Abstract:

Abstract:LysM receptor-like kinases （LysM-RLKs） belong to the multi-gene family whose extracellular domains are directly involved in the perception of glycosyl compounds including chitin， peptidoglycans， and lipochitooligosaccharides， thereby activating pathways of plant immunity or symbiotic signal transduction. The function of the first LysM receptor gene， LYK3， in the model legume Medicago truncata was characterized in 2003. Subsequently， the function of more and more LysM receptor kinases was identified. This article provided a detailed enumeration and functional characterization of the LysM-RLK family in M. truncatula. The progress on studying LysM receptor kinase family in nodulation symbiosis， mycorrhizal symbiosis， and immune perception of Medicago truncata was summarized. It is indicated that the expansion of the number of LysM-RLKs genes within the M. truncatula has led to functional differentiation， but there is a phenomenon of functional redundancy among some genes as well. In addition， a close cross-linking between immune and symbiotic signals at the level of receptor perception mediated by LysM-RLKs was revealed. It will provide effective references for further studying LysM-RLKs genes in M. truncatula.

Abstract:Senescence is one of the major factors affecting the efficiency of nitrogen fixation in legume nodules， and in-depth studying the regulatory mechanisms of the senescence of nodule is of great significance. This article reviewed the progress on studying the senescence of nodule from the aspects including morphological characteristics， physiological and biochemical changes， pathways of senescence， and the regulation of material metabolism. The functions of senescence-related genes in both legume and rhizobia during the process of symbiotic nitrogen fixation were summarized. It is put forward that developing new methods and technologies of studying can contribute to a more thorough elucidation of the molecular mechanisms underlying the metabolism of key substances in the senescence of nodules. A thorough understanding of the molecular mechanisms of the senescence of nodule can be helpful for the genetic modification of delaying the senescence of nodule， thereby improving the efficiency of nitrogen fixation in leguminous plants and promoting the sustainable development of agricultural production.

Abstract:Interfacial reaction is the foundation and prerequisite for bacteria to adhere，colonize，form biofilms，and perform ecological functions in the environment. It is of great significance for plants to absorb nutrients and antagonize pathogenic microorganisms. Most studies on the microbe-plant rhizosphere interactions are conducted from the perspectives of ecology and molecular biology，using multi-omics methods to study the effects of root exudates on the quantity of colonization，the composition of community，and the physiological functions of rhizosphere microorganisms. However，the physical and chemical interfacial mechanisms involved in bacterial colonization and their contributions to adhesion have been ignored. This article reviewed the regulatory effects of different types of root exudates on the properties of bacterial surface，the molecular composition of extracellular polymeric substances （EPS），and the function of adhesion in term of the mechanisms of interfacial interactions. The main modes and micro mechanisms of the interaction between bacteria and plant bio-macromolecules during the process of adhesion were summarized. The visualization methods for studying the process of rhizosphere colonization and methods for analyzing the interaction between microorganisms and plant bio-macromolecules were discussed. The directions of studies that urgently need to be strengthened including analyzing the biomolecular composition of rhizosphere，predicting the function of adhesion protein，and the in situ methods for observing the colonization of rhizosphere were proposed.

Abstract:Consolidated bioprocessing （CBP） is considered as the most ideal form for lignocellulose conversion. Although the modification of metabolic engineering can achieve CBP based on a single strain， excessive metabolic pressure alone leads to the suboptimal transformation efficiency of strain. This article focused on the interspecific division in the microbial community of degrading natural lignocellulosic to systematically understand the interspecific division of labor and realize the rational design of CBP. The current patterns of interspecific division of labor were reviewed in terms of the synergistic hydrolysis of substrate， the cross-feeding of nutritional factors， and the restriction of “sugar cheaters”. The application of interspecific division of labor in lignocellulose conversion， the challenges and development directions of studying interspecific division in microbial communities of natural lignocellulose were introduced. It will provide principles for designing the construction of a microbial community with consolidated bioprocessing to promote the efficient biotransformation of lignocellulose.

