Distribution Of Bacterial Communities Research Articles

Composition and distribution of bacterial communities and potential radiation-resistant bacteria at different elevations in the eastern Pamirs.

Altitude and ultraviolet (UV) radiation may affect the community composition and distribution of microorganisms in soil ecosystems. In this study, 49 soil samples from 10 locations were collected from different elevations on the eastern Pamir Plateau and analyzed for soil microbial community structure and function using high-throughput sequencing. The results showed that soil samples from different elevations of the eastern Pamir Plateau contained 6834 OTUs in 26 phyla and 399 genera. The dominant phyla common to different elevations were Actinobacteria, Proteobacteria, Bacteroidota, Acidobacteriota, and Gemmatimonadota. The dominant genera were Rubrobacter, Sphingomonas, Nocardioides, and Solirubrobacter. Species richness increased slightly with elevation, and there were significant differences in community composition between the elevations. Elevation and UV exposure are important factors that drive changes in bacterial communities. The results of the KEGG pathway showed that drug resistance, antineoplastic, aging, replication, and repair were enhanced and then slightly decreased with increasing elevation. Bacterial communities at different elevations were rich in radiation-resistant microorganisms, and the main genera were Rubrobacter, Sphingomonas, Nocardioides, Pontibacter, and Streptomyces. The findings have shown the composition and distribution of bacterial communities at different elevations on the Eastern Pamir Plateau. Potentially radiation tolerant microbial species were also examined. The results are of considerable importance for the succession of bacterial microorganisms in the plateau region, the study of radiation tolerant bacterial germplasm resources, and the application of biofunctionality.

Association between bacterial community and cadmium distribution across Colombian cacao crops.

Cadmium (Cd) content in cacao crops is an issue that generates interest due to the commercialization of chocolate for human consumption. Several studies provided evidence about the non-biological factors involved in its translocation into the cacao plant. However, factors related to this process, including soil bacterial community composition (SBCC), still need to be addressed. It is well known that soil microbiome could impact compounds' chemical transformation, including Cd, on the field. Here, we found the first evidence of the link between soil bacterial community composition and Cd concentration in cacao soils and seeds. It highlights the importance of including the variation of bacterial communities to assess the factors driving the Cd translocation into cacao seeds. Moreover, the results highlight the relevance of the spatial heterogeneity within and across cacao farms, influencing the variability of Cd concentrations.

Spatial distribution and assembly processes of bacterial communities in riverine and coastal ecosystems of a rapidly urbanizing megacity in China

Rapid urbanization has precipitated significant anthropogenic pollution (nutrients and pathogens) in urban rivers and their receiving systems, which consequentially disrupted the compositions and assembly of bacterial community within these ecosystems. However, there remains scarce information regarding the composition and assembly of both planktonic and benthic bacterial communities as well as pathogen distribution in such environments. In this study, full-length 16S rRNA gene sequencing was conducted to investigate the bacterial community composition, interactions, and assembly processes as well as the distribution of potential pathogens along a riverine-coastal continuum in Shenzhen megacity, China. The results indicated that both riverine and coastal bacterial communities were predominantly composed of Gammaproteobacteria (24.8 ± 12.6 %), Alphaproteobacteria (16.1 ± 9.8 %), and Bacteroidota (14.3 ± 8.6 %), while sedimentary bacterial communities exhibited significantly higher diversity compared to their planktonic counterparts. Bacterial community patterns exhibited significant divergences across different habitats, and a significant distance-decay relationship of bacterial community similarity was particularly observed within the urban river ecosystem. Moreover, the urban river ecosystem displayed a more complex bacterial co-occurrence network than the coastal ecosystem, and a low ratio of negative:positive cohesion suggested the inherent instability of these networks. Homogeneous selection and dispersal limitation emerged as the predominant influences on planktonic and sedimentary bacterial communities, respectively. Pathogenic genera such as Vibrio, Bacteroides, and Acinetobacter, known for their roles in foodborne diseases or wound infection, were also identified. Collectively, these findings provided critical insights into bacterial community dynamics and their implications for ecosystem management and pathogen risk control in riverine and coastal environments impacted by rapid urbanization.

