Sequestration of arsenic to biogenic sulfide minerals is known from As-contaminated anoxic environments. Despite numerous successful laboratory experiments, the process remains difficult to predict in moderate arsenic conditions. We performed microcosm experiments using naturally contaminated groundwater (containing ca. 6 mg/L As) and natural organic matter (NOM) particles both collected from wetland soil. Macroscopic realgar precipitates, occasionally accompanied by bonazziite, a FeS phase, elementary S, calcite, and whewellite, appeared after 4 to 18 months. Realgar only precipitated in microcosms moderately poisoned by azide or antibiotics and those in which oxidation of hydrogen sulfide to sulfur took place. The biomineralization process was not affected by the presence of additional carbon sources or the diversity, community structure, and functional composition of the microbial community. Hydrogen sulfide concentration was greater in the realgar-free microcosms, suggesting that arsenic thiolation prevented precipitation of realgar. We compared our data to available microbial community data from soils with different rates of realgar precipitation, and found that the communities from realgar-encrusted NOM particles usually showed limited sulfate reduction and the presence of fermentative metabolisms, whereas communities from realgar-free NOM particles were strongly dominated by sulfate reducers. We argue that the limited sulfate supply and intensive fermentation amplify reducing conditions, which make arsenic sulfide precipitation plausible in high-sulfate, low-arsenic groundwaters.

• Klíčová slova
• Arsenic, Arsenic thiolation, Fermentation, Microcosm, Realgar biomineralization, Sulfate reduction,
• MeSH
• arsenikové přípravky analýza   MeSH
• biomineralizace * MeSH
• chemické látky znečišťující vodu analýza   MeSH
• huminové látky analýza   MeSH
• mikrobiota * MeSH
• mokřady MeSH
• oxidace-redukce MeSH
• podzemní voda chemie   mikrobiologie   MeSH
• půda chemie   MeSH
• sírany chemie   MeSH
• sulfidy analýza   MeSH
• teoretické modely MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• arsenic disulfide MeSH Prohlížeč
• arsenikové přípravky MeSH
• chemické látky znečišťující vodu MeSH
• huminové látky MeSH
• půda MeSH
• sírany MeSH
• sulfidy MeSH

BACKGROUND, AIMS AND SCOPE: Microcystins (MCs) are a family of natural toxins produced by cyanobacteria (blue-green algae). As a result of eutrophication, massive cyanobacterial blooms occur more frequently and MCs represent important contaminants of freshwater ecosystems. Bacterial biodegradation is considered a main mechanism for MC breakdown in environmental conditions. While existing studies were mostly focused on MC biodegradation by planktonic bacteria, our experiments examined the fate and kinetics of MC degradation in river-originated phototrophic biofilms and investigated factors influencing the rate of MC removal. METHODS: The fate of dissolved MCs was studied in laboratory microcosms with different composition (containing water only, water with phytoplankton and/or phototrophic biofilms). Biofilms originated from river ecosystem were pre-incubated under various conditions (with/without presence of cyanobacterial biomass or model organic substrates: glucose and protein--casein). Changes in MC concentration (0-14 days) in water columns were measured by HPLC-DAD after external additions of purified MCs (160 microg L(-1), MC-LR and MC-YR), and halftimes (t1/2) of MC removal were estimated. RESULTS AND DISCUSSION: The slow degradation of MC was revealed in tap water (t1/2 approximately 14 days) and river water without cyanobacteria (t1/2 approximately 8 days). Enhanced removal occurred in the presence of natural planktonic cyanobacteria (t1/2 approximately 44 h), most probably due to microorganisms associated with the biomass of cyanobacterial bloom. More rapid MC elimination occurred in the variants containing phototrophic biofilms, and was particularly pronounced at those biofilms pre-cultivated in the presence of cyanobacterial blooms (t1/2 approximately 20 h). Much slower removal was observed in the variants simulating possible substrate-dependent induction of microorganism metabolism (biofilms pre-incubated with glucose: t1/2 approximately 35 h, and casein: t1/2 approximately 80 h). After termination of experiments, total amounts of MCs accumulated in the biofilms were below 5% of the initial toxin level revealing significant biodegradation processes. CONCLUSION: The microcosm studies contributed to understanding of the environmental fate of MCs and revealed a rapid biodegradation by phototrophic biofilms. The rate of MC elimination depends on history of biofilm community, previous contact with cyanobacteria seems to be a selective factor improving the biodegradation potential. RECOMMENDATION AND OUTLOOK: Our results experimentally showed a positive role of biofilms in MC elimination during water treatment processes such as bank filtration or slow sand filtration, and could eventually serve for further research of biofilm-based technological applications for MCs removal in small-scale drinking water treatment facilities.