Abstract:Algae and bacteria play important roles in the biogeochemical cycle，energy flows of important elements in the ecosystem.Some bacteria can have beneficial interactions with algae by promoting the growth of algae and helping algae resist stress，thereby having important impacts on the survival，competition，and physiological functions of both partners.This article reviewed the main ways of interaction，microbial communities，molecular mechanisms，and the recent applications of beneficial interactions between algae and bacteria in the treatment of environmental pollution，biomass energy，and synthetic biology to in-depth study the beneficial interactions between algae and bacteria.The studies on the beneficial interactions between algae and bacteria were prospected.It will not only play an important role in understanding the structure and function of microbial community in aquatic environments，and the mechanisms and effects of relationships among microbial species，but also provide important scientific basis for maintaining the health of ecosystems，mining and utilizing the biological resources for the benefit of humanity.

Abstract:Biological soil crusts are the main cover of the soil surface in arid areas， in which the microorganisms play an important role in regulating the climate sensitivity of carbon cycling in dry areas. At present， there are still disagreements in the studies on the effects of climate warming on the microbial communities and their respiration in biological soil crusts. This article summarized the emission patterns of carbon in biological soil crusts in different experimental cycles， seasons， and types of biological soil crusts through the warming experiments of simulating climate warming to more accurately predict the carbon balance in arid areas in the future. The intrinsic reasons for the differences in carbon emissions were analyzed by combining changes in microbial abundance and organic carbon. The results showed that short-term warming （below 2 year） led to a significant decrease in the abundance of moss or lichens in the biological soil crust， thereby increasing the content of organic carbon in soil， with a synchronous increase in the emissions of net carbon depending on the content of moisture in soil. Long-term warming （greater than 5 year） reduced the sensitivity of microorganisms to temperature and humidity， and the abundance and composition of microorganisms tended to stabilize， resulting in relatively stable content of organic carbon and the emissions of net carbon. The existing results reflect the patterns of and reasons for carbon emissions in biological soil crusts， but the underlying regulatory mechanisms involved by microorganisms are still unclear. Therefore， it is necessary to focus on studying the response mechanism of the carbon metabolism of microorganisms in biological soil crusts to warming in the future. It will provide important theoretical basis for evaluating carbon balance in arid areas.

Abstract:The specific predatory bacteria Bdellovibrio and like organisms （BALOs） are been highly valued due to their potential applications in agriculture， industry and medicine， especially in treating the infections caused by pathogenic bacteria with antibiotic resistance. However， many fundamental scientific issues regarding BALOs have been unclear in the past decades， which is the bottom cause why these types of bacteria have not been effectively developed and utilized yet. In recent years， significant progress has been made in the life cycle， mechanisms of predation， the distribution of resource and the diversity of BALOs， and the applications of BALOs in medicine， agriculture， and industry. Especially since the formal establishment of the phylum Bdellovibrionota in 2021， there has been an explosive growth in studies related to BALOs. This article systematically reviewed the progress on studying BALOs. It was focused on introducing the latest reports on predatory mechanisms of BALOs and other outstanding achievements to promote the understanding and further application of BALOs resources， and to guide the studies on BALOs in the future.

Abstract:Carbon in soil is an important component of the global carbon cycle，and the processes of carbon cycling play a crucial role in regulating climate，with microorganisms being the key driving force behind carbon cycling in soil. This article reviewed the roles and mechanisms of microorganisms in the input of organic carbon in soil，formation and stabilization of organic matter in soil，the processes of decomposing and mineralizing organic matter in soil，and the effects of soil properties，climate conditions，plant factors，and human activities on microorganisms mediated carbon cycling in soil，especially the progress and theoretical updates in related studies. Microorganisms in soil can indirectly promote the photosynthesis in plant and the input of carbon in soil through its symbiosis with plants，and can directly participate in the fixation and transformation of carbon in soil. Microbial residues and their secretions play a crucial role in the formation of mineral-associated organic matter and aggregates in soil，which is beneficial for the long-term stability of organic carbon in soil. The microorganisms mediated effect of priming has a regulatory effect on the decomposition of organic matter in soil，which can affect the emissions of greenhouse gases such as CO₂ and CH₄ from the soil. Studies on the mechanism of microorganisms mediated processes of stabilizing the organic carbon and storing carbon in soil in the future should be strengthened and focus on the complex relationship between the structure and function of microbial community and the carbon cycling in soil，as well as their response to global changes. It will provide new insights for China to achieve its major strategic goals of “carbon peak” and “carbon neutrality” through enhancing the potential of carbon sequestration or the function of carbon sink with microbial activity.

