The temperature and precipitation variations caused by global climate change have profoundly impacted soil microbial communities. Understanding the impacts of the variations on the structure and function of microbial communities over time is crucial for predicting and adapting to future climate changes. [Objective] To explore the variations in the diversity, composition, structure, and succession of bacterial communities in mollisol soil in the context of climate change. [Methods] Based on a long-term soil transplantation experiment platform of Hailun, Fengqiu and Yingtan Agroecosystem Field Experiment Stations of the Chinese Academy of Sciences, we translocated the mollisol soil from a cold-temperate region (Hailun) to a warm-temperate region (Fengqiu) and a mid-subtropical region (Yingtan) to simulate the increasing conditions of temperature and precipitation. We collected 63 mollisol soil samples from Hailun, Fengqiu, and Yingtan during 2005–2011. We employed high-throughput sequencing of the 16S rRNA gene to study the diversity, composition, and structure of soil bacterial communities under different temperature and precipitation conditions. With consideration to the soil physicochemical properties, we analyzed the relationship between environmental factors and microbial community characteristics and calculated the species turnover rate. [Results] After six years of transplantation of the mollisol soil from the cold temperate zone to warm temperate and mid-subtropical zones, significant changes occurred in soil physicochemical properties, including decreases in soil organic matter and total nitrogen, along with a noticeable reduction in aboveground biomass. Moreover, the bacterial diversity in the soil decreased, and significant changes occurred in the community composition and structure. The dominant bacteria includedVerrucomicrobia,Proteobacteria,Acidobacteria, andActinobacteria, among whichVerrucomicrobia showed increased relative abundance after the soil transplantation to the warmer area Yingtan. Additionally, climatic factors were highly correlated with microbial community characteristics. The nonmetric multidimensional scaling analysis showed that the bacterial community structure evolved with changes in temperature and precipitation and over time, which was related to the increased microbial species turnover rate. The species turnover rates of bacterial communities varied significantly under different temperature and precipitation conditions, following an increasing trend of Hailun (0.030) < Fengqiu (0.033) < Yingtan (0.045). [Conclusion] A six-year increase in temperature and precipitation significantly reduced the bacterial diversity, altered the bacterial community composition and structure, and accelerated the species turnover.

[Objective] To compare the physicochemical properties and fungal community characteristics between rhizosphere soil and non-rhizosphere soil ofHippophae rhamnoides growing for different years in Pisha sandstone area of Inner Mongolia. [Methods] A total of 12 rhizosphere and non-rhizosphere soil samples were collected from the Pisha sandstone area of Ordos. Chemical methods were used to analyze soil physicochemical properties, and the fungal community composition in soil was analyzed by high-throughput sequencing. The correlations between fungal community characteristics and soil properties were analyzed. [Results] Total nitrogen (TN), available nitrogen (AN), available potassium (AK), organic matter (OM), and electrical conductivity (EC) of rhizosphere soil were higher than those of non-rhizosphere soil (P < 0.05). Soil moisture content (SMC) increased as the planting years increased (P < 0.05). The fungal richness and diversity in rhizosphere soil were higher than those in non-rhizosphere.Ascomycota andMortierellomycota were the common dominant phyla in rhizosphere soil and non-rhizosphere soil, andMortierella,Penicillium, andAspergillus were the common dominant genera. The key fungal groups in non-rhizosphere soil and rhizosphere soil wereMortierella andGibberella, respectively. The redundancy analysis showed that OM was a key soil factor affecting the soil fungal distribution.Mortierella was correlated with OM, AN, and total potassium (TK) (P < 0.05).Gibberella was correlated with AN, OM, and EC (P < 0.05). [Conclusion] The planting ofH.rhamnoides in Pisha sandstone area of Inner Mongolia increases the nutrients and fungal richness in the rhizosphere soil, improving the stability of the soil environment. Moreover, the cultivation ofH.rhamnoides increases the soil moisture, improving soil and water conservation and contributing to the ecological restoration. This study provides a theoretical basis for biodiversity conservation in the study area as well as for the ecological restoration and sustainable management ofH.rhamnoides shrubland.

