一株具有抗菌和细胞毒活性的海洋嗜盐菌XD20的筛选和鉴定

Screening and identification of an anti-bacterial and cytotoxic marine halophilic strain XD20

目的：从中国东海分离筛选活性海洋微生物，进而确定所获取的活性菌株的分类地位。方法：乘坐专业考察船只在中国东海海域进行系统采样，采用抗菌模型和细胞毒模型进行活性筛选。对获取的活性菌株进行形态特征研究、盐需求测试、核糖体rDNA ITS区序列分析，并将所测得序列在NCBI数据库中进行相似性搜索，选取其中相似性较高的序列以邻接法构建系统进化树，将该菌株分类鉴定到种。结果：从我国东海海域C01站位（122°26′30″，30°43′48″）30m水深处分离获得一活性菌株XD20，是一嗜盐菌株，能耐受高达10．0％的盐浓度，合适的生长盐浓度范围为2．5％～7．5％；它对白念珠菌具有抑菌活性，对SMMC7721细胞株和HeLa细胞株具有细胞毒活性。以菌丝断裂方式产生节孢子，孢子大小及形态与Wallemia sebi相符；rDNAITS区测序发现，该菌株序列与Wallemia sebi的多条序列相似程度较高，且差异均在ITS1和ITS2区，属于可变区。结论：活性菌株XD20首次从海洋中分离获得，为一嗜盐海洋菌株，鉴定为Wallemia sebi（Fr．）Arx。

Objective：To isolate and screen the active marine microorganisms from East China Sea and to identify the phenotypes of the isolated active strains. Methods： The samples were widely collected from East China Sea and the active strains were screened out through an anti-bacterial model and a cytotoxic model. The isolated strains were subjected to phenotypical study, salt-aggregation test and rDNA ITS sequencing. Neighbor-joining phylogenetic trees were drawn by comparing the results of rDNA ITS sequencing with sequences of described species in the BLAST server of the National Center for Biotechnology Informa tion （NCBI）. One of the strains, subsequently named XD20, was identified to species level. Results： XD20, a halophilic strain with a highest tolerable salt concentration of 10.0% and suitable concentration range of 2.5% to 7.5%, was collected and isolated on the site of C01 （122°26′30″,30°43′48″） 30 meters under water. XD20 showed an inhibitory effect on the growth of Candida albicans and a cytotoxic activity toward SMMC7721 and HeLa cells. XD20 produced arthroconidia by mycelium break and the arthroconidia had similar size and morphology to those of Wallemia sebi. rDNA ITS sequencing showed that the sequence of XD20 had a higher similarity to those of Wallemia sebi and the differences were located in ITS1 and ITS2 areas, both belong to variable region. Conclusion： XD20, an active halophilic strain fungus, has been obtained from the sea for the first time, and has been identified to be Wallemia sebi （Ft.） Arx.