Abstract:Prokaryotic Argonautes （pAgos） are programmable nucleases involved in cellular defense against foreign DNA invasion. In vitro， pAgos can bind to small single stranded guide nucleic acid （ssDNA/ssRNA） to recognize and cleave complementary DNA/RNA. In vivo， pAgos preferentially target multiple copies of genetic elements， bacteriophages， and plasmids， thereby inhibiting the propagation of invading nucleic acids and bacteriophage infections. Prokaryotic Argonautes （pAgos）， as an emerging class of programmable nucleases， are more flexible than the most widely used CRISPR Cas system and has shown great potential in biotechnology. Previous studies were primarily focused on the thermophilic pAgos. Nowadays， the main applications based on thermophilic pAgos include molecular diagnosis and DNA assembly in vitro. Researchers have gradually shifted their focus to pAgos from mesophilic biological sources to promote the application of Ago-based biotechnology in vivo， such as gene editing. Although genome editing has not yet been achieved by pAgos， it’s possible to develop the next generation techniques for genome-editing based on pAgos with more and more pAgos being discovered and researchers studying the catalytic mechanism of pAgos in depth. This article summarized the known representative pAgos and biotechnologies based on the development of pAgos. The challenges and potential strategies faced by the application of pAgos in prokaryotic and eukaryotic organisms were briefly analyzed.

Abstract:Gamma-aminobutyric acid （GABA） is a four carbon and non-protein amino acid with broad application prospects in food， agriculture， medicine， chemical and other fields. The production of GABA with microbial methods has been received increasing attention due to its advantages of mildness and sustainable development. Therefore， this article systematically introduced the methods of producing GABA， the biosynthetic pathways in organisms， and the progress in studying the microbial production of GAB to achieve an environment-friendly， convenient， and more efficient method of producing GABA that meets the strict requirements for additives in the food， pharmaceutical， and animal husbandry industries. It summarized the current level of whole-cell catalysis and de novo microbial synthesis of GABA. Researchers are committed to screening and optimizing enzymes with high efficiency and stability of catalysis， and improving the efficiency of synthesizing GABA by finely regulating the metabolic pathways of microorganisms. Studies in the future need to optimize the performance of enzymes and strains， reduce costs of production， and explore pathways for industrialized production at larger scale.

Abstract:Microplastics are an emerging pollutant that poses potential environmental risks to ecosystems in soil due to the widespread use and improper treating of plastic materials. Microplastics provide new habitats for microorganisms in soil and form a unique ecosystem with the surrounding environment - the plastisphere. Artificial plastics are not easily degraded in soil environments， posing a severe and persistent ecological threat to the original environment in soil. Recent studies on the plastisphere have mainly focused on aquatic ecosystems， and understanding of the combined effects of plastisphere in soil on microorganisms， microplastics， environment in soil， and other pollutants is still very limited. This article reviewed the progress on studying ecological risks of the plastisphere as new habitats for microorganisms in soil to investigate the mechanism of the interaction between microorganisms and microplastics of plastisphere in soil and the resulting ecological effects. The selection effect of plastisphere in soil on microorganisms and the migration and transformation of microplastics， the changes of soil structure and carbon cycle in soil caused by plastisphere in soil， and the combined effect with other environmental pollutants were mainly discussed. It will provide valuable guidance for studying the plastisphere of ecosystems in soil in the future.

Abstract:Pollution of heavy metals poses a huge threat to food security and human health， and many methods for repairing the pollution of heavy metals in farmland have been developed. The supplementation of selenium significantly reduces the absorption of heavy metals by crops， while promoting their growth in soils polluted by heavy metals. The application of selenium has become a new way to mitigate the absorption of heavy metals by crops. This article reviewed five mechanisms including the alteration of the bioavailability of heavy metals in soil， competition between selenium and heavy metals in plant uptake channels， the promotion of forming iron plaque in plant roots， the induction of morphological and structural changes in plant roots， the regulation of gene expression involved in the chelation and transport of heavy metals in plants by which selenium mitigates the absorption of heavy metals by crops. The potential risks and priorities of studying selenium in mitigating the absorption of heavy metals by crops in the future were prospected. It will provide insights and a scientific basis for the use of selenium as a highly efficient inhibitor of the absorption of heavy metals in agricultural practices.

