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A range of fungal species showed variable abilities to colonize and penetrate a mortar substrate. Calcium biomineralization was a common feature with calcium-containing crystals deposited in the microenvironment or encrusting hyphae, regardless of the specific mortar composition. Several species caused significant damage to the mortar surface, exhibiting burrowing and penetration, surface etching, and biomineralization. In some cases, extensive biomineralization of hyphae, probably by carbonatization, resulted in the formation of crystalline tubes after hyphal degradation on mortar blocks, including those amended with Co or Sr carbonate. Ca was the only metal detected in the biomineralized formations with Co or Sr undetectable. Aspergillus niger , Stemphylium sp. and Paecilomyces sp. could penetrate mortar with differential responses depending on the porosity. Fluorescent staining of thin sections recorded penetration depths of ∼530 um for A. niger and ∼620 um for Stemphylium sp. Penetration depth varied inversely with porosity and greater penetration depths were achieved in mortar with a lower porosity (lower water/cement ratio). These results have provided further understanding of biodeteriorative fungal interactions with cementitious substrates that can clearly affect structural integrity. The potential significance of fungal colonization and such biodeteriorative phenomena should not be overlooked in built environment contexts, including radionuclide storage and surface decontamination. [ABSTRACT FROM AUTHOR]

Fungi show a variety of abilities in affecting metal speciation, toxicity, and mobility and mineral formation, dissolution or deterioration through several interacting biomechanical and biochemical mechanisms. A consequence of many metal-mineral interactions is the production of nanoparticles which may be in elemental, mineral or compound forms. Organisms may benefit from such nanomaterial formation through removal of metal toxicity, protection from environmental stress, and their redox properties since certain mycogenic nanoparticles can act as nanozymes mimicking enzymes such as peroxidase. With the development of nanotechnology, there is growing interest in the application of biological systems for nanomaterial production which may provide economic benefits and a lower damaging environmental effect than conventional chemical synthesis. Fungi offer some advantages since most are easily cultured under controlled conditions and well known for the secretion of metabolites and enzymes related to nanoparticle or nanomineral formation. Nanoparticles can be formed intracellularly or extracellularly, the latter being favourable for easy harvest, while the cell wall also provides abundant nucleation sites for their formation. In this article, we focus on the synthesis of nanoparticles and nanominerals by fungi, emphasizing the mechanisms involved, and highlight some possible applications of fungal nanomaterials in environmental biotechnology. [ABSTRACT FROM AUTHOR]

Cerium is the most sought-after rare earth element (REE) for application in high-tech electronic devices and versatile nanomaterials. In this research, biomass-free spent culture media of Aspergillus niger and Neurospora crassa containing precipitant ligands (oxalate, carbonate) were investigated for their potential application in biorecovery of Ce from solution. Precipitation occurred after Ce3+ was mixed with biomass-free spent culture media and >99% Ce was recovered from media of both organisms. SEM showed that biogenic crystals with distinctive morphologies were formed in the biomass-free spent medium of A. niger. Irregularly-shaped nanoparticles with varying sizes ranging from 0.5 to 2 μm and amorphous biominerals were formed after mixing the carbonate-laden N. crassa supernatant, resulting from ureolysis of supplied urea, with Ce3+. Both biominerals contained Ce as the sole metal, and X-ray diffraction (XRD) and thermogravimetric analyses identified the biominerals resulting from the biomass-free A. niger and N. crassa spent media as cerium oxalate decahydrate [Ce 2 (C 2 O 4) 3 ·10H 2 O] and cerium carbonate [Ce 2 (CO 3) 3 ·8H 2 O], respectively. Thermal decomposition experiments showed that the biogenic Ce oxalates and carbonates could be subsequently transformed into ceria (CeO 2). FTIR confirmed that both amorphous and nanoscale Ce carbonates contained carbonate (CO 3 2−) groups. FTIR-multivariate analysis could classify the biominerals into three groups according to different Ce concentrations and showed that Ce carbonate biominerals of higher purity were produced when precipitated at higher Ce3+ concentrations. This work provides new understanding of fungal biotransformations of soluble REE species and their biorecovery using biomass-free fungal culture systems and indicates the potential of using recovered REE as precursors for the biosynthesis of novel nanomaterials. [Display omitted] • Biomass-free spent fungal media achieved >99% biorecovery of cerium from solution. • Carbonate-laden N. crassa media precipitated Ce carbonate [Ce 2 (CO 3) 3 ·8H 2 O]. • Oxalate-laden A. niger media precipitated Ce oxalate decahydrate [Ce 2 (C 2 O 4) 3 ·10H 2 O]. • Biogenic Ce oxalates and carbonates were thermally transformed into ceria (CeO 2). • Demonstration of REE biorecovery by biomass-free fungal culture systems. [ABSTRACT FROM AUTHOR]

