Macroecological distributions of gene variants highlight the functional organization of soil microbial systems

Distribution and response of electroactive microorganisms to freshwater river pollution

Electroactive microorganisms (EAMs) play a vital role in biogeochemical cycles by facilitating extracellular electron transfer. They demonstrate remarkable adaptability to river sediments that are characterized by pollution and poor water quality, significantly contributing to the sustainability of river ecosystems. However, the distribution and diversity of EAMs remain poorly understood. In this study, 16S rRNA gene high-throughput sequencing and real-time fluorescence quantitative PCR were used to assess EAMs in 160 samples collected from eight rivers within the Pearl River Delta of Southern China. The results indicated that specialized EAMs communities in polluted sediments exhibited variations in response to water quality and sediment depth. Compared to clean sediment, polluted sediments showed a 4.5% increase in the relative abundances of EAMs communities (59 genera), with 45- and 17-times higher abundances of Geobacter and cable bacteria. Additionally, the abundance of cable bacteria decreased with increasing sediment depth in polluted sediments, while the abundance of L. varians GY32 exhibited an opposite trend. Finally, the abundances of Geobacter, cable bacteria, and L. varians GY32 were positively correlated with the abundance of filamentous microorganisms (FMs) across all samples, with stronger interactions in polluted sediments. These findings suggest that EAMs demonstrate heightened sensitivity to polluted environments, particularly at the genus (species) level, and exhibit strong adaptability to conditions characterized by high levels of acid volatile sulfide, low dissolved oxygen, and elevated nitrate nitrogen. Therefore, environmental factors could be manipulated to optimize the growth and efficiency of EAMs for environmental engineering and natural restoration applications.

Strategies for tailoring functional microbial synthetic communities

Natural ecosystems harbor a huge reservoir of taxonomically diverse microbes that are important for plant growth and health. The vast diversity of soil microorganisms and their complex interactions make it challenging to pinpoint the main players important for the life support functions microbes can provide to plants, including enhanced tolerance to (a)biotic stress factors. Designing simplified microbial synthetic communities (SynComs) helps reduce this complexity to unravel the molecular and chemical basis and interplay of specific microbiome functions. While SynComs have been successfully employed to dissect microbial interactions or reproduce microbiome-associated phenotypes, the assembly and reconstitution of these communities have often been based on generic abundance patterns or taxonomic identities and co-occurrences but have only rarely been informed by functional traits. Here, we review recent studies on designing functional SynComs to reveal common principles and discuss multidimensional approaches for community design. We propose a strategy for tailoring the design of functional SynComs based on integration of high-throughput experimental assays with microbial strains and computational genomic analyses of their functional capabilities.

GDPF: a data resource for the distribution of prokaryotic protein families across the global biosphere

Microorganisms encode most of the functions of life on Earth. However, conventional research has primarily focused on specific environments such as humans, soil and oceans, leaving the distribution of functional families throughout the global biosphere poorly comprehended. Here, we present the database of the global distribution of prokaryotic protein families (GDPF, http://bioinfo.qd.sdu.edu.cn/GDPF/), a data resource on the distribution of functional families across the global biosphere. GDPF provides global distribution information for 36 334 protein families, 19 734 superfamilies and 12 089 KEGG (Kyoto Encyclopedia of Genes and Genomes) orthologs from multiple source databases, covering typical environments such as soil, oceans, animals, plants and sediments. Users can browse, search and download the distribution data of each entry in 10 000 global microbial communities, as well as conduct comparative analysis of distribution disparities among multiple entries across various environments. The GDPF data resource contributes to uncovering the geographical distribution patterns, key influencing factors and macroecological principles of microbial functions at a global level, thereby promoting research in Earth ecology and human health.