[Objective] Currently, there are few studies on microorganisms in Antarctic ice cores, and the available studies mostly employ the pure culture and high-throughput sequencing methods, with limited knowledge about the microbial diversity. We studied the microbial community composition of the meltwater at −183 m depth of the Dalk Glacier in eastern Antarctica, aiming to provide a reference for the development of extremophiles in Antarctica. [Methods] We employed the culture, single-cell sorting, and high-throughput sequencing methods to study the microbial community composition in the meltwater at −183 m depth of the Dalk Glacier. [Results] We obtained bacterial isolates belonging to 94 genera, 19 orders of 10 phyla, in whichProteobacteria,Alphaproteobacteria, andSphingomonas were the dominant phylum, order, and genus, respectively. This result indicated high microbial diversity in the meltwater. The culture, single-cell sorting, and high-throughput sequencing yielded 25 bacterial strains, 24 bacterial strains, and 55 183 sequences (116 operational taxonomic units), respectively. The dominant taxa were different among the three methods. By the culture and single-cell sorting methods, we identified 7 bacterial strains with the 16S rRNA gene identity less than 98.65% compared with their closest relatives in GenBank, of which two strains had the identity less than 95.00% identity. Accordingly, we inferred that there may be two potential new genera and five potential new species. [Conclusion] We studied the microbial diversity in the meltwater of the Dalk Glacier in eastern Antarctica by using the culture, single-cell sorting, and high-throughput sequencing method and discovered rich bacterial species in the meltwater. Each method has its own advantages and limitations. This means that when studying microbial diversity, more comprehensive information about the composition of the microbial community can be obtained by combining different methods. The results of this study can serve as a reference for further research on the genetic resources in Antarctica.

Yuncheng Salt Lake, located in the southwest of Shanxi Province, has a long history and unique climatic and geographical features, harboring rich microbial resources. The soil ecosystem is of great significance for understanding the diversity and functions of bacteria in the saline-alkali soil. [Objective] To explore the diversity of bacteria in the soil and sediment of Yuncheng Salt Lake, analyze its influencing factors, and provide a scientific basis and reference for the sustainable management of saline-alkali soil ecosystems and the mining of pure cultures. [Methods] Eighteen soil samples were collected from six sampling sites of Yuncheng Salt Lake. We measured the soil physicochemical properties and carried out high-throughput sequencing of the 16S rRNA gene to analyze the impact of environmental factors on bacterial diversity. [Results] Pseudomonadota,Bacteroidota, andBacillota were the dominant bacteria in the soil of Yuncheng Salt Lake. The bacterial diversity and community composition showed significant differences among different sampling sites. The results of canonical correlation analysis indicated that total dissolved solids (TDS), total nitrogen (TN), total carbon (TC), and SO₄²⁻ had the greatest impacts on soil microbial diversity, followed by Na⁺, Ca²⁺, Cl⁻, available phosphorous (A-P), and pH. HCO₃⁻, nitrate nitrogen (NO₃⁻-N), ammonia nitrogen (NH₄⁺-N), K⁺, and Mg²⁺ had mild impacts on the diversity. [Conclusion] The soil microorganisms of Yuncheng Salt Lake had high diversity which was closely related to environmental factors. This study provides comprehensive biological information on the bacterial resources in the soil of Yuncheng Salt Lake, offering a theoretical basis for the exploration and research of bacterial resources in this lake.

[Objective] To reveal the dynamic changes of soil microbial community and nutrient cycling process in the artificial grass squares dominated by pioneering plants such asLeymus secalinus andCarex praeclara in the alpine sandy land. [Methods] Metagenomic sequencing and qPCR were performed for the structure analysis, functional gene annotation, and absolute abundance determination of soil microbial communities, which were combined with soil physico-chemical factors for redundancy analysis. [Results] The artificial establishment of grass squares increased the total nitrogen by 20%–68%, available phosphorus by 10%–247%, and organic carbon by 19%–56% in sandy soils. Furthermore, it increased the bacterial and fungal abundance by 17%–81% and 2%–95%, respectively. Specifically, it increased the relative abundance of plant growth-promoting bacteria, such asSphingomonas,Bradyrhizobium,Nitrospira,Solirubrobacter, andNocardioides. Furthermore, the artificial establishment of grass squares enriched theamoCAB gene cluster and thenxrAB gene cluster associated with ammonia oxidation and nitrite oxidation in the nitrogen cycle. In addition, a genetic signature for complete ammonia oxidation was identified. [Conclusion] The artificial establishment of grass squares increases the content of soil nutrients and microbial abundance and promotes the nutrient cycling in alpine sandy areas. Moderate grazing can increase the diffusivity of nitrogen sinks and promote the colonization of native pioneer plants in the sandy ecosystem. The findings provide theoretical references for future restoration of sandy ecosystems in similar high-altitude areas.

