A Study On The Diversity Of Culturable Bacteria In Sedimental Samples From The Indian Ocean And Multilocus Sequence Analysis Of The Isolates Of The Genus Streptomyces

The ocean covers more than70%of the Earth’s surface, and the extreme environment with the depth more than200m deep-sea accounts for about64%of the Earth’s surface. The marine environment is the hidden source of important bioactive compounds, so marine microorganisms are the main focus of the microbiologists. It is a challengeable work to culture those microorganisms under extreme environment in a laboratory, such as deep sea specific environmental conditions. So it is attempted to optimize the culture conditions to probe into the bacterial diversity and distribution in marine sediment environment of the Indian Ocean and find new taxa with potential applications. Moreover, the method of MLSA was adopted to analyze the new isolates of the genus Streptomyces in this thesis.There were total five factors selected in the test to optimize experimental conditions by response surface methodology, the results of optimization were wet and heat treatment temperature55℃and time1.2727min, air drying time1.697d, inhibitor concentration0.9697time, sea salt2.1212%. In this study we selected15kinds of media to isolate marine bacteria and total427bacterial strains were isolated. After dereplication by morphological characteristics,343bacteria were identified by analysing their16S rRNA gene sequences and they were distributed in4phyla,5classes,13orders,26families,39genera,121species. Phylum Actinobacteria was composed of1class,71species in20genera,13families,6orders, while phylum Firmicutes was found to contain1class,21species in4genera,3families,1order. Phylum Proteobacteria was found to contain,2classes,26species in14genera,9families,5orders, and3species in1genus of1family of phylum Bacteroidetes were distubuted. During this work, the genera Streptomyces、Bacillus、Kocuria、 Staphylococcus、Dietzia、Rhodococcus、Microbacterium、Arthrobacter、Nocardioides and Nocardiopsis were predominant groups. The result of these seven different types of media M2, M3, M7, M9, M10, M12and M13were better for isolation. Twenty three strains were identified to be potential novel taxa, three strains, YIM M12122、YIM M12139and YIM M12140were found to have16S rRNA gene sequence similarities less than95%, these three strains may represent potential new genera. So, there are lots of undiscovered microbial groups in deep sea sediments of the Indian Ocean and it is really a huge resource storehouse.At last of this paper, total21strains of Streptomyces pratensis,11strains of Streptomyces cavourensis and7strains of Streptomyces albidoflavus, these three kinds of highly similar39strains were further analyzed by the method of MLSA. The results showed that the method of MLSA was more effective to distinguish members of the genus Streptomyces and find the gene locus mutation between different strains. In addition, the evolutionary trees were more stable builded by MLSA analysis and the systematic evolutionary relationships more clearly.