Oxalate is a key metabolite that plays a significant role in many metal and mineral transformations mediated by fungi. Metal and mineral transformations are central to geomycological processes including nutrient and element cycling, rock, mineral and metal transformations, bioweathering and mycogenic biomineral formation. Some fungal transformations have potential applications in environmental biotechnology, e.g. metal and radionuclide leaching, biorecovery, detoxification and bioremediation, and in the production or deposition of biominerals or metallic elements with catalytic or other properties. Metal and mineral transformations may also result in adverse effects when these processes result in biodeterioration of natural and synthetic materials, rock and mineral-based building materials (e.g. concrete), biocorrosion of metals, alloys and related substances, and adverse effects on radionuclide speciation, mobility and containment. Oxalate is ubiquitous in all these contexts. This paper seeks to draw together salient information from environmental and applied research to emphasize the importance of oxalate in geomycology, biodeterioration, environmental biotechnology and bioremediation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Up-to-date critical review. [•] Covers concept, definition and application. [•] Provides directions for future research. [Copyright &y& Elsevier]

• Environmental adaptation of bacterioplankton decreased after dredging. • Stochastic processes of bacterioplankton community increased after dredging. • Sediment total phosphorus mediated balance between stochasticity and determinism. Disentangling ecological mechanisms behind dredging is meaningful to implement environmental policy for improving water quality. However, environmental adaptation and community assembly processes of bacterioplankton in response to dredging disturbance are poorly understood. Based on Illumine MiSeq sequencing and multiple statistical analyses, we estimated interactions, functions, environmental breadths, phylogenetic signals, phylogenetic clustering, and ecological assembly processes of bacterioplankton community before and after dredging. We found distinct change in community composition, comparable decreases in diversity, functional redundancy and conflicting interaction, relatively low phylogenetic clustering, and relatively weak environmental adaptation after dredging. The bacterioplankton community assembly was affected by both stochastic and deterministic processes before dredging, but dominated by stochasticity after dredging. Sediment total phosphorus was a decisive factor in balancing determinism and stochasticity for bacterioplankton community assembly before and after dredging. Consequently, taxonomic and phylogenetic α-diversities of bacterioplankton exhibited higher contributions to the water trophic level represented by chlorophyl α before dredging than afterwards. Our results emphasized bacterioplankton in response to environmental changes caused by dredging, with nutrient loss and ecological drift playing important roles. These findings extend knowledge of contribution of bacterioplankton diversity to water trophic level and decipher mechanisms of bacterioplankton diversity maintenance in response to dredging, which is useful for guiding mitigation of cyanobacterial blooms. [Display omitted] [ABSTRACT FROM AUTHOR]

