Distribution Of Microbial Communities Research Articles

New insights into assembly processes and driving factors of urban soil microbial community under environmental stress in Beijing

Rapid urbanization leads to drastic environmental changes, directly or indirectly affecting the structure and function of soil microbial communities. However, the ecological response of soil microbes to environmental stresses has not yet been fully explored. In this study, we used high-throughput sequencing to analyze the assembly mechanism and driving factors of soil microbial community under environmental stresses. The results indicated that environmental stresses significantly affected soil properties and the levels of beryllium, cobalt, antimony, and vanadium contamination in soil generally increased from the suburban areas toward the city core. The composition and distribution of soil microbial communities demonstrated clear differences under different levels of environmental stress, but there was no significant difference in microbial diversity. Random forest and partial least squares structural equation modeling results suggested that multiple factors influenced microbial diversity, but antimony was the key driver. The influence of environmental stress led to deterministic processes dominating microbial community assembly processes, which promoted the regional homogenization of soil microbes. Therefore, this study provides new insights into urban soil microbial management under environmental stresses.

Anthropogenic activity shapes the assemble and co-occurrence pattern of microbial communities in fishing harbors around the Bohai economic circle

This study aimed to elucidate the effects of coastal environmental stress on the composition of sediment bacterial communities and their cooccurrence patterns in fishing harbors around the Bohai Economic Circle, China. Compared with the natural sea area, fishing harbors contained higher levels of organic pollution (organic pollution index = 0.12 ± 0.026) and considerably reduced bacterial richness and evenness. The distributions of sediment microbial communities clustered along the pollutant concentration gradients across fishing harbors. Betaproteobacteria dominated (76%) organically polluted fishing harbors, which were mostly disturbed by anthropogenic activities. However, the harbors also revealed the absence of numerous pathogenic (Coxiella and Legionella) and photosynthetic (Synechococcus and Leptolyngbya) bacteria. Abundant genera, including Thiobacillus and Arenimonas, exhibited a positive correlation with total phosphorus and a negative correlation with total nitrogen in sediments. Meanwhile, Sulfurovum, Psychrobacter, and Woeseia showed the opposite trend. Pollutant accumulation and anthropogenic activities caused the decrease in the sediment microbial diversity and dispersal ability and promoted convergent evolution. Severely polluted harbors with simplified cooccurrence networks revealed the presence of destabilized microbial communities. In addition, the modularity of bacterial networks decreased with organic pollution. Our results provide important insights into the adjustment mechanism of microbial communities to community organization and functions under environmental pollution stress. Overall, this study enhanced our understanding of how microbial communities in coastal sediments adapted and survived amidst anthropogenic activities like oily effluent discharges from large ships, wash water, domestic sewage, garbage, and fisheries wastes. It also examined their resilience to future contamination.

Prokaryotic community structure and key taxa in the Arabian Sea’s oxygen minimum zone

Microbial communities within oxygen minimum zones (OMZs) play crucial roles in the marine biogeochemical cycling. Arabian Sea (AS) has one of the largest OMZs among the global oceans, however, knowledge about the microbial ecology of the AS OMZ remained limited. In the present study, 44 water samples collected from six stations across the AS, spanning from the deep chlorophyll maximum (DCM) layer to 4000m depth were analyzed. High-throughput sequencing of 16S rRNA genes revealed the structural diversity of bacterial and archaeal communities, influenced primarily by depth and dissolved oxygen (DO) levels. Distinct community compositions were observed across different oxygen gradients, with shifts in the relative abundance of key taxa. Notably, Desulfosarcinaceae, UBA10353, Nitrospina, SUP05, Sva0996_marine_group, Microtrichaceae, and Nitrosopumilus emerged as bioindicator taxa in the AS hypoxic zones. Co-occurrence network analysis identified SAR324, Alteromonadaceae, and Sphingomonadaceae as keystone taxa. The spatial and depth-wise distribution patterns revealed that Desulfosarcinaceae was predominantly found in the hypoxic zones of the Arabian Sea, whereas UBA10353, Nitrospina, SUP05, Microtrichaceae and SAR324 were ubiquitous across AS, Bay of Bengal (BOB), and Eastern Tropical North Pacific (ETNP) OMZs, with OTU-level niche differentiation observed for the latter two. Functional profiling using FAPROTAX predicted higher metabolic potential for nitrogen and sulfur in the OMZ compared to other layers of the AS. Our findings provide valuable insights into the distribution, structure, and diversity of microbial communities in the AS OMZ, highlighting the ecological roles of key taxa in hypoxic environments. The established sequence database offers a foundation for further research into the complex interactions within these microbial ecosystems.

