Intensive shrimp aquaculture has led to the excessive accumulation of nitrite, resulting in shrimp mortality and posing a widespread challenge to aquaculture systems. In this study, we analyzed the gut bacterial communities of shrimp that either survived or died after exposure to a semi-lethal concentration of nitrite for 72 h. We isolated 17 bacterial strains to construct a potential endogenous probiotic consortium, which significantly enhanced shrimp survival under acute nitrite stress. Colonization experiments revealed that three of these strains successfully colonized the shrimp gut. Strain LvS229, belonging to the genus Tenacibaculum, emerged as a key member of the consortium, exhibiting a distinct colonization advantage. Pre-treatment with LvS229 conferred sustained protection, significantly enhancing shrimp survival rates under nitrite challenge and highlighting its pivotal role in EnPB-mediated tolerance. Mechanistically, genomic and metabolism assays revealed its possession of functional nitrite-reductase genes, enabling the reduction of ambient nitrite. By alleviating oxidative stress and boosting immune and antioxidant enzyme activities, LvS229 transplantation effectively promoted host resilience. Collectively, these findings provide novel insights and a promising probiotic strategy for mitigating environmental stress in shrimp aquaculture.

Urbanization exerts profound impacts on freshwater ecosystems including rivers, triggering shifts in plankton communities, yet long-term data remain scarce. Therefore, we present an extensive 11-year dataset (2012-2022) spanning a distinct rural-to-urban gradient within the Houxi River watershed in subtropical China. Our systematic sampling characterized multiple plankton communities: phytoplankton were analyzed bi-annually (summer and winter) via microscopy, while bacterioplankton and eukaryotic plankton were investigated seasonally through amplicon sequencing of the 16S rRNA gene (V3-V4) and 18S rRNA gene (V9) regions, respectively. Concurrently collected water quality and nutrient data provide comprehensive environmental context. The BEPE (Bacterioplankton, Eukaryotic plankton, Phytoplankton and Environmental variables) dataset reveals distinct trends across space and time, enhancing our understanding of the impacts of urbanization and land use on river-reservoir ecosystems, particularly plankton communities and serves as a valuable foundation for future ecological conservation and restoration efforts.

The gut virome plays a pivotal role in shaping the host’s microbiota. However, gut viruses across different mammalian models, and their connections with the human gut microbiota remain largely unknown. Here, we identified 977 high-confidence species-level viral operational taxonomic units (vOTUs) in mice (hcMGV), 12896 in pigs (hcPGV), and 1480 in cynomolgus macaques (hcCMGV) from metagenomes, respectively. Clustering these vOTUs at approximately genus level uncovered novel clades with high prevalence across animal guts (>=30%). In particular, crAss-like phages and cas-harboring jumbo phages were characterized. Comparative analysis revealed that hcCMGV had a closer relationship with hcPGV than hcMGV, despite the animal-specific characteristics, and that 55.88% hcCMGV had connections with the human microbiota. Viral functional analysis indicated a low risk in disseminating antibiotic and virulent genes. In summary, our findings shed light on the diversity of gut viruses across these three animals, contributing to future gut microbial studies using model animals.

Pathogenic bacteria like Vibrio have been suggested to be the causative factor of scallop mortality, yet specific bacterial groups and the related mechanisms that cause high scallop mortality in their aquaculture environment remain unclear. To address this research gap, Zhikong scallops were collected during a mass mortality event in which the death rate was nearly 70 %. Transmission electron microscopy showed an extensive presence of bacteria in both the gills and guts of the moribund scallops. Subsequent analysis using 16S rRNA gene amplicon sequencing revealed a significant reduction in gut microbiota diversity and a shift in its composition among moribund individuals. A specific Vibrio group, designated ASV00009, was found to have proliferated extensively in the gut microbiota of moribund scallops. Genomic comparison between ASV00009 with other Vibrio groups revealed that the ASV00009 group may have developed unique survival strategies during the invasion process, including antibiotic resistance, as well as the absorption and utilization of arginine, phosphate, zinc, and magnesium. We propose that the proliferation of pathogenic bacteria in gut environments, in particular the Vibrio ASV00009 group, is accountable for the mortality observed in Zhikong scallops. These findings provide a groundwork for developing strategies against large-scale scallop mortalities.