Fungi are one of the most biogeochemically active components of the soil microbiome, becoming particularly important in metal polluted terrestrial environments. There is scant information on the mycobiota of uranium (U) polluted sites and the effect of metallic depleted uranium (DU) stress on fungal communities in soil has not been reported. The present study aimed to establish the effect of DU contamination on a fungal community in soil using a culture-independent approach, fungal ribosomal intergenic spacer analysis (F-RISA). Experimental soil microcosms also included variants with plants (Pinus silvestris) and P. silvestris/Rhizopogon rubescens ectomycorrhizal associations. Soil contamination with DU resulted in the appearance of RISA bands of the ITS fragments of fungal metagenomic DNA that were characteristic of the genus Mortierella (Mortierellomycotina: Mucoromycota) in pine-free microcosms and for ectomycorrhizal fungi of the genus Scleroderma (Basidiomycota) in microcosms with mycorrhizal pines. The precise taxonomic affinity of the ITS fragments from the band appearing for non-mycorrhizal pines combined with DU remained uncertain, the most likely being related to the subphylum Zoopagomycotina. Thus, soil contamination by thermodynamically unstable metallic depleted uranium can cause a significant change in a soil fungal community under experimental conditions. These changes were also strongly affected by the presence of pine seedlings and their mycorrhizal status which impacted on DU biocorrosion and the release of bioavailable uranium species. [ABSTRACT FROM AUTHOR]

Abstract Salinity can be a significant environmental stress which can govern the fate of nanoparticles in the environment as well as other factors such as pH, natural organic matter and minerals. In this research, the effects of salinity on the behavior of biogenic selenium nanoparticles (BioSeNPs) and consequences for elemental mercury (Hg0) immobilization in soil and soil solutions were investigated. It was found that homoaggregation and sedimentation of BioSeNPs were enhanced significantly with increasing salinity. Compression of the electric double layers of BioSeNPs at high ionic strengths resulted in attractive van der Waals forces dominating and leading to enhanced aggregation. Moreover, neutralization of the surface negative charge of BioSeNPs by divalent cations and the bridging of BioSeNPs via calcium binding to surface functional groups were also associated with enhanced aggregation. Such enhanced aggregation exerted inhibition of Hg0 immobilization in soil solutions/soils of varying salinity. These results indicate that salinity is an important environmental factor governing aggregation of BioSeNPs and therefore influencing the efficiency of Hg0 immobilization, and possible remediation treatments, as a consequence. Graphical abstract Unlabelled Image Highlights • Salinity is an important environmental factor governing the fate of SeNPs in soil. • Compressed EDLs, charge neutralization and Ca-bridging enhanced SeNPs aggregation. • Hg0 immobilization efficiency using SeNPs was suppressed with increased aggregation. [ABSTRACT FROM AUTHOR]

Abstract Molecular weight (MW) heterogeneity is a fundamental property of dissolved organic matter (DOM) in soil, which has been demonstrated to influence the binding behaviour between DOM and engineered nanoparticles. In the present study, DOM, extracted from black soil, was dialyzed into four fractions: above 10,000 Da, 3500–10,000 Da, 1000–3500 Da and 100–1000 Da. Homoaggregation and fluorescence quenching titration of selenium nanoparticles (SeNPs) was examined in the presence of the different DOM fractions, as well as the consequences for immobilization of elemental mercury. It was found that the intermediate MW fraction (3500–10,000 Da) rather than the high MW DOM fraction was likely to adsorb to SeNPs. Generally, low MW DOM was expected to adsorb initially due to faster diffusion and these compounds would be displaced by high MW DOM over longer time period. However, the electrostatic barrier imparted by adsorbed DOM limited such displacement, leading to preferential adsorption of the intermediate MW fraction over the high MW fraction. Adsorbed DOM fractions, especially that of intermediate MW, enhanced the stability of SeNPs which favoured immobilization of elemental mercury. These findings show that MW exerts an important impact on DOM binding with SeNPs which, in consequence, governs the fate of SeNPs and mercury bioremediation performance. Graphical abstract Unlabelled Image Highlights • Dissolved organic matter (DOM) affects Hg removal by selenium nanoparticles (SeNPs). • Intermediate molecular weight DOM preferentially adsorbed to SeNPs. • Intermediate molecular weight DOM limited its displacement by other DOM fractions. • Intermediate molecular weight DOM enhanced the stability of SeNPs and Hg removal. [ABSTRACT FROM AUTHOR]