Seasonal freeze‒thaw processes impact microbial communities of soil aggregates associated with soil pores on the Qinghai–Tibet Plateau

BackgroundSeasonal freeze‒thaw (FT) processes alter soil formation and cause changes in soil microbial communities, which regulate the decomposition of organic matter in alpine ecosystems. Soil aggregates are basic structural units and play a critical role in microbial habitation. However, the impact of seasonal FT processes on the distribution of microbial communities associated with soil pores in different aggregate fractions under climate change has been overlooked. In this study, we sampled soil aggregates from two typical alpine ecosystems (alpine meadow and alpine shrubland) during the seasonal FT processes (UFP: unstable freezing period, SFP: stable frozen period, UTP: unstable thawing period and STP: stable thawed period). The phospholipid fatty acid (PLFA) method was used to determine the biomass of living microbes in different aggregate fractions.ResultsThe microbial biomass of 0.25–2 mm and 0.053–0.25 mm aggregates did not change significantly during the seasonal FT process while the microbial biomass of > 2 mm aggregates presented a significant difference between the STP and UTP. Bacterial communities dominated the microbes in aggregates, accounting for over 80% of the total PLFAs. The microbial communities of soil aggregates in the surface layer were more sensitive to the seasonal FT process than those in other soil layers. In the thawing period, Gram positive bacteria (GP) was more dominant. In the freezing period, the ratio of Gram-positive to Gram-negative bacterial PLFAs (GP/GN) was low because the enrichment of plant litter facilitated the formation of organic matter. In the freezing process, pores of 30–80 μm (mesopores) favored the habitation of fungal and actinobacterial communities while total PLFAs and bacterial PLFAs were negatively correlated with mesopores in the thawing process.ConclusionsThe freezing process caused a greater variability in microbial biomass of different aggregate fractions. The thawing process increased the differences in microbial biomass among soil horizons. Mesopores of aggregates supported the habitation of actinobacterial and fungal communities while they were not conducive to bacterial growth. These findings provide a further comprehension of biodiversity and accurate estimation of global carbon cycle.

Ubiquitous but unique: Water depth and oceanographic attributes shape methane seep communities

AbstractIn the past decade, thousands of previously unknown methane seeps have been identified on continental margins around the world. As we have come to appreciate methane seep habitats to be abundant components of marine ecosystems, we have also realized they are highly dynamic in nature. With a focus on discrete depth ranges across the Cascadia Margin, we work to further unravel the drivers of seep‐associated microbial community structure. We found highly heterogenous environments, with depth as a deterministic factor in community structure. This was associated with multiple variables that covaried with depth, including surface production, prevailing oxygen minimum zones (OMZs), and geologic and hydrographic context. Development of megafaunal seep communities appeared limited in shallow depth zones (~ 200 m). However, this effect did not extend to the structure or function of microbial communities. Siboglinid tubeworms were restricted to water depths > 1000 m, and we posit this deep distribution is driven by the prevailing OMZ limiting dispersal. Microbial community composition and distribution covaried most significantly with depth, but variables including oxygen concentration, habitat type, and organic matter, as well as iron and methane concentration, also explained the distribution of the microbial seep taxa. While members of the core seep microbiome were seen across sites, there was a high abundance of microbial taxa not previously considered within the seep microbiome as well. Our work highlights the multifaceted aspects that drive community composition beyond localized methane flux and depth, where environmental diversity adds to margin biodiversity in seep systems.