[Objective] Microbial prospecting for oil and gas, characterized by high resolution, high signal-to-noise ratio, minimal environmental interference, low costs, and short time consumption, garners increasing attention from exploration experts. However, in most cases, microbial prospecting is based on laboratory culture and analysis, which cannot accurately and comprehensively reflect thein-situ dynamic changes of microbiota in oil and gas resources in the geological history. In this study, we compared the microbial community structure and developmental characteristics between the gas-producing zone and the background zone in Hangjinqi Gas Field, aiming to identify the surface microbial anomalies related to oil and gas. [Methods] We conducted the bacterial 16S rRNA gene sequencing for the soil samples collected from Xinzao and Shiguhao areas of Hangjinqi. Furthermore, we compared the microbial diversity, analyzed the impacts of physicochemical parameters on microbial distribution, and identified microbial anomalies. The co-occurrence network analysis was employed to explore the assembly process and functional composition of microbial community in the surface soil above the reservoir. [Results] In the Hangjinqi area,Actinobacteria andProteobacteria were dominant, accounting for 72.47% of the total microbial abundance. The correlation analysis of environmental factors with microbial abundance showed that the distribution of microorganisms in this area was not significantly correlated with environmental factors. The microbial community structure presented significant differences between the gas-producing area and the background area. The co-occurrence network analysis of the gas-producing area revealed non-randomness and connectivity in the microbial community, indicating deterministic factors play a dominant role in the construction of microbial communities. Modular co-occurrence network analysis revealed the formation of specific functional modules within the microbial community, and different modules possibly served different functions. [Conclusion] By comparing the microbial diversity between the gas-producing and background area of Hangjinqi area, we identified the indicator genera in the gas-producing fields of Xinzao and Shiguhao. Furthermore, the co-occurrence network analysis identifiedGemmatimonas,Solirubrobacter,Pseudonocardia,Brevibacillus,Aeromicrobium, andNocardioides as the key taxa in the gas-producing area, which were associated with the main functional modules of carbon and nitrogen cycling and organic matter degradation, contributing to the degradation of hydrocarbons in the surface soil of the gas-producing area.

Endophytic bacteria in the roots of a healthy plant not only form a symbiotic relationship with the host plant but also promote plant growth and enhance plant uptake of nutrients, being of importance for maintaining terrestrial ecological balance and improving the comprehensive management of karst rocky desertification. [Objective] To explore the endophytic bacterial communities in the roots of host plants and provide a theoretical basis for deeply understanding the interaction mechanisms between host plants and endophytic bacteria. [Methods] The community structures of endophytic bacteria and physicochemical properties of rhizosphere soil ofCerasus humilis (Bge.) Sok. introduced for the control of rocky desertification in the karst graben basin with different years were studied. [Results] Planting years ofC.humilis had a direct and significant influence on the rhizosphere soil quality and an indirect effect on the bacterial community in the roots. The endophytic bacterial community was mainly characterized by symbiotic interactions. The top three dominant bacterial genera identified by the co-occurrence network in the first year and third year wereStreptomyces,Burkholderia-Caballeronia-Paraburkholderia andChitinophaga, and the top three dominant bacterial genera in the fifth year wereStreptomyces,Chitinophaga and Haliangium, which had biocontrol effects. The endophytic bacterial community was shaped by stochastic ecological drift processes. [Conclusion] The differences of endophytic bacterial communities along the planting year gradient are due to the microbial diversity endowed by stochastic processes. The interactions among endophytic bacteria and the dominant bacteria with biocontrol effects could promote the colonization and growth ofC.humilis, thereby enhancing the ecological and economic benefits ofC.humilis for the comprehensive control of rocky desertification in the karst graben basin.