Explaining nitrogen turnover in sediments and water through variations in microbial community composition and potential function

Anthropogenic activities greatly impact nitrogen (N) biogeochemical cycling in aquatic ecosystems. High N concentrations in coastal aquaculture waters threaten fishery production and aquaculture ecosystems and have become an urgent problem to be solved. Existing microbial flora and metabolic potential significantly regulate N turnover in aquatic ecosystems. To clarify the contribution of microorganisms to N turnover in sediment and water, we investigated three types of aquaculture ecosystems in coastal areas of Guangdong, China. Nitrate nitrogen (NO3--N) was the dominant component of total nitrogen in the sediment (interstitial water, 90.4%) and water (61.6%). This finding indicates that NO3--N (1.67-2.86 mg/L and 2.98-7.89 mg/L in the sediment and water) is a major pollutant in aquaculture ecosystems. In water, the relative abundances of assimilation nitrogen reduction and aerobic denitrifying bacteria, as well as the metabolic potentials of nitrogen fixation and dissimilated nitrogen in fish monoculture, were only 61.0%, 31.5%, 47.5%, and 27.2% of fish and shrimp polyculture, respectively. In addition, fish-shrimp polyculture reduced NO3--N content (2.86 mg/L) compared to fish monoculture (7.89 mg/L), which was consistent with changes in aerobic denitrification and nitrate assimilation, suggesting that polyculture could reduce TN concentrations in water bodies and alleviate nitrogen pollution risks. Further analysis via structural equation modeling (SEM) revealed that functional pathways (36% and 31%) explained TN changes better than microbial groups in sediment and water (13% and 11%), suggesting that microbial functional capabilities explain TN better than microbial community composition and other factors (pH, O2, and aquaculture type). This study enhances our understanding of nitrogen pollution characteristics and microbial community and functional capabilities related to sediment-water nitrogen turnover in three types of aquaculture ecosystems, which can contribute to the preservation of healthy coastal ecosystems.

Metagenomics combined with metabolomics reveals the effect of Enterobacter sp. inoculation on the rhizosphere microenvironment of Bidens pilosa L. in heavy metal contaminated soil

Metagenomics analysis was performed to determine the effects of Enterobacter sp. FM-1 (FM-1) on key genera as well as functional genes in the rhizosphere of Bidens pilosa L. (B. pilosa L.). Moreover, metabolomics was used to reveal the differences among rhizosphere metabolites after FM-1 inoculation. FM-1 inoculation significantly increased the activity of enzymes associated with the carbon cycle in soil; among them, invertase activity increased by 5.52 units compared to a control. Specifically, the relative abundance of beneficial genera increased significantly, such as Lysobacter (0.45-2.58 unit increase) in low-contamination soils (LC) and Pseudomonas (31.17-45.99 unit increase) in high-contamination soils (HC). Comparison of different transformation processes of the C cycle revealed that inoculation of FM-1 increased the abundance of functional genes related to the carbon cycle in LC soil. In contrast, the nitrogen cycling pathway was significantly elevated in both the LC and HC soils. FM-1 inoculation reduced HM resistance gene abundance in the rhizosphere soil of B. pilosa L. in the LC soil. Moreover, FM-1 and B. pilosa L. interactions promoted the secretion of rhizosphere metabolites, in which lipids and amino acids played important roles in the phytoremediation process. Overall, we explored the rhizosphere effects induced by plantmicrobe interactions, providing new insights into the functional microbes and rhizosphere metabolites involved in phytoremediation.

Distinct Responses of Abundant and Rare Soil Bacteria to Nitrogen Addition in Tropical Forest Soils

