DPA loss measured for spore populations and single spores. Primary findings were: i) germinant receptor (GR)-dependent germination was less sensitive to changes in aw than were other germination mechanisms; ii) HPP germination was less sensitive to changes in aw than was germination by other germinants, and iii) the irreversible commitment step was more sensitive to inhibition by lowering aw than were DPA release or cortex peptidoglycan hydrolysis. Presently, we use the three-step Quasi-chemical Germination Kinetics (QCGK) model, Transition State Theory, and Extrathermodynamics' Bunnett equation to determine the effects of humectants on spore germination rates. The QCGK model is an ordinary differential equation system that postulates spore germination occurs as a sequence of two productive steps with associated rate constants (k1 is irreversible and k2) and one nonproductive step (k3). The QCGK model fits the germination kinetics data well for changes in the observed dynamics with decreasing aw. Transition State Theory calculated negative activation volumes (ΔV∗) from the pressure-dependences of k1 and k2, and Bunnett equation calculations established linear relationships for the model's rate parameters, including rate constants and maximum germination rates, with variations in aw. Taken together, these results suggest that the irreversible step (k1) is rate-limiting and the inverse dependence of k1 and k2 on humectant concentration could occur through shielding of the activated complex by the solvated nonelectrolytes at low aw, which prevents the germination intermediate from linking to the aqueous environment. Practical applications High pressure processing is a food safety method that provides the least alteration of food appearance, texture and flavor. This research shows that food additives such as sugar can diminish the efficiency of high pressure food processing.

Cereals are a central resource for the human diet and are traditionally assumed to have evolved from wild grasses at the onset of the Neolithic under the pressure of agriculture. Here we demonstrate that cereals may have a significantly longer and more diverse lineage, based on the study of a 0-2.3 Ma, 601 m long sedimentary core from Lake Acgol (South-West Anatolia). Pollen characteristic of cereals is abundant throughout the sedimentary sequence. The presence of large lakes within this arid bioclimatic zone led to the concentration of large herbivore herds, as indicated by the continuous occurrence of coprophilous fungi spores in the record. Our hypothesis is that the effects of overgrazing on soils and herbaceous stratum, during this long period, led to genetic modifications of the Poaceae taxa and to the appearance of proto-cereals. The simultaneous presence of hominins is attested as early as about 1.4 Ma in the lake vicinity, and 1.8 Ma in Georgia and Levant. These ancient hominins probably benefited from the availability of these proto-cereals, rich in nutrients, as well as various other edible plants, opening the way, in this region of the Middle East, to a process of domestication, which reached its full development during the Neolithic., TUBITAK-CNRS bilateral cooperation [114Y723]; ECCOREV (CNRS (ACIGoL project)); LABEX OT-MED (Bilat project); ANR (MRSEI, ACIGoL project); ALKM Company, This research was conducted as part of the TUBITAK-CNRS bilateral cooperation with the grant number of 114Y723 during 2015-2017. The researches were further funded by ECCOREV (CNRS (ACIGoL project), the LABEX OT-MED (Bilat project) and by the ANR (MRSEI, ACIGoL project). The long coring of Acgol (core 3) was funded by ALKM Company due to the Acgol Drilling Project signed between Cahit Helvac (DEU) and the ALKM and SODAS Companies. We are grateful to the companies of ALKM and SODAS, particularly to the courtesy of their respective owner and Mr Cihat Kora who permitted us to access and work on the Acgol Core-3. Moreover, Mr Huseyin unlu, the general director of ALKM Company during the coring, Mr. unal Ark director of ALKM and Mr. Mahmut Eser, the correspondent of the core is greatly appreciated as well as Mr. Serdar Salanc, the general director, and Mr. Necati Demirer the director of SODAS Cardak Plant. We thank Dahvya Belkacem for having extracted the pollen from the series of Acgol and Kocaba. We thank Michelle Leydet for storing our pollen data in EPD. We thank Alain Tonetto and the Platform for Analytical Technological and Imaging Research (PRATIM), from Aix Marseille University, for the confocal photographies of the pollen. Finally, we would like to thank Dr Chenglong Deng (Editorial Board Member of Scientific Reports) and the reviewer, Dr Li Quan, for very pertinent remarks, which helped to improve the manuscript significantly.

Contamination of toxic spore-forming bacteria is problematic since spores can survive a plethora of disinfection chemicals and it is hard to rapidly detect if the disinfection chemical has inactivated the spores. Thus, robust decontamination strategies and reliable detection methods to identify dead from viable spores are critical. In this work, we investigate the chemical changes of Bacillus thuringiensis spores treated with sporicidal agents such as chlorine dioxide, peracetic acid, and sodium hypochlorite using laser tweezers Raman spectroscopy. We also image treated spores using SEM and TEM to verify if we can correlate structural changes in the spores with changes to their Raman spectra. We found that over 30 min, chlorine dioxide did not change the Raman spectrum or the spore structure, peracetic acid showed a time-dependent decrease in the characteristic DNA/DPA peaks and similar to 20% of the spores were degraded and collapsed, and spores treated with sodium hypochlorite showed an abrupt drop in DNA and DPA peaks within 20 min and some structural damage to the exosporium. Structural changes appeared in spores after 10 min, compared to the inactivation time of the spores, which is less than a minute. We conclude that vibrational spectroscopy provides powerful means to detect changes in spores but it might be problematic to identify if spores are live or dead after a decontamination procedure.