Abstract:Strong-flavor Baijiu is one of the important types of Chinese liquor. The ethyl caproate is the characteristic flavor compound in strong-flavor Baijiu. The precursor caproic acid required for the synthesis of ethyl caproate mainly relies on the metabolism of caproic acid-producing bacteria （CPBs） during the process of fermentation. Studies on the isolation， identification and metabolic functions of CPBs have become one of the hotspots in improving the quality of Baijiu. This article reviewed the isolation of CPBs from pit mud. Three types of CPBs commonly used in the fermentation system of strong-flavor Baijiu and the pathway of synthesizing caproic acid were introduced. The effects of pH and the composition of substrate on the yield of caproic acid were discussed. The impacts of other microorganisms in the microbial community on CPBs were introduced as well. It will provide a theoretical basis for improving the quality of strong-flavor by investigating the mechanism and affecting factors of producing caproic acid driven by microorganisms in the fermentation system of strong-flavor Baijiu.

Abstract:Bioinformatics analysis， spatiotemporal expression localization， GUS staining localization and gene silencing were used to study the mechanism of SBT family proteins in the soybean-rhizobia symbiosis to investigate the function of the GmSBT1 gene in symbiotic nitrogen fixation between rhizobia and host plants. The results showed that the GmSBT1 gene was specifically induced by rhizobia and only expressed at high levels in the nodules， possibly functioned in the rhizobia cortex and bacterial cells. RNA interference significantly reduced the fresh weight， nodule weight， and nitrogenase activity aboveground. It is indicated that the GmSBT1 protein plays an important role in the formation and development of nodules， and the nitrogen fixation in nodules as well.

Abstract:A pot culture method with vermiculite mixed soil as substrate under greenhouse conditions was used to study the effects of single or double inoculation of rhizobia and arbuscular mycorrhizal fungi on the growth of 10 soybean lines planted in most regions of China to investigate the dual inoculation effect of arbuscular mycorrhizal fungi （AMF） and soybean rhizobia and their matching with different soybean lines. The results showed that both rhizobium Bradyrhizobium japonicum USDA110 and mycorrhizal fungus Rhizophagus irregularis infected 10 lines of soybean plants， forming a symbiotic structure. Single inoculation of rhizobia or mycorrhizal fungi significantly increased the aboveground fresh weight of soybean. Among them， single inoculation of rhizobia increased the aboveground fresh weight of soybean line 119， 851， and 921 by 102% to 429%， and single inoculation of mycorrhizal fungi increased the aboveground fresh weight of most soybean lines by 39% to 255%. The symbiotic colonization of mycorrhizal fungi showed a delayed phenomenon under the dual inoculation conditions of rhizobia and mycorrhizal fungi. The single nodule volume of soybean line 985， 851， and 115 increased， and the nitrogenase activity was enhanced when mycorrhizal fungi were present. Therefore， the same inoculation method had different effects on different lines of soybeans， and the same line of soybeans had differences in growth after being treated with different inoculation methods. Soybean line 985 and 115 had the best effect with dual inoculation method， soybean line 167， 509， 921， and 187 had the best effect with single inoculation method， while single inoculation of rhizobia or mycorrhizal fungi in soybean line 119， 909， and 045 can be used to increase yield.

Abstract:Antibiotics and heavy metals are persistent pollutants in the environment， and the assessment of their toxicity to organisms has always been a hotspot of study. This article investigated the effects of single and combined pollution of tetracycline/sulfamethoxazole and cadmium ions on the growth of Synechocystis sp. PCC6803. The results showed that a single exposure to 100 ng/L sulfamethoxazole（SMX） stimulated the growth and photosynthetic activity of Synechocystis， whereas treatment with tetracycline（TC） had no significant effect. Cadmium ions（Cd²⁺） at 0.001 mg/L did not significantly affect the physiology of Synechocystis， but Cd²⁺ at 0.5 mg/L significantly inhibited the growth and photosynthesis of Synechocystis. This concentration downregulated photosynthesis-related gene（psbA2）， disrupted the antioxidant system of Synechocystis， damaged its cell membranes， and stimulated the secretion of its extracellular polysaccharides. When 100 ng/L TC coexisted with 0.001 mg/L Cd²⁺ synergistically， the cellular esterase activity was stimulated. 100 ng/L SMX alleviated oxidative damage caused by 0.5 mg/L Cd²⁺， resulting in the reduced production of reactive oxygen species（ROS）， the decreased activity of superoxide dismutase（SOD）， and the low content of malonaldehyde（MDA） compared to the group treated by single 0.5 mg/L Cd²⁺. When both were present simultaneously， they synergistically stimulated the activity of esterase in Synechocystis. Low concentrations of tetracycline had minimal impact on cell growth and did not significantly alter the cytotoxicity of Cd²⁺ on cells. In contrast， low concentrations of sulfamethoxazole promoted cell growth and mitigated the cytotoxic effects of Cd²⁺ on cells. It is indicated that it is necessary to comprehensively consider the combined pollution of antibiotics and heavy metals when pollution is assessed.

