Bacterial Community Structure and Diversity in the Aqueous Environment of Shihou Lake and its Relationship with Environmental Factors

Characterization of Microbial Carbon Metabolism in Karst Soils from Citrus Orchards and Analysis of Its Environmental Drivers

Karst regions (KRs) have created significant karst carbon sinks globally through the carbon cycling process involving "water-carbon dioxide-carbonate rock-biota". Soil organic carbon (SOC) represents a crucial component of these carbon sinks. Microorganisms play a vital role in the soil carbon cycle, influencing the formation and preservation of SOC. Therefore, investigating the carbon metabolism of soil microorganisms in KRs is essential for clarifying the unique biogeochemical cycling mechanisms within these regions. In this paper, soils from karst regions (KRs), mixed regions (MRs) and non-karst regions (NKRs) were collected from citrus orchards in Mao Village, Karst Experimental Field, Guilin City, Guangxi Zhuang Autonomous Region, China. The ability to use different carbon sources was analyzed by Biolog-Eco microtiter plate technique; the number of microorganisms was detected by the plate colony counting method, and the microbial biomass was determined by the chloroform fumigation method. The results showed that the soil bacterial number (5.69 ± 0.39 × 106 CFU/g), microbial biomass carbon (MBC) (608.24 ± 63.80 mg/kg), microbial quotient (SMQ) (3.45 ± 0.18%), and Shannon's index (H') (3.28 ± 0.05) of the KR were significantly higher than those of the NKR. The pH showed a significant positive correlation (p < 0.05) with the bacterial number and H' (p < 0.05); SOC showed a highly significant positive correlation with bacterial number (p < 0.01), and a significant positive correlation with MBC, H', and average well change development (AWCD) (p < 0.05). Total nitrogen (TN) showed a significant positive correlation with MBC (p < 0.05); available potassium (AK) showed a significant positive correlation with bacterial number and MBC (p < 0.05). Exchangeable calcium (Ca2+) demonstrated significant positive correlations with bacterial number, MBC, and H' (p < 0.05). The above results indicate that soil bacterial number, carbon metabolic ability and diversity were highest in the KR. pH, SOC and exchangeable Ca2+ were the main influencing factors for the differentiation of soil microbial carbon metabolic diversity between the KR and NKR.

Seasonal dynamics and driving mechanisms of microbial biogenic elements cycling function, assembly process, and co-occurrence network in plateau lake sediments

Microbial community diversity significantly varies with seasonality. However, little is known about seasonal variation of microbial community functions in lake sediments and their associated environmental influences. In this study, metagenomic sequencing of sediments collected from winter, summer, and autumn from Caohai Lake, Guizhou Plateau, were used to evaluate the composition and function of sediment microbial communities, the potential interactions of functional genes, key genes associated with seasons, and community assembly mechanisms. The average concentrations of nitrogen (TN) and phosphorus (TP) in lake sediments were higher, which were 6.136 and 0.501 g/kg, respectively. TN and organic matter (OM) were the primary factors associated with sediment community composition and functional profiles. The diversity and structure of the microbial communities varied with seasons, and Proteobacteria relative abundances were significantly lower in summer than in other seasons (58.43-44.12 %). Seasons were also associated with the relative abundances of functional genes, and in particular korA, metF, narC, nrfA, pstC/S, and soxB genes. Network complexity was highest in the summer and key genes in the network also varied across seasons. Neutral community model analysis revealed that the assembly mechanisms related to carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) cycle-related genes were primarily associated with random processes. In summary, diverse functional genes were identified in lake sediments and exhibited evidence for synergistic interactions (Positive proportion: 74.91-99.82 %), while seasonal factors influenced their distribution. The results of this study provide new insights into seasonal impacts on microbial-driven biogeochemical cycling in shallow lakes.

Spatial distribution of benthic taxonomic and functional diversity in the Yellow River Basin: From ecological processes to associated determinant factors