International audience; Food industry cleaning operations must efficiently mitigate any risk of remaining unwanted contamination without consuming large amounts of water, chemicals and energy. This study's originality was in analysing the capacity of flowing foams to remove Bacillus spores from stainless steel surfaces. A set-up was designed to allow the formation of wet foams to flow under three differing regimes: bubble-size rearrangement was observed at the wall with increased velocity, thus reducing cleaning efficiency. Foam at 50% air/water and low velocities permitted a 2 log removal of B. amyloliquefaciens spores, which is comparable to similar CIP conditions. Removal kinetics were modelled showing potentially very high constant rates at the start of cleaning. Such efficient cleaning was related to the local high wall shear stress fluctuations and to the capillary forces (low velocities, favorable bubble-size repartition and to the hydrophilicity of bacteria spores).

Little is known about final spores components when bacteria undergo sporulation under different nutrient conditions. Different degrees of resistance and germination rates were observed in the three types of spores of Lysinibacillus boronitolerans YS11 (SD, Spores formed in Difco sporulation medium™; SC and SF, Spores formed in an agricultural byproduct medium with 10 mM CaCl2 and with 10 mM FeSO4, respectively). Stronger UV resistance was recorded for SF with 1.8-2.3-fold greater survival than SC and SD under UV treatment. The three spore types showed similar heat resistances at 80°C, but survival rates of SC and SD were much higher (∼1,000 times) than those of SF at 90°C. However, germination capacity of SF was 20% higher than those of SD and SC on Luria-Bertani agar plates for 24 h. SF germinated more rapidly in a liquid medium with high NaCl concentrations than SC and SD, but became slower under alkaline conditions. Raman spectroscopy was used to analyze the heterogeneities in the three types of vegetative cells and their spores under different nutritional conditions. Exponentially grown-each vegetative cells had different overall Raman peak values. Raman peaks of SC, SD, and SF also showed differences in adenine and amide III compositions and nucleic acid contents. Our data along with Raman spectroscopy provided the evidence that spores formed under under different growth conditions possess very different cellular components, which affected their survival and germination rates.

In this work, the electro-mechanical stresses induced by pulsed electric fields (PEF) on bacterial spore germination was modeled and empirically tested using Bacillus atrophaeus spores. Specifically, a new model, termed as Qiu-Wu’s electro-mechanical (QW’s EM) spore model, was derived to analyze the effect of electro-mechanical stresses on spores subjected under electric fields. A non-linear inverse relationship was found between electric fields and thickness change of spore coat. SEM, pH, hydrophobicity and electrochemical measurements were implemented for verification of the model. PEF-treated spores germinated with a faster rate and a higher degree of homogeneity. The longer the treatment time, the better the homogeneity. The speed of dipicolinic acid (DPA) release was around 20% faster in PEF-treated samples, while the peak intensity of terbium-DPA from PEF-treated samples was up to 80% lower. Theoretical analysis and empirical results were consistent to show that PEF introduces electro-mechanical stresses to expedite spore germination. The significance and impact of this study is obvious: bacterial spore is implicated in food spoilage and foodborne diseases primarily via the process of germination, and PEF technology has been introduced to inactivate microorganisms in food. Understanding the mechanism of germination under PEF can provide deep understanding for inactivation of foodborne pathogens and better food preservation methods.

Bacteria belonging to the orders Bacillales and Clostridiales form spores in response to nutrient starvation. From a simplified morphological perspective, the spore can be considered as comprising a central protoplast or core, that is, enveloped sequentially by an inner membrane (IM), a peptidoglycan cortex, an outer membrane, and a proteinaceous coat. All of these structures are characterized by unique morphological and/or structural features, which collectively confer metabolic dormancy and properties of environmental resistance to the quiescent spore. These properties are maintained until the spore is stimulated to germinate, outgrow and form a new vegetative cell. Spore germination comprises a series of partially overlapping biochemical and biophysical events – efflux of ions from the core, rehydration and IM reorganization, disassembly of cortex and coat – all of which appear to take place in the absence of de novo ATP and protein synthesis. If the latter points are correct, why then do spores of all species examined to date contain a diverse range of mRNA molecules deposited within the spore core? Are some of these molecules “functional,” serving as translationally active units that are required for efficient spore germination and outgrowth, or are they just remnants from sporulation whose sole purpose is to provide a reservoir of ribonucleotides for the newly outgrowing cell? What is the fate of these molecules during spore senescence, and indeed, are conditions within the spore core likely to provide any opportunity for changes in the transcriptional profile of the spore during dormancy? This review encompasses a historical perspective of spore ribonucleotide biology, from the earliest biochemical led analyses – some of which in hindsight have proved to be remarkably prescient – through the transcriptomic era at the turn of this century, to the latest next generation sequencing derived insights. We provide an overview of the key literature to facilitate reasoned responses to the aforementioned questions, and many others, prior to concluding by identifying the major outstanding issues in this crucial area of spore biology.