Quantitative effects of anthropogenic and natural factors on the spatial distribution of heavy metals and bacterial communities in sediments of the Pearl River Delta

Heavy metal (HM) contamination of aquatic ecosystems has increasingly posed threats to ecological balance and health. Analysis of sediments to determine water pollution sources is widely reported, while quantitative research about the effects of environmental factors on the distribution of HMs and relevant microbial communities is limited. Here, we investigated 6 kinds of HM pollution characteristics (As, Cd, Cr, Cu, Pb, and Zn) of the Pearl River Delta (PRD) by collecting surface sediment samples around the main stream and estuary and explored the influencing factors with a geographical detector method (GDM). The shifts in the corresponding microbial community was further analyzed, and the influence mechanism was clearly elucidated using partial least squares path modeling (PLS-PM). Results showed that (i) most HM contents of the sediments greatly exceeded the local background values, wherein, Cd had the highest pollution level; (ii) temperature was considered the dominant natural factor of HM distribution, except for Pb, with an influence degree of 0.68–0.97; (iii) industrial activity is an significant anthropogenic factor for HM distribution, and the electroplating industry was the main source for Cr, Cu and Zn; (iv) the network analysis revealed that As, Cu and Cr were enriched in some HM-tolerant bacteria (mainly Chloroflexi, Acidobacteriota and Proteobacteria), while heavy Cd pollution induced a reduction in sensitive bacterial taxa; (v) PLS-PM demonstrated that human activities largely affect bacterial communities by causing HM pollution. This study could provide guidance for better management of HM pollution control practices, such as specific industrial governance and layout optimization.

Salinity shapes vertical distribution of sediment microbial community in Ebinur Lake, China

The microbial communities in saline lakes play important roles in maintaining their unique ecosystems. However, little is known about the vertical distribution of the sediment microbial communities in saline lakes. We therefore studied the vertical distribution of the sediment microbial communities and their relationships with environmental factors in Ebinur Lake, China. Our sediment cores, collected in 2018, were analyzed using Illumina MiSeq sequencing. The results indicated that microbial diversity significantly increased in the sediment core with increasing salinity. At the phylum level, the six most abundant microbes were Proteobacteria, Chloroflexi, Bacteroidetes, Firmicutes, Gemmatimonadetes and Deinococcus-Thermus, accounting for 42.9%, 10.7%, 9.6%, 5.2%, 4.6% and 3.6% of the total reads, respectively; At the genus level, the six most abundant genera were Halothiobacillus, Desulfotignum, Truepera, Salipaludibacillus, Marinobacter and Halomonas, accounting for 15.4%, 4.8%, 3.6%, 2.7%, 2.6% and 2.3% of the total reads respectively. There were significant vertical variations in microbial community composition (MCC) between upper layers and lower layers. Canonical correspondence analysis demonstrated that salinity was the dominant environmental factor affecting the vertical variation of sediment MCC. Thus, this study could greatly improve our understanding of the MCC of saline lakes in the arid and semi-arid ecosystems.

Unveiling the airborne microbial menace: Novel insights into pathogenic bacteria and fungi in bioaerosols from nursery schools to universities

Bacterial and fungal aerosol pollution is widespread in indoor school environments, and poses potential health risks to students and staff. Understanding the distribution and diversity of microbial communities within aerosols is crucial to mitigate their adverse effects. Existing knowledge regarding the composition of bacterial and fungal aerosols, particularly the presence of potential pathogenic microorganisms in fine particulate matter (PM2.5) from nursery schools to universities, is limited. To bridge this knowledge gap, in the present study, we collected PM2.5 samples from five types of schools (i.e., nursery schools, primary schools, junior schools, and high schools and universities) in China. We used advanced single-molecule real-time sequencing to analyze the species-level diversity of bacterial and fungal components in PM2.5 samples based on 16S and ITS ribosomal genes, respectively. We found significant differences in microbial diversity and community composition among the samples obtained from different educational institutions and pollution levels. In particularly, junior schools exhibited higher PM2.5 concentrations (62.2–86.6 μg/m3) than other schools (14.4–48.4 μg/m3). Moreover, microbial variations in PM2.5 samples were associated with institution type. Notably, the prevailing pathogenic microorganisms included Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Streptococcus pneumoniae, and Schizophyllum commune, all of which were identified as Class II Pathogenic Microorganisms in school settings. Four potentially novel strains of S. commune were identified in PM2.5 samples collected from the university; the four strains showed 92.4 %–94.1 % ITS sequence similarity to known Schizophyllum isolates. To the best of our knowledge, this is the first study to explore bacterial and fungal diversity within PM2.5 samples from nursery schools to universities. Overall, these findings contribute to the existing knowledge of school environmental microbiology to ensure the health and safety of students and staff and impacting public health.