• MeSH
• bakteriální toxiny izolace a purifikace   metabolismus   MeSH
• biodegradace účinky léků   MeSH
• biofilmy * MeSH
• chemické látky znečišťující vodu izolace a purifikace   metabolismus   MeSH
• Chlorophyta metabolismus   MeSH
• čištění vody metody   MeSH
• cyklické peptidy izolace a purifikace   metabolismus   MeSH
• glukosa farmakologie   MeSH
• kaseiny farmakologie   MeSH
• mikrocystiny MeSH
• řeky MeSH
• rozsivky metabolismus   MeSH
• sinice metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriální toxiny MeSH
• chemické látky znečišťující vodu MeSH
• cyklické peptidy MeSH
• glukosa MeSH
• kaseiny MeSH
• microcystin MeSH Prohlížeč
• mikrocystiny MeSH

In all terrestrial ecosystems, testate amoebae (TA) encounter fungi. There are strong indications that both groups engage in multiple interactions, including mycophagy and decomposition of TA shells, processes which might be fundamental in nutrient cycling in certain ecosystems. Here, we present the results of an experiment focusing on interactions between TA and saprotrophic microfungi colonizing Scots pine (Pinus sylvestris L.) litter needles. The needles were collected from a temperate pine forest and cultivated in damp chambers. Over a few weeks, melanized mycelium of Anavirga laxa Sutton started to grow out of some needles; simultaneously, the common forest-soil TA Phryganella acropodia (Hertwig and Lesser) Hopkinson reproduced and spread around the mycelium. We investigated whether a potential relationship between TA and saprotrophic microfungi exists by comparing the composition of TA communities on and around the needles and testing the spatial relationship between the A. laxa mycelium and P. acropodia shells in the experimental microcosm. Additionally, we asked whether P. acropodia utilized the A. laxa mycelium as a nutrient source and screened whether P. acropodia shells were colonized by the microfungi inhabiting the experimental microcosm. Our results indicate that saprotrophic microfungi may affect the composition of TA communities and their mycelium may affect distribution of TA individuals in pine litter. Our observations suggest that P. acropodia did not graze directly on A. laxa mycelium, but rather fed on its exudates or bacteria associated with the exudates. The fungus Pochonia bulbillosa (Gams & Malla) Zare & Gams was often found parasitising encysted shells or decomposing already dead individuals of P. acropodia. TA and pine litter microfungi engage in various direct and indirect interactions which are still poorly understood and deserve further investigation. Their elucidation will improve our knowledge on fundamental processes influencing coexistence of soil microflora and microfauna.