In this work, the inactivation kinetics of Alicyclobacillus acidoterrestris spores by temperature-assisted high hydrostatic pressure was assessed by means of the Weibull model. Spores from two A. acidoterrestris strains (a wild-type strain and a reference strain) were inoculated in commercial orange juice and subjected to high pressure levels (500 and 600 MPa) combined with four temperature regimes (25, 45, 60 and 70 &deg, C) for time up to 30 min. Results showed that for a given high-pressure level spore inactivation was higher as temperature progressively increased. Furthermore, the Weibull model consistently produced satisfactory fit to the inactivation data based on the values of the root mean squared error (RMSE &lt, 0.54 log colony-forming units (CFU)/mL) and the coefficient of determination (R2 &gt, 0.90 in most cases). The shape of inactivation curves was concave upward (p &lt, 1) for all temperature/high pressure levels tested, indicating rapid inactivation of the sensitive cells of the bacterium whereas the remaining ones adapted to high hydrostatic pressure (HHP) treatment. The values of the shape (p) and scale (&delta, ) parameters of the Weibull model were dependent on the applied temperature for a given high pressure level and they were further described in a secondary model using first-order fitting curves to provide predictions of the surviving spore population at 55 and 65 &deg, C. Results revealed a systematic over-prediction for the wild-type strain regardless of temperature and high pressure applied, whereas for the reference strain under-prediction was evident after 3 log-cycles reduction of the surviving bacteria spores. Overall, the results obtained indicate that the effectiveness of high hydrostatic pressure against A. acidoterrestris spores is strain-dependent and also underline the need for temperature-assisted HPP for effective spore inactivation during orange juice processing.

In this study, novel spore pouches were developed using mashed potato as a food model inoculated with either Geobacillus stearothermophilus or Clostridium sporogenes spores. These spore pouches were used to evaluate the sterilization efficiency of Coaxially induced microwave pasteurization and sterilization (CiMPAS) as a case study. CiMPAS technology combines microwave energy (915 MHz) along with hot water immersion to sterilize food in polymeric packages. The spore pouches were placed at pre-determined specific locations, especially cold spots in each food tray before being processed using two regimes (R-121 and R-65), which consisted of 121 &deg, C and 65 &deg, C at 12 and 22 kW, respectively, followed by recovery and enumeration of the surviving spores. To identify cold spots or the location for inoculation, mashed potato was spiked with Maillard precursors and processed through CiMPAS, followed by measurement of lightness values (*L-values). Inactivation equivalent to of 1&ndash, 2 Log CFU/g and &gt, 6 Log CFU/g for Geobacillus stearothermophilus and Clostridium sporogenes spores, respectively was obtained on the cold spots using R-121, which comprised of a total processing time of 64.2 min. Whereas, inactivation of &lt, 1 and 2&ndash, 3 Log CFU/g for G. stearothermophilus and C. sporogenes spores, respectively on the cold spots was obtained using R-65 (total processing time of 68.3 min), whereas inactivation of 1&ndash, 3 Log CFU/g of C. sporogenes spores was obtained on the sides of the tray. The results were reproducible across three processing replicates for each regime and inactivation at the specific locations were clearly distinguishable. The study indicated a strong potential to use spore pouches as a tool for validation studies of microwave-induced sterilization.

Contamination of toxic spore-forming bacteria is problematic since spores can survive a plethora of disinfection chemicals. It is also problematic to rapidly detect if the disinfection chemical was active, leaving spores dead. Robust decontamination strategies, as well as reliable detection methods to identify dead from viable spores, are thus critical. Vibrational detection methods such as Raman spectroscopy has been suggested for rapid diagnostics and differentiation of live and dead spores. We investigate in this work, using laser tweezers Raman spectroscopy, the changes in Raman spectra of Bacillus thuringiensis spores treated with sporicidal agents such as chlorine dioxide, peracetic acid, and sodium hypochlorite. We also imaged treated spores using SEM and TEM to verify if any changes to the spore structure can be correlated to the Raman spectra. We found that chlorine dioxide did not change the Raman spectrum or the spore structure; peracetic acid shows a time-dependent decrease in the characteristic DNA/DPA peaks and ∼20 % of the spores were degraded and collapsed; spores treated with sodium hypochlorite show an abrupt drop in DNA and DPA peaks within 20 minutes all though the spore structure was overall intact, however, the exosporium layer was reduced. Structural changes appeared over several minutes, compared to the inactivation time of the spores, which is less than a minute. We conclude that vibrational spectroscopy provides powerful means to detect changes in spores but it might be problematic to identify if spores are live or dead after a decontamination procedure.

To date, heat is still the most used technology in food preservation. The calculus of heat treatments is usually based on Bigelow observations i.e. treatment time is an exponential function of the heat treatment temperature. However, a number of researchers have reported deviations from linearity in heat inactivation curves that caused errors in the calculus. This research was designed to evaluate the variability of shoulder length among different sporulated species, the impact of treatment temperature on these shoulders and the relationship between the traditional DT value and shoulder length. The heat inactivation kinetics of five bacterial spores of importance for the food industry was evaluated. B. weihenstephanensis and B. cereus did not show shoulders and DT values calculated ranged from 0.99 to 0.23 and from 1.33 to 0.56 respectively at temperatures from 100 to 102.5 °C. On the other side B. subtilis, B. licheniformis and G. stearothermophilus showed shoulders of 1.75–0.42, 1.92–0.43 and 3.22–0.78 and DT values of 1.52–0.32, 2.12–0.59 and 2.22–0.48 respectively in the range of temperatures tested. From the results obtained it was concluded that the presence and magnitude of shoulders depended on the bacterial spore species, the longest being those on the bacterial spores which showed greatest heat resistance. It has also been proved that shoulder lengths vary with treatment temperature in the same proportion of traditional DT values, with the relationship Sl/DT being constant. Thus, an equation which included the constant Sl/DT was proposed.

