MLSA Analysis Of A Group Of Marine Actinomycetes And The Study Of DNA Degradation Phenomenon

As long-term living in deep-sea extreme environments with low-temperature, high pressure and darkness,the deep-sea micro-organisms may form a very unique genotype and metabolic mechanisms.The study of deep-sea micro-organisms is an important part of modern marine microorganism.In extreme environment,few deep-sea actinomycetes were found,with limited study on their taxonomy,physiology, genetics,ecology and adaptation mechanism because of slow growth and difficulties in separation,therefore,to find marine indigenous actinomycetes and study on their genetic and metabolic mechanism is of great significance.22 Streptomyces strains with high homology of 16S rDNA were isolated from 14 deep-sea sediment samples,halophile test and cell fatty acid analysis suggested that they might a group of indigenous marine actinomyces.These streptomyces strains were classified to three clusters based on 16S rDNA phylogenetic tree,MLSA and BOX-PCR.The growth temperature range,culture characteristics,antibacterial activity were also tested,and a potential novel Streptomyces species was found among them.DNA sulfur modification was first found to be a kind of skeleton physical modification of DNA.and the sulfur-modified DNA of the strain suffered double-stranded cleavage at the modification sites during normal and pulsed-field gel electrophoresis(Dnd phenotype).Abundant analysis of marine environment DNA suggested that DNA sulfur modification was likely to widely exist in marine environment.We screened the actinomyces,including 86 actinomyces from deep-sea sediment and 157 actinomyces from mangroves soil,obtained 17 strains with the dnd gene and Dnd phenotypes.16S rDNA showed that they belonged to nine species of the genus Streptomyces and one species of the genus Nocardia.Three strains(S.graminearus 2H31-7,S.xiamenensis 15N30-1,N.antarctica 23H41-1 ) were selected based on dnd gene homology to clone the dnd gene clusters The analysis of these obtained clusters showed 84%,97%,and 75%homology to the known dnd clusters,respectively,and the putative conserved domains of Dnd proteins were also analysised.In this paper,the marine Streptomyces resources obtained before were studied in detail by phylogenesis technology,and a potential novel Streptomyces species was found among them.Additionally,the novel dnd gene clusters cloned from marine actinomycetes laied a good foundation for future DNA degradation phenomenon study of marine microorganism.