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Investigating microbial response to environmental variables is of great importance for understanding of microbial acclimatization and evolution in natural environments. However, little is known about how microbial communities responded to environmental factors (e.g. salinity, geographic distance) in lake surface sediments of the Qinghai-Tibetan Plateau (QTP). In this study, microbial diversity and community structure in the surface sediments of nine lakes on the QTP were investigated by using the Illumina Miseq sequencing technique and the resulting microbial data were statistically analyzed in combination with environmental variables. The results showed total microbial community of the studied lakes was significantly correlated (r = 0.631, P  < 0.001) with lake salinity instead of geographic distance. This suggests that lake salinity is more important than geographic distance in shaping the microbial diversity and community structure in the studied samples. In addition, the abundant and rare taxa (OTUs with relative abundance higher than 1% and lower than 0.01% within one sample, respectively) were significantly ( P  < 0.05) correlated (r = 0.427 and 0.783, respectively) with salinity, suggesting rare taxa might be more sensitive to salinity than their abundant counterparts, thus cautions should be taken in future when evaluating microbial response (abundant vs. rare sub-communities) to environmental conditions.

Lakes receive large amounts of terrestrially derived dissolved organic matter (tDOM). However, little is known about how aquatic microbial communities interact with tDOM in lakes. Here, by performing microcosm experiments we investigated how microbial community responded to tDOM influx in six Tibetan lakes of different salinities (ranging from 1 to 358 g/l). In response to tDOM addition, microbial biomass increased while dissolved organic carbon (DOC) decreased. The amount of DOC decrease did not show any significant correlation with salinity. However, salinity influenced tDOM transformation, i.e., microbial communities from higher salinity lakes exhibited a stronger ability to utilize tDOM of high carbon numbers than those from lower salinity. Abundant taxa and copiotrophs were actively involved in tDOM transformation, suggesting their vital roles in lacustrine carbon cycle. Network analysis indicated that 66 operational taxonomic units (OTUs, affiliated with Alphaproteobacteria , Actinobacteria ,  Bacteroidia , Bacilli ,  Gammaproteobacteria ,  Halobacteria , Planctomycetacia ,  Rhodothermia , and  Verrucomicrobiae ) were associated with degradation of CHO compounds, while four bacterial OTUs (affiliated with Actinobacteria, Alphaproteobacteria, Bacteroidia and Gammaproteobacteria ) were highly associated with the degradation of CHOS compounds. Network analysis further revealed that tDOM transformation may be a synergestic process, involving cooperation among multiple species. In summary, our study provides new insights into a microbial role in transforming tDOM in saline lakes and has important implications for understanding the carbon cycle in aquatic environments.

Background Bacteria from the genus Polaromonas are dominant phylotypes found in a variety of low-temperature environments in polar regions. The diversity and biogeographic distribution of Polaromonas have been largely expanded on the basis of 16 S rRNA gene amplicon sequencing. However, the evolution and cold adaptation mechanisms of Polaromonas from polar regions are poorly understood at the genomic level. Results A total of 202 genomes of the genus Polaromonas were analyzed, and 121 different species were delineated on the basis of average nucleotide identity (ANI) and phylogenomic placements. Remarkably, 8 genomes recovered from polar environments clustered into a separate clade (‘polar group’ hereafter). The genome size, coding density and coding sequences (CDSs) of the polar group were significantly different from those of other nonpolar Polaromonas . Furthermore, the enrichment of genes involved in carbohydrate and peptide metabolism was evident in the polar group. In addition, genes encoding proteins related to betaine synthesis and transport were increased in the genomes from the polar group. Phylogenomic analysis revealed that two different evolutionary scenarios may explain the adaptation of Polaromonas to cold environments in polar regions. Conclusions The global distribution of the genus Polaromonas highlights its strong adaptability in both polar and nonpolar environments. Species delineation significantly expands our understanding of the diversity of the Polaromonas genus on a global scale. In this study, a polar-specific clade was found, which may represent a specific ecotype well adapted to polar environments. Collectively, genomic insight into the metabolic diversity, evolution and adaptation of the genus Polaromonas at the genome level provides a genetic basis for understanding the potential response mechanisms of Polaromonas to global warming in polar regions.