Contamination that decreased chicken meat quality could be prevented using natural preservatives. Bay leaves (Syzygium polyanthum) contain volatile fatty acids, tannin, and flavonoid that possess bacteriological and fungicidal activity as well as preventing bacterial spore growth. The purpose of this study was to determine the effect of fresh bay leaf infusion on microbiological, chemical, and physical qualities of chicken meat. This study used bay leaves, water, chicken meat, eight strain of bacteria, chemicals and materials for the analysis of chicken meat. The experiment consisted of two steps, the first was the antibacterial properties of bay leaves and the second was the application of bay leaf infusion for chicken meat. Eight bacteria was used for the bacterial inhibition of bay leaf at the concentration of 0, 5, 10, 15 and 20%. The experiment on antibacterial properties of bay leaf (Syzygium polyanthum) used one way randomized design with five concentration treatments, while the application of bay leaf infusions on chicken meat using factorial completely randomized design 2x5 (2 types of soaking and 5 observation time). At the second step, chicken meat was divided into 2 groups, the first group was soaked in water only and the second group was soaked in 15% bay leaf infusion. They were then stored for 0 (control), 2, 4, 6, and 8 hours at the room temperature. Each treatment was repeated four times. The microbiological, chemical, physical qualities of chicken meat were observed. The results showed that bay leaf infusion had the ability to inhibit the growth of bacteria (P

The metal-organic frameworks (MOFs) functionalized palygorskite (Pal) hybrid as a novel multicolor fluorescence probe for the detection of bacterial spore biomarker-dipicolinic acid (DPA), had been prepared via in-situ growth. The MOFs can effectively encapsulate dye molecules on the surface of Pal, and the rich carboxyl groups on its surface can coordinate with europium ions (Eu3+), forming a highly sensitive recognition group. The results indicated that the limit of detection (LOD) of this multicolor fluorescence probe was as low as 9.3 nM and was obviously lower than the amount of anthrax spores infecting the human body (60 μM). Moreover, a wide linear range from 0 to 35 μM was obtained. The high specific surface area of Pal, as well as the permanent porosity and suitable binding sites of Eu3+-doped MOFs may play a major role in the sensitivity and linear detection range. The multicolor fluorescence strategy made full use of the diversity of fluorescence signals collected by dye molecules and lanthanide ions, which can realize the real-time and on-site detection through the smartphone with a color-scanning application (APP). The practicability of this probe was further verified by detecting DPA released by non-infectious Bacillus subtilis.

Bacterial spores pose the largest hurdle for the preservation of perishable food due to their extreme resistance to processing steps. Conventionally, food industries apply intensive decontamination processing steps, most commonly thermal processing, to inactivate bacterial spores. However, this is not suitable for heat-sensitive products, ingredients, and materials. Moreover, the high thermal load of treated products often leads to reduced quality concerning their organoleptic and nutritional attributes. To meet consumer needs of fresher, minimally processed food products, food industries and scientists have been searching for novel non-thermal, mild but efficient spore control strategies. Among the emerging decontamination technologies, low energy electron beam (LEEB) and high pressure (HP) technologies have shown high potential because of the reduced thermal-load and improved quality retention of the treated foods. Therefore, in this research, these two non-thermal processing technologies were investigated for their spore inactivation efficiency and mechanisms. The results revealed that the inactivation efficiency of LEEB technology was in a comparable range to that of the other ionizing irradiation technologies and was influenced by various factors, including spore species and sporulation conditions. The mechanistic study revealed that DNA damage was one of the causes of spore inactivation by LEEB and the investigation of a newly developed continuous industrial LEEB system demonstrated a high potential to upscale LEEB processing for the decontamination of low water activity food surfaces (e.g. for spices). HP can inactivate bacterial spores by first triggering germination. The key limitation for the application of HP-based germination-inactivation approaches is that spore germination is extremely heterogeneous under HP. This research optimized and thoroughly validated the use of flow cytometry to study spore germination behavior under HP. Results revealed four distinct responses of spores under HP treatment at 150 MPa and 37°C. A protocol based on fluorescence-activated cell sorting was further developed to isolate spores of different physiological states after HP treatment. The methods developed in this study provide a foundation for future research on spore inactivation using LEEB and heterogeneous spore behavior upon HP treatment. The outcome can further help the development and implementation of LEEB and HP technologies as non-thermal, gentle spore control approaches, which will help deliver safe and minimally processed foods to consumers in the future., ISBN:978-3-907234-31-0

Removing arsenic from aquatic environments has become an urgent problem worldwide. In this study, Ti 4+ - loaded bacterial spore were adopted as a novel adsorbent (spore@Ti 4+ microspheres) for the adsorption efficient removal of arsenite (As(III)) and arsenate (As(V)). The developed adsorbents were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS). Results indicated that the adsorption kinetics was well described by a pseudo-second-order kinetic model, and the adsorption process rapidly achieved equilibrium within 15 min at pH 7.0. The adsorption mechanism was also investigated. The maximum adsorption capacities for As(III) and As(V) were 97.26 mg g −1 and 137.01 mg g −1 , respectively, based on the isothermal studies. These properties suggest that spore@Ti 4+ microspheres can be potentially applied in water treatment.