[Objective] Loess-paleosol sequence (LPS) is a good carrier recording the changes of Quaternary climate and environment, and the characteristics of soil microorganisms in it indicates important information about the changes of soil environment. Due to the climate difference between loess and paleosoil, the soil microbial community may have different responses in the structural characteristics. The research on this problem, however, is limited. [Methods] In this paper, the loess (RL and JL)-paleosol (RS and JS) sequences in Renjiapo (R) and Jiuzhoutai (J) were selected, and high-throughput sequencing and linear discriminant analysis effect size (LEfSe) were employed to gain insights into the community structure and group differences of soil prokaryotes. Furthermore, functional annotation of prokaryotic taxa (FAPROTAX) was used to predict the community function, and the Mantel test was carried out to identify the environmental factors affecting the community stability of soil prokaryotes. [Results] The carbon and nitrogen in soil showed changes consistent with the magnetic susceptibility and Rb/Sr ratio, the alternative indicators of climate change. The content of carbon and nitrogen was high in the paleosol (RS and JS, especially in RS) and low in the corresponding loess (RL and JL). In the same climate era, Jiuzhoutai was drier and colder than Renjiapo. The paleosol deposition stage in Jiuzhoutai was affected by strong winter monsoon, which ultimately led to the gradual change from the dry-cold to wet-warm climate. In the prokaryotic community, thermophilic or mesophilic bacteria and archaea, such asAcidobacteria,Crenarchaeota, andChloroflexi, were abundant in RL and RS, while those with tolerance to drought and extreme environments, such asGemmatimonadetes,Actinobacteria,Firmicutes,Euryarchaeota, andDeinococcus-Thermus, had high abundance in JL and JS. The functional genes related to energy source and nitrogen, manganese, iron, and chlorine cycling had the highest expression levels in RS, while those involved in carbon, hydrogen, and sulfur cycling showed the highest expression levels in RL. The prokaryotic community in Jiuzhoutai had higher species diversity and fewer functional species than that in Renjiapo. Mantel test results indicated that soil organic carbon (SOC), soil water content (SWC), total nitrogen (TN), and nitrate nitrogen (NO₃⁻-N) were the key environmental factors influencing the stability and functions of the prokaryotic community in Renjiapo, while the influencing factors in Jiuzhoutai were TN, SOC, pH, and ammonium nitrogen (NH₄⁺-N). [Conclusion] During the warm-humid period, the microbial community differentiated into more functional categories and exhibited more vigorous life activities. When the climate was dry and cold, the microbial community completed the main life activities by improving species diversity and jointly maintaining the community survival and stability to adapt to environmental stress. The findings are of great significance for understanding the impacts of climate change on the diversity and functions of soil microorganisms.

[Objective] Coastal wetland ecosystems, situated at the interface of freshwater and seawater, are characterized by the seepage of groundwater with high Fe²⁺ concentrations into the surface layers of sediments, which forms wetland runoff. This runoff, combined with periodic tidal flooding, creates an oxic-anoxic interface conducive to the bio-oxidation of Fe²⁺ by Fe-oxidizing bacteria. However, there is a lack of comprehensive assessment of Fe-oxidizing bacterial communities in coastal wetland ecosystems. [Methods] We measured the basic environmental parameters such as the oxygen penetration depth in the sediments of five coastal wetland sites in Xisha Wetland Park in Chongming, Shanghai and Dongsha Beach in Zhujiajian Island in Zhoushan, Zhejiang. The community composition and distribution of bacteria and Fe-oxidizing bacteria were comprehensively deciphered by 16S rRNA gene amplicon sequencing. [Results] Dongsha Beach in Zhujiajian Island exhibited deeper oxygen penetration (reaching more than 10 mm) than Xisha Wetland in Chongming. The non-metric multidimensional scaling (NMDS) results indicated that the bacterial community structure was primarily influenced by environmental conditions that varied with geographical location, while the community structure of Fe-oxidizing bacteria was influenced by both the geographical location of the sampling sites and the oxygen penetration depth of the sediments. The dominant bacteria in Xisha Wetland and Dongsha Beach wereCyanobacteria,Gammaproteobacteria,Bacteroidetes,Alphaproteobacteria, andActinobacteria. The dominant genera of Fe-oxidizing bacteria wereGallionella,Rhodobacter,Lepthothrix, andSideroxydans. [Conclusion] We studied the Fe-oxidizing bacteria in the sediments of Xisha Wetland in Chongming and Dongsha Beach in Zhujiajian Island and discovered that the composition of Fe-oxidizing bacterial communities was closely linked to the oxygen penetration depth variations caused by different types of wetland sediments.

As an interdisciplinary subject combined with deep space exploration, astrobiology studies the habitability of extraterrestrial planets by the analogical study of the extreme environments on Earth, the exploration of carrier information of ancient life, and simulation. Notably, suitable environmental conditions are crucial for evaluating the habitability of planets. Recently, a large number of lava landforms suspected of lava tubes have been found on the Moon and planets such as Mars. These giant tube-shaped underground spaces may provide shelters for life to survive in consideration of the relative stable temperature inside and the function of radiation protection. Therefore, the analogical studies based on lava tubes on Earth can provide fundamental clues for exploring the traces of extraterrestrial life. Here, we review the microbial studies about the lava tubes on Earth, the implications of microbial metabolism of trace gas for astrobiology, and the recent progress in astrobiology, aiming to provide ideas for astrobiological research on lava tubes on Earth and other planets.