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Background Freshwater salinization may result in significant changes of microbial community composition and diversity, with implications for ecosystem processes and function. Earlier research has revealed the importance of large shifts in salinity on microbial physiology and ecology, whereas studies on the effects of smaller or narrower shifts in salinity on the microeukaryotic community in inland waters are scarce. Our aim was to unveil community assembly mechanisms and the stability of microeukaryotic plankton networks at low shifts in salinity. Results Here, we analyzed a high-resolution time series of plankton data from an urban reservoir in subtropical China over 13 consecutive months following one periodic salinity change ranging from 0 to 6.1‰. We found that (1) salinity increase altered the community composition and led to a significant decrease of plankton diversity, (2) salinity change influenced microeukaryotic plankton community assembly primarily by regulating the deterministic-stochastic balance, with deterministic processes becoming more important with increased salinity, and (3) core plankton subnetwork robustness was higher at low-salinity levels, while the satellite subnetworks had greater robustness at the medium-/high-salinity levels. Our results suggest that the influence of salinity, rather than successional time, is an important driving force for shaping microeukaryotic plankton community dynamics. Conclusions Our findings demonstrate that at low salinities, even small increases in salinity are sufficient to exert a selective pressure to reduce the microeukaryotic plankton diversity and alter community assembly mechanism and network stability. Our results provide new insights into plankton ecology of inland urban waters and the impacts of salinity change in the assembly of microbiotas and network architecture. -E3MKQHtp7WR1f_cJEBdqX Video abstract

Soil microbial diversity has major influences on ecosystem functions and services. However, due to its complexity and uneven distribution of abundant and rare taxa, quantification of soil microbial diversity remains challenging and thereby impeding its integration into long-term monitoring programs. Using metabarcoding, we analyzed soil bacterial and fungal communities at 30 long-term soil monitoring sites from the three land-use types arable land, permanent grassland, and forest with a yearly sampling between snowmelt and first fertilization over five years. Unlike soil microbial biomass and alpha-diversity, microbial community compositions and structures were site- and land-use-specific with CAP reclassification success rates of 100%. The temporally stable site core communities included 38.5% of bacterial and 33.1% of fungal OTUs covering 95.9% and 93.2% of relative abundances. We characterized bacterial and fungal core communities and their land-use associations at the family-level. In general, fungal families revealed stronger land-use associations as compared to bacteria. This is likely due to a stronger vegetation effect on fungal core taxa, while bacterial core taxa were stronger related to soil properties. The assessment of core communities can be used to form cultivation-independent reference lists of microbial taxa, which may facilitate the development of microbial indicators for soil quality and the use of soil microbiota for long-term soil biomonitoring.

The ecological functions of core and non-core bacteria are gradually being identified, yet little is known about their responses to environmental changes and assembly processes, especially in urban river ecosystems. Here, we investigated bacterioplankton communities over 1 year in an urban section of the Ganjiang River, China. The results revealed that the alpha- and beta-diversity of bacterioplankton communities had no significant spatial differences along the urbanization gradient, but they presented distinct seasonal variations. The bacterioplankton communities were comprised of a few core taxa (11.8%) and a large number of non-core taxa (88.2%), of which the non-core taxa were the most active component responsible for community dynamics. Most non-core taxa (76.84%) belonged to non-typical freshwater bacteria, implying that they are more likely to derive from allochthonous inputs than the core taxa. Variance partitioning analyses showed that air temperature, flow rate and water chemistry together explained 58.2 and 38.9% of the variations of the core taxa and non-core taxa, respectively. In addition, the relative importance of temperature and water chemistry on the bacterioplankton communities prevailed over that of flow rate alone. This means that deterministic processes and stochastic processes simultaneously control the bacterioplankton community assembly, with deterministic processes contributing more than stochastic processes.

