Salinity Drives Functional and Taxonomic Diversities in Global Water Metagenomes

Hydraulic and thermal performance trigger the deterministic assembly of water microbiomes: From biogeographical homogenization to machine learning model

Water quality at the point of consumption has long been a health issue because of the potential for microbial ecology. However, research on water hydraulic performance remains in its infancy, and in particular, little is known about the effects of thermal performance during winter. This study explored the effects of stagnation and municipal heating on microbial communities in tap water, focusing on spatial and temporal variations in microbial community composition. The results revealed that stagnation significantly alters the microbial community, especially in heating areas, where the temperature exacerbates microbial growth. Furthermore, hydraulic and thermal performance drive deterministic assembly processes in microbial communities, as evidenced by the reductions in β-diversity, normalized stochasticity ratio (NST), and neutral community model (NCM) fit. Machine learning models revealed that stagnation time greater than 8 h results in increased community abundance because of longer exposure to organic matter and nutrients. The study finding illustrate the importance of environmental influences on microbial community dynamics, and provide valuable insights into the water microbial community, particularly in areas with prolonged stagnation.

SALINITY-Induced Changes in Diversity, Stability, and Functional Profiles of Microbial Communities in Different Saline Lakes in Arid Areas

Saline lakes, characterized by high salinity and limited nutrient availability, provide an ideal environment for studying extreme halophiles and their biogeochemical processes. The present study examined prokaryotic microbial communities and their ecological functions in lentic sediments (with the salinity gradient and time series) using 16S rRNA amplicon sequencing and a metagenomic approach. Our findings revealed a negative correlation between microbial diversity and salinity. The notable predominance of Archaea in high-salinity lakes signified a considerable alteration in the composition of the microbial community. The results indicate that elevated salinity promotes homogeneous selection pressures, causing substantial alterations in microbial diversity and community structure, and simultaneously hindering interactions among microorganisms. This results in a notable decrease in the complexity of microbial ecological networks, ultimately influencing the overall ecological functional responses of microbial communities such as carbon fixation, sulfur, and nitrogen metabolism. Overall, our findings reveal salinity drives a notable predominance of Archaea, selects for species adapted to extreme conditions, and decreases microbial community complexity within saline lake ecosystems.

Metagenomics unravel distinct taxonomic and functional diversities between terrestrial and aquatic biomes

Microbes in terrestrial and aquatic ecosystems play crucial roles in driving ecosystem functions, but currently, there is a lack of comparison regarding their taxonomic and functional diversities. Here, we conducted a global analysis to investigate the disparities in microbial taxonomy and microbial-mediated biogeochemical cycles between terrestrial and aquatic ecosystems. Results showed a higher relative abundance of bacteria, especially Actinobacteria and Acidobacteria, in soil than water metagenomes, leading to a greater proportion of genes related to membrane transport, regulatory, and cellular signaling. Moreover, there was a higher abundance of genes associated with carbohydrate, sulfur, and potassium metabolisms in the soil, while those involved in nitrogen and iron metabolisms were more prevalent in the water. Thus, both soil and water microbiomes exhibited unique taxonomic and functional properties associated with biogeochemical processes, providing valuable insights into predicting and understanding the adaptation of microbes in different ecosystems in the face of climate change.

Biodiversity of microorganisms in the Baltic Sea: the power of novel methods in the identification of marine microbes

Until recently, the data on the diversity of the entire microbial community from the Baltic Sea were relatively rare and very scarce. However, modern molecular methods have provided new insights into this field with interesting results. They can be summarized as follows. (i) Although low salinity causes a reduction in the biodiversity of multicellular species relative to the populations of the North-East Atlantic, no such reduction occurs in bacterial diversity. (ii) Among cyanobacteria, the picocyanobacterial group dominates when considering gene abundance, while filamentous cyanobacteria dominate in means of biomass. (iii) The diversity of diatoms and dinoflagellates is significantly larger than described a few decades ago; however, molecular studies on these groups are still scarce. (iv) Knowledge gaps in other protistan communities are evident. (v) Salinity is the main limiting parameter of pelagic fungal community composition, while the benthic fungal diversity is shaped by water depth, salinity, and sediment C and N availability. (vi) Bacteriophages are the predominant group of viruses, while among viruses infecting eukaryotic hosts, Phycodnaviridae are the most abundant; the Baltic Sea virome is contaminated with viruses originating from urban and/or industrial habitats. These features make the Baltic Sea microbiome specific and unique among other marine environments.

Examining the impacts of salt specificity on freshwater microbial community and functional potential following salinization

The degradation of freshwater systems by salt pollution is a threat to global freshwater resources. Salinization is commonly identified by increased specific conductance (conductivity), a proxy for salt concentrations. However, conductivity fails to account for the diversity of salts entering freshwaters and the potential implications this has on microbial communities and functions. We tested 4 types of salt pollution-MgCl2, MgSO4, NaCl, and Na2SO4-on bacterial taxonomic and functional α-, β-diversity of communities originating from streams in two distinct localities (Nebraska [NE] and Ohio [OH], USA). Community responses depended on the site of origin, with NE and OH exhibiting more pronounced decreases in community diversity in response to Na2SO4 and MgCl2 than other salt amendments. A closer examination of taxonomic and functional diversity metrics suggests that core features of communities are more resistant to induced salt stress and that marginal features at both a population and functional level are more likely to exhibit significant structural shifts based on salt specificity. The lack of uniformity in community response highlights the need to consider the compositional complexities of salinization to accurately identify the ecological consequences of instances of salt pollution.

