A Study On The Diversity Of Culturable Bacteria And Their Producing Amylase And Cellulase Activities In Sedimental Environments From The North Of South China Sea

The ocean covers more than70%of the Earth’s surface, and the extreme environment with the depth deeper than200m deep-sea accounts for about64%of the Earth’s surface. South China Sea is China’s largest tropical marginal sea, with complex and diverse submarine sediment environment, and is rich in biological resources, but the utilization of microbial resources in the deep-sea sedimental environment is still in its infancy. In this study, from the point of pure culture, the bacterial diversity and distribution in marine sedimental environment of the northern part of the South China Sea was investigated to find new taxa with potential application value, and the strains producing amylase and cellulase were further screened and investigated their distribution characteristic in the of phylogenetic position.By drawing experiences from previous studies in our laboratory, this study selected15kinds of isolation media with better isolation ratio, at two incubation temperature (4and28℃) fot isolating marine bacteria, and total387bacterial strains were obtained. After dereplication by morphological characteristics,305bacteria were identified by analysing their16S rRNA gene sequences, and they distributed in four phyla:96species in37genera,18families,8suborders,1class of phylum Actinobacteria,35species in12genera,3families,1orders,1classes of phylum Firmicutes,21species in12genera,8families,6orders,2classes of phylum Proteobacteria and7species in4genera of family Flavobacteriaceat of phylum Bacteroidetes. Moreover,27strains were identified to be potential novel taxa, and25of them shared16S rRNA gene sequence similarities were less than98.5%. The most predominant groups were those members in genera Streptomyces, Bacillus. Erythrobacter, Dietzia and Microbaclerium. And15genera isolated in this study had not been reported to have been isolated from marine environment before.Two potential novel species YIM M13028T, Y1M M13141T were further investigated by using a polyphasic approach, including morphological and cultural characteristics tests, physiological and biochemical tests, chemotaxonomic tests, phylogenetic analysis based on their16S rRNA gene sequences. Their accurate taxonomic positions were identified and the names Mycobacterium sediminis sp. nov., Pseudonocardia sediminis sp. nov. were proposed, respectively. Among of the strains obtained in this study,130isolated strains were selected to carry out amylase and cellulase producing activity tests. The results showed that the strains producing amylase, cellulase and both enzymes account for30.0%,28.5%and16.9%, respectively, in which Streptomyces and Bacillus made up a large percentage. All the results above showed that bacterial resources in the marine sedimental environment of the northern part of the South China Sea is extremely rich, a large number of them had not been discovered before, and that it is deversed, promissing and valuable to exploit the bacterial resources.