Abstract:Integrated fertilizer management（IFM） with a higher N dose and more fertilizer splits has been designed to increase rice yield for the full double rice system instead of for farmers in the subtropical regions of China.Higher levels of chemical fertilizers negatively affect the environment and microbial ecology， but more splits to meet plant demand might reduce adverse effects and promote soil function.A field experiment for double rice cropping conducted in 2013-2014 was used to study whether integrated fertilizer management has beneficial effects on the microbial community and microbial function compared with conventional practices of farmers（FP）.A randomized block including integrated fertilizer management（IFM） and conventional practices of farmers（FPs） was designed.Rhizosphere and non-rhizosphere soils were collected at three time points during the season of growing late rice to investigate the chemical properties and enzyme activity in soil.The phospholipid fatty acids（PLFA） were used to identify microbial biomass and community composition.The results showed that IFM treatment reduced the ratio of Gram-positive bacteria（GP） to Gram-negative bacteria（GN） and the index of microbial stress in rhizosphere soil compared with the FP treatment.IFM promoted the activity of sucrase， acid phosphatase， and arylsulfatase in the rhizosphere soil at the stage of panicle differentiation and full-heading， while inhibiting the activity of urease at the stage of maturity.The results of analyzing redundancy showed that available nitrogen and total nitrogen explained 15.9% and 12.5% of the variability in the microbial community and enzyme activities， indicating that N availability and its level play key roles in regulating the microbial community and enzyme functions in paddy soil.The enzyme activity was significantly explained by Gram-negative bacteria（GN，5.39%）， fungi（3.88%） and AM fungi（3.09%）.The index of microbial stress was negatively correlated with the activity of phosphatase and sucrase， indicating that both bacteria and fungi are involved in the regulation of enzyme activity in soil.It is indicated that IFM mainly regulates the rhythm of nitrogen incorporation in paddy soil to change the composition of microbial communities， thereby enhancing enzyme activity in soil before maturity and promoting nutrient cycling during the growth of rice.