One of the prerequisites of successful address delivery is controlling the release of encapsulated drugs. The new method of bacterial spore encapsulation in polyelectrolyte microcapsules allows for degrading the nanoscale membrane shell of microcapsules. The possibility of encapsulating spore forms of Bacillus subtilis in polystyrenesulfonate sodium/ polyallylamine hydrochloride (PSS/PAH) polyelectrolyte microcapsules was demonstrated. The activation and growth on a nutrient medium of encapsulated bacterial spores led to 60% degradation of the microcapsules nanoscale membrane shell. As a result, 18.5% of Fluorescein isothiocyanatedextran was encapsulated into polyelectrolyte microcapsules, and 28.6% of the encapsulated concentration of FITC-dextran was released into the solution.

Exposure to specific germinant can induce germination in dormant bacterial spores converting them into vegetative cells which are metabolically active and fragile. This phenomenon of conversion of spores from one phase to another could be a keynote potential strategy for development of different type of techniques ranging from spore detection to their eradication and spore-based biosensing. To extend this biphasic spore germination-based approach in order to facilitate development of detection systems, mechanistic details of markers that signals the process of germination initiation in bacterial spores are required. These markers possess a high level of specificity for differentiation in germinating and dormant spores. In this line, present review underscores the structural properties, sporulation and germination in bacterial spores, and covers a detailed description on various biomarkers namely absorbance (600 nm), dipicolinic acid (DPA), refractility of spores, nucleic acid, ATP, spore’s heat resistance, and enzymes which could be valuable in perceiving germination in bacterial spores. Assaying germination using these markers can further explore the efficient use of spores in development of detection devices for food and environment safety.

Background and aims: Drinking water pollution is a serious threat for public water supply. Water disinfection has a very important role in the reduction of pathogenic microorganism. Water electrodisinfection is an efficient and cost-effective method in water disinfection. The aim of this study was the survey of inactivation in two types bacteria (as index and resistant) by electrochemical process in the presence of supporting electrolytes. Materials and methods:Inactivation of E.Coli and Bacillus subtilis spore was studied at current intensity of 500mA, with each of the supporting electrolytes including CuI, NaBr and KCl. The type of electrodes was steel and the distance between electrodes was 2cm. Furthermore, the tests carried out in monopolar mode Fe-Fe, neutral pH and experimental temperature (21o c). The number of bacteria, amount of supporting electrolyte, voltage, and electrochemical action time were investigated. Results:Adding the supporting electrolytes to the electrochemical disinfection process decreased bacterial resistan Copper iodide (CuI) on 2 mg/l concentration showed more efficiency in bacterial inactivation. Conclusion:Supporting electrolyte CuI with concentration of 2 mg/l both enhances the electrochemical process performance due to an increase in ionic transmission rate and voltage current. Also, this decreases electrochemical inactivation time and increases bactericidal effect.

Isostatic high pressure (HP) of 150 MPa can trigger the germination of bacterial spores, making them lose their extreme resistance to stress factors, and increasing their susceptibility to milder inactivation strategies. However, germination response of spores within a population is very heterogeneous, and tools are needed to study this heterogeneity. Here, classical methods were combined with more recent and powerful techniques such as flow cytometry (FCM) and fluorescence activated cell sorting (FACS) to investigate spore germination behavior under HP. Bacillus subtilis spores were treated with HP at 150 MPa and 37°C, stained with SYTO16 and PI, and analyzed via FCM. Four sub-populations were detected. These sub-populations were for the first time isolated on single cell level using FACS and characterized in terms of their heat resistance (80°C, 10 min) and cultivability in a nutrient-rich environment. The four isolated sub-populations were found to include (1) heat-resistant and mostly cultivable superdormant spores, i.e., spores that remained dormant after this specific HP treatment, (2) heat-sensitive and cultivable germinated spores, (3) heat-sensitive and partially-cultivable germinated spores, and (4) membrane-compromised cells with barely detectable cultivability. Of particular interest was the physiological state of the third sub-population, which was previously referred to as “unknown”. Moreover, the kinetic transitions between different physiological states were characterized. After less than 10 min of HP treatment, the majority of spores germinated and ended up in a sublethally damaged stage. HP treatment at 150 MPa and 37°C did not cause inactivation of all geminated spores, suggesting that subsequent inactivation strategies such as mild heat inactivation or other inactivation techniques are necessary to control spores in food. This study validated FCM as a powerful technique to investigate the heterogeneous behavior of spores under HP, and provided a pipeline using FACS for isolation of different sub-populations and subsequent characterization to understand their physiological states., Frontiers in Microbiology, 10, ISSN:1664-302X