The Tibetan Plateau in Northwest China hosts a number of hot springs that represent a biodiversity hotspot for thermophiles, yet their diversity and relationship to environmental conditions are poorly explored in these habitats. In this study we investigated microbial diversity and community composition in 13 Tibetan hot springs with a wide range of temperatures (22.1-75°C) and other geochemical conditions by using the 16S rRNA gene pyrosequencing approach. Bacteria (10(8)-10(11) copy/g; 42 bacterial phyla) in Tibetan hot springs were more abundant and far more diverse than Archaea (10(7)-10(10) copy/g; 5 archaeal phyla). The dominant bacterial phyla systematically varied with temperature. Moderate temperatures (75-66°C) favored Aquificae, GAL35, and novel Bacteria, whereas low temperatures (60-22.1°C) selected for Deinococcus-Thermus, Cyanobacteria, and Chloroflexi. The relative abundance of Aquificae was correlated positively with temperature, but the abundances of Deinococcus-Thermus, Cyanobacteria, and Chloroflexi were negatively correlated with temperature. Cyanobacteria and Chloroflexi were abundant in Tibetan hot springs and their abundances were positively correlated at low temperatures (55-43°C) but negatively correlated at moderate temperatures (75-55°C). These correlation patterns suggest a complex physiological relationship between these two phyla. Most archaeal sequences were related to Crenarchaeota with only a few related to Euryarchaeota and Thaumarchaeota. Despite the fact that microbial composition in Tibetan hot springs was strongly shaped by temperature, microbial diversity (richness, evenness and Shannon diversity) was not significantly correlated with temperature change. The results of this study expand our current understanding of microbial ecology in Tibetan hot springs and provide a basis for a global comparison.

Identifying interactions among river water, groundwater and salt lake brine is important for sustainable exploitation of brine mineral resources. In this study, we investigated the water exchange rate in dry and wet seasons, and assessed the influence of seasonal water exchange on brine concentration and crystallization process in the Nalenggele (NLGL) catchment of Qaidam Basin, China. The results show that the surface water infiltration and groundwater recharge rates in the wet season were 2.81 × 10−3 and 1.15 × 10−3 m3/(s·m) in upstream, 1.63 × 10−2 and 1.53 × 10−2 m3/(s·m) in midstream, and 2.83 × 10−4 and 6.82 × 10−5 m3/(s·m) in downstream, respectively; while their counterparts in the dry season were 9.81 × 10−4 and 5.05 × 10−4 m3/(s·m) in upstream, and 8.34 × 10−3 and 7.78 × 10−3 m3/(s·m) in midstream, respectively. The water exchange strongly influenced brine concentration and crystallinzation process, with brine chemistry belonging to 3K2SO4·Na2SO4 and KCl types in wet and dry seasons, respectively. The strong water exchange in wet season destroyed the water-salt balance, while the low water exchange rate in dry season facilitated preparation of KCl products.

Continuous cropping often leads to an unbalanced soil microbial community, which in turn negatively affects soil functions. However, systematic research of how these effects impact the bacterial composition, microbial functional traits, and soil metabolites is lacking. In the present study, the rhizosphere soil samples of Tibetan barley continuously monocropped for 2 (CCY02), 5 (CCY05), and 10 (CCY10) years were collected. By utilizing 16S high-throughput sequencing, untargeted metabolomes, and quantitative microbial element cycling smart chips, we examined the bacterial community structure, soil metabolites, and bacterial functional gene abundances, respectively. We found that bacterial richness (based on Chao1 and Phylogenetic Diversity [PD] indices) was significantly higher in CCY02 and CCY10 than in CCY05. As per principal component analysis (PCA), samples from the continuous monocropping year tended to share more similar species compositions and soil metabolites, and exhibited distinct patterns over time. The results of the Procrustes analysis indicated that alterations in the soil metabolic profiles and bacterial functional genes after long-term continuous cropping were mainly mediated by soil microbial communities ( P  < 0.05). Moreover, 14 genera mainly contributed to the sample dissimilarities. Of these, five genera were identified as the dominant shared taxa, including Blastococcus , Nocardioides , Sphingomonas , Bacillus , and Solirubrobacter . The continuous cropping of Tibetan barley significantly increased the abundances of genes related to C-degradation ( F  = 9.25, P  = 0.01) and P-cycling ( F  = 5.35, P  = 0.03). N-cycling significantly negatively correlated with bacterial diversity ( r  =  − 0.71, P  = 0.01). The co-occurrence network analysis revealed that nine hub genera correlated with most of the functional genes and a hub taxon, Desulfuromonadales, mainly co-occurred with the metabolites via both negative and positive correlations. Collectively, our findings indicated that continuous cropping significantly altered the bacterial community structure, functioning of rhizosphere soils, and soil metabolites, thereby providing a comprehensive understanding of the effects of the long-term continuous cropping of Tibetan barley.