Abstract:FeOB were enriched with modified wolf’s mineral medium （MWMM） to screen microaerobic Fe²⁺ oxidizing bacteria （FeOB） with better oxidative abilities to Fe²⁺，evaluate its effects on improving soil and the microbial communities and functions of soil in gleyed paddy field，and lay a foundation for establishing technologies of improving microorganism in gleyed paddy fields.The FeOB strain was taxonomically identified with combined technologies including 16S rRNA sequencing.The 100 mL fermentation liquid of the strain with different concentration of 10⁶ （T1），10⁷ （T2），10⁸ （T3） CFU/mL was used to treat the soil in gleyed paddy field and evaluate the effects of the strain on the reducing substances，nutrients，abundances of functional genes for nitrogen cycling （NCFG） and rice seedlings of soil in gleyed paddy field.16S rRNA high-throughput sequencing technology was used to evaluate the effect of this strain on the soil microecology.The results showed that the FeOB strain screened with strong oxidative effect on Fe²⁺ was identified as Lysinibacillus sphaericus WH07.Compared to CK，the soil redox potential （Eh） was significantly increased （P<0.05） and shifted from negative potential to positive potential.The total amount of reducing substance in soil treated with T1，T2，and T3 decreased by 26.47%，41.53%，and 53.19%，respectively.The content of ferrous decreased by 0.37%，21.50%，and 50.09%，while the content of manganese decreased by 7.84%，21.57%，and 37.25%.The content of alkaline hydrolyzed nitrogen in soil significantly increased by 15.50%，27.38%，and 48.90% （P<0.05），while the available phosphorus significantly increased by 12.52%，17.34%，and 27.38% （P<0.05）.The available potassium significantly increased by 11.56%，17.20%，and 19.34% （P<0.05），and the organic matter significantly increased by 8.66%，22.22%，and 45.05% （P<0.05）.The pH significantly increased by 3.40%，8.94%，and 16.99% （P<0.05）.The abundance of AOA-amoA gene in soil increased by 11.94%，14.68%，and 33.83%，respectively.The abundance of nosZ gene increased by 42.97%，75.78%，and 118.75%，while the abundance of nifH gene increased by 38.29%，51.05%，and 216.13%.The abundance of UreC gene increased by 16.74%，54.51%，and 60.94%.The plant height of rice increased by 5.44%，10.98%，36.00%，the leaf age of rice increased by 10.21%，23.42%，36.94%，the fresh weight of rice increased by 12.61%，22.52%，28.38%，and the white root number of rice increased by 10.14%，32.92%，and 46.81%.The Chao1 and Shannon index of microbial diversity in soil was significantly decreased compared to CK （P<0.05）.Among the top 10 bacteria in soil with relative abundance at the Phylum level，8 phyla including Proteobacteria were significantly downregulated （P<0.05），while 2 phyla including Bacteroidetes and Firmicutes were significantly upregulated.Among the top 10 bacteria in soil with relative abundance at the Phylum level，8 phyla including Proteobacteria were significantly downregulated （P<0.05），while 2 phyla including Bacteroidetes and Firmicutes were significantly upregulated.Among the top 50 bacteria in soil with relative abundance at the genus level，20，19，and 22 genera including 6 FeOBs such as Macellibacteroides et al were significantly upregulated （P<0.05） in the three treatments，while 25 genera including 4 Fe reducing bacteria such as MBNT15 et al were significantly down-regulated in all three treatments （P<0.05）.The results of analyzing regulatory network showed that the strain WH07 had the potential to synergistically improve the physicochemical properties and biological activity of soil with FeOB，ultimately promoting the growth of rice seedlings.It is indicated that the application of strain WH07 significantly improves the physicochemical properties of soil in the gleyed paddy field and change the structure and function of microbial community in soil.

Abstract:The changes in the physicochemical properties， the diversity of microorganisms and the structure of microbial community in the soil planted continuously with flue-cured tobaccos of different planting years including continuous cropping for 0 year （CK）， continuous cropping for 2 years （T1）， continuous cropping for 4 years （T2）， continuous cropping for 6 years （T3）， and continuous cropping for 8 years （T4） in Hanzhong area of Shaanxi Province were analyzed to study the key factors affecting the obstacles for continuous cropping of flue-cured tobacco and its patterns. The results showed that the organic matter， pH， and the content of total carbon in soil decreased with the increasing years of planting. The organic matter， pH， and the content of total carbon in the soil of T4 was 8.34%， 25.39%， and 25.20% lower than that of CK. The diversity and abundance of bacteria and fungi in soil showed a trend of increasing first and then decreasing， with the dominant bacterial phyla being Actinobacteriota， Proteobacteria， Acidobacteriota， Chloroflexi and Firmicutes. The dominant fungal phyla were Ascomycota， Basidiomycota， and Mucoromycota. Compared with CK， the relative abundance of microorganisms under T3 changed significantly， with change in Actinobacteria， Firmicutes， and Basidiomycota of 4.04%， 6.24%， and 28.86%， respectively. It is indicated that continuous cropping of flue-cured tobaccos reduces the content of organic matter， pH， and the content of total carbon in soil， affecting the composition of microbial community in soil.

Abstract:The dilution coating plate method was used to isolate and screen a salt-tolerant strain SF-18 with significant antibacterial activity from soil samples in Aksu saline alkali land，Xinjiang to obtain biocontrol agents with elite antibacterial activity from extreme environments. The stability of the antagonistic activity of the supernatant of strain SF-18 cell-free fermentation was determined using the Oxford Cup method，with the Verticillium dahliae as an indicator strain. The whole genome of strain SF-18 was sequenced with Illumina Novaseq platform and PacBio sequel platform. Data sequenced were used to assembly gene，annotate the function of gene，and predict gene clusters involved in synthesizing secondary metabolites. The results showed that strain SF-18 had a significant inhibitory effect on Staphylococcus aureus and Verticillium dahliae，and grew in the broth containing 18% NaCl. The supernatant of strain SF-18 cell-free fermentation had strong antibacterial activity at -20-80 ℃ and tolerated pH 5-12 environments. The strain SF-18 was identified as belonging to the genus Bacillus based on analyzing the sequence of 16S rDNA gene and gyrB gene. The results of whole genome analysis showed that there were 480 genes of strain SF-18 involved in the metabolism of multiple carbon sources，including genes encoding compounds related to stress resistance such as spermidine and trehalose，and genes related to enzymes such as glucanase and chitinase that can hydrolyze the cell wall of pathogen. The results of predicting secondary metabolites showed that strain SF-18 contained gene clusters involved in synthesizing a various of resistant compounds including bacillaene，bacillibactin，mersacidin，fengycin，zwittermicin. It is speculated that strain SF-18 may achieve antibacterial effects by producing antibacterial secondary metabolites and related degradation enzymes，and has good application prospects in biological control of agriculture.