Nitrogen is a key limiting factor for crop growth, and improving nitrogen use efficiency (NUE) is critical for achieving high crop yields. In this study, both culture-independent and culture-dependent approaches were employed to systematically analyze the community composition and functional traits of seed endophytic bacteria in rice varieties with contrasting NUE. The results revealed diverse endophytic bacterial communities across the four rice varieties, with Shannon indices ranging from 2.95 to 3.23. However, significant compositional differences were observed among varieties. Rare taxa accounted for over 51% of operational taxonomic units (OTUs) in each variety and were the primary drivers of community diversity and differentiation. In contrast, core taxa (shared OTUs) were highly conserved across varieties, largely composed of abundant taxa (OTUs > 39%, total relative abundance > 93%), and occupied central positions in co-occurrence networks, thereby contributing to community stability. Five representative strains exhibited diverse plant growth-promoting (PGP) traits in vitro , including siderophore production, phosphate solubilization, and indole - 3 - acetic acid (IAA) synthesis. These functions were partially redundant, but individual strains exhibited distinct strengths, indicating functional complementarity. Inoculation experiments demonstrated that all strains improved rice growth, nitrogen accumulation, and NUE, with their effectiveness modulated by both strain identity and nitrogen availability. This study reveals rice seed endophytic bacteria as “natural microbial allies” that support host growth and adaptation under low-nitrogen conditions. These endophytes represent valuable microbial resources for the development of next-generation biofertilizers in sustainable agriculture.

The gut microbiota of dung beetles comprises bacteria, archaea, and fungi. Most studies have only considered the bacterial element and focused on differences between species reared in the lab. This study considered microorganisms from the gut of Trypocopris pyrenaeus and concentrated on differences among wild individuals of an alpine Italian population. We revealed remarkable interindividual variation in the taxonomic composition of microbiota. Core taxa were few, while individuals harboured many exclusive taxa. Therefore, considering only a few individuals to describe the microbiota of a species is not sufficient. The study also revealed that the nMDS ordination of individuals based on prokaryotes was different from that based on fungi, meaning that both groups should be considered in microbiota analyses and that one microbic group cannot be considered a surrogate of the other. We identified many functions potentially provided by the microbiota and found the taxonomic richness of prokaryotes to be positively correlated with their functional richness. The analysis of the functions potentially provided by these microorganisms confirmed that the gut microbiota, in addition to being essential for the health of their host, may also contribute to the effective functioning of the ecosystems of which dung beetles are part.

The gut microbiota of dung beetles comprises bacteria, archaea, and fungi. Most studies have only considered the bacterial element and focused on differences between species reared in the lab. This study considered microorganisms from the gut of Trypocopris pyrenaeus and concentrated on differences among wild individuals of an alpine Italian population. We revealed remarkable interindividual variation in the taxonomic composition of microbiota. Core taxa were few, while individuals harboured many exclusive taxa. Therefore, considering only a few individuals to describe the microbiota of a species is not sufficient. The study also revealed that the nMDS ordination of individuals based on prokaryotes was different from that based on fungi, meaning that both groups should be considered in microbiota analyses and that one microbic group cannot be considered a surrogate of the other. We identified many functions potentially provided by the microbiota and found the taxonomic richness of prokaryotes to be positively correlated with their functional richness. The analysis of the functions potentially provided by these microorganisms confirmed that the gut microbiota, in addition to being essential for the health of their host, may also contribute to the effective functioning of the ecosystems of which dung beetles are part.

Ips (Curculionidae: Scolytinae) bark beetles (BBs) are ecologically and economically devastating coniferous pests in the Northern Hemisphere. Although the microbial diversity associated with these beetles has been well studied, mechanisms of community assembly and the functional roles of key microbes remain poorly understood. This study investigates the microbial community structures and functions in both intestinal and non-intestinal environments of five Ips BBs using a metagenomic approach. The findings reveal similar microbial community compositions, though the α-diversity of dominant taxa differs between intestinal and non-intestinal environments due to the variability in bark beetle species, host trees, and habitats. Intestinal microbial communities are predominantly shaped homogenizing dispersal (HD) and undominated processes (UP), whereas non-intestinal microbial communities are primarily driven by heterogeneous selection (HS). Functional analysis shows that genes and enzymes associated with steroid biosynthesis and oxidative phosphorylation are primarily found in non-intestinal fungal symbionts Ogataea , Wickerhamomyce , Ophiostoma , and Ceratocystis of Ips species. Genes and enzymes involved in degrading terpenoids, phenolic compounds, and polysaccharides are predominately found in the intestinal Acinetobacter , Erwinia , and Serratia . This study provides valuable and in-depth insights into the symbiotic relationships between Ips BBs and their microbial partners, enhancing our understanding of insect-microbe coevolution and suggesting new strategies for pest management.