Effect of Mineral Fertilizers and Pesticides Application on Bacterial Community and Antibiotic-Resistance Genes Distribution in Agricultural Soils

Soils are a hotspot for the emergence and spread of antibiotic resistance. The effects of agrochemical treatments on the bacterial community of agricultural soils and the content of antibiotic-resistance genes (ARGs) were studied. Treatments included the following: control, mineral fertilizers (NPKs), pesticides, and the combined treatment of soils under soya (Glycine max), sunflower (Helianthus annuus L.), and wheat (Triticum aestivum). Bacterial community taxonomic composition was studied using 16S rRNA gene sequencing. The content of 10 ARGs and 3 integron genes (intI1, intI2, intI3) was determined using quantitative real-time PCR. The results showed that the treatments had little effect on the taxonomic composition and diversity of the soil bacterial community. The most significant factors determining differences in the microbial community were sampling time and soil physico-chemical parameters. A significant role of the bacterial community in ARG distribution in soils was demonstrated. Representatives of the Pseudomonas, Bacillus, Sphingomonas, Arthrobacter genera, and the Nocardioidaceae and Micrococcaceae families were likely ARG hosts. The presence of integron genes of all three classes was detected, the most numerous being intI3. This work provides important information on the role of agricultural soils in ARG transfer, and the findings may be useful for sustainable and safe agricultural development.

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.

The Impact of Artificial Restoration of Alpine Grasslands in the Qilian Mountains on Vegetation, Soil Bacteria, and Soil Fungal Community Diversity.

To understand how the soil microbial community structure responds to vegetation restoration in alpine mining areas, this study specifically examines the grassland ecosystem in the Qianmalong mining area of the Qilian Mountains after five years of artificial restoration. High-throughput sequencing methods were employed to analyze soil bacteria and fungi microbial characteristics in diverse grassland communities. Combined with modifications in vegetation diversity as well as soil physicochemical properties, the impact of vegetation restoration on soil microbiome diversity in this alpine mining area was investigated. The findings indicated that the dominant plants were Cyperus rotundus, Carex spp., and Elymus nutans. As the extent of the grassland's restoration increased, the number of plant species, importance values, and plant community diversity showed an increasing trend. The plant functional groups were mainly dominated by Cyperaceae, followed by Poaceae. Plant height, density, plant cover, frequency, and aboveground biomass showed an increasing trend, and soil water content (SWC) increased. While soil pH and soil electrical conductivity (EC) exhibited a declining trend, available phosphorus (AP), total phosphorus (TP), total nitrogen (TN), nitrate nitrogen (NO3-N), soil organic carbon (SOC), and soil water content (SWC) showed an increasing trend. The dominant bacterial communities were Actinobacteriota, Proteobacteria, Acidobacteriota, Chloroflexi, Firmicutes, and Gemmatimonadota, while the dominant fungal communities were Ascomycota, Mortierellomycota, Basidiomycota, unclassified_k_Fungi, and Glomeromycota. Significant differences were detected within soil microbial community composition among different degrees of restoration grasslands, with bacteria generally dominating over fungi. SWC, TP, and TN were found to be the main soil physicochemical factors affecting the distribution of soil bacterial communities' structure; however, SOC, TN, and NO3-N were the primary factors influencing the soil distribution of fungal communities. The results of this study indicate that different degrees of vegetation restoration in alpine mining areas can significantly affect soil bacterial and fungal communities, and the degree of restoration has varying effects on the soil bacteria and fungi community structure in alpine mining areas.

Bacterial community analysis of the skin microbiota of cultured Chinese giant salamander infected with Ranavirus.

Skin microorganisms are an important component of host innate immunity and serve as the first line of defense against pathogenic infections. The relative abundance of bacterial species, microbial community assembly, and secretion of specific bacterial metabolites are closely associated with host health. In this study, we investigated the association between the skin microbiome and Ranavirus, and compared the bacterial community assemblage, alpha and beta diversity, and functional predictions of the skin bacterial assemblage in cultured healthy Chinese giant salamanders (Andrias davidianus) and individuals infected with Chinese giant salamander iridovirus (GSIV or ADRV). To achieve this, we employed 16S rRNA amplicon sequencing. The results identified Proteobacteria, Firmicutes, Bacteroidota, and Actinobacteriota as the dominant phyla in the diseased and healthy groups. Alpha diversity analysis indicated that the skin bacterial community in the diseased group exhibited no significant differences in bacterial species diversity and lower species richness compared to the healthy group. Beta diversity suggested that the two group bacterial community was quite different. Kyoto encyclopedia of genes and genomes (KEGG) pathway analyze and clusters of orthologous groups of proteins (COG) function predictions revealed that changes and variations occurred in the metabolic pathways and function distribution of skin bacterial communities in two groups.