Abstract:Three genera of myxobacteria including Corallococcus sp. EGB， Myxococcus xanthus DK1622 and Cystobacter sp. 1404 were used to study the physiological function of thiamine I from myxobacteria. The relationship between the pathway of synthesizing thiamine and the growth and development of strain in the genomes of three myxobacteria was identified. The results showed that three myxobacteria had complete pathway of synthesizing thiamine in their genomes， and contained genes related to the recovery of thiamine precursor pyrimidine （4-amino-5-hydroxymethyl-2-methylpyrimidine， HMP）， but no genes related to the recovery of thiamine or its precursor thiazole was found. The presence of TPP-riboswitch at the upstream of the HMP synthase gene thiC regulated the transcription level of the thiC gene based on the concentration of thiamine in the environment. Mutant CL1006 and Mutant CL1007 were constructed by inserting the thiC gene into strain DK1622 and thiaminase I knockout mutant CL1003， respectively. It was found that CL1006 required additional addition of thiamine or HMP to recover growth in thiamine-free medium. The HMP treatment group significantly increased the colony diameter by 9.0% compared to the thiamine-treated group. CL1007 only grew on HMP plates， and the addition of intact thiamine alone did not restore its growth. However， when CcThi1 and thiamine were added together， the growth of CL1007 was restored. It is indicated that myxobacteria do not directly utilize exogenous thiamine， but can utilize pyrimidine precursors produced by decomposing thiamine through thiaminase I.

Abstract:Enterobacter sp.A11 and Comamonas sp.A23 with the ability to oxidize Fe and Mn compounds was used to study the feasible methods for co-removing the cadmium （Cd） and arsenic （As） in soil.The effects of the biological Fe and Mn oxides （BFMO） generated by the mixed strains of A11 and A23 on the absorption of cadmium and arsenic in B. rapa. The results of scanning electron microscopy （SEM） showed that iron and manganese oxides were located on the surface of cells and led bacteria to aggregate into clusters.The results of pot experiment showed that strains A11 and A23 immobilized Cd and As in soil，reduced the proportion of bioavailable Cd and As，increased the proportion of unavailable Cd and As，and exhibited the absorption and accumulation of Cd and As in the aboveground and root parts of Brassica rapa L. as well.It is indicated that the biological iron manganese oxide generated by the mixed strains of A11 and A23 has a good adsorption effect on cadmium and arsenic in B. rapa.

Abstract:The wet heartwood and normal wood of 6-year-old Populus deltoides Bartr. ‘Huashi2’ in the Jianghan Plain were used to study the role of bacterial and microbial communities in the pathogenesis in the wet heartwood of Populus. High-throughput sequencing was used to sequence the V5-V7 region of the 16S rRNA gene. The results of sequencing were analyzed with bioinformatics. Methods including principal component analysis， α-diversity index analysis， and microbial network analysis were used to study the differences in the structure and composition of the bacterial and microbial communities in the wet heartwood and normal wood of 6-year-old Populus deltoides Bartr. The results of principal component analysis showed that the bacterial abundance of the genera Ralstonia and Bacteroides was the highest， while the proportion of the genera Bacteroides， Pleomorphomonas and Hydrogenispora in wet heartwood was significantly higher than that in normal wood （P<0.05） at the genus level of the bacterial and microbial communities in the wet heartwood and normal wood of 6-year-old Populus deltoides Bartr. The results of analyzing the functions of microbial communities showed that Ralstonia were mostly phytopathogenic bacteria， which widely existed in wet heartwood. The results of analyzing the alpha diversity index showed that the diversity and species distribution uniformity of the community in the wet heartwood were higher than those in the normal wood， and the total number of species in the wet heartwood was lower than that in the normal wood. The results of analyzing the co-occurrence network showed that there was a lot of competition and antagonism between bacteria and microorganisms in the normal wood of Populus deltoides Bartr， and the community was relatively unstable. There were more synergistic and mutualistic relationships among bacteria in wet heartwood， and the microbial community was relatively stable. The results of analyzing key microorganisms showed that the key bacterial microorganisms in the wet heartwood of 6-year-old Populus deltoides Bartr. were Aquabacterium， WCHB1-32， etc.， and the key bacterial microorganisms in the normal heartwood of 6-year-old Populus deltoides Bartr. were Pleomorphomonas， Dysgonomonas， etc. These key microorganisms played an important role in stabilizing the structure of microbial network in the wet heartwood. It is indicated that the formation of wet heartwood in Populus deltoides Bartr. is affected by multiple factors and is the result of the joint action of microbial communities.