Lakes are the main reservoirs of persistent organic pollutants (POPs) from land, atmosphere and rivers. POPs in lakes undergo complex exchange, transformation, and degradation between water-air-sediment-biota interfaces, which are constrained and regulated by various physical, chemical and biological factors. POPs can affect ecological conditions, chemical properties of water and sediments, and biodiversity of the lake system. Therefore, it is important to study the sources, migration, transformation, environmental behavior and ecological impacts of POPs in lake ecosystems. This review summarizes research progress on detection technologies, diversity and origins, historical records, migration and transformation, distribution patterns, degradation and toxic effects of POPs in lakes. Finally, future directions related to POPs in lakes were summarized.

Background Southwest China is one of the largest karst regions in the world. Karst environment is relatively fragile and vulnerable to human activities. Due to the discharge of sewage and domestic garbage, the karst system may be polluted by pathogenic bacteria. The detection of bacterial distribution and identification of phage capable of infecting them is an important approach for environmental assessment and resource acquisition. Methods Bacteria and phages were isolated from karst water in southwest China using the plate scribing and double plate method, respectively. Isolated phage was defined by transmission electron microscopy, one-step growth curve and optimal multiplicity of infection (MOI). Genomic sequencing, phylogenetic analysis, comparative genomic and proteomic analysis were performed. Results A Klebsiella quasipneumoniae phage was isolated from 32 isolates and named KL01. KL01 is morphologically identified as Caudoviricetes with an optimal MOI of 0.1, an incubation period of 10 min, and a lysis period of 60 min. The genome length of KL01 is about 45 kb, the GC content is 42.5%, and it contains 59 open reading frames. The highest average nucleotide similarity between KL01 and a known Klebsiella phage 6939 was 83.04%. Conclusions KL01 is a novel phage, belonging to the Autophagoviridae , which has strong lytic ability. This study indicates that there were not only some potential potentially pathogenic bacteria in the karst environment, but also phage resources for exploration and application.

Investigating the microbial community structure and stress-tolerance mechanisms in the rhizospheres of salt-adapted plants along saline lakes is critical for understanding plant–microbe interactions in extreme environments and developing effective strategies for saline–alkaline soil remediation. This study explored the rhizosphere microbiomes of four salt-adapted species (Suaeda glauca, Artemisia carvifolia, Chloris virgata, and Limonium bicolor) from the Yuncheng Salt Lake region in China using high-throughput sequencing. Cultivable salt-tolerant plant growth-promoting rhizobacteria (PGPR) were isolated and characterized to identify functional genes related to stress resistance. Results revealed that plant identity and soil physicochemical properties jointly shaped the microbial community composition, with total organic carbon being a dominant driver explaining 17.6% of the variation. Cyanobacteria dominated low-salinity environments, while Firmicutes thrived in high-salinity niches. Isolated PGPR strains exhibited tolerance up to 15% salinity and harbored genes associated with heat (htpX), osmotic stress (otsA), oxidative stress (katE), and UV radiation (uvrA). Notably, Peribacillus and Isoptericola strains demonstrated broad functional versatility and robust halotolerance. Our findings highlight that TOC (total organic carbon) plays a pivotal role in microbial assembly under extreme salinity, surpassing host genetic influences. The identified PGPR strains, with their stress-resistance traits and functional gene repertoires, hold significant promise for biotechnological applications in saline–alkaline soil remediation and sustainable agriculture.