Vertical distribution of arsenic and bacterial communities in calcareous farmland amending by organic fertilizer and iron-oxidizing bacteria: Field experiment on concomitant remediation

The migration and transformation mechanisms of arsenic (As) in soil environments necessitate an understanding of its influencing processes. Here, we investigate the subsurface biogeochemical transformation of As and iron (Fe) through amended in the top 20 cm with iron oxidizing bacteria (FeOB) and organic fertilizer (OF). Our comprehensive 400-day field study, conducted in a calcareous soil profile sectioned into 20 cm increments, involved analysis by sequential extraction and assessment of microbial properties. The results reveal that the introduction of additional OF increased the release ratio of As/Fe from the non-specific adsorption fraction (136.47 %) at the subsoil depth (40–60 cm), underscoring the importance of sampling at various depths and time points to accurately elucidate the form, instability, and migration of As within the profile. Examination of bacterial interaction networks indicated a disrupted initial niche in the bottom layer, resulting in a novel cooperative symbiosis. While the addition of FeOB did not lead to the dominance of specific bacterial species, it did enhance the relative abundance of As-tolerant Acidobacteria and Gemmatimonadetes in both surface (39.2 % and 38.76 %) and deeper soils (44.29 % and 23.73 %) compared to the control. Consequently, the amendment of FeOB in conjunction with OF facilitated the formation of poorly amorphous Fe (hydr)oxides in the soil, achieved through abiotic and biotic sequestration processes. Throughout the long-term remediation process, the migration coefficient of bioavailable As within the soil profile decreased, indicating that these practices did not exacerbate As mobilization. This study carries significant implications for enhancing biogeochemical cycling in As-contaminated Sierozem soils and exploring potential bioremediation strategies. Environmental implicationThe long-term exposure of sewage irrigation has potential adverse effects on the local ecosystem, causing serious environmental problems. Microorganisms play a vital role in the migration and transformation of arsenic in calcareous soil in arid areas, which highlights the necessity of understanding its dynamics. The vertical distribution, microbial community and fate of arsenic in calcareous farmland soil profile in northwest China were studied through field experiments. The results of this work have certain significance for the remediation of arsenic-contaminated soil in arid areas, and provide new insights for the migration, transformation and remediation of arsenic in this kind of soil.

Fungal community shows more variations by season and particle size than bacteria

The global concern regarding the health risk associated with airborne microorganisms has prompted research in this field. However, there is a lack of systematic investigation into the particle-size distribution of airborne bacterial and fungal communities associated with seasons, which determines where they are deposited in the human respiratory tract. To address this gap, we conducted a study in Nanchang, located in central China, where we collected both coarse and fine particles during summer and winter seasons. The results demonstrated that microbial community exhibited obvious seasonal and particle-size variations except bacterial community in fine particles. Certain taxa (e.g., Bacteroidales, Ktedonobacterales, Capnodiales) displayed either seasonal and/or particle-size preferences. Furthermore, airborne microorganisms in coarse particles were more sensitive to season and particle size compared to those in fine particles, with fungal community being more susceptible than bacterial community. The susceptibility can be attributed to their high vulnerability to air pollutants and meteorological conditions, primarily PM2.5 and PM10. Additionally, a greater relative abundance of pathogenic fungi was observed in fine particles, even though microbial diversity in coarse particles was noticeably higher than that in fine particles. Furthermore, some predominant pathogens such as Alternaria, Nigrospora, and Escherichia-Shigella not only had particle size and/or seasonal preferences, but also were strongly correlated with environmental factors. This study advances our understanding of atmospheric pathogenic microorganisms and highlights the fungal health threat.