Abstract:Poria cocos was cultured on the solid medium using Lentinula edodes stalk as the sole substrate to study whether the mycelia of P. cocos can ferment and utilize L. edodes stalk substrate and improve its nutritional value and biological activity. The activity of key enzymes， the components of main nutrient， and the antioxidant activity of water extracts from the fermented substrate during solid-state fermentation of P. cocos were measured. The results showed that the activity of cellulose exonuclease reached 46.14 U/g at the 6th day of fermentation， then rapidly decreased to 17.15 U/g， and remained basically unchanged at the 18th day of fermentation as the process of fermentation progressed. The activity of carboxymethyl cellulase and xylanase reached 77.70 U/g and 74.23 U/g at the 12th day of fermentation， and then gradually decreased. The activity of β-glucosidase reached 75.06 U/g at the 18th day of the fermentation and then gradually decreased. Compared with the unfermented L. edodes stalk substrate， the content of total sugar， soluble protein， and insoluble dietary fiber in the fermented L. edodes stalk substrate significantly decreased， but the content of reducing sugar， polysaccharides， total phenols， total flavone， amino nitrogen， and soluble dietary fiber significantly increased. The antioxidant activity of water extracts from the fermented substrate was significantly increased. The scavenging rate of DPPH radical and hydroxyl radical increased by 97.75% and 38.15%， compared to the 0 day of fermentation. It is indicated that P. cocos can ferment L. edodes stalk， alter the composition of nutrient in L. edodes stalks， and that the fermented substrate has good ability to scavenge free radicals.

Abstract:Traditional high-temperature Daqu is produced by spontaneous fermentation， which has disadvantages including complex composition of microbial community and difficulty in controlling the components and content of required flavor. Wheat was used to prepare the solid microbial agents of Bacillus licheniformis BL44， Saccharomyces cerevisiae SCY62， Paecilomyces variotii PV3， Rhizomucor pusillus RP1 and Thermoascus crustaceus TC1 isolated and screened from the high-temperature Daqu to optimize the structure of microbial community in high-temperature Daqu and improve the quality of high-temperature Daqu. Two synthetic microbial communities were constructed with different addition ratios to replace the traditional Muqu （CK） in producing high-temperature Daqu. Brewing experiments in laboratory were conducted and analyzed. The results of high-throughput sequencing showed that the dominant fungal genus and the dominant bacterial genus of the three kinds of Daqu was Lichtheimia and Bacillus， respectively. The results of measuring the physicochemical indexes of the Daqu showed that the liquefaction and saccharification abilities of the high-temperature Daqu inoculated with the synthetic microbial communities were significantly improved compared to CK. The results of analyses with gas chromatography-mass spectrometry showed that inoculating synthetic microbial communities instead of traditional Muqu significantly increased the content of tetramethylpyrazine in Daqu and fermented grains. The content of tetramethylpyrazine in Daqu inoculated with synthetic microbial group 1 and microbial group 2 was 31.90 mg/kg and 56. 73 mg/kg， increased by 2.80 and 4.99 times compared to that of CK. In the high-temperature stacked fermentation mash， the content of tetramethylpyrazine inoculated with synthetic microbial group 1 and microbial group 2 was 0.76 mg/kg and 2.74 mg/kg， increased by 4.03 and 14.61 times compared to that of CK. It is indicated that the synthetic microbial community has potential application in directionally regulating the activity of enzymes in Daqu and the components and contents of some specific flavors in Baijiu.