Since the 2001 anthrax attacks, researchers have focused on the development of a bacterial spore biomarker detector with rapid response time and high sensitivity and selectivity. Hence, a ratiometric fluorescent nanosensor based on lanthanide-functionalized attapulgite (Atta) was designed and prepared using dye-doped Atta as an internal reference. Atta, which is famous because of Maya Blue, is a hydrated magnesium aluminum silicate present in nature, with pronounced adsorption and a large specific surface area rich in silicon hydroxyl. The adsorption of dye molecules benefits the formation of an internal reference with orange fluorescence. Meanwhile, silicon hydroxyl would be available for terbium (Tb 3+ ) complex grafting, which favors the sensitization of the bacterial spore biomarker. With increasing dipicolinic acid (DPA) concentrations, energy transfer from DPA to Tb 3+ gradually enhanced, thereby resulting in strong and predominant green fluorescence. The ratiometric fluorescence intensity is highly sensitive. It has a limit of detection of 9.8 nM, which is much lower than the infectious dosage of Bacillus anthracis spores (60 μM) for humans. The rapid response time (10s), high selectivity, and reliable and practical performances in actual applications make this ratiometric fluorescent nanosensor useful in the detection of biomarkers for various bacterial spores. Moreover, the reported construction of visual ratiometric detection system follows the sustainable development idea of ‘‘from nature, for nature, into the nature’’ and promotes the use of naturally renewable resources to produce promising and eco-friendly functional materials for various applications.

The advantage of using high pressure (HP) cycling treatment compared with continuous HP treatment was investigated for the inactivation of bacterial spores. The effects of parameters such as pulse number, pressure level, treatment temperature, compression and decompression rates, and time between pulses were evaluated. For this purpose, Bacillus subtilis and B. cereus spores (108 and 106 CFU/mL respectively) were suspended in 2-(N-morpholino) ethanesulfonic acid (MES) buffer solution, tryptone salt (TS) buffer solution, or infant milk and treated by HP cycling at 300–400 MPa, at 38–60 °C, for 1–5 pulses. Pressure cycling reduced the number of viable spores by 1.8 and 5.9 log respectively for B. subtilis and B. cereus species. Continuous HP treatments were performed at the same pressure and temperature for similar treatment durations. Our results showed that the spore inactivation ratio was correlated with the cumulative exposure time to pressure rather than to effects of the cycling process. Greater spore inactivation caused by HP cycling was observed only when faster compression and decompression rates were applied, probably due to adiabatic heating. A three-step kinetic model was developed, which seemed to support our hypothesis regarding the mechanisms of inactivation by pressure cycling and continuous HP treatments. Industrial relevance The resistance of bacterial spores to HP limits the industrial applications to refrigerated food products. In this study, we investigated the use of pressure cycling as a means to improve spore baroinactivation at moderate temperatures (T

We report an extremely sensitive and ultra-low-cost PVDF-based SERS substrate using an easy fabrication process that can be conducted in a laboratory and scaled up for industrial applications. Hydrophilic PVDF membranes were sequentially dipped in ethanol and aqueous sodium chloride solution, following which multi-shaped Ag nanoparticles were deposited on the surface of the membranes by suction filtration. The simple solvating pretreatment led to an approximately 188-fold enhancement in the SERS signal intensity of R6G. Using the hydrophilic PVDF-based SERS substrate, subnanomolar sensitivity for R6G was achieved using 3 μL of sample volume on a 3×3 mm2 SERS substrate within 1 min detection time and without the need for concentration or drying processes. To demonstrate the feasibility of the developed SERS substrate as a sensor for bacterial spore detection, it was applied for the detection of the representative biomarker dipicolinic acid (DPA). The limits of detection of DPA and Bacillus spores were measured as 1 ppm and 5×103 spores/mL, respectively. The optimized configuration of low substrate area and wet micro-analyte volume makes the PVDF-based SERS substrate a simple and low-cost tool for the trace-level detection of small molecules in a rapid, sensitive, and high-throughput manner.

This study compares the crack healing performances of biological self-healing concretes using cell/nutrient dropping and immobilization methods to produce microbially induced calcium carbonate precipitation (MICP). Vegetative cells and microencapsulated bacterial spores of Bacillus sphaericus (LMG 22257) were used to heal pre-cracked mortars. Mortar specimens were cured for 7 and 28 days before pre-cracking, and then repaired under wet-dry cycles for 7 days. Comparisons were made in terms of crack-width and crack-area healing and load recovery after repairing. Results showed that the vegetative cell dropping method was more effective in closing cracks and recovering ultimate load after repair than the method of using immobilized microencapsulated bacterial spores for mortar repair. In fact, specimens mixed with microencapsulated bacterial spores exhibited lower ultimate loads than comparable control specimens.

