广西北仑河口红树林植物根际淤泥放线菌的分离、鉴定、多样性及抗菌活性研究

从红树林根际淤泥中分离鉴定放线菌并进行多样性分析及抗菌活性研究，为新抗生素的发现提供药用放线菌资源。方法 用6种分离培养基，利用涂布平板法分离放线菌；通过PCR扩增获得菌株16S rRNA基因并进行同源性比对，分析放线菌多样性；发酵液经处理分别形成发酵液酯相、发酵液水相和菌丝丙酮浸提液3类样品；纸片扩散法进行抗菌活性测试。结果 从5份红树林植物根际淤泥样品中分离纯化得到56株放线菌，分布于7个目7个科12个属，优势菌属为小单孢菌属和红球菌属；菌株L9T122、L1T1Jb1的16S rRNA基因序列与有效发表菌株Agromyces bracchium IFO 16238T(AB023359)、Streptomyces radiopugnans R97T(DQ912930)的相似率最高，分别为97.49%和97.07%，为潜在壤霉菌属和链霉菌属新种；抗菌活性检测结果表明，在20株放线菌中，15株具有抗菌活性，总阳性率为75.00%。其中L2T1Gb21、L9T122对金黄色葡萄球菌和铜绿假单胞菌均有较强的抑菌作用。结论 广西北仑河口红树林植物根际土壤中含有较为丰富的放线菌资源，菌株L2T1Gb21、L9T122有较强的抗菌活性，具有开发抗菌新药的潜力。

The antimicrobial activity of actinomycetes isolated from mangrove rhizosphere sludge in Beilun Estuary,Guangxi

To investigate the diversity and antimicrobial activity of actinomycetes isolated from mangrove rhizosphere sludge in Beilun estuary, Guangxi. Methods Actinomycetes were isolated using the traditional dilution plating method with six isolation media. To analyze the diversity of actinomycetes, sequences of 16S rRNA gene obtained by PCR amplification were submitted to gene database for BLAST searches. To test antimicrobial activity by using the disk diffusion method, three samples were obtained, including the organic layer, water layer, and acetone extraction of mycelium. Results A total of 56 strains, distributed in 12 genera affiliated to 7 families within 7 orders were isolated and purified from five sludge samples collected from mangrove rhizosphere. The dominant actinomycetes were Micromonospora and Rhodococcus. The highest similarities of 16s rRNA gene sequences between strain L9T122 and the validly described species Agromyces bracchium IFO 16238T (AB023359), and between strain L1T1Jb1 and Streptomyces radiopugnans R97T (DQ912930) were 97.49% and 97.07%, respectively. The results indicated that two strains were potential new taxa. Antimicrobial activity of the secondary metabolites from twenty strains were tested. Fifteen strains exhibited positive results, and the total positive rate was 75.00%. Strains L2T1Gb21 and and L9T122 showed remarkable antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Conclusion The study showed that there were rich of cultivable actinomycetes in mangrove rhizosphere sludge from BeiLun Estuary, and most strains exhibited antimicrobial activity, which could be a potential resource for the discovery of new