Planktonic eukaryotes in the Chesapeake Bay: contrasting responses of abundant and rare taxa to estuarine gradients.

Deep sequencing analysis of planktonic eukaryotes in the Chesapeake Bay reveals high community diversity with many newly recognized phytoplankton taxa. The Chesapeake Bay planktonic eukaryotes show distinct seasonal and spatial variability, with recurring annual patterns of total, abundant, and rare groups. Rare taxa mainly contribute to eukaryotic diversity compared to abundant groups, and they are more sensitive to spatiotemporal variations and environmental filtering. Temporal variations, nutrient availability, and spatial gradients significantly affect the distribution of eukaryotic microbial communities. Similar spatiotemporal patterns in prokaryotes and eukaryotes suggest common mechanisms of adjustment, substitution, and species interactions in planktonic microbiomes under strong estuarine gradients. Interannually recurring patterns demonstrate that diverse eukaryotic taxa have well adapted to the estuarine environment with a long residence time. Further investigations of how human activities impact estuarine planktonic eukaryotes are critical in understanding their essential ecosystem roles and in maintaining environmental safety and public health.

Microbial succession and denitrifying woodchip bioreactor performance at low water temperatures

Mining activities are increasingly recognized for contributing to nitrogen (N) pollution and possibly also to emissions of the greenhouse gas nitrous oxide (N2O) due to undetonated, N-based explosives. A woodchip denitrifying bioreactor, installed to treat nitrate-rich leachate from waste rock dumps in northern Sweden, was monitored for two years to determine the spatial and temporal distribution of microbial communities, including the genetic potential for different N transformation processes, in pore water and woodchips and how this related to reactor N removal capacity. About 80 and 65 % of the nitrate was removed during the first and second operational year, respectively. There was a succession in the microbial community over time and in space along the reactor length in both pore water and woodchips, which was reflected in reactor performance. Nitrate ammonification likely had minimal impact on N removal efficiency due to the low production of ammonium and low abundance of the key gene nrfA in ammonifiers. Nitrite and N2O were formed in the bioreactor and released in the effluent water, although direct N2O emissions from the surface was low. That these unwanted reactive N species were produced at different times and locations in the reactor indicate that the denitrification pathway was temporally as well as spatially separated along the reactor length. We conclude that the succession of microbial communities in woodchip denitrifying bioreactors treating mining water develops slowly at low temperature, which impacts reactor performance.

Taxonomic and functional dynamics of nirS denitrifiers along a salinity gradient in the Pearl River Estuary

Understanding the factors that shape the diversity, distribution, and function of denitrifying microbes is vital for managing nitrogen cycling in these ecosystems. This study explores the diversity, biogeographic distribution, assembly processes, interaction, and denitrification potential of the nirS-encoding microbial community (nirS denitrifier) in the Pearl River Estuary based on high-throughput and metagenomics sequencing dataset. The results of this study show that salinity is a crucial regulatory environmental factor that determines the spatial distribution, phylogenetic turnover, and co-occurrence patterns of nirS denitrifiers. Additionally, the dissolved organic carbon (DOC), suspended sediment concentration (SSC), and dissolved oxygen (DO) in water also significantly impact the biodiversity and abundance of nirS denitrifiers. Furthermore, our findings demonstrate that, in comparison to environmental factors, the ecological and evolutionary characteristics of nirS denitrifiers play a more prominent role in regulating their denitrification potential, suggesting that alterations in the microbial community within dynamic changes in estuarine water can profoundly affect its denitrification function. Our results indicate the significant roles of denitrification microbial structure and phylogenetic characteristics in maintaining their ecological functions. Future studies should continue to explore the interactions between microbial communities and environmental factors to further elucidate the denitrification process in estuaries and its implications for ecosystem health and water quality.