Biological warfare incidents generate both immediate and delayed hazards, potentially resulting from reaerosolization of deposited hazardous particles from surfaces. Understanding the causes and effects of the initial deposition method and environmental conditions on reaerosolization is important in hazard prediction and selection of mitigation approaches. This study was conducted to determine the amount of reaerosolization of various bacterial spores and 1 µm polystyrene latex microspheres deposited wet or dry and incubated at 20 or 80% relative humidity (RH). The organisms used in this study were Bacillus atrophaeus var. globigii (Bg), B. thuringiensis (Bt), B. anthracis ΔSterne (Ba-ΔSterne), Ba-ΔSterne ΔbclA mutant (BclA), and Ba-ΔSterne ΔcotE mutant (CotE). These organisms represent a range of spore types with different outer surfaces: spores with exosporium hairs and a basal layer (Ba-ΔSterne and Bt), spores with a basal layer (BclA), and spores with a spore coat only (no exosporium, Bg and C...

cited By 3; International audience; In this work, our goal was to study the capability of a single metallic oxide to neutralize a chemical agent and to exhibit an antibacterial effect. We tested two types of magnesium oxides, MgO. The first MgO sample tested, which commercial data size characteristic was −325 mesh (MgO-1) destroyed in 3 h, 89.7% of paraoxon and 93.2% of 4-nitrophenol, the first degradation product. The second MgO sample, which commercial data size was

High pressure processing (HPP) is an emerging non-thermal technology that is growing exponentially in use worldwide for the pasteurization of commercial foodstuffs. At combinations of elevated pressures and temperatures, HPP inactivates bacterial spores, but HPP has not yet been implemented commercially for food sterilization. Studies of the mechanisms of bacterial spore inactivation by HPP using primarily spores of Bacillus species have shown that spore germination precedes inactivation, with the release of dipicolinic acid from the spore core as the rate-determining step. Investigations probing spore resistance to and germination by HPP using Bacillus subtilis, a number of selected B. subtilis mutants, Bacillus amyloliquefaciens, and Clostridium difficile spores have compiled a wealth of detailed mechanistic information, while also accumulating abundant germination kinetics data that has not previously been analyzed by predictive models. Presently, we devise a “quasi-chemical” model for bacterial spore germination dynamics by HPP. This quasi-chemical germination model (QCGM) hypothesizes a three-step mechanism and derives a set of ordinary differential equations to model the observed germination dynamics. The results with this model are viewed in the context of historical studies of spore activation, germination, and inactivation, with an eye toward potentially integrating differential equation models for germination and inactivation into a single, comprehensive model for spore dynamics by HPP. With the increasing use of high hydrostatic pressure to investigate mechanisms of bacterial spore resistance and physiology, the QCGM results help promote the efficient control of bacterial spores, whether for the inactivation of Clostridium botulinum spores in low-acid foods or aerosolized Bacillus anthracis spores on textiles used in protective clothing, tents, or shelters.

Bacterial spores are ubiquitous in nature. They are stress resistant entities that are a concern to microbiological food stability due to their environmental stress resistance. In addition germinating and outgrowing spores at undesired times and places pose a significant health burden. The challenge is amplified due to the heterogeneous germination and outgrowth behaviour of isogenic spore populations. We discuss the role of different 'omics' techniques, proteomics in particular, to study spore biology in detail. With examples, the use of label-based and label-free quantitative proteomics approaches in understanding the spore physiology is demonstrated. Also the need of genomics, single cell analyses and analysis of cellular physiology is discussed briefly. Certainly accurate comprehensive data obtained from omics methods and molecular physiology will underpin the development of robust molecular models of bacterial spore germination and outgrowth.

Methods for microbial inactivation are important in the food industry; however, conventional external heating (CH) reduces food quality. Accordingly, the nonthermal effects of ohmic heating (OH) on Bacillus subtilis spores in a sodium chloride aqueous solution at 101°C (i.e., the boiling point), as well as the effects of electric field intensity and frequency during OH, were investigated. Survival kinetics were compared between OH and external CH. The inactivation effect on B. subtilis was greater for all electric field conditions (5, 10, and 20 V/cm) than for CH. In particular, 20 V/cm showed a significantly higher inactivation effect (P0.05) on B. subtilis than those of CH at 8, 10, 12, 14, and 16 min. The survival data were fitted to various primary kinetic models. In the Weibull model and the log-linear model, there were significant differences (P0.05) in the rate parameters δ and k

High pressure (HP) processing, typically at 600 MPa in combination with mild temperatures, makes it possible to produce safe and high quality foods while inactivating pathogenic microorganisms such as Enterohaemorrhagic Escherichia coli (EHEC). In the last decade much research was conducted to understand the inactivation of spores at high pressures and elevated temperatures. Bacterial spore inactivation by HPP in complex food matrices is assessed with an emphasis on mechanisms of inactivation and treatment of products that have low or non-uniform water activity (a w ) profiles. Low a w can be the result of a high concentration in solutes and the presence of oils/fats or other ingredients in the food. The synergistic effect of pressure and temperature leads to lower thermal loads applied to the product and consequently less unwanted compounds can be formed during the process. Future applications of high pressure and elevated temperature processes are assed. These processes could lead to healthier products, safer products and a smarter usage of emerging technologies. Industrial relevance The next step for high pressure processing in addition to pasteurization could be for food sterilization in combination with elevated temperatures. This would have a big impact on many sectors of the industry. Elevated temperatures could be used in existing “cold” HP systems using insulated carriers. The extra cost and construction problems could be minimized. Product quality and health attributes could be increased in comparison to conventional technologies.