For the first time, the International Symposium on Fungal Stress was joined by the XIII International Fungal Biology Conference. The International Symposium on Fungal Stress (ISFUS), always held in Brazil, is now in its fourth edition, as an event of recognized quality in the international community of mycological research. The event held in São José dos Campos, SP, Brazil, in September 2022, featured 33 renowned speakers from 12 countries, including: Austria, Brazil, France, Germany, Ghana, Hungary, México, Pakistan, Spain, Slovenia, USA, and UK. In addition to the scientific contribution of the event in bringing together national and international researchers and their work in a strategic area, it helps maintain and strengthen international cooperation for scientific development in Brazil. [Display omitted] [ABSTRACT FROM AUTHOR]

A phenol-degrading fungus, Fusarium oxysporum GJ4, was isolated from contaminated soil and was able to use phenol as a sole carbon and energy source. Catechol was detected during phenol degradation and this was polymerized by Cu2O added to the medium. F. oxysporum GJ4 was unable to degrade phenol at concentrations greater than 2mM when Cu2O was present in the liquid growth medium. Catechol polymerization and deposition on the fungal surface was thought to be the main reason for the cessation of phenol degradation by F. oxysporum GJ4. Such catalytic polymerization of catecholic products by Cu2O during the biodegradation of phenol or other phenolic products must be considered as a possible interference factor in bioremediation. [Copyright &y& Elsevier]

• AgNP/PTFE coatings are prepared by a layer-by-layer technique. • The sol–gel matrix serves as a platform for PTFE immobilization and AgNP deposition. • The coating procedures offer an ease of control over the silver release. • The AgNP/PTFE coatings demonstrate significant antibacterial activity and corrosion resistance. In this research, a silver nanoparticle/polytetrafluorethylene (AgNP/PTFE) coating for metallic implants was fabricated using a facile layer-by-layer coating method. PTFE nanoparticles were immobilized in a sol–gel matrix and dip-coated onto 316L stainless steel via a mussel-inspired approach followed by AgNP deposition. Benefiting from the synergistic effect of antibacterial AgNP and non-stick PTFE, the AgNP/PTFE coating exhibited superior antibiofilm activity against Escherichia coli WT F1693 and enhanced corrosion resistance. Compared with surfaces only coated with PTFE, the AgNP/PTFE coated surfaces were capable of sustained release of silver ions, inhibiting up to ~50% bacterial biomass accumulation after 7 days. To understand the anti-adhesion mechanism, both classic DLVO and XDLVO theories were used to model and explain bacterial adhesion. Despite concerns that an over-release of silver ions may cause toxic effects towards mammalian cells, the coating procedures offered ease of control over the silver loading, making it potentially useful for preventing metallic implant-associated infections. [ABSTRACT FROM AUTHOR]

Several geoactive fungi were investigated for their biocorrosion impact on metallic copper, to further understanding of the potential roles that fungi may have in the biotransformation of such substrate, and the mechanisms involved. Copper metal showed little toxicity and test fungi were able to grow in direct or indirect contact with copper and to colonize copper sheet. A. niger was able to biodeteriorate copper metal through proton- and ligand-mediated dissolution mechanisms, leading to significant mass loss and surface etching. The formation of a secondary copper oxalate (moolooite) biomineral crust together with cuprite deposition lead to alteration of surface topography and visual appearance, highlighting the significance of oxalate excretion in effecting fungal metal biotransformations. The metal transforming influence of fungal colonization may have some implications for biodeterioration, protection and preservation of cultural relics and artefacts as well as certain components of the built environment. Image 1 • Geoactive fungi were able to colonize and biodeteriorate copper metal. • Main biodeterioration mechanisms were mediated by protons and oxalic acid. • Fungal activity led to loss of mass as well as etching patterns of colonization. • A copper oxalate and cuprite crust formed on the surface of copper metal. [ABSTRACT FROM AUTHOR]