Nitrite exposure has become a significant concern in the aquaculture industry, posing a severe threat to aquatic animals such as shrimp. While studies have reported the adverse effects of nitrite on shrimp growth, the part played by the gut microbiota in shrimp mortality resulting from nitrite exposure is poorly understood. Here, the effects of nitrite on shrimp gut bacterial community were investigated using 16S rRNA amplicon sequencing, bacterial isolation, genomic analysis, and infection experiments. Compared to the control_healthy group, changes in the bacterial composition of the nitrite_dead group were associated with reduced abundance of specific beneficial bacteria and increased abundance of certain pathogenic bacteria. Notably, members of the Photobacterium genus were found to be significantly enriched in the nitrite_dead group. Genomic analysis of a representative Photobacterium strain (LvS-8n3) revealed a variety of genes encoding bacterial toxins, including hemolysin, adhesin, and phospholipase. Furthermore, it was also found that LvS-8n3 exhibits strong pathogenicity, probably due to its high production of pathogenic factors and the ability to utilize nitrite for proliferation. Therefore, the proliferation of pathogenic Photobacterium species appears pivotal for driving shrimp mortality caused by nitrite exposure. These findings provide novel insights into the disease mechanism in shrimp under conditions of environmental change.

Acute ammonia exposure has detrimental effects on shrimp, but the underlying mechanisms remain to be fully explored. In the present study, we investigated the impact of acute ammonia exposure on the gut microbiota of the white shrimp Litopenaeus vannamei and its association with shrimp mortality. Exposure to a lethal concentration of ammonia for 48 h resulted in increased mortality in L. vannamei, with severe damage to the hepatopancreas. Ammonia exposure led to a significant decrease in gut microbial diversity, along with the loss of beneficial bacterial taxa and the proliferation of pathogenic Vibrio strains. A phenotypic analysis revealed a transition from the dominance of aerobic to facultative anaerobic strains due to ammonia exposure. A functional analysis revealed that ammonia exposure led to an enrichment of genes related to biofilm formation, host colonization, and virulence pathogenicity. A species-level analysis and experiments suggest the key role of a Vibrio harveyi strain in causing shrimp disease and specificity under distinct environments. These findings provide new information on the mechanism of shrimp disease under environmental changes.

Microbial lysis of dimethylsulfoniopropionate (DMSP) is a key step in marine organic sulfur cycling and has been recently demonstrated to play an important role in mediating interactions between bacteria, algae, and zooplankton. To date, microbes that have been found to lyse DMSP are largely confined to free-living and surface-attached bacteria. In this study, we report for the first time that a symbiont (termed "Rhodobiaceae bacterium HWgs001") in the gill of the marine scallop Argopecten irradians irradians can lyse and metabolize DMSP. Analysis of 16S rRNA gene sequences suggested that HWgs001 accounted for up to 93% of the gill microbiota. Microscopic observations suggested that HWgs001 lived within the gill tissue. Unlike symbionts of other bivalves, HWgs001 belongs to Alphaproteobacteria rather than Gammaproteobacteria, and no genes for carbon fixation were identified in its small genome. Moreover, HWgs001 was found to possess a dddP gene, responsible for the lysis of DMSP to acrylate. The enzymatic activity of dddP was confirmed using the heterologous expression, and in situ transcription of the gene in scallop gill tissues was demonstrated using reverse-transcription PCR. Together, these results revealed a taxonomically and functionally unique symbiont, which represents the first-documented DMSP-metabolizing symbiont likely to play significant roles in coastal marine ecosystems.

