微生物来源的天然产物是开发抗生素药物的重要资源，而目前临床使用的天然产物来源的抗生素药物均开发于上世纪中叶。由于抗生素滥用而导致的细菌耐药性是人类面临的最大医学挑战之一。土壤微生物是重要的次生代谢产物（如药物）的资源库，多数天然抗生素来自于土壤微生物。因此，挖掘和开发新型土壤微生物资源及天然产物是当前医药领域的迫切需求。本研究以金乡大蒜根际土壤为研究对象，采用宏基因组测序方法，对根际土壤微生物群落多样性进行分析，并将菌群与土壤因子做相关分析；在此基础上，对根际土壤中的可培养的微生物进行抑菌条件筛选后，结合质谱技术和测序技术预测其相关的生物合成基因簇，以期筛选出具有潜力的链霉菌菌株，为新抗生素的发现提供种质资源。主要研究结果如下：

（1）通过宏基因测序技术对大蒜根际土壤微生物群落结构和功能多样性进行分析， 在细菌群落特征组成中，变形菌门、放线菌门和拟杆菌门占主导地位，占比约为90%；类诺卡氏属和鞘脂单胞菌属为属水平上的优势种群，占总菌比例的40%以上。真菌群落特征组成中，子囊菌门、担子菌门、毛霉菌门和壶菌门占主导地位，占比约为98%；曲霉属为主要优势菌，占比约20%。

（2）在微生物群落功能多样性方面，氨基酸的运输和代谢、碳水化合物的运输和代谢、能源产生和转换和信号转导机制为大蒜根际土壤微生物的主要功能；其中，变形菌门和放线菌门在参与ABC运输功能中相比于其他微生物具有较大的贡献度，辅因子生物合成功能在亚硝化球菌门中贡献度相对突出。另外，土壤理化因子OM、TN、TP、TK、AN和AK均可以显著影响大蒜根际土壤细菌的群落组成，OM、TN和TP是金乡大蒜根际土壤真菌的主要影响因子。

（3）利用纯培养的方法从大蒜根际土壤中共分离了138株放线菌，通过抗菌实验筛 选出42株具有生物活性的菌株，其中16株菌株对三种病原菌B. subtilis、E. coli和C. albicans均表现出抑制作用。利用二代和三代测序技术，对13株放线菌进行基因组测定， 序列比对结果为6株链霉菌属、4株小单孢菌属和3株马杜拉放线菌属，而T131菌株的序 列相似度只有93.93%且与Streptomyces sp. BPPL-273在同一分支，确定T131为链霉菌属， 命名为Streptomyces sp. T131。

（4）通过GNPS数据库对6株链霉菌属发酵粗提物的MS2数据进行分析，共比对到 60个已知化合物，包括萜类、生物碱类、萜类、肽类、脂肪酸类、苯丙素类和聚酮类化 合物。通过构建混合菌株的分子网络发现T131单一分子笼较多，且节点数和分子笼个数 最多，其可能存在结构比较新颖的天然产物。在此基础上，通过antiSMASH比对预测 Streptomyces sp. T131含有37个BGCs，包含NRPS、PKS、terpene、siderophore、ectoine、 RiPP-like等多种类型的生物合成基因簇，且很多基因簇与已知的具备研究价值的天然产

Natural products derived from microorganisms are important resources for the development of antibiotic drugs, and the antibiotic drugs derived from natural products currently used clinically were all developed in the middle of the last century. Bacterial resistance caused by the overuse of antibiotics is one of the biggest medical challenges facing mankind. Soil microorganisms are important resource libraries of secondary metabolites (such as drugs), and most natural antibiotics come from soil microorganisms. Therefore, mining and developing new soil microbial resources and natural products is an urgent need in the current medical field. In this study, the diversity of rhizosphere soil microbial community in Jinxiang garlic was analyzed by metagenome sequencing method, and the correlation between microbial community and soil factors was analyzed. and conducts correlation analysis between bacterial communities and soil factors. After screening the culturable microorganisms in rhizosphere soil, the related biosynthetic gene clusters were predicted by combining mass spectrometry and sequencing technology to screen potential Streptomyces strains and provide germplasm resources for the discovery of new antibiotics.The main results were described as follows:

(1) The structure and functional diversity of the garlic rhizosphere soil microbial community were analyzed by metagenomic sequencing technology. Among the bacterial community characteristics, Proteobacteria, Actinobacteria, and Bacteroidetes account for 90% of the total bacterial proportion. Nocardioides and Sphingomonas are the dominant populations at the genus level, accounting for 40%. In the characteristic composition of the fungal community, Ascomycota, Basidiomycota, Mucoromycota, and Chytridiomycota are dominant, accounting for 98%. Aspergillus is the main dominant fungus, accounting for 20% .

(2) In terms of functional diversity of microbial communities, amino acid transport, and metabolism, carbohydrate transport and metabolism, energy production and conversion, and signal transduction mechanisms are the main functions of garlic rhizosphere soil microorganisms. Among them, compared with other microorganisms, Proteobacteria and Actinobacteria have a greater contribution to participate in ABC transportation function, and the cofactor biosynthesis function is relatively in Nitrososphaerota. In addition, soil physical and chemical factors OM, TN, TP, TK, AN, and AK can significantly affect the community composition of garlic rhizosphere soil bacteria. OM, TN, and TP are the main influencing factors of garlic rhizosphere soil fungi.

(3) A total of 138 strains of actinomycetes were isolated from garlic rhizosphere soil. 42strains with biological activity were screened out by antibacterial experiments, among which 16 strains were effective against three pathogenic bacteria (B. subtilis, E. coli, and C. albicans). The genomes of 13 strains were sequenced by second- and third-generation sequencing technology. Based on the sequence comparison and morphological characteristics, 13 strains included 6 Streptomyces, 4 Micromonospora, and 3 Actinomadura. The T131 strain and Streptomyces sp. BPPL-273 are in the same branch, and the sequence similarity is only 93.93%. Therefore, T131 is identified as Streptomyces sp. T131.

(4) The MS² data of the extracts of 6 Streptomyces were analyzed through the GNPS database, and a total of 60 known compounds were compared, including terpenes, alkaloids, terpenoids, peptides, fatty acids, phenylpropanoid, and polyketides. By constructing the molecular network of mixed strains, it was found that T131 has more single molecular cages, the largest number of nodes and molecular cages. It may contain natural products with relatively novel structures. On this basis, antiSMASH predicted that Streptomyces sp. T131 contains 37 BGCs, including NRPS, PKS, terpene, siderophore, ectoine, RiPP-like and other types of biosynthetic gene clusters. Many gene clusters are highly similar to known natural product gene clusters with research value or have the same core genes, which have good development potential.