Dissolved carbohydrates and its influence on bacterioplankton diversity in the euphotic zone of Equatorial Indian Ocean during southwest monsoon

The Equatorial Indian Ocean (EIO) is oligotrophic in nature, low in productivity and characterised by relatively high bacterial biomass and heterotrophic productivity. The microbial biomass is fuelled by dissolved organic carbon (DOC) whose lability depends upon its chemistry. During an expedition in the EIO, samples for dissolved carbohydrates (DCHO), dissolved monosaccharide (MCHO), dissolved polysaccharide (PCHO), total bacterial abundance, total organic carbon (TOC), nutrients, chlorophyll a (chl a), bacterial diversity, and phytoplankton composition were estimated along two transects (TS-1 & TS-2) in the euphotic depth (200 m). DCHO and MCHO samples were analysed using 3-methyl-2-benzothiozolinone hydrazone hydrochloride (MBTH) method. The DCHO, MCHO, and PCHO concentrations in TS-1 ranged from 2.4 to 5.8 μM; 0.7 to 2.7 μM; 0.7 to 3.4 μM, while in TS-2 it ranged from 2.2 to 4.8 μM; 0.3 to 2.8 μM; 0.2 to 3.8 μM, respectively. Vertically, DCHO concentrations decreased within the photic depths in most stations. PCHO concentrations were relatively greater in TS-2 than TS-1, which may be due to preferential removal of MCHO in TS-2. In the top 200 m of the water column, Proteobacteria was the most abundant bacterial phylum followed by Cyanobacteria, Actinobacteriota, Bacteroidota, and SAR-324 while dinoflagellates dominated the phytoplankton population. The distribution of DCHO and PCHO were inversely correlated to salinity, temperature, and chl a. The bacterial heterotrophs like alpha-Proteobacteria, Chloroflexii, and Verrumicrobiota along with SAR324 and Actinobacteriota were clustered with nutrients, while Bdellovibriota and Dadabacteria clustered with MCHO, PCHO, and DCHO. These results highlight the impact of DCHO & PCHO lability on the distribution of bacterial community and delineate oceanographic factors that regulate the distribution of DCHO and its constituents in EIO waters.

Drivers and human impacts on topsoil bacterial and fungal community biogeography across Australia.

Soil microbial diversity mediates a wide range of key processes and ecosystem services influencing planetary health. Our knowledge of microbial biogeography patterns, spatial drivers and human impacts at the continental scale remains limited. Here, we reveal the drivers of bacterial and fungal community distribution in Australian topsoils using 1384 soil samples from diverse bioregions. Our findings highlight that climate factors, particularly precipitation and temperature, along with soil properties, are the primary drivers of topsoil microbial biogeography. Using random forest machine-learning models, we generated high-resolution maps of soil bacteria and fungi across continental Australia. The maps revealed microbial hotspots, for example, the eastern coast, southeastern coast, and westcoast were dominated by Proteobacteria and Acidobacteria. Fungal distribution is strongly influenced by precipitation, with Ascomycota dominating the central region. This study also demonstrated the impact of human modification on the underground microbial community at the continental scale, which significantly increased the relative abundance of Proteobacteria and Ascomycota, but decreased Chloroflexi and Basidiomycota. The variations in microbial phyla could be attributed to distinct responses to altered environmental factors after human modifications. This study provides insights into the biogeography of soil microbiota, valuable for regional soil biodiversity assessments and monitoring microbial responses to global changes.

Geographic distribution of bacterial communities of inland waters in China

Microorganisms are integral to freshwater ecological functions and, reciprocally, their activity and diversity are shaped by the ecosystem state. Yet, the diversity of bacterial community and its driving factors at a large scale remain elusive. To bridge this knowledge gap, we delved into an analysis of 16S RNA gene sequences extracted from 929 water samples across China. Our analyses revealed that inland water bacterial communities showed a weak latitudinal diversity gradient. We found 530 bacterial genera with high relative abundance of hgcI clade. Among them, 29 core bacterial genera were identified, that is strongly linked to mean annual temperature and nutrient loadings. We also detected a non-linear response of bacterial network complexity to the increasing of human pressure. Mantel analysis suggested that MAT, HPI and P loading were the major factors driving bacterial communities in inland waters. The map of taxa abundance showed that the abundant CL500-29 marine group in eastern and southern China indicated high eutrophication risk. Our findings enhance our understanding of the diversity and large-scale biogeographic pattern of bacterial communities of inland waters and have important implications for microbial ecology.