• MeSH
• Ascomycota fyziologie   MeSH
• borovice lesní mikrobiologie   MeSH
• Lobosea mikrobiologie   fyziologie   MeSH
• mikrobiální interakce * MeSH
• mycelium fyziologie   MeSH
• půdní mikrobiologie * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: Soil microorganisms are key determinants of soil fertility and plant health. Soil phytopathogenic fungi are one of the most important causes of crop losses worldwide. Microbial biocontrol agents have been extensively studied as alternatives for controlling phytopathogenic soil microorganisms, but molecular interactions between them have mainly been characterised in dual cultures, without taking into account the soil microbial community. We used an RNA sequencing approach to elucidate the molecular interplay of a soil microbial community in response to a plant pathogen and its biocontrol agent, in order to examine the molecular patterns activated by the microorganisms. RESULTS: A simplified soil microcosm containing 11 soil microorganisms was incubated with a plant root pathogen (Armillaria mellea) and its biocontrol agent (Trichoderma atroviride) for 24 h under controlled conditions. More than 46 million paired-end reads were obtained for each replicate and 28,309 differentially expressed genes were identified in total. Pathway analysis revealed complex adaptations of soil microorganisms to the harsh conditions of the soil matrix and to reciprocal microbial competition/cooperation relationships. Both the phytopathogen and its biocontrol agent were specifically recognised by the simplified soil microcosm: defence reaction mechanisms and neutral adaptation processes were activated in response to competitive (T. atroviride) or non-competitive (A. mellea) microorganisms, respectively. Moreover, activation of resistance mechanisms dominated in the simplified soil microcosm in the presence of both A. mellea and T. atroviride. Biocontrol processes of T. atroviride were already activated during incubation in the simplified soil microcosm, possibly to occupy niches in a competitive ecosystem, and they were not further enhanced by the introduction of A. mellea. CONCLUSIONS: This work represents an additional step towards understanding molecular interactions between plant pathogens and biocontrol agents within a soil ecosystem. Global transcriptional analysis of the simplified soil microcosm revealed complex metabolic adaptation in the soil environment and specific responses to antagonistic or neutral intruders.

• Klíčová slova
• Biological control, Gene expression, Microbial interaction, Plant pathogen, RNA-Seq, Soil microbial community, Soil transcriptome, Transcriptomics,
• MeSH
• anotace sekvence MeSH
• ekosystém * MeSH
• exprese genu MeSH
• interakce hostitele a patogenu genetika   MeSH
• kořeny rostlin genetika   mikrobiologie   MeSH
• metagenom MeSH
• metagenomika metody   MeSH
• půdní mikrobiologie * MeSH
• shluková analýza MeSH
• stanovení celkové genové exprese MeSH
• transkriptom * MeSH
• výpočetní biologie metody   MeSH
• vysoce účinné nukleotidové sekvenování MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The aim of this study was to analyze the occurrence of sulfonamide resistance genes (sul1-3) and other genetic elements as antiseptic resistance gene (qacEΔ1) and class 1 and class 2 integrons (int1-2) in the upper layer of substrate and in the effluent of microcosm constructed wetlands (CWs) treating artificial wastewater containing diclofenac and sulfamethoxazole (SMX), which is a sulfonamide antibiotic. The bacteria in the substrate and in the effluents were equipped with the sul1-2, int1, and qacEΔ1 resistance determinants, which were introduced into the CW system during inoculation with activated sludge and with the soil attached to the rhizosphere of potted seedlings of Phalaris arundinacea 'Picta' roots (int1). By comparing the occurrence of the resistance determinants in the upper substrate layer and the effluent, it can be stated that they neither were lost nor emerged along the flow path. The implications of the presence of antibiotic resistance genes in the effluent may entail a risk of antibiotic resistance being spread in the receiving environment. Additionally, transformation products of SMX were determined. According to the obtained results, four (potential) SMX transformation products were identified. Two major metabolites of SMX, 2,3,5-trihydroxy-SMX and 3,5-dihydroxy-SMX, indicated that SMX may be partly oxidized during the treatment. The remaining two SMX transformation products (hydroxy-glutathionyl-SMX and glutathionyl-SMX) are conjugates with glutathione, which suggests the ability of CW bacterial community to degrade SMX and resist antimicrobial stress.

• Klíčová slova
• Antibiotic resistance genes, Pharmaceuticals, Transformation products, Treatment wetlands,
• MeSH
• antibakteriální látky analýza   MeSH
• antibiotická rezistence * MeSH
• biodegradace MeSH
• integrony MeSH
• léčivé přípravky MeSH
• mokřady MeSH
• odpadní voda * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antibakteriální látky MeSH
• léčivé přípravky MeSH
• odpadní voda * MeSH