Thiosulfate oxidation by microbes has a major impact on global sulfur cycling. Here, we provide evidence that bacteria within various Roseobacter lineages are important for thiosulfate oxidation in marine biofilms. We isolate and sequence the genomes of 54 biofilm-associated Roseobacter strains, finding conserved sox gene clusters for thiosulfate oxidation and plasmids, pointing to a niche-specific lifestyle. Analysis of global ocean metagenomic data suggests that Roseobacter strains are abundant in biofilms and mats on various substrates, including stones, artificial surfaces, plant roots, and hydrothermal vent chimneys. Metatranscriptomic analysis indicates that the majority of active sox genes in biofilms belong to Roseobacter strains. Furthermore, we show that Roseobacter strains can grow and oxidize thiosulfate to sulfate under both aerobic and anaerobic conditions. Transcriptomic and membrane proteomic analyses of biofilms formed by a representative strain indicate that thiosulfate induces sox gene expression and alterations in cell membrane protein composition, and promotes biofilm formation and anaerobic respiration. We propose that bacteria of the Roseobacter group are major thiosulfate-oxidizers in marine biofilms, where anaerobic thiosulfate metabolism is preferred.

The database contained annotated nucleotide sequences (FASTA + GFF), archaeal viral hallmark genes, accompanied with a metadata file (Table S6) describing the origin of each contig, taxonomy, including VC, host prediction information, completeness score etc.

Longitudinal environmental heterogeneity and directionality of the water movement are key features that may exert contrasting forces on riverine plankton assembly. Directionality strengthens dispersal-driven assembly, but this can be masked by urbanization-induced environmental heterogeneity along the river continuum. In the light of this contrast, we aimed at delineating the relative importance of assembly processes generating distribution patterns of bacterioplankton and phytoplankton communities in a river draining an urbanizing watershed in Southeast China. We applied variation partitioning analysis, neutral community model, and quantitative process estimate on molecular and morphological plankton data obtained over the years 2012-2016. Despite a relatively short distance between sampling sites (< 20 km), plankton community similarity decreased with increasing distance from the upstream pristine site toward the downstream urban area, and formed clusters that roughly corresponded to five habitat patches, predefined based on hydrology and longitudinal landscape change. These distribution patterns were predominantly driven by deterministic and stochastic processes for phytoplankton and bacterioplankton, respectively, indicating a balance between dispersal due to fluvial connectivity and local selective pressures. Considering the global loss of river connectivity due to downstream fragmentation and flow regulation, our findings imply that plankton-based ecological approaches could be useful to hedge against an uncertain future of rivers draining urbanizing watersheds in an ecologically sustainable way.

The human gut microbiome has been extensively explored, while the archaeal viruses remain largely unknown. Here, we present a comprehensive analysis of the archaeal viruses from the human gut metagenomes and the existing virus collections using the CRISPR spacer and viral signature-based approach. This results in 1279 viral species, of which, 95.2% infect Methanobrevibacteria_A, 56.5% shared high identity (> 95%) with the archaeal proviruses, 37.2% have a host range across archaeal species, and 55.7% are highly prevalent in the human population (> 1%). A methanogenic archaeal virus-specific gene for pseudomurein endoisopeptidase (PeiW) frequently occurs in the viral sequences (n = 150). Analysis of 33 Caudoviricetes viruses with a complete genome often discovers the genes (integrase, n = 29; mazE, n = 10) regulating the viral lysogenic-lytic cycle, implying the dominance of temperate viruses in the archaeal virome. Together, our work uncovers the unexplored diversity of archaeal viruses, revealing the novel facet of the human gut microbiome.