Differences of bacterioplankton communities between the source and upstream regions of the Yangtze River: microbial structure, co-occurrence pattern, and environmental influencing factors.

The source area of the Yangtze River is located in the hinterland of the Qinghai-Tibet Plateau, which is known as the "Earth's third pole." It is the water conservation area and the natural barrier of the ecosystem of the Yangtze River basin. It is also the most sensitive area of the natural ecosystem, and the ecological environment is very fragile. Microorganisms play key roles in the biogeochemical processes of water. In this paper, the bacterioplankton communities in the source and upstream regions of the Yangtze River were studied based on 16S rRNA high-throughput sequencing, and their environmental influencing factors were further analyzed. Results showed that the upstream region had higher richness and diversity than the source region. The predominant bacterial phyla in the source and upstream regions were Proteobacteria, Firmicutes, and Actinobacteriota. The bacterial phyla associated with municipal pollution and opportunistic pathogen, such as Firmicutes and Actinobacteriota, were more abundant in the upstream. By contrast, distinct planktonic bacterial genera associated with mining pollution, such as Acidiphilium and Acidithiobacillus, were more abundant in the source region. The co-occurrence network showed that the interaction of bacterioplankton community is more frequent in the upstream. The bacterioplankton community compositions, richness, and functional profiles were affected by the spatial heterogeneity. Moreover, variation partitioning analysis further confirmed that the amount of variation in the source region independently explained by variables of altitude was the largest, followed by water nutrient. This paper revealed the spatial distribution of planktonic bacterial communities in the source and upstream regions of the Yangtze River and its correlation with environmental factors, providing information support for ensuring the health and safety of aquatic ecosystems in the Yangtze River Basin.

Bacterial community distribution and functional potentials provide key insights into their role in the ecosystem functioning of a retreating Eastern Himalayan glacier.

Himalayan glaciers are receding at an exceptional rate, perturbing the local biome and ecosystem processes. Understanding the microbial ecology of an exclusively microbe-driven biome provides insights into their contributions to the ecosystem functioning through biogeochemical fluxes. Here, we investigated the bacterial communities and their functional potential in the retreating East Rathong Glacier (ERG) of Sikkim Himalaya. Amplicon-based taxonomic classification revealed the dominance of the phyla Proteobacteria, Bacteroidota, and candidate Patescibacteria in the glacial sites. Further, eight good-quality metagenome-assembled genomes (MAGs) of Proteobacteria, Patescibacteria, Acidobacteriota, and Choloflexota retrieved from the metagenomes elucidated the microbial contributions to nutrient cycling. The ERG MAGs showed aerobic respiration as a primary metabolic feature, accompanied by carbon fixation and complex carbon degradation potentials. Pathways for nitrogen metabolism, chiefly dissimilatory nitrate reduction and denitrification, and a complete sulphur oxidation enzyme complex for sulphur metabolism were identified in the MAGs. We observed that DNA repair and oxidative stress response genes complemented with osmotic and periplasmic stress and protein chaperones were vital for adaptation against the intense radiation and stress conditions of the extreme Himalayan niche. Current findings elucidate the microbiome and associated functional potentials of a vulnerable glacier, emphasizing their significant ecological roles in a changing glacial ecosystem.

Distribution pattern and influencing factors of bacterial communities in different soil depths of Caragana jubata shurb in Luya Mountain, China.

Soil microorganisms are important components of terrestrial ecosystems, affecting soil formation and fertility, plant growth and stress tolerance, nutrient turnover and carbon storage. In this study, we collected soil samples (humus layer, 0-10 cm, 10-20 cm, 20-40 cm, and 40-80 cm) from Caragana jubata shrubland in Shanxi subalpine to explore the composition, diversity, and assembly of soil bacterial communities at different depths across the soil profile. The results showed that Actinomycota (19%-28%), Chloromycota (10%-36%) and Acidobacteria (15%-24%), and Proteobacteria (9%-25%) were the dominant bacterial phyla. α-diversity of soil bacterial community significantly decreased with the increases of soil depth. Soil bacterial β-diversity varied across different soil depths. Soil pH, water content, and enzyme activity were the main ecological factors affecting the distribution of soil bacterial communities. Soil bacterial communities had more complex interactions in humus layer and 0-10 cm layer. On the whole, soil bacterial communities were dominated by coexistence in C. jubata shrubland, and the soil bacterial community assembly was driven by random process.