The functional relevance of microbiota is a key aspect for understanding host-microbiota interactions. Mammalian skin harbours a complex consortium of beneficial microorganisms known to provide health and immune-boosting advantages. As yet, however, little is known about functional microbial communities on avian feathers, including their co-evolution with the host and factors determining feather microbiota (FM) diversity. Using 16S rRNA profiling, we investigated how host species identity, phylogeny and geographic origin determine FM in free-living passerine birds. Moreover, we estimated the relative abundance of bacteriocin-producing bacteria (BPB) and keratinolytic feather damaging bacteria (FDB) and evaluated the ability of BPB to affect FM diversity and relative abundance of FDB. Host species identity was associated with feather bacterial communities more strongly than host geographic origin. FM functional properties differed in terms of estimated BPB and FDB relative abundance, with both showing interspecific variation. FM diversity was negatively associated with BPB relative abundance across species, whereas BPB and FDB relative abundance was positively correlated. This study provides the first thorough evaluation of antimicrobial peptides-producing bacterial communities inhabiting the feather integument, including their likely potential to mediate niche-competition and to be associated with functional species-specific feather microbiota in avian hosts.

• MeSH
• Bacteria klasifikace   genetika   izolace a purifikace   MeSH
• bakteriociny biosyntéza   MeSH
• druhová specificita MeSH
• fylogeneze MeSH
• hostitelská specificita MeSH
• mikrobiota * MeSH
• peří mikrobiologie   MeSH
• ptáci mikrobiologie   MeSH
• RNA ribozomální 16S genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriociny MeSH
• RNA ribozomální 16S MeSH

Phytoplankton is a key component of aquatic microbial communities, and metabolic coupling between phytoplankton and bacteria determines the fate of dissolved organic carbon (DOC). Yet, the impact of primary production on bacterial activity and community composition remains largely unknown, as, for example, in the case of aerobic anoxygenic phototrophic (AAP) bacteria that utilize both phytoplankton-derived DOC and light as energy sources. Here, we studied how reduction of primary production in a natural freshwater community affects the bacterial community composition and its activity, focusing primarily on AAP bacteria. The bacterial respiration rate was the lowest when photosynthesis was reduced by direct inhibition of photosystem II and the highest in ambient light condition with no photosynthesis inhibition, suggesting that it was limited by carbon availability. However, bacterial assimilation rates of leucine and glucose were unaffected, indicating that increased bacterial growth efficiency (e.g., due to photoheterotrophy) can help to maintain overall bacterial production when low primary production limits DOC availability. Bacterial community composition was tightly linked to light intensity, mainly due to the increased relative abundance of light-dependent AAP bacteria. This notion shows that changes in bacterial community composition are not necessarily reflected by changes in bacterial production or growth and vice versa. Moreover, we demonstrated for the first time that light can directly affect bacterial community composition, a topic which has been neglected in studies of phytoplankton-bacteria interactions.IMPORTANCE Metabolic coupling between phytoplankton and bacteria determines the fate of dissolved organic carbon in aquatic environments, and yet how changes in the rate of primary production affect the bacterial activity and community composition remains understudied. Here, we experimentally limited the rate of primary production either by lowering light intensity or by adding a photosynthesis inhibitor. The induced decrease had a greater influence on bacterial respiration than on bacterial production and growth rate, especially at an optimal light intensity. This suggests that changes in primary production drive bacterial activity, but the effect on carbon flow may be mitigated by increased bacterial growth efficiencies, especially of light-dependent AAP bacteria. Bacterial activities were independent of changes in bacterial community composition, which were driven by light availability and AAP bacteria. This direct effect of light on composition of bacterial communities has not been documented previously.

• Klíčová slova
• AAP community composition, aerobic anoxygenic phototrophic bacteria, bacterial community composition, phytoplankton-bacteria coupling,
• MeSH
• aerobní bakterie růst a vývoj   metabolismus   MeSH
• ekosystém * MeSH
• fotosyntéza MeSH
• fototrofní procesy * MeSH
• fyziologie bakterií MeSH
• mikrobiota * MeSH
• mořská voda mikrobiologie   MeSH
• sladká voda mikrobiologie   MeSH
• světlo MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• Publikační typ
• časopisecké články MeSH
• tisková chyba MeSH