This work investigated the effect of static magnetic field (SMF) on Bacillus atrophaeus endospore germination. Germination was triggered by L-alanine in 1.3-T SMF and characterized by ion release, Ca2+-dipicolinic acid release, and water influx. These events were monitored by electrical conductivity, Tb-DPA fluorescence, and optical density, respectively. Culturability of endospore germinated in SMF exposure was evaluated by CFU enumeration. Results indicated that 1.3-T SMF failed to significantly affect endospore germination and culturability, suggesting that the three aforementioned processes were not sensitive to SMF. Bioelectromagnetics. 38:121–127, 2017. © 2016 Wiley Periodicals, Inc.

Numerous cases have been reported globally showing outbreaks, dissemination of infections and/or spoilage of medicinal products, food and other consumables that affects human life and may lead to death in some cases. One of the most critical measures of microbial contamination that should be taken into consideration is the use of proper disinfectant depending on the type of activities and the work load of the healthcare institution, subjects or media for microbial transfer and the affected population. The current study shows significant difference in sporicidal activity between two types of commercial peroxygen/Silver based disinfectants obtained from same manufacturer and delivered through same distributor at the same time. The peroxygen component in one of the disinfectant products is Hydrogen peroxide while in the other product is Peroxyacetic acid/Hydrogen Peroxide mixture. Preliminary rapid assessment of the disinfectants activity was required using the most resistance microbial form (bacterial spore) as a reference microorganism to challenge the biocidal products. Bacillus pumilus and B. subtilis spores were exposed to both disinfectants at three different concentrations levels covering the range recommended by the manufacturer: 1, 3 and 5% (v/v). The first formula did not exceed 0.5 logarithmic reduction(LR) even after 30 minutes. While the other product achieved more than two folds LR (more than 100 times reduction in microbial population) after ten minutes contact time. Appropriate initial screening of biocidal activity in commercial disinfectants market is critical step that should be performed by the healthcare facilities before practical application. Otherwise, inefficient control on bioburden may lead to devastating consequences on human health. An initial, non-laborious, time-saving and non-expensive screening test using the most resistance microorganisms is encouraged to be performed by healthcare facilities prior to practical application of disinfectant rather than reliance solely on random selection of biocidal agents using informational data without confirmatory experiments.

Concrete cracks must be repaired promptly in order to prevent structural damage and to prolong the structural life of the building (or other such construction). Biological self-healing concrete is a recent alternative technology involving the biochemical reaction of microbial induced calcium carbonate precipitation (MICP). This study determined the most appropriate technique to encapsulate spores of Bacillus sphaericus LMG 22257 with sodium alginate so as to protect the bacterial spores during the concrete mixing and hardening period. Three techniques (extrusion, spray drying and freeze drying) to encapsulate the bacterial spores with sodium alginate were evaluated. The freeze-drying process provided the highest bacterial spore survival rate (100%), while the extruded and spray-dried processes had a lower spore survival rate of 93.8% and 79.9%, respectively. To investigate the viability of microencapsulated spores after being mixed with mortar, the decomposed urea analysis was conducted. The results revealed that the freeze-dried spores also showed the highest level of urea decomposition (metabolic activity assay used as a surrogate marker of spore germination and vegetative cell viability). Thus, the self-healing performance of concrete mixed with freeze-dried spores was evaluated. The results showed that the crack healing ratio observed from the mortar specimens with freeze-dried microencapsulated spores were significantly higher than those without bacteria. This study revealed that freeze drying has a high potential as a microencapsulation technique for application to self-healing concrete technology.

Background Bacillus cells faced with unfavorable environmental conditions undergo an asymmetric division process ultimately leading to the formation of the bacterial spore. In some instances the spore serves as an infectious agent; such is the case with the spore of Bacillus anthracis and the disease anthrax. Spores are resistant to a variety of environment conditions including traditional decontamination techniques due to the formation of specialized cellular structures. One such structure, the spore cortex, is a thick layer of modified peptidoglycan that contributes to spore dormancy through maintenance of the dehydrated state of the spore core. During spore germination, degradation of the cortex is required to facilitate complete hydration of the core and a return to vegetative growth. Degradation of the cortex is accomplished through the action of germination-specific lytic enzymes. One of these enzymes, SleB, has been previously shown to require the presence of the YpeB protein for its stable incorporation and subsequent function in spores of B. anthracis. The focus of the present study is to identify protein interactions of YpeB through in vivo chemical cross-linking and two-hybrid analysis. Results Conserved residues within YpeB PepSY domains were altered to facilitate implementation of a site-specific chemical cross-linker, 4-Azidophenacyl bromide. Analyses of crosslinked-spore extracts suggests that YpeB exists as a dimer or larger multimer within the spore, potentially mediated through interactions of the C-terminal domains. Spores expressing stable truncated forms of YpeB were crosslinked and corresponding truncated dimers were detected. Further characterization of individual YpeB domains using bacterial two-hybrid analysis indicated a possible role for both N-and C-terminal domains in YpeB oligomerization. Conclusions The YpeB protein likely exists as dimer or higher-order multimer in the dormant spore. Both the N- and C-terminal YpeB domains contribute to multimerization. SleB likely also exists as an oligomer, and SleB and YpeB may be found together within a protein complex. Disassembly of this complex during spore germination likely allows SleB to become active in spore cortex degradation. Further study of this protein complex may contribute to the development of methods to inhibit or stimulate germination, allowing more effective spore decontamination. Electronic supplementary material The online version of this article (10.1186/s12866-019-1544-1) contains supplementary material, which is available to authorized users.