Bacterial biofilms are structured cell communities embedded in a matrix of extracellular polymeric substances (EPS) and a ubiquitous growth form of bacteria in the environment. A wide range of interactions between biofilms and nanoparticles have been reported. In the present study, the influence of a mixed bacterial biofilm on retention of biogenic selenium nanoparticles (BioSeNPs) and consequences for immobilization of elemental mercury (Hg0) in a porous quartz sand system were examined. BioSeNPs were significantly retained in the presence of a biofilm through electrical double layer effects, hydrogen bonding, and hydrophobic, steric and bridging interactions. Moreover, enhanced surface roughness, pore clogging, sieving and entrapment effects mediated by the biofilm also contributed to deposition of BioSeNPs. Whereas, thiol groups associated with the biofilm is a little helpful for the capture of Hg0. It is proposed that oxidative complexation between Hg0 and thiol compounds or S containing organic matter in the biofilm may result in the formation of Hg2+-thiolate complexes and HgS during the binding of Hg0 with BioSeNPs. The formation of mercury selenide was also involved in Hg0 immobilization in the porous quartz sand system. Unlabelled Image • The coating of a microbial biofilm on quartz sand enhanced retention of BioSeNPs. • The biofilm facilitated Hg0 capture during Hg0 immobilization using BioSeNPs. • Oxidative complexation between Hg0 and thiol contributed to Hg0 removal. [ABSTRACT FROM AUTHOR]

Abstract Particulate organic matter (POM), composed of fine root fragments and other organic debris, is an important fraction of soil organic matter which can affect the fate of nanoparticles and influence their performance in nanoparticle-based remediation technologies due to aggregation. Effects of POM are not well studied compared with those of dissolved organic matter. In this research, POM was extracted from black soil by sieving, and heteroaggregation of selenium nanoparticles (SeNPs) with POM and consequences for elemental mercury (Hg0) immobilization were investigated. It was found that low concentrations of more negatively charged POM (0–60 mg L−1) inhibited homoaggregation as well as heteroaggregation with SeNPs which had a lower negative charge through electrostatic repulsion. In the presence of high concentrations of POM (80–100 mg L−1), SeNPs were more likely to attach to POM with more Hg0 remaining in the POM since a larger concentration of nanoparticles would lead to more effective collisions. However, Hg0 immobilization efficiency using SeNPs was not significantly influenced by the addition of POM. This work is helpful to further understand the nanoparticle's behaviour in the environment and consequences for toxic metal remediation. Graphical abstract Image 102269 Highlights • POM can affect the fate of SeNPs in the environment. • POM (0–60 mg L−1) inhibited its homoaggregation and heteroaggregation with SeNPs. • Hg0 immobilization efficiency by SeNPs was not inhibited in the presence of POM. [ABSTRACT FROM AUTHOR]

Recent reports have drawn attention to the uranium contamination arising from coal mining activities in the Yili region of Xinjiang, China due to the mixed distribution of uranium and coal mines, and some of the coal mines being associated with a high uranium content. In this study, we have collected water samples, solid samples such as soil, mud, coal, and coal ash, and hair and urine samples from local populations in order to evaluate the uranium level in this environment and its implications for humans in this high uranium coal mining area. Our results showed that uranium concentrations were 8.71–10.91 μg L −1 in underground water, whereas lower levels of uranium occurred in river water. Among the solid samples, coal ash contained fairly high concentrations of uranium (33.1 μg g −1 ) due to enrichment from coal burning. In addition, uranium levels in the other solid samples were around 2.8 μg g −1 (the Earth's average background value). Uranium concentrations in hair and urine samples were 22.2–634.5 ng g −1 (mean: 156.2 ng g −1 ) and 8.44–761.6 ng L −1 (mean: 202.6 ng L −1 ), respectively, which are significantly higher than reference values reported for unexposed subjects in other areas. Therefore, these results indicate that people living in this coal mining area have been subjected to uranium exposure for long periods of time. [ABSTRACT FROM AUTHOR]

The Fungal Kingdom is responsible for many ecosystem services as well as many industrial and agricultural products. Nevertheless, how these fungal species function and carry out these services is dependent on their capacity to grow under different stress conditions caused by a variety of abiotic factors such as ionizing radiation, UV radiation, extremes of temperature, acidity and alkalinity, and environments of low nutritional status, low water activity, or polluted with, e.g. toxic metals or xenobiotics. This article reviews some natural or synthetic environments where fungi thrive under stress and have important impacts in agriculture and forestry. [ABSTRACT FROM AUTHOR]

