Sugarcane smut caused by Sporisorium scitamineum is one of the major diseases affecting the development of China's sugar industry, and biocontrol is currently the most efficient and safe means, which necessitates the screening of antagonists with strong environmental adaptability and inhibitory effects. [Objective] To isolate and identify the strains with good antagonistic effects against S. scitamineum from soil and provide high-quality biocontrol strain resources for the efficient prevention and control of sugarcane smut. [Methods] The antagonists were isolated by the plate confrontation assay, and their taxonomic status was determined by morphological observation, physiological and biochemical tests, and 16S rRNA gene sequencing. The pot and field experiments were conducted to study the inhibition effects of the antagonists on sugarcane smut. [Results] Three strains of bacteria with significant antagonistic effects were obtained. Strains GB-3 and GH16-3 were identified as Bacillus velezensis and GH16-8 as B. amyloliquefaciens, with the inhibition zone diameters of (30.00±1.07), (44.00±1.21), and (18.00±0.89) mm and the inhibition rates of 16.12%, 31.92%, and 5.91%, respectively. The inhibition effects of the three strains against sugarcane smut were 74.33%, 76.57%, and 69.07% in pots and 20.08%, 55.59%, and 50.08% in fields, respectively. All the three strains had phosphorus-solubilizing ability, tolerance to extreme salt-alkaline environments, and inhibitory effects on a variety of phytopathogenic bacteria and fungi, with the indole-3-acetic acid (IAA) yields of 2.12, 1.30, and 1.22 mg/L, respectively. The application of the three strains increased the sugarcane plant height by 28.25%, 17.09%, and 23.31%, respectively. [Conclusion] Strain GH16-3 has strong environmental adaptability, growth-promoting effect, and prevention effect against sugarcane smut, demonstrating a promising application prospect.

[Objective] To investigate the effects of hydrogen sulfide (H₂S) on the structures of phyllosphere and rhizosphere microbial communities of soybean plants under drought stress. [Methods] High-throughput sequencing of the 16S rRNA gene was combined with bioinformatics analyses (α and β diversity, species composition, co-occurrence networks analysis, etc.) to study the phyllosphere and rhizosphere microbial communities of soybean plants before and after NaHS treatment. [Results] For the soybean plants under normal moisture conditions, the addition of NaHS decreased the diversity and increased the endemic species of phyllosphere microbial community. The addition of NaHS increased the diversity of rhizosphere microbial community of soybean plants under normal moisture conditions but not under severe drought. In addition, exogenous addition of NaHS altered the bacterial co-occurrence network, and the microbial communities in both phyllosphere and rhizosphere were so aggregated that neither rhizobium inoculation nor NaHS addition had significant influences on them. The addition of NaHS mildly affected the relative abundance of operational taxonomic unit (OTU) in the phyllosphere and decreased the relative abundance of OTU in the rhizosphere, which was particularly pronounced under severe drought. Rhizobium inoculation and NaHS addition enriched different microbial taxa in both phyllosphere and rhizosphere. [Conclusion] Under drought stress, H₂S had an insignificant modulating effect on the microbial community structure in the phyllosphere but a pronounced effect on the microbial community structure in the rhizosphere of soybean plants. H₂S reduced the relative abundance of total OTU in the rhizosphere and altered the bacterial co-occurrence network, thus influencing soybean adaptation to drought stress.

[Objective] To explore the effects of CbrB from the carbon catabolite repression system on the biocontrol performance of Pseudomonas protegens Pf-5. [Methods] The mutant Pf5274 with the markerless deletion of the coding region of cbrB was constructed by a double-crossover recombination event based on pJQ200SK. Moreover, the complementary strain of cbrB and the control strains were constructed by the plasmid complementation method based on pBBR1Am. Lastly, the effects of CbrB on the growth, biofilm formation, motility, antifungal activity, and pyoluteorin synthesis of Pf-5 were analyzed by the measurement of OD₆₀₀, crystal violet staining, agar plate culture, plate confrontation method, and pltL'-'lacZ fusion report strains, respectively. [Results] CbrB greatly slowed the growth of Pf-5 in the natural medium LB, but greatly sped up the growth of Pf-5 in the basic medium M9-glucose. In addition, CbrB significantly promoted the motility but inhibited the biofilm formation, antifungal activity, and pyoluteorin synthesis of Pf-5. [Conclusion] CbrB plays a role in regulating the growth, biofilm formation, motility, antifungal activity, and pyoluteorin synthesis of P. protegens Pf-5, thus regulating the biocontrol performance of this strain. This study provides a theoretical basis for the biocontrol capabilities of strains by genetic engineering and lays a foundation for probing into the biosynthesis of pyoluteorin.