Although the occurrence and distribution of antibiotic resistance genes (ARGs) in various aquatic ecosystems are well explored, understanding of the ecological processes and mechanisms governing the composition and dynamics of bacterial ARGs still remains limited across space and time. Here, we used high-throughput approaches to detect spatial patterns of bacterial ARGs and operational taxonomic units (OTUs) in an urbanizing subtropical watershed, Xiamen, southeast China over a five-year period. At watershed scale, the OTU profiles were undergoing a directional change, but the ARG profiles showed a high stability or stochastic change over time. Compared with the upstream and midstream, the richness, absolute abundance, normalized abundance and diversity of ARGs were significantly higher in the downstream waters. Our results revealed a clear rural-urban disparity in ARG and OTU profiles which were mainly governed by deterministic and stochastic assembly processes, respectively. With the increase of urban building area along the river, the ecological processes of ARG profiles shifted from stochastic to deterministic. In downstream waters, the bacterial ARG profiles were much more stable than bacterial OTUs. Further, our results indicated that both human-dominated environment (e.g., land use) and mobile genetic elements (MGEs) played an important role in shaping the ARG profiles and dynamics. Overall, this was a response to spatially extensive human-landscape interactions that included urban development in the river downstream region, which were common across subtropical coastal cities of China and can alter the ARG profile dynamics along rural-urban gradient. Therefore, watershed management actions aiming at reducing threats posed by ARGs in urbanizing watershed should first consider the surrounding urbanization level and the mode and intensity of human activity. Our findings also imply that due to the decoupling of bacterial function and taxonomy, both aspects should be studied separately.

River-bay system is a transitional zone connecting land and ocean and an important natural source for methane emission. Methanogens play important roles in the global greenhouse gas budget and carbon cycle since they produce methane. The abundance and community assemblage of methanogens in such a dynamic system are not well understood. Here, we used quantitative PCR and high-throughput sequencing of the mcrA gene to investigate the abundance and community composition of methanogens in the Shenzhen River-Bay system, a typical subtropical river-bay system in Southern of China, during the wet and dry seasons. Results showed that mcrA gene abundance was significantly higher in the sediments of river than those of estuary, and was higher in wet season than dry season. Sequences of mcrA gene were mostly assigned to three orders, including Methanosarcinales, Methanomicrobiales, and Methanobacteriales. Specifically, Methanosarcina, Methanosaeta, and Methanobacterium were the most abundant and ubiquitous genera. Methanogenic communities generally clustered according to habitat (river vs. estuary), and salinity was the major factor driving the methanogenic community assemblage. Furthermore, the indicator groups for two habitats were identified. For example, Methanococcoides, Methanoculleus, and Methanogenium preferentially existed in estuarine sediments, whereas Methanomethylovorans, Methanolinea, Methanoregula, and Methanomassiliicoccales were more abundant in riverine sediments, indicating distinct ecological niches. Overall, these findings reveal the distribution patterns of methanogens and expand our understanding of methanogenic community assemblage in the river-bay system. Key Points • Abundance of methanogens was relatively higher in riverine sediments. • Methanogenic community in estuarine habitat separated from that in riverine habitat. • Salinity played a vital role in regulating methanogenic community assemblage.

Free‐living and particle‐associated microbial communities play critical roles in nutrient cycles in aquatic systems. However, little is known about their assembly process, function, and interactions. Here, by using 16S rRNA gene amplicon sequencing of size‐fractionated samples collected during the wet and dry seasons, we investigated the assembly processes and co‐occurrence patterns of bacterial and archaeal communities in the Shenzhen River‐Bay system, South China. The bacterial and archaeal communities showed specific distribution patterns according to the size fraction (free‐living vs. particle‐associated), habitat (river vs. estuary), and seasonality (wet vs. dry season). Neutral modeling revealed that the stochastic pattern was more pronounced for bacteria than archaea, although both deterministic and stochastic processes significantly influenced the assembly of bacterial and archaeal communities. Homogeneous selection had a relatively higher importance in structuring bacterioplankton in free‐living fractions, while this process was more important in structuring archaeaplankton in particle‐associated fractions. Aquatic microbial community composition and assembly processes were most strongly associated with salinity and water temperature. Network analysis for each size fraction of the plankton revealed higher connectivity in the particle‐associated communities than the free‐living communities for intra‐bacteria, inter‐bacteria/archaea, and intra‐archaea associations, accordingly, when nonlinear associations were considered. These findings expand the current understanding of the ecological mechanisms and Archaea‐Bacteria interactions, underlying the size‐fractionated plankton dynamics in the river‐bay system.

