Actinobacterial Diversity In The Yellow Sea And The Bohai Sea Sediments And Identification Of A Novel Antartica Actinomycete Species

Located at the warm-temperate district in China, the Yellow Sea and the BohaiSea contain rich natural resources and biological resources. However, little is knownabout the actinbacterial diversity in these marine ecosystem. So the actinobacterialdiversity analysis is very necessary and will be of great significance for the isolationof actinomycetes strains and the further exploitation of the novel medicinal microbialresources.Culture-independent method was used to estimate the diversity of actinomycetesof four samples from the Yellow Sea and Bohai Sea based on16S rRNA gene clonelibrary technology. The four samples showed high genetic diversity, which bothcontained Actinomycetes, Acidimicrobiia, Nitriliruptoria and Thermoleophilia fourclasses. Sample B42-2from the Bohai Sea exhibited the best actinomycetes diversityincluding17genera. Actinomycetes diversity of sample H42-3from the Yellow Seawas less than B42-2, comprising16genera;15genera were obtained from4mixedsites from the Bohai Sea;4mixed sites from the Yellow Sea containing13genera wasfound to have the least diversity. The Neighbor-Joining phylogenetic tree showed thatmany sequences of those four sites formed independent branches and had a longgenetic distance with known species sequences. It indicates that the sediments of theYellow Sea and the Bohai Sea Imbued with a lot of resources of new species, thespecies and community structure of actinomycetes are abundant and diverse.15media were used to isolate actinomycetes strains from6sediments samples ofthe Yellow Sea and12sediments samples of the Bohai Sea and119strains wereobtained. According to the morphological characteristics and cultural features, somestrains were selected to sequence the16S rDNA. Sequence analysis and blast resultsshowed that these strains belong to10different genera and25different species. Itindicates the abundant and huge resources diversity of the sediments in the Yellow Sea and the Bohai Sea. The Neighbor-Joining phylogenetic tree was constructed fromthe alignments of the sequences between all these strains and maximum homologystrains. The actinobacterial diversity is abundant and massive new speices resourcesare contained.Sequence Guided Genetic screening was performed to evaluate the potentialability and diversity of synthesizing natural products. Three pairs of degenerateprimers were used to amplify the type I polyketide synthetase (PKS-I) gene, the typeII polyketide synthetase (PKS-II) gene and non-ribosomal peptide synthetase (NRPS)gene respectively. The result showed that there were9strains containing PKS-I gene,15strains containing PKS-II gene, and7strains containing NRPS gene. Some genefragments had a low similarity with existing sequences submitted into Gene Bank,which could illustrate that there were new compounds produced from some strains.A Gram-staining-positive, aerobic, white-coloured strain GW9-2Twas isolatedfrom a soil sample collected from the west coast of the Fildes Peninsula near theChinese Antarctic Great Wall Station, King George Island, West Antarctica.Phylogenetic analysis based on16S rDNA gene sequences showed strain GW9-2Twas most closely related to members of established species in the genus Nocardiopsiswith sequence similarities of94%–97.73%, particularly N. lucentensis DSM44048T(97.93%), followed by N. flavescens SA6T(97.72%), N. alba DSM43377T(97.65%),N. halotolerans DSM44410T(97.60%); DNA–DNA hybridization studies showednone of the DNA–DNA relatedness values between strain GW9-2Tand members ofthe genus Nocardiopsis exceeded40%. The DNA G+C content of the genomic DNAof the type strain is76.8mol%. The predominant respiratory quinone is MK-9(H4).Major cellular fatty acids are iso-C16:0, anteiso-C17:0, ω9c-C18:1, iso-C15:0andiso-C17:0.Based on the phylogenetic, DNA–DNA hybridization, chemotaxonomic andphenotypic data, the type strain GW9-2T(=CGMCC4.7023T=DSM45699T=NRRLB-24873T) represents a novel species within the genus Nocardiopsis for which thename Nocardiopsis fildesensissp. nov. is proposed。Now the paper of classificationand identification of new species experiments has been published in InternationalJournal Systematic and Evolutionary Microbiology.