Widely used conazole fungicides (CFs) belong to the most frequently detected pesticides in Central European arable soils. However, data on their environmental behaviour and bioavailability to soil organisms are surprisingly scarce. In the present laboratory microcosm study prochloraz, tebuconazole, epoxiconazole and flusilazole were applied to 12 different agricultural soils at background levels. Bioaccumulation to earthworm E. andrei and lettuce L. sativa roots and leaves was evaluated in non-aged (biota exposure after addition of pesticides) and aged (exposure started three months later) systems. In contrast with expectations from ageing effect (decrease of bioavailability), bioaccumulation in E. andrei was both reduced and enhanced after ageing depending on soil properties. The reduction of bioaccumulation correlated positively to the percentage of clay but negatively to soil organic matter. The affinity of compost worm E. andrei towards organic matter where hydrophobic pesticide molecules are sorbed is discussed as a possible explanation. An apparent effect of ageing (reduction of bioavailability) was particularly observed in lettuce roots, where bioaccumulation was significantly reduced in time. However, bioaccumulation in leaves changed ambiguously in aged variants among CFs, possibly as a combined result of bioconcentration, dilution by plant growth and metabolism. This study brings first insights into how the bioaccumulation of conazole fungicides is affected by sequestration in agricultural soils. The results indicate that in complex systems, the ageing is not necessarily connected with decrease of bioaccumulation.

• Klíčová slova
• Bioavailability, Current-use pesticides, Earthworm, Microcosm, Plant,
• MeSH
• bioakumulace MeSH
• biologická dostupnost MeSH
• epoxidové sloučeniny MeSH
• fungicidy průmyslové analýza   metabolismus   MeSH
• jíl MeSH
• látky znečišťující půdu analýza   metabolismus   MeSH
• Oligochaeta metabolismus   MeSH
• pesticidy analýza   MeSH
• půda chemie   MeSH
• salát (hlávkový) metabolismus   MeSH
• silany MeSH
• triazoly MeSH
• zemědělství MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• epoxiconazole MeSH Prohlížeč
• epoxidové sloučeniny MeSH
• flusilazole MeSH Prohlížeč
• fungicidy průmyslové MeSH
• jíl MeSH
• látky znečišťující půdu MeSH
• pesticidy MeSH
• půda MeSH
• silany MeSH
• tebuconazole MeSH Prohlížeč
• triazoly MeSH

The objective of this study is to characterize changes in the fate, behaviour and bioavailability of four conazole fungicides - CFs (prochloraz - PRO, tebuconazole - TEB, epoxiconazole - EPO, flusilazole - FLU) in 12 diverse agricultural soils in complex microcosm systems consisting of agriculturally-used fluvisols, plants (Lactuca sativa), earthworms (Eisenia fetida) and passive samplers (SPME, Empore™ discs, silicone rubber). Due to great variability of the data and other methodological problems, the in-matrix passive samplers failed to be indicators of pore-water concentration and (bio)availability/(bio)accessibility of CFs. A dissipation of all CFs followed the first order kinetics (usually after initial lag phase) with large span of resulting half-lives (7-670 d) depending on soils and compounds. In many soils, the model revealed the ending plateau, which indicates the non-degradable or slowly-degradable residues. The half-lives and the residues were generally higher for EPO and FLU, than for PRO and TEB. Greater but slower total dissipation of CFs was observed in soils with higher percentage of organic matter. Earthworm concentrations were highest at first sampling time (14 days) and considerably decreased afterwards often resulting in PRO concentration below LOQ. Earthworm uptake was influenced by amount of organic matter and soil texture. Accumulation to lettuce roots was generally higher than to leaves and differed greatly among CFs. Concentration shoot to root ratios were generally the lowest for FLU (0.04) and highest for TEB (0.37). PRO was not detected in lettuce leaves during experiment. The study brings new results on fate and bioavailability of CFs in soils.

• Klíčová slova
• Bioaccumulation, Conazole fungicides, Degradation, Earthworm, Plant, Soil microcosm,
• MeSH
• biologická dostupnost MeSH
• fungicidy průmyslové analýza   MeSH
• látky znečišťující půdu analýza   MeSH
• Oligochaeta chemie   MeSH
• půda chemie   MeSH
• salát (hlávkový) chemie   MeSH
• triazoly analýza   MeSH
• zemědělství MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fungicidy průmyslové MeSH
• látky znečišťující půdu MeSH
• půda MeSH
• tebuconazole MeSH Prohlížeč
• triazoly MeSH