With a pinch of salt: metagenomic insights into Namib Desert salt pan microbial mats and halites reveal functionally adapted and competitive communities

IMPORTANCE

The hyperarid Namib Desert is one of the oldest deserts on Earth. It contains multiple clusters of playas which are saline-rich springs surrounded by halite evaporites. Playas are of great ecological importance, and their indigenous (poly)extremophilic microorganisms are potentially involved in the precipitation of minerals such as carbonates and sulfates and have been of great biotechnological importance. While there has been a considerable amount of microbial ecology research performed on various Namib Desert edaphic microbiomes, little is known about the microbial communities inhabiting its multiple playas. In this work, we provide a comprehensive taxonomic and functional potential characterization of the microbial, including viral, communities of sediment mats and halites from two distant salt pans of the Namib Desert, contributing toward a better understanding of the ecology of this biome.

Metagenomic insights into the functional genes across transects in a typical estuarine marsh

Salt marshes are potentially one of the most efficient carbon (C) sinks worldwide and perform important ecosystem functions, but sea level rise alters marsh sediments properties and thus threatens microbial roles in ecosystem functioning. Yet, the mechanisms of interactions of biochemical processes with microorganisms and their functions are still not fully understood. Here, this study investigated metagenomic taxonomic and functional profiling from the water-land conjugation up to about 300 m, 1000 m, and 2500 m in three parallel transects, respectively, in Hangzhou Bay, China. The results showed that soil physicochemical factors drove metagenomic taxonomic and functional genes in the 2500-m transect significantly different from other sites. The 2500-m transect had a greater abundance of Chloroflexi and Acidobacteria but lower in Proteobacteria. The metagenomic functional genes related to Phosphorus Metabolism (PHO) and Potassium Metabolism (POT) increased in the 2500 m. Additionally, nutrient-cycling functions and the genera of Anaeromyxobacter, Roseiflexus, and Geobacter related to PHO, POT at 2500 m were significantly greater than those of other transects. Carbon cycling functions within Carbohydrates (CHO) also differed significantly across transects. These research results demonstrated that the relative abundance of metagenomic microorganisms and their functional genes were significantly separated across the three transects. The vegetation type, salinity, and soil properties might be among the influencing factors.

Negative impacts of sea-level rise on soil microbial involvement in carbon metabolism

Sea-level rise has been threatening the terrestrial ecosystem functioning of coastal islands, of which the most important component is carbon (C) cycling. However, metagenomic and metabolomic evidence documenting salt intrusion effects on molecular biological processes of C cycling are still lacking. Here, we investigated microbial communities, metagenomic taxonomy and function, and metabolomic profiles in the marine-terrestrial transition zone of low- and high-tide, and low- and high-land areas based on distances of 0 m, 50 m, 100 m, and 200 m, respectively, to the water-land junction of Neilingding Island. Our results showed that soil salinity (EC) was the dominant driver controlling bacterial abundance and community composition and metagenomic taxonomy and function. The metabolomic profiling at the low-tide site was significantly different from that of other sites. The low-tide site had greater abundance of Proteobacteria and Bacteroidetes (1.6-3.7 fold), especially Gammaproteobacteria, but lower abundance (62-83%) of Acidobacteria and Chloroflexi, compared with other three sites. The metagenomic functional genes related to carbohydrate metabolism decreased at the low-tide site by 15.2%, including the metabolism of aminosugars, di- and oligo-saccharides, glycoside hydrolases, and monosaccharides, leading to significant decreases in 21 soil metabolites, such as monosaccharide (l-gulose), disaccharide (sucrose and turanose), and oligosaccharides (stachyose and maltotetraose). Our study demonstrates that elevated salinity due to sea-level rise may suppress C-cycling genes and their metabolites, therefore having negative impacts on microbial metabolism of organic matter.

Functional Redundancy in Soil Microbial Community Based on Metagenomics Across the Globe

Understanding the contribution of soil microbial communities to ecosystem processes is critical for predicting terrestrial ecosystem feedbacks under changing climate. Our current understanding lacks a consistent strategy to formulate the linkage between microbial systems and ecosystem processes due to the presumption of functional redundancy in soil microbes. Here we present a global soil microbial metagenomic analysis to generalize patterns of microbial taxonomic compositions and functional potentials across climate and geochemical gradient. Our analyses show that soil microbial taxonomic composition varies widely in response to climate and soil physicochemical gradients, while microbial functional attributes based on metagenomic gene abundances are redundant. Among 17 climate zones, microbial taxonomic compositions were more distinct than functional potentials, as climate and edaphic properties showed more significant influence on microbial taxonomic compositions than on functional potentials. Microbial taxonomies formed a larger and more complex co-occurrence network with more module structures than functional potentials. Functional network was strongly inter-connected among different categories, whereas taxonomic network was more positively interactive in the same taxonomic groups. This study provides strong evidence to support the hypothesis of functional redundancy in soil microbes, as microbial taxonomic compositions vary to a larger extent than functional potentials based on metagenomic gene abundances in terrestrial ecosystems across the globe.