Bathyarchaeota is a diverse, abundant, and widespread archaeal phylum that may play an important role in global carbon cycling. The vertical distribution of Bathyarchaeota and environmental impact on bathyarchaeotal community in deep-sea and lake sediments are known; however, little information is available on Bathyarchaeota in eutrophic and brackish environments, such as mangrove wetlands. In the current study, we investigated the bathyarchaeotal community in the mangrove ecosystem of Futian Nature Reserve, Shenzhen. By slicing the profile into 2-cm layers from the surface to bottom, 110 sediment samples were obtained from three mangrove and three mud flat profiles. High-throughput sequencing of archaeal 16S rRNA genes, quantification of bathyarchaeotal 16S rRNA genes with optimized quantitative primers, and the ensuing statistical analyses revealed the vertical distribution of Bathyarchaeota in the mangrove ecosystem, indicating that Bathyarchaeota was the dominant archaeal phylum therein, with Bathyarchaeota subgroups 6, 8, 15, and 17 as the most abundant subgroups. The abundance of Bathyarchaeota was higher in the mangrove than in the mud flat and other oligotrophic or freshwater habitats. Total organic carbon (TOC) and nitric oxide were significantly correlated with the abundance of Bathyarchaeota, and pH was the major factor shaping the community composition. Further, the data suggested that Bathyarchaeota subgroup 6 preferentially dwelled in slightly acidic, high TOC, and subsurface environments, indicating a potentially distinct role in the global geochemical cycle. These findings expand the knowledge of the distribution and niche preference of Bathyarchaeota, emphasizing the need for continuous characterization of bathyarchaeotal subgroups.

Mangroves, as a blue carbon reservoir, provide an environment for a variety of microorganisms. Mangroves lie in special locations connecting coastal and estuarine areas and experience fluctuating conditions, which are expected to intensify with climate change, creating a need to better understand the relative roles of stochastic and deterministic processes in shaping microbial community assembly. Here, a study of microbial communities inhabiting mangrove sediments across southeastern China, spanning mangroves in six nature reserves, was conducted. We performed high-throughput DNA sequencing of these samples and compared them with data of 1,370 sediment samples collected from the Earth Microbiome Project (EMP) to compare the microbial diversity of mangroves with that of other biomes. Our results showed that prokaryotic alpha diversity in mangroves was significantly higher than that in other biomes and that microbial beta diversity generally clustered according to biome types. The core operational taxonomic units (OTUs) in mangroves were mostly assigned to Gammaproteobacteria, Deltaproteobacteria, Chloroflexi, and Euryarchaeota. The majority of beta nearesttaxon index values were higher than 2, indicating that community assembly in mangroves was better explained through a deterministic process than through a stochastic process. Mean annual precipitation (MAP) and total organic carbon (TOC) were main deterministic factors explaining variation in the microbial community. This study fills a gap in addressing the unique microbial diversity of mangrove ecosystems and their microbial community assembly mechanisms. IMPORTANCE Understanding the underlying mechanisms of microbial community assembly patterns is a vital issue in microbial ecology. Mangroves, as an important and special ecosystem, provide a unique environment for examining the relative importance of stochastic and deterministic processes. We made the first global-scale comparison and found that microbial diversity was significantly different in mangrove sediments compared to that of other biomes. Furthermore, our results suggest that a deterministic process is more important in shaping microbial community assembly in mangroves.