Mercury contamination is a global concern because of its high toxicity, persistence, bioaccumulative nature, long distance transport and wide distribution in the environment. In this study, the efficiency and multiple-pathway remediation mechanisms of Hg 2 + by a selenite reducing Escherichia coli was assessed. E. coli can reduce Hg 2 + to Hg + and Hg 0 and selenite to selenide at the same time. This makes a multiple-pathway mechanisms for removal of Hg 2 + from water in addition to biosorption. It was found that when the original Hg 2 + concentration was 40 μg L − 1 , 93.2 ± 2.8% of Hg 2 + was removed from solution by E. coli . Of the total Hg removed, it was found that 3.3 ± 0.1% was adsorbed to the bacterium, 2.0 ± 0.5% was bioaccumulated, and 7.3 ± 0.6% was volatilized into the ambient environment, and most (80.6 ± 5.7%) Hg was removed as HgSe and HgCl precipitates and Hg 0 . On one hand, selenite is reduced to selenide and the latter further reacts with Hg 2 + to form HgSe precipitates. On the other hand Hg 2 + is successively reduced to Hg + , which forms solid HgCl, and Hg 0 . This is the report on bacterially transformation of Hg 2 + to HgSe, HgCl and Hg 0 via multiple pathways. It is suggested that E. coli or other selenite reducing microorganisms are promising candidates for mercury bioremediation of contaminated wastewaters, as well as simultaneous removal of Hg 2 + and selenite. [ABSTRACT FROM AUTHOR]

Ubiquitous colloidal minerals such as goethite can have a significant impact on the performance of nanoparticles-based groundwater remediation due to aggregation. Heteroaggregation and retention of Se nanoparticles (SeNPs) by goethite in groundwater, and its impact on Hg 0 remediation by SeNPs were investigated in this study. In order to mitigate the adverse effects of aggregation, the effects of bacterial extracellular polymeric substances (EPS) on the stability of SeNPs and Hg 0 sequestration using SeNPs were also evaluated. Heteroaggregation of SeNPs with goethite in groundwater was stronger than homoaggregation of SeNPs or goethite. Addition of EPS could slightly decrease homoaggregation of SeNPs and significantly reduce heteroaggregation. Column transport experiments showed that goethite coated quartz sand could retain 1.36 times a higher amount of SeNPs than uncoated quartz sand. Hg 0 remediation by SeNPs was significantly inhibited by heteroaggregation of SeNPs with goethite and EPS could effectively mitigate this inhibitory effect. The Hg 0 removal efficiency decreased to 71.6% and 66.9%, respectively in the presence of 20 and 100 mg L − 1 goethite. When 200 mg L − 1 EPS was added together with 100 mg L − 1 goethite, 81.2% of the supplied Hg 0 was removed from the groundwater. This study demonstrates that the widespread presence of goethite could significantly reduce the remediation efficiency of Hg 0 contaminated groundwater and that EPS is a promising amendment for mitigating the adverse effects of heteroaggregation. This research also contributes to a further understanding of the environmental behaviour of nanoparticles. [ABSTRACT FROM AUTHOR]

Anaerobic oxidation of methane (AOM) can be coupled to the reduction of sulfate, nitrate and nitrite, which effectively reduces methane emission into the atmosphere. Recently, metal-dependent AOM (metal-AOM, AOM coupled to metal reduction) was demonstrated to occur in both environmental samples and enrichment cultures. Anaerobic methanotrophs are capable of respiration using Fe(III) or Mn(IV), whether they are in the form of soluble metal species or insoluble minerals. Given the wide distribution of Fe(III)/Mn(IV)-bearing minerals in aquatic methane-rich environments, metal-AOM is considered to be globally important, although it has generally been overlooked in previous studies. In this article, we discuss the discovery of this process, the microorganisms and mechanisms involved, environmental significance and factors influencing metal-AOM. Since metal-AOM is poorly studied to date, some discussion is included on the present understanding of sulfate- and nitrate-AOM and traditional metal reduction processes using organic substrates or hydrogen as electron donors. Metal-AOM is a relatively new research field, and therefore more studies are needed to fully characterize the process. This review summarizes current studies and discusses the many unanswered questions, which should be useful for future research in this field. [ABSTRACT FROM AUTHOR]