A Comparative Investigation of the Bile Microbiome in Patients with Choledocholithiasis and Cholecystolithiasis through Metagenomic Analysis.

While the precise triggers of gallstone formation remain incompletely understood, it is believed to arise from a complex interplay of genetic and environmental factors. The bile microbiome is being increasingly recognized as a possible contributor to the onset of gallstone disease. The primary objective of this study was to investigate distinctions in the microbial communities within bile specimens from patients with choledocholithiasis (common bile duct stones) and cholecystolithiasis (gallbladder stones). We employed massively parallel sequencing of the 16S rRNA gene to examine the microbial communities within bile samples obtained from 28 patients with choledocholithiasis (group DS) and cholecystolithiasis (group GS). The taxonomic composition of the bile microbial communities displayed significant disparities between the group DS and the group GS. Within the 16 prevalent genera, only Streptococcus, Ralstonia, Lactobacillus, and Enterococcus were predominantly found in the group GS. In contrast, the group DS displayed a more diverse range of genera. The alpha diversity of bile specimens was also notably lower in the group GS compared to the group DS (p = 0.041). Principal coordinate analysis unveiled distinct clustering of bile microbial communities depending on the location of the gallstone. Linear discriminant analysis effect size analysis, with a score threshold of >3 and the Kruskall-Wallis test (α < 0.05), recognized Bacilli and Lactobacillales as potential taxonomic markers for distinguishing patients with cholecystolithiasis limited to the gallbladder. Significant variations were found in the distribution and diversity of bile microbial communities between patients with choledocholithiasis and cholecystolithiasis. This observation suggests that alterations in the bile microbiome may contribute to the development of gallstones in these patients.

Spatiotemporal Dynamics of Assyrtiko Grape Microbiota.

Vitis vinifera, an economically significant grapevine species, is known for wine, juice, and table grape production. The berries of wine grapes host a diverse range of microorganisms influencing both grapevine health and the winemaking process. Indigenous to Greece, the emblematic variety Assyrtiko, renowned for high-quality white wines, originated from Santorini and spread to various Greek regions. Despite existing studies on the microbiota of several varieties, the carposphere microbiota of Assyrtiko grapes remains unexplored. Thus, we conducted a spatiotemporal metagenomic study to identify the epiphytic microbial community composition of Assyrtiko grapes. The study was conducted in two consecutive vintage years (2019 and 2020) across three different and distinct viticulture regions in Greece (Attica, Thessaloniki, Evros). We performed amplicon sequencing, targeting the 16S rRNA gene for bacteria and the ITS region for fungi, with subsequent comprehensive bioinformatic analysis. Our data indicate that the distribution and relative abundance of the epiphytic carposphere microbial communities of the Assyrtiko variety are shaped both by vintage and biogeography.

Sentinel protist taxa of the McMurdo Dry Valley lakes, Antarctica: a review

High-latitude meromictic lakes such as those in the Antarctic McMurdo Dry Valleys (MDV) harbor aquatic ecosystems dominated by the microbial loop. Within this habitat, which is limited year-round by light and nutrients, protists, or single celled eukaryotes, play outsized roles in the food web as the dominant primary producers and the apex predators. Thus, the MDV lake ecosystem represents an ideal system to study the role of sentinel protist taxa in carbon and nutrient cycling. The perennially ice-covered lakes are part of the McMurdo Long Term Ecological Research (McM LTER; mcmlter.org) established in 1993. In this review we will highlight the diversity and trophic roles of the MDV lake protist community and compare environmental factors driving spatiotemporal patterns in key protist taxa in two lakes within the McM LTER, Lakes Bonney and Fryxell. We will then discuss lessons learned from manipulated experiments on the impact of current and future climate-driven environmental change on sensitive protist taxa. Last, we will integrate knowledge gained from 25 years of lab-controlled experiments on key photosynthetic protists to extend our understanding of the function of these extremophiles within the MDV aquatic food webs. Our research group has studied the distribution and function of the MDV microbial community for nearly two decades, training the next generation of scientists to tackle future problems of these globally significant microbes. This review article will also highlight early career scientists who have contributed to this body of work and represent the future of scientific understanding in the Anthropocene.