[Objective] To detail the molecular evolution and ecological adaptation ofPseudoalteromonas arabiensis. [Methods] Illumina HiSeq X Ten and Oxford Nanopore PromethION were used for the whole genome sequencing ofPseudoalteromonas arabiensis N1230-9 isolated from the surface seawater of the Pacific Ocean. Bioinformatics tools were used to assemble and annotate the original sequencing data, and the type strainPseudoalteromonas arabiensis JCM 17292 was used for comparative genomic analysis. [Results] The genome of strain N1230-9 consisted of two chromosomes, with a size of 4 627 470 bp and the G+C content of 40.85%, encoding a total of 4 202 proteins. Genome annotation showed that strain N1230-9 carried functional genes contributing to the adaption to the marine environment. These genes were mainly involved in heavy metal resistance, iron-uptake systems, anti-phage defense systems, hydrolytic enzymes, carbohydrate metabolism, and two-component signaling systems. Comparative genomic analysis revealed that strain N1230-9 and strain JCM 17292 possessed unique genes conferring adaption to different ecological niches. These genes were primarily involved in heme uptake, heavy metal resistance, anti-phage defense, two-component signaling, and horizontal gene transfer. [Conclusion] P. arabiensis N1230-9 isolated from surface seawater has evolved unique genes for adaption to its ecological niche.

[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.

Anabaena azotica, as a photoautotrophic microorganism, has good carbon and nitrogen sequestration abilities. The application ofA.azotica could improve soil fertility and reduce the application of chemical fertilizers. However, the mechanism of carbon and nitrogen sequestration in soil byA.azotica and the sequestration efficiency of different strains remain to be studied. Therefore, it is important to screenA.azotica strains and probe into the processes of C and N sequestration in soil by the strains at the single-cell level. In view of the complex and dynamic process of element changes inA.azotica at the single-cell level, this study introduced the carbon and nitrogen sequestration process in soil byA.azotica. In addition, we expounded the principle, progress, and difficulties of using nano-secondary ion mass spectrometry combined with stable isotopic probing (NanoSIMS-SIP) and Raman spectroscopy imaging combined with stable isotopic probing (Raman-SIP) to analyze the spatiotemporal distribution of carbon and nitrogen at the single-cell level. This review focuses on the latest technological development and application of single-cell stable isotope technology for quantitative visualization of carbon and nitrogen sequestration inA.azotica. At the same time, future research on the visualization technology is prospected. This review is of great scientific significance for understanding the mechanism of carbon and nitrogen sequestration and the difference in nitrogen fixation efficiency of differentA.azotica strains in soil. It provides a theoretical basis for reducing the use of chemical fertilizers and improving soil fertility in agricultural production.

[Objective] To further understand the community structure, distribution, and ecological function differentiation mechanism of anammox bacteria in the groundwater of red soil areas. [Methods] We employed physical and chemical tests and high-throughput sequencing to study the microbial community structure, distribution of anammox bacteria, and their influencing factors in the groundwater of Ji'an. [Results] The nitrogen content exceeded the limit at three sites among the 11 groundwater sampling sites, with an over-limit rate of 27.3%. The water quality of only two sites met the requirements of the Standard for Drinking Water Quality (GB 5749—2022), which indicated an over-limit rate of 81.8%. Anammox bacteria presented wide distribution in groundwater, and the abundance ofhzsB gene in the 11 samples ranged from 3.67×10⁴ copies/g to 6.62×10⁸ copies/g. Compared with other habitats, the groundwater in red soil areas showed increased copy number of functional genes of anammox bacteria, which indicated that the environmental characteristics of groundwater were more suitable for the growth and metabolism of anammox bacteria. Four genera of anammox bacteria were detected at each site. Specifically,Candidatus Brocadia,Candidatus Scalindua,Candidatus Jettenia, andCandidatus Kuenenia showed the average abundance of 62.47%, 17.44%, 14.41%, and 5.67%, respectively. The correlation analysis suggested that the gene abundance of anammox bacteria was significantly correlated with ammonia nitrogen, manganese, and chloride, which indicated that the increases in ammonia nitrogen, manganese, and chloride in groundwater may enhance the activity and abundance of anammox bacteria. [Conclusion] The results of this study highlight the importance of anammox bacteria in the geochemical and biological cycling of elements in the groundwater of red soil areas, which will provide basic data for the bioremediation of groundwater pollution in the red soil areas of China.

[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.

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.