Impacts of polypropylene microplastics on the distribution of cadmium, enzyme activities, and bacterial community in black soil at the aggregate level

Microplastics (MPs) can co-occur widely with heavy metals in soil. This study intended to investigate the influences of the co-exposure of polyethylene MPs (0.5 %, w/w) and cadmium (Cd) in black soil on the Cd distribution, enzyme activities, and bacterial communities in both bulk soil and different sized soil aggregates (> 1, 0.50–1, 0.25–0.50, and < 0.25 mm aggregates) after a 90-day incubation. Our results showed that the existence of MPs increased the distributions of Cd in >1 mm and < 0.25 mm soil aggregates and decreased its distributions in 0.50–1 mm and 0.25–0.50 mm soil aggregates. About 12.15 %–17.65 % and 9.03 %–11.13 % of Cd were distributed in the exchangeable and oxidizable forms in bulk soil and various sized soil aggregates after the addition of MPs which were higher than those in the only Cd-treated soil (11.17 %–14.72 % and 8.66 %–10.43 %, respectively), while opposite tendency was found for Cd in the reducible form. Urease and β-glucosidase activities in the Cd-treated soils were 1.14–1.18 and 1.07–1.31 times higher than those in the Cd-MPs treated soils. MPs disturbed soil bacterial community at phylum level and increased the bacteria richness in bulk soil. The levels of predicted functional genes which are linked to the biodegradation and metabolism of exogenous substances and soil C and N cycles were altered by the co-exposure of Cd and MPs. The findings of this study could help deepen our knowledge about the responses of soil properties, especially microbial community, to the co-occurrence of MPs and heavy metals in soil.

The impact of mariculture biofilters on the distribution of benthic nutrient fluxes, organic matters and bacterial community in a mariculture wastewater treatment system

Constructed-wetlands, biofilms, and sedimentation are among biological filters used in mariculture wastewater treatments, however, their impacts on the distribution of benthic microbial community and inorganic-nutrient fluxes have not been fully explored. This study applied 16 S rRNA high-throughput sequencing technology to investigate the microbial community distribution and their impacts on nutrient fluxes in mariculture biofilters system. Results showed that bacterial community compositions were significantly different in the constructed-wetland and biofilm treatments (p < 0.05) relative to sedimentation. The composition of the 16 S rRNA genes among the treatments were enriched with Proteobacteria (73%), Bacteroidetes (69%), Firmicutes (62%), and Flavobacteria (61%) in Biofilm compared to Proteobacteria (53%), Bacteroidetes (39%), Firmicutes (32%), and Flavobacteria (21%) in constructed wetlands. NMDS analysis showed that bacterial composition in constructed-wetland and biofilms clustered separately compared to sedimentation treatment. Functional-Annotation-of-Prokaryotic-Taxa analysis indicated that the proportions of sediment-microbial-functional groups (aerobic-chemoheterotrophy, chemoheterotrophy, and nitrate-ammonification) were 47% in the constructed-wetland, 32% in biofilm and 13% in sedimentation system. Benthic-nutrient fluxes for phosphate, ammonium, nitrite, nitrate and sediment oxygen consumption differed markedly among the treatments (p < 0.05). Canonical correspondence analysis indicated constructed-wetland had the strongest association between biogeochemical contents and the bacterial community relative to other treatments. This study suggests that the mariculture wastewater biofilters promoted microbial community distributions, sediment bacterial functional-groups including chemoheterotrophy, aerobic-chemoheterotrophy, denitrification, and nitrification and interactions with nutrient fluxes which was more pronounced in the constructed-wetland system.

Prevalence of Escherichia coli in electrogenic biofilm on activated carbon in microbial fuel cell.