Whether bacterioplankton are assembled in the same way as microeukaryotes is a key question that has been answered only partially in microbial ecology. In particular, relating distribution patterns to the underlying ecological processes for plankton communities in highly dynamic ecosystems, such as river–reservoirs subjected to anthropogenic impacts, remains largely unstudied. Here, we analyzed taxonomic distribution patterns, and unraveled community assembly processes underlying the core and random bacterioplankton and microeukaryotes from a subtropical river–reservoir system. These plankton domains were modelled using the spatial abundance distributions (SpADs) of the operational taxonomic units (OTUs) as a proxy for abundant and rare taxa delineation. Both bacterioplankton and microeukaryote plankton communities exhibited significant distance–decay relationships, and samples were grouped depending on reservoir or river habitats. The neutral community model showed that 35–45% of the plankton community variation could be explained by neutral processes. The phylogenetic null model revealed that dispersal limitation accounted for the largest percentage of pairwise comparisons (42–68%), followed by environmental selection (18–25%). We concluded that similar prevalence of ecological processes acting on particular subsets of the bacterioplankton and microeukaryotes might have resulted from similar responses to environmental change, potentially induced by human activities in the watershed.

Although the influence of microbial community assembly processes on aquatic ecosystem function and biodiversity is well known, the processes that govern planktonic communities in human-impacted rivers remain largely unstudied. Here, we used multivariate statistics and a null model approach to test the hypothesis that environmental conditions and obstructed dispersal opportunities, dictate a deterministic community assembly for phytoplankton and bacterioplankton across contrasting hydrographic conditions in a subtropical mid-sized river (Jiulong River, southeast China). Variation partitioning analysis showed that the explanatory power of local environmental variables was larger than that of the spatial variables for both plankton communities during the dry season. During the wet season, phytoplankton community variation was mainly explained by local environmental variables, whereas the variance in bacterioplankton was explained by both environmental and spatial predictors. The null model based on Raup-Crick coefficients for both planktonic groups suggested little evidences of the stochastic processes involving dispersal and random distribution. Our results showed that hydrological change and landscape structure act together to cause divergence in communities along the river channel, thereby dictating a deterministic assembly and that selection exceeds dispersal limitation during the dry season. Therefore, to protect the ecological integrity of human-impacted rivers, watershed managers should not only consider local environmental conditions but also dispersal routes to account for the effect of regional species pool on local communities.

The spatiotemporal distribution of microbial diversity, community composition, and their major drivers are fundamental issues in microbial ecology. In this study, the planktonic bacterial and microeukaryotic communities of the Jiulong River were investigated across both wet and dry seasons by using denaturing gradient gel electrophoresis (DGGE). We found evidence of temporal change between wet and dry seasons and distinct spatial patterns of bacterial and microeukaryotic communities. Both bacterial and microeukaryotic communities were strongly correlated with temperature, NH 4 -N, PO 4 -P, and chlorophyll a , and these environmental factors were significant but incomplete predictors of microbial community composition. Local environmental factors combined with spatial and temporal factors strongly controlled both bacterial and microeukaryotic communities in complex ways, whereas the direct influence of spatial and temporal factors appeared to be relatively small. Path analysis revealed that the microeukaryotic community played key roles in shaping bacterial community composition, perhaps through grazing effects and multiple interactions. Both Betaproteobacteria and Actinobacteria were the most dominant and diverse taxa in bacterial communities, while the microeukaryotic communities were dominated by Ciliophora (zooplankton) and Chlorophyta (phytoplankton). Our results demonstrated that both bacterial and microeukaryotic communities along the Jiulong River displayed a distinct spatiotemporal pattern; however, microeukaryotic communities exhibited a stronger distance-decay relationship than bacterial communities and their spatial patterns were mostly driven by local environmental variables rather than season or spatial processes of the river. Therefore, we have provided baseline data to support further research on river microbial food webs and integrating different microbial groups into river models.