In the present study, we evaluated whether the nasopharyngeal, ruminal, and vaginal microbiota would diverge (1) in virgin yearling beef heifers (9 months old) due to the maternal restricted gain during the first trimester of gestation; and (2) in pregnant beef heifers in response to the vitamin and mineral (VTM) supplementation during the first 6 months of pregnancy. As a secondary objective, using the microbiota data obtained from these two cohorts of beef heifers managed at the same location and sampled at the same time, we performed a holistic assessment of the microbial ecology residing within the respiratory, gastrointestinal, and reproductive tract of cattle. Our 16S rRNA gene sequencing results revealed that both α and β-diversity of the nasopharyngeal, ruminal and vaginal microbiota did not differ between virgin heifers raised from dams exposed to either a low gain (targeted average daily gain of 0.28 kg/d, n = 22) or a moderate gain treatment (0.79 kg/d, n = 23) during the first 84 days of gestation. Only in the vaginal microbiota were there relatively abundant genera that were affected by maternal rate of gain during early gestation. Whilst there was no significant difference in community structure and diversity in any of the three microbiota between pregnant heifers received no VTM (n = 15) and VTM supplemented (n = 17) diets, the VTM supplementation resulted in subtle compositional alterations in the nasopharyngeal and ruminal microbiota. Although the nasopharyngeal, ruminal, and vaginal microbiota were clearly distinct, a total of 41 OTUs, including methanogenic archaea, were identified as core taxa shared across the respiratory, gastrointestinal, and reproductive tracts of both virgin and pregnant heifers.

Background Climate change and anthropogenic activities intensify salinity stress impacting significantly on plant productivity and biodiversity in agroecosystems. There are naturally salt-tolerant plants (halophytes) that can grow and withstand such harsh conditions. Halophytes have evolved along with their associated microbiota to adapt to hypersaline environments. Identifying shared microbial taxa between halophyte species has rarely been investigated. We performed a comprehensive meta-analysis using the published bacterial 16S rRNA gene sequence datasets to untangle the rhizosphere microbiota structure of two halophyte groups and non-halophytes. We aimed for the identification of marker taxa of plants being adapted to a high salinity using three independent approaches. Results Fifteen studies met the selection criteria for downstream analysis, consisting of 40 plants representing diverse halophyte and non-halophyte species. Microbiome structural analysis revealed distinct compositions for halophytes that face high salt concentrations in their rhizosphere compared to halophytes grown at low salt concentrations or from non-halophytes. For halophytes grown at high salt concentrations, we discovered three bacterial genera that were independently detected through the analysis of the core microbiome, key hub taxa by network analysis and random forest analysis. These genera were Thalassospira , Erythrobacter , and Marinobacter . Conclusions Our meta-analysis revealed that salinity level is a critical factor in affecting the rhizosphere microbiome assembly of plants. Detecting marker taxa across high-halophytes may help to select Bacteria that might improve the salt tolerance of non-halophytic plants.

ABSTRACT Animal bodies are colonized by many microorganisms which can provide indispensable services to their hosts. Although nematode gut microbiota has been extensively studied in recent years, the driving factors of gut microbiome of soil nematodes from a long-term fertilization field are unclear. Here, using 16S rRNA gene amplicon sequencing, we explored the nematode gut microbiota under different fertilization patterns (control, inorganic fertilizers and mixed fertilizers) and fertilization durations (5 y, 8 y and 10 y). Our results revealed that nematode gut microbiota was dominated by core bacterial taxa AF502208 (anaerobic bacteria), Enterobacter (plant litter decomposition) and Ancylobacter (organic matter decomposition and nitrogen cycling), significantly distinct from soil microbiome, and the assembly of that was a non-random process, which suggested host conditions contributed to maintaining the gut microbiota. Moreover, fertilization pattern had a greater influence on nematode gut microbiome than fertilization duration. Inorganic fertilization (5.19) significantly reduced the diversity of the nematode gut microbiota (6.68) shown by Shannon index (P < 0.05). Canonical correspondence analysis demonstrates that soil properties such as pH, organic matter, total phosphorus, available phosphorus, ammonium nitrogen, moisture content, nitrate nitrogen and total nitrogen have significant effects on the nematode microbiome. Structured equation models further revealed that fertilization could obviously affect the nematode gut microbiota, and the effects were maintained even when accounting simultaneously for the drivers of soil bacteria and soil properties. This study provides a solid evidence that the shifting of nematode gut microbiota under long-term fertilization was resulted from environmental factors and host conditions, and advance the insights into host-microbiome in the agricultural ecosystems. The research provides a better comprehension over the driving factors of shaping nematode intestinal microbiota under long-term fertilization and extends our knowledge of host-microbiome interactions in fields.