For a better understanding of the distribution of depth-dependent electrochemically active bacteria at in the anode zone, a customized system in a microbial fuel cell (MFC) packed with granular activated carbon (GAC) was developed and subsequently optimized via electrochemical tests. The constructed MFC system was sequentially operated using two types of matrice solutions: artificially controlled compositions (i.e., artificial wastewater, AW) and solutions obtained directly from actual sewage-treating municipal plants (i.e., municipal wastewater, MW). Notably, significant difference(s) of system efficiencies between AW or MW matrices were observed via performance tests, in that the electricity production capacity under MW matrices is < 25% that of the AW matrices. Interestingly, species of Escherichia coli (E. coli) sampled from the GAC bed (P1: deeper region in GAC bed, P2: shallow region of GAC near electrolytes) exhibited an average relative abundance of 75 to 90% in AW and a relative abundance of approximately 10% in MW, while a lower relative abundance of E. coli was found in both the AW and MW anolyte samples (L). Moreover, similar bacterial communities were identified in samples P1 and P2 for both the AW and MW solutions, indicating a comparable distribution of bacterial communities over the anode area. These results provide new insights into E. coli contribution in power production for the GAC-packed MFC systems (i.e., despite the low contents of Geobacter (> 8%) and Shewanella (> 1%)) for future applications in sustainable energy research. KEY POINTS: • A microbial community analysis for depth-dependence in biofilm was developed. • The system was operated with two matrices; electrochemical performance was assessed. • E. coli spp. was distinctly found in anode zone layers composed of activated carbon.

Deciphering the spatial distribution and function profiles of soil bacterial community in Liao River estuarine wetland, Northeast China

Soil microbes play vital roles in estuarine wetlands. Understanding the soil bacterial community structure and function profiles is essential to reveal the ecological functions of microbes in estuarine wetlands. Herein, soil samples were collected from Liao River estuarine wetland, Northeast China, along the river to the estuarine mouth, and soil bacterial communities were explored. Results showed that soil physiochemical properties, bacterial community structure and functions exhibited distinct variations influenced by geographical location. Bacterial phyla in soils were dominated by Proteobacteria and Bacteroidetes, while Gillisia and Woeseia were the predominant genera. Soil pH, electrical conductivity and nitrogen-related nutrients were the important factors affecting bacterial community structure. Based on PICRUSt prediction, the genes related to metabolism of nitrogen, sulfur and methane showed spatial distribution patterns, and the abundances of most biomarker genes increased as the distance from estuarine mouth extended. These findings could enrich the understanding of soil microbiome in estuarine wetlands.

Effects of Cascade Reservoirs on Spatiotemporal Dynamics of the Sedimentary Bacterial Community: Co-occurrence Patterns, Assembly Mechanisms, and Potential Functions.

Dam construction as an important anthropogenic activity significantly influences ecological processes in altered freshwater bodies. However, the effects of multiple cascade dams on microbial communities have been largely overlooked. In this study, the spatiotemporal distribution, co-occurrence relationships, assembly mechanisms, and functional profiles of sedimentary bacterial communities were systematically investigated in 12 cascade reservoirs across two typical karst basins in southwest China over four seasons. A significant spatiotemporal heterogeneity was observed in bacterial abundance and diversity. Co-occurrence patterns in the Wujiang Basin exhibited greater edge counts, graph density, average degree, robustness, and reduced modularity, suggesting more intimate and stronger ecological interactions among species than in the Pearl River Basin. Furthermore, Armatimonadota and Desulfobacterota, identified as keystone species, occupied a more prominent niche than the dominant species. A notable distance-decay relationship between geographical distance and community dissimilarities was identified in the Pearl River Basin. Importantly, in the Wujiang Basin, water temperature emerged as the primary seasonal variable steering the deterministic process of bacterial communities, whereas 58.5% of the explained community variance in the neutral community model (NCM) indicated that stochastic processes governed community assembly in the Pearl River Basin. Additionally, principal component analysis (PCA) revealed more pronounced seasonal dynamics in nitrogen functional compositions than spatial variation in the Wujiang Basin. Redundancy analysis (RDA) results indicated that in the Wujiang Basin, environmental factors and in Pearl River Basin, geographical distance, reservoir age, and hydraulic retention time (HRT), respectively, influenced the abundance of nitrogen-related genes. Notably, these findings offer novel insights: building multiple cascade reservoirs could lead to a cascading decrease in biodiversity and resilience in the river-reservoir ecosystem.