Shifts in C-degradation genes and microbial metabolic activity with vegetation types affected the surface soil organic carbon pool

The incorporation of plant-derived biomass by microorganisms into deceased microbial biomass, i.e., a “microbial carbon pump”, is essential for forming a soil carbon (C) pool. Therefore, microbial communities and associated functions could shape the formation of soil organic C (SOC) composition and persistence. However, the mechanism by which microorganisms mediate the degradation of various types of biomass (such as plant or microbial) and its impact on SOC formation under different vegetation types remains unclear. Herein, we analyzed microbial communities, carbohydrate-activated enzymes (CAZymes), absolute quantification of C-degradation genes, and extracellular enzyme activities to track microbial-mediated SOC formation under three vegetation types on the Loess Plateau. Changes in vegetation type influenced microbial community structure and distributions of certain bacterial groups. Specifically, dominant bacterial taxa shifted from oligotrophic Actinobacteria to eutrophic Proteobacteria from grass to forest soil. The proportion of microbial CAZymes responsible for decomposing plant-derived components (86–89%) exceeded that of microbial-derived components (11–14%), suggesting a greater capacity for the degradation of deceased plant biomass by microorganisms. There was a reduction of 14%–17% in the absolute abundance of specific C-degradation genes for hemicellulose and cellulose in forest soil compared to grass, while an increase of 20%–32% was observed in lignin and chitin degradation. This indicated a higher decomposition potential of lignin and chitin by microorganisms in forest soil. The number of CAZymes genes involved in the degradation of bacteria-derived biomass (peptidoglycan) was higher than fungi-derived biomass (chitin and glucans) and had a close correlation with the qCO2, microbial biomass C (MBC), and particulate organic C (POC). The abundance of C-degrading genes increased with the increase in the corresponding enzyme activity, indicating that enzyme activity is regulated by functional genes. In conclusion, shifts in CAZymes genes encoding for the degradation of diverse carbon sources could impact microbial metabolic activity through a microbial “carbon pump” regulation process. This mechanism could facilitate the formation of soil organic carbon and its fractions across different vegetation types.

Metal-oxide precipitation influences microbiome structure in hyporheic zones receiving acid rock drainage.

In streams receiving acid-rock and mine drainage, the abundant precipitation of iron minerals can alter how groundwater and surface water mix along streams (in what is known as the "hyporheic zone") and may shape the distribution of microbial communities. The findings presented here suggest that neutral pH streams with large, well-mixed hyporheic zones may harbor and transport diverse microorganisms attached to particles/colloids through hyporheic pore spaces. In acidic streams where metal oxides clog pore spaces and limit hyporheic exchange, iron-oxidizing bacteria may dominate and phylogenetic diversity becomes low. The abundance of iron-oxidizing bacteria in acid mine drainage streams has the potential to contribute to additional clogging of hyporheic pore spaces and the accumulation of toxic metals in the hyporheic zone. This research highlights the dynamic interplay between hydrology, geochemistry, and microbiology at the groundwater-surface water interface of acid mine drainage streams.

Temporal Profile of the Microbial Community and Volatile Compounds in the Third-Round Fermentation of Sauce-Flavor baijiu in the Beijing Region.

Sauce-flavor baijiu produced in the Beijing and Guizhou regions has regional characteristic flavors, but the differences in flavor compounds and reasons for their formation remain unclear. The sauce-flavor baijiu brewing process involves several rounds of fermentation. In this study, we investigated the temporal distribution of microbial communities and flavor substances during the third round of sauce-flavor baijiu fermentation in the Beijing region, and we then compared and analyzed the differences of flavor substances and microorganisms in the fermented grains of sauce-flavor baijiu in the Beijing and Guizhou regions. It was found that 10 bacterial genera and 10 fungal genera were dominant in the fermented grains. The acidity of the fermented grains had a significant driving effect on the microbial community succession. A total of 81 volatile compounds were identified and quantified in the fermented grains, of which esters and alcohols were relatively abundant. The differences in 30 microbial community compositions and their resulting differences in terms of the fermentation parameters of fermented grains are responsible for the differences in the profiles of flavor compounds between sauce-flavor baijiu produced in the Beijing and Guizhou regions.