One of the fundamental objectives in ecology is to investigate the ecological processes and associated factors governing the abundance and spatial distribution patterns of biodiversity. However, the reaction of biological communities to environmental degradation remains relatively unknown, even for ecologically crucial communities like macroinvertebrates in aquatic ecosystems. Here, we sampled 117 locations to quantify relative contributions of geographical and environmental factors, including water quality, land use, climate, and hydrological factors, to determine the absolute and relative compositions of macroinvertebrate communities and their spatial distribution in the Yellow River Basin (YRB), the sixth-longest river system on Earth. We assessed relative roles of species sorting and dispersal in determining macroinvertebrate community structure along YRB. Our results demonstrated that alpha and beta diversity indices showed an increase from the up- to low-reaches of YRB. The middle and low-reaches exhibited elevated species diversity and both regions exhibited relatively stable community compositions. The biodiversity of macroinvertebrates was influenced by a combination of geographical factors and environmental variables, with environmental factors predominantly serving as the principal determinants. Results of multiple linear regression and variance decomposition showed that the effect of environmental factors was approximately three times greater than that of spatial factors. These findings provide support for the hypothesis that species sorting, driven by environmental gradients, plays a significant role in shaping the community structure of macroinvertebrates in running water ecosystems at the basin scales. Moreover, the factors contributing to substantial shifts in biodiversity across different segments of YRB indicate that distinct river sections have been influenced by varying stressors, with downstream areas being more susceptible to the impacts of water pollution and urbanization resulting from human activities.

Synthetic consortia of four strains promote Schisandra chinensis growth by regulating soil microbial community and improving soil fertility

MAIN CONCLUSION

Synthetic consortia performed better in promoting Schisandra chinensis growth than individual strains, and this result provides valuable information for the development of synthetic microbial fertilizers. Schisandra chinensis is an herbal medicine that can treat numerous diseases. However, the excessive reliance on chemical fertilizers during the plantation of S. chinensis has severely restricted the development of the S. chinensis planting industry. Plant growth-promoting rhizobacteria (PGPR) can promote the growth of a wide range of crops, and synthetic consortia of them are frequently superior to those of a single strain. In this study, we compared the effects of four PGPR and their synthetic consortia on S. chinensis growth. The pot experiment showed that compared with the control, synthetic consortia significantly increased the plant height, biomass, and total chlorophyll contents of S. chinensis, and their combined effects were better than those of individual strains. In addition, they improved the rhizosphere soil fertility (e.g., TC and TN contents) and enzyme activities (e.g., soil urease activity) and affected the composition and structure of soil microbial community significantly, including promoting the enrichment of beneficial microorganisms (e.g., Actinobacteria and Verrucomicrobiota) and increasing the relative abundance of Proteobacteria, a dominant bacterial phylum. They also enhanced the synergistic effect between the soil microorganisms. The correlation analysis between soil physicochemical properties and microbiome revealed that soil microorganisms participated in regulating soil fertility and promoting S. chinensis growth. This study may provide a theoretical basis for the development of synthetic microbial fertilizers for S. chinensis.

Ammonia distribution and ecological risk assessment in nine fresh lakes in China

With the development of industry and economy, ammonia nitrogen pollutions in surface water are of great concern worldwide. This study investigated the historical contents of total ammonia nitrogen (TAN) and unionized ammonia molecules (NH3) in nine fresh lakes in China during 2014-2022. Three different classification methods (flood season, season, and geographical distribution) were used to analyze the concentration variation of TAN and NH3. The concentration of TAN first decreased and then increased in the flood season, showing a lower concentration in summer and a higher concentration in winter. The variation trend of NH3 was in an opposite way with TAN. Correlation analysis between ammonia and 10 water quality parameters and 4 pollution emission and treatment parameters showed that the correlation coefficient between TAN and total phosphorus (total nitrogen) was 0.44 (0.43), respectively. The correlation coefficients between average annual TAN concentration and total emissions (waste water treatment input) were 0.35 (0.53), respectively. Combined with ecotoxicity data from a series of aquatic species, the ecological risks of TAN and NH3 in lakes were evaluated using hazard quotient and joint probability curve methods. From 2014 to 2022, the probability of 5% species affected in the acute ecological risk of TAN and NH3 is lower than 0.01, but for the chronic ecological risk of TAN and NH3, the probabilities of 5% species affected are 0.003-0.030 and 0.04-0.14, respectively. The chronic ecological risks were higher than the acute ecological risks, and high risks in plateau lakes like Dianchi Lake should be paid more attention to.

Analysis of intestinal flora in elderly Uygur patients with sarcopenia

OBJECTIVE

This study was designed to analyze the structural characteristics of the intestinal flora of elderly Uygur patients with sarcopenia, thereby providing new ideas for clinical treatment.

METHODS

Firstly, fecal samples were collected from 40 elderly Uygur patients with sarcopenia (Sarcopenia group) and 40 healthy people (Control group). Next, significant differences in the intestinal flora between the two groups were analyzed based on 16S rDNA high-throughput sequencing. The linear discriminant analysis effect size (LEfSe) was used to estimate the magnitude of the effect of each component (species) abundance on the differential effect. Additionally, an analysis was also performed on the relationship between the intestinal flora and the cytokines in the peripheral blood of patients with sarcopenia.