Selenium (Se) nanoparticles are often synthesized by anaerobes. However, anaerobic bacteria cannot be directly applied for bioremediation of contaminated top soil which is generally aerobic. In this study, a selenite-reducing bacterium, Citrobacter freundii Y9, demonstrated high selenite reducing power and produced elemental nano-selenium nanoparticles (nano-Se 0 ) under both aerobic and anaerobic conditions. The biogenic nano-Se 0 converted 45.8–57.1% and 39.1–48.6% of elemental mercury (Hg 0 ) in the contaminated soil to insoluble mercuric selenide (HgSe) under anaerobic and aerobic conditions, respectively. Addition of sodium dodecyl sulfonate enhanced Hg 0 remediation, probably owing to the release of intracellular nano-Se 0 from the bacterial cells for Hg fixation. The reaction product after remediation was identified as non-reactive HgSe that was formed by amalgamation of nano-Se 0 and Hg 0 . Biosynthesis of nano-Se 0 both aerobically and anaerobically therefore provides a versatile and cost-effective remediation approach for Hg 0 -contaminated surface and subsurface soils, where the redox potential often changes dramatically. [ABSTRACT FROM AUTHOR]

Microbial activity following invasion of human-made structures and artifacts can have profound social and economic consequences including the permanent loss of cultural heritage. The unique frescoes in the 11th century Saint Sophia's Cathedral (Kyiv, Ukraine) have recently suffered from dark-spot biodeterioration. The aim of this work was to elucidate the microbial nature of biodeterioration and the biogeochemical processes occurring in the areas of the dark spots. Culture-independent approaches including scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), micro-X-ray diffraction and real-time quantitative polymerase chain reaction (qPCR) analysis were used in this study. SEM and qPCR data demonstrated that the main agents of fresco biodeterioration were mycelial fungi, with bacteria unlikely to play a major role in the development of the dark spots. SEM-EDS results showed that fungi colonization of the dark spotted areas resulted in mechanical and chemical weathering involving dissolution of mineral components of the plaster (mainly calcite) and displacement of mineral grains, which compromise the stability of the plaster or fresco. SEM-EDS also detected fungal biomineralization of secondary mycogenic minerals: calcium malate, hydrated aluminium and ferric phosphates. Biomineralization of calcium malate by fungi, as found in this study, is a rare biogeochemical phenomenon, possibly linked to the presence of calcite and nitrogen limitation. • 11th century frescoes in Saint Sophia's Cathedral (Kyiv, Ukraine) were affected by dark spot biodeterioration. • The main agents causing fresco defacement were filamentous fungi. • Fungi acted on fresco plaster through biomechanical and biochemical mechanisms. • Fungal activity resulted in dissolution of mineral components of the plaster, e.g. calcite. • Calcium malate, hydrated aluminum and ferric phosphate minerals were formed by fungi. [ABSTRACT FROM AUTHOR]

β-Hexachlorocyclohexane (β-HCH) is a persistent organic pollutant (POP) of global concern with potentially toxic effects on humans and ecosystems. Fungal tolerance and biotransformation of toxic substances hold considerable promise in environmental remediation technologies as many fungi can tolerate extreme environmental conditions and possess efficient extracellular degradative enzymes with relatively non-specific activities. In this research, we have investigated the potential of a saprotrophic soil fungus, Penicillium griseofulvum Dierckx, isolated from soils with high concentrations of isomers of hexachlorocyclohexane, to biotransform β-HCH, the most recalcitrant isomer to microbial activity. The growth kinetics of the fungus were characterized after growth in stirred liquid Czapek-Dox medium. It was found that P. griseofulvum was able to grow in the presence of 1 mg L −1 β-HCH and in stressful nutritional conditions at different concentrations of sucrose in the medium (0 and 5 g L −1 ). The effects of β-HCH and the toluene, used as a solvent for β-HCH addition, on P. griseofulvum were investigated by means of a Phenotype MicroArray™ technique, which suggested the activation of certain metabolic pathways as a response to oxidative stress due to the presence of the xenobiotics. Gas chromatographic analysis of β-HCH concentration confirmed biodegradation of the isomer with a minimum value of β-HCH residual concentration of 18.6%. The formation of benzoic acid derivatives as dead-end products of β-HCH biotransformation was observed and this could arise from a possible biodegradation pathway for β-HCH with important connections to fungal secondary metabolism. [ABSTRACT FROM AUTHOR]