Extracellular polymeric substances in electroactive biofilms play a crucial role in improving the efficiency of microbial fuel and electrolysis cells.

In microbial electrochemical cells (MECs), electroactive microbial biofilms can transmit electrons from organic molecules to anodes. To further understand the production of anodic biofilms, it is essential to investigate the composition and distribution of extracellular polymeric substance (EPS) in the MECs. In this study, the structure of EPS was examined in microbial electrolysis cells from mixed cultures forming biofilm using carbon fiber fabric anode. EPS was extracted from the anode biofilm of microbial electrolysis cells inoculated with mixed microbial culture. The anode biofilm yielded 0.4mg of EPS, of which 51.2% was humic substance, 16.2% was protein, 12.6% was carbohydrates, and 20% consisted of undetermined substances. Using epifluorescence microscopy, the composition of bacterial cells and their location inside EPS were studied, and the distribution of microbial communities was compared based on current density results in the presence of various carbohydrates. On the electrode surface, bacteria and EPS gathered or overlapped in various locations can affect microbial electrochemical performance. Our findings showed that EPS formation in electroactive biofilms would be important for enhanced efficiency of electricity- or hydrogen-producing microbial electrolysis cells.

Effects of radiofrequency field from 5G communication on fecal microbiome and metabolome profiles in mice

With the rapid development of 5G networks, the influence of the radiofrequency field (RF) generated from 5G communication equipment on human health is drawing increasing attention in public. The study aimed at assessing the effects of long-term exposure to 4.9 GHz (one of the working frequencies of 5G communication) RF field on fecal microbiome and metabolome profiles in adult male C57BL/6 mice. The animals were divided into Sham group and radiofrequency group (RF group). For RF group, the mice were whole body exposed to 4.9 GHz RF field for three weeks, 1 h/d, at average power density (PD) of 50 W/m2. After RF exposure, the mice fecal samples were collected to detect gut microorganisms and metabolites by 16S rRNA gene sequencing and LC–MS method, respectively. The results showed that intestinal microbial compositions were altered in RF group, as evidenced by reduced microbial diversity and changed microbial community distribution. Metabolomics profiling identified 258 significantly differentially abundant metabolites in RF group, 57 of which can be classified to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Besides, functional correlation analysis showed that changes in gut microbiota genera were significantly correlated with changes in fecal metabolites. In summary, the results suggested that altered gut microbiota and metabolic profile are associated with 4.9 GHz radiofrequency exposure.

Spatial variation of oomycetes and bacteria on surfaces, solutions, and plants from a commercial hydroponic greenhouse

The spatial distribution and diversity of plant pathogens and other microbial communities in commercial operations is the first step in identifying critical control points where crops may be at risk of disease. Our objective was to characterize the spatial variation of oomycete pathogens and bacteria across the production system of a greenhouse producing lettuce in hydroponics. We utilized DNA metabarcoding to identify oomycetes and 16S rRNA gene sequencing of bacteria from different production stages and sample types (surfaces, solutions, and roots) collected from a commercial greenhouse producing lettuce in deep-water culture. Pythium was the genus with the highest relative abundance (41 - 100%) across all production stages. Pythium dissotocum was detected in most samples, except for sowing and seeding surfaces and municipal water where Pythium myriotylum was the most abundant species. Oomycete communities showed distinct clustering by production stages and sample types, where sowing and seedling surfaces and municipal water were separated from the rest. Proteobacteria had the highest relative abundance in the surfaces at the sowing (98%) and seeding (85%) stages. Municipal water was the only sample with less than 20% relative abundance of Proteobacteria and dominated by Cyanobacteria. Negative correlations between Pythium and 13 bacteria genera points to potential antagonists in hydroponics that should be further studied. Mapping the spatial variation of oomycetes and bacterial communities in a commercial greenhouse indicates that production stage and sample type influence microbial composition and potentially the risk to disease.