RESULTS

The results of β diversity showed that there were differences in the structure of the intestinal flora between the two groups. Besides, the phylum level of intestinal flora between the two groups was not significantly different. However, the difference was significant in the intestinal flora at the order, family, and genus levels between the two groups. Among them, Lachnoclostridium, Photobacterium, Anaerobic Bacillus, Hydrogenophilus, and Eubacterium were enriched in the Sarcopenia group; Prevotella 9, Firmicutes FCS020 group, Streptobacillus, Aggregatibacter, Corynebacterium, Clostridium Difficile, and Haloanaerobium were enriched in the Control group. The LEfSe outcomes further showed that Lachnoclostridium was highly enriched in the Sarcopenia group; Prevotella 9 and Firmicutes FCS020 group were significantly enriched in the Control group. Furthermore, the relative abundance of Lachnoclostridium and Streptobacillus were significantly different in patients with high and low IL-6 levels.

CONCLUSION

In conclusion, Lachnoclostridium is significantly enriched in the intestines of elderly Uygur patients with sarcopenia; the increase in Lachnoclostridium abundance and the decrease in Streptobacillus abundance are associated with high levels of IL-6. Therefore, abnormal intestinal flora is related to inflammatory reflexes in patients with sarcopenia.

The investigation of the physiochemical factors and bacterial communities indicates a low-toxic infectious risk of the Qiujiang River in Shanghai, China

The overall water quality of urban rivers is closely related to the community structure and the physiochemical factors in them. In this study, the bacterial communities and physiochemical factors of the Qiujiang River, an important urban river in Shanghai, were explored. Water samples were collected from nine sites of the Qiujiang River on November 16, 2020. The water quality and bacterial diversity were studied through physicochemical detection, microbial culture and identification, luminescence bacteria method, and 16S rRNA Illumina MiSeq high-throughput sequencing technology. The water pollution of the Qiujiang River was quite serious with three water quality evaluation indexes, including Cd²⁺, Pb²⁺, and NH₄⁺-N, exceeding the Class V standard set by the Environmental Quality Standards for Surface Water (China, GB3838-2002), while the luminescent bacteria test indicated low toxicity of nine sampling sites. Through 16S rRNA sequencing, a total of 45 phyla, 124 classes, and 963 genera were identified, in which Proteobacteria, Gammaproteobacteria, and Limnohabitans were the most abundant phylum, class, and genus, respectively. The Spearman correlation heatmap and redundancy analysis showed that the bacterial communities in the Qiujiang River were correlated with pH; the concentrations of K⁺, and NH₄⁺-N, and the Limnohabitans were significantly correlated with the concentrations of K⁺, and NH₄⁺-N in the Zhongyuan Road bridge segment. In addition, opportunistic pathogens Enterobacter cloacae complex and Klebsiella pneumoniae in the samples collected in the Zhongyuan Road bridge segment and Huangpu River segment, respectively, were successfully cultured. The Qiujiang River was a heavily polluted urban river. The bacterial community structure and diversity were greatly affected by the physiochemical factors of the Qiujiang River, and it displayed low toxicity while a relatively high infectious risk of intestinal and lung infectious diseases.

Determinants and Assembly Mechanism of Bacterial Community Structure in Ningxia Section of the Yellow River

The Yellow River is a valuable resource in the Ningxia Hui Autonomous Region and plays a vital role in local human activities and biodiversity. Bacteria are a crucial component of river ecosystems, but the driving factors and assembly mechanisms of bacterial community structure in this region remain unclear. Herein, we documented the bacterial community composition, determinants, co-occurrence pattern, and assembly mechanism for surface water and sediment. In comparison to sediment, the bacterioplankton community showed significant seasonal variation, as well as less diversity and abundance. The network topology parameters indicated that the sediment bacterial network was more stable than water, but the bacterioplankton network had higher connectivity. In this lotic ecosystem, COD_Mn, Chl a, and pH affected the structure of the bacterioplankton community, while TP was the primary factor influencing the structure of the sediment bacterial community. The combined results of the neutral community model and the phylogenetic null model indicate that Bacterial communities in both habitats were mainly affected by stochastic processes, with ecological processes dominated by ecological drift for bacterioplankton and dispersal limitation for sediment bacteria. These results provide essential insights into future research on microbial ecology, environmental monitoring, and classified management in the Ningxia section of the Yellow River.