The cathode reaction is one of the most important limiting factors in bioelectrochemical systems even with precious metal catalysts. Since aerobic bacteria have a much higher affinity for oxygen than any known abiotic cathode catalysts, the performance of a microbial fuel cell can be improved through the use of electrochemically-active oxygen-reducing bacteria acting as the cathode catalyst. These consume electrons available from the electrode to reduce the electron acceptors present, probably conserving energy for growth. Anaerobic bacteria reduce protons to hydrogen in microbial electrolysis cells (MECs). These aerobic and anaerobic bacterial activities resemble those catalyzing microbially-influenced corrosion (MIC). Sulfate-reducing bacteria and homoacetogens have been identified in MEC biocathodes. For sustainable operation, microbes in a biocathode should conserve energy during such electron-consuming reactions probably by similar mechanisms as those occurring in MIC. A novel hypothesis is proposed here which explains how energy can be conserved by microbes in MEC biocathodes. [ABSTRACT FROM AUTHOR]

Many approaches have been proposed to reduce the toxicity of hazardous substances such as lead in the environment. Several techniques using microorganisms rely on metal removal from solution by non-specific biosorption. However, immobilization of metals through formation of biominerals mediated by metabolic processes offers another solution but which has been given limited attention. In this work, we have investigated lead biomineralization by Paecilomyces javanicus, a fungus isolated from a lead-contaminated soil, in a liquid medium. P. javanicus was able to grow in the presence of metallic lead, supplied as lead shot, and secondary lead minerals were deposited on the lead surfaces as revealed by scanning electron microscopy. Energy dispersive X-ray analysis and X-ray powder diffraction revealed that pyromorphite was formed in the presence of the fungus, but not in abiotic controls. Our results clearly demonstrate that fungal activities can play an important role in lead biocorrosion and biomineralization in an aqueous environment. These findings are relevant to bioremediation approaches for liquid wastes contaminated with lead, or other metals, and also to the immobilization and biorecovery of rare or valuable elements. They also provide further understanding of microbial roles in environmental lead cycling. [ABSTRACT FROM AUTHOR]

Concrete can face serious deterioration issues due to different physical, chemical, or biochemical factors. Structural integrity and durability are significantly impaired by cracks which provide channels for water or gases to penetrate concrete matrices, ultimately attacking the steel reinforcements. In this research, we show that a urease-positive fungus, Neurospora crassa , can deposit calcium carbonate on mortar through microbiologically-induced calcium carbonate precipitation (MICP) forming a dense biomineralized mycelial network resulting in a protective coating on Portland cement, fly ash, and ground granulated blast furnace slag based mortar. Rietveld refinement of X-ray diffraction data showed that greater amounts of calcium carbonate were precipitated with increasing mortar porosity. Water repellence was enhanced after fungal colonization and carbonate biodeposition on the surface, and water absorption coefficients improved 17% at least after development of the boioprotective coating. Overall, this work demonstrates that fungal biomineralization could act as biocement to protect porous mineral-based materials from water infiltration, thus improving their durability. [Display omitted] • A urease positive fungus was able to colonize and protect porous infrastructure materials. • Calcite accumulated on the surface of concrete resulting from fungal-induced calcium carbonate precipitation during growth. • Physical shielding by biomass and pore clogging by calcium carbonate were predominant mechanisms involved in bioprotection. • The formation of a biocrust can prevent water infiltration into the underlying concrete. [ABSTRACT FROM AUTHOR]