Soil microbial responses to anthropogenic nitrogen (N) enrichment at the overall community level has been extensively studied. However, the responses of community dynamics and assembly processes of the abundant versus rare bacterial taxa to N enrichment have rarely been assessed. Here, we present a study in which the effects of short- (2 years) and long-term (13 years) N additions to two nearby tropical forest sites on abundant and rare soil bacterial community composition and assembly were documented. The N addition, particularly in the long-term experiment, significantly decreased the bacterial α-diversity and shifted the community composition toward copiotrophic and N-sensitive species. The α-diversity and community composition of the rare taxa were more affected, and they were more closely clustered phylogenetically under N addition compared to the abundant taxa, suggesting the community assembly of the rare taxa was more governed by deterministic processes (e.g., environmental filtering). In contrast, the abundant taxa exhibited higher community abundance, broader environmental thresholds, and stronger phylogenetic signals under environmental changes than the rare taxa. Overall, these findings illustrate that the abundant and rare bacterial taxa respond distinctly to N addition in tropical forests, with higher sensitivity of the rare taxa, but potentially broader environmental acclimation of the abundant taxa. IMPORTANCE Atmospheric nitrogen (N) deposition is a worldwide environmental problem and threatens biodiversity and ecosystem functioning. Understanding the responses of community dynamics and assembly processes of abundant and rare soil bacterial taxa to anthropogenic N enrichment is vital for the management of N-polluted forest soils. Our sequence-based data revealed distinct responses in bacterial diversity, community composition, environmental acclimation, and assembly processes between abundant and rare taxa under N-addition soils in tropical forests. These findings provide new insight into the formation and maintenance of bacterial diversity and offer a way to better predict bacterial responses to the ongoing atmospheric N deposition in tropical forests.

Microbial Journey: Mount Everest to Mars

A rigorous exploration of microbial diversity has revealed its presence on Earth, deep oceans, and vast space. The presence of microbial life in diverse environmental conditions, ranging from moderate to extreme temperature, pH, salinity, oxygen, radiations, and altitudes, has provided the necessary impetus to search for them by extending the limits of their habitats. Microbiology started as a distinct science in the mid-nineteenth century and has provided inputs for the betterment of mankind during the last 150 years. As beneficial microbes are assets and pathogens are detrimental, studying both have its own merits. Scientists are nowadays working on illustrating the microbial dynamics in Earth's subsurface, deep sea, and polar regions. In addition to studying the role of microbes in the environment, the microbe-host interactions in humans, animals and plants are also unearthing newer insights that can help us to improve the health of the host by modulating the microbiota. Microbes have the potential to remediate persistent organic pollutants. Antimicrobial resistance which is a serious concern can also be tackled only after monitoring the spread of resistant microbes using disciplines of genomics and metagenomics The cognizance of microbiology has reached the top of the world. Space Missions are now looking for signs of life on the planets (specifically Mars), the Moon and beyond them. Among the most potent pieces of evidence to support the existence of life is to look for microbial, plant, and animal fossils. There is also an urgent need to deliberate and communicate these findings to layman and policymakers that would help them to take an adequate decision for better health and the environment around us. Here, we present a glimpse of recent advancements by scientists from around the world, exploring and exploiting microbial diversity.

Comparative Microbial Nitrogen Functional Gene Abundances in the Topsoil vs. Subsoil of Three Grassland Habitats in Northern China

The microbial groups of nitrogen fixers, ammonia oxidizers, and denitrifiers play vital roles in driving the nitrogen cycle in grassland ecosystems. However, the understanding of the abundance and distribution of these functional microorganisms as well as their driving factors were limited mainly to topsoil. In this study, the abundances of nitrogen functional genes (NFGs) involved in nitrogen fixation (nifH), ammonia oxidation (amoA), and denitrification (nirK, nirS, and nosZ) were investigated in both topsoil (0-10 cm, soil layer with concentrated root) and subsoil (30-40 cm, soil layer with spare root) of three grassland habitats in northern China. The abundance of NFGs decreased with soil depth except for the archaeal amoA gene and the distribution of nifH, archaeal amoA, nirK, and nirS gene was significantly impacted by grassland habitats. Moreover, the distribution of NFGs was more responsive to the vertical difference than horizontal spatial heterogeneity. Redundancy analysis revealed that the distribution pattern of overall NFGs was regulated by grassland habitats, and these regulations were more obvious in the subsoil than in the topsoil. Variance partitioning analysis further indicated that soil resource supply (e.g., organic matter) may control the vertical distribution of NFGs. Taken together, the findings in this study could fundamentally improve our understanding of the distribution of N cycling-associated microorganisms across a vertical scale, which would be useful for predicting the soil N availability and guiding the soil N management in grassland ecosystems.