The Diversity Analysis Of Culturable Bacteria In South China Sea And The Polyphasic Taxonomy Of Two Deep-sea Strains

The South China Sea is a marginal sea of China. It extends from the Strait of Malacca inthe southwest to the Strait of Taiwan in the northeast and covers an area around3,500,000km2. The South China Sea has a remarkable amount of biological diversity, including over30%of the world’s coral reefs, many valuable fisheries and a large number of microbialgroups. The South China Sea area contains huge numbers of marine microorganisms withextremely diversities.Because of its special geographical position and climate environment;these microorganisms have evolved unique physiological and metabolic characteristics andplay important ecological role in marine ecosystem. In this study, we analysis the diversityof bacterias of several samples in South China Sea, surface seawater samples，sedimentsamples and sandy samples, clarifyed the Community distribution and the dominantbacterial community. In addition, two novel strains were isolated, and were taxonomicallycharacterized by using polyphasic methods, including morphological observations,examinations of growth conditions, tests for physiological properties and biochemicalproperties, determination of cellular fatty Acid and polar lipid compositions, analysis ofmolecular genetics analysis. Based on The polyphasic data obtained in this study, the twostrains’ exact taxonomic positions were finally determined.1. The culturable bacteria diversity analysis in the South China Sea samplesThe samples were collected by the South China Sea Open Cruise of R/VDongFangHong2in the September of2011, using a grab sampler for seabed sediment,sandy and a filter membrane filtrated the surface water samples, a total of twelve samples.The study showed that the microorganisms in surface seawater samples are composed ofγ-proteobacteria (Pseudoalteromonas, Vibrio, Alteromonas, Psychrobacter), α-proteobacteria (Sphingorhabdus), firmicutes (Bacillus), actinobacteria (Kouria,Rhodococcus), bacteroidetes (Maribacter, Cellulophage, Flavobacterium, Olleya); themicroorganisms in sediment samples are constituted of γ-proteobacteria (Enterobacteria,Vibrionaceae, Alteromonas, Psychrobacter), micrococcales (Microcobacteria), firmicutes(Bacillus), flavobacteria (Flavobacteriaceae) and γ-proteobacteria (Pseudoalteromonas,Psychrobacter, Oceanospirillaceae, Planococcaseae). 2. Polyphasic taxonomic study of strain SM1222TStrain SM1222Twas isolated from a2022m sediment sample at the site-42of theSouth China Sea. Strain SM1222Tcolony color is slightly greyish yellow, smooth edgesand cells of the type strain are gram-negative, rods and flagellated.The type strain grew at4-35°C (optimum at25–30°C), in0.58%NaCl (w/v,optimum at23%) and at pH5.5–10.5(optimum at pH7.5–8.0). Cells were Oxidase-andCatalyse positive, could not reduce nitrate to nitrite, hydrolyze urea citrate and pyruvate,but not agar, DNA, gelatin, casein, starch, Tween20, Tween40, Tween60, Tween80oraesculin.The major fatty acids (>5%) are summed feature3(C16:1ω7c and/or iso-C15:02-OH),C16:0, C18:1ω7c, summed feature2(C14:03-OH and/or iso-C16:1I) and C12:0.The majorrespiratory quinone is Q-8and the major polar lipids of strain SM1222Twerephosphatidylethanolamine (PE), phosphatidylglycerol (PG) and diphosphatidylglycerol(DPG). The genomic DNA G+C content of strain SM1222Twas51.5mol%.Analysis of16S rRNA gene sequences showed that strain SM1222Tshared the highest16S rRNA gene sequence similarity (94.3%) with type strain of Oceanisphaera ostreaeKCTC23422T. In the neighbour-joining tree based on16S rRNA gene sequence, strainSM1222T, together with Oceanisphaeraostreae, formed a distinct branch in the genusOceanisphaera.On the basis of the polyphasic data from this study, strain SM1222Trepresents a novelspecies in the genus Oceanisphaera of the class Gammaproteobacteria, for which thename Oceanisphaera profunda sp. nov. is proposed. The type strain of Oceanisphaeraprofunda is SM1222T(=CCTCCAB2013241T=KCTC32510T).3. Polyphasic taxonomic study of strain SM1341TA novel marine bacterial strain, designated strain SM1341T, was isolated froma4300m sediment sample at the site-103of the South China Sea. The bacterium was found to beGram-negative, white-colored, aerobic and non-flagellated. The strain grew at15–40°C(optimum at35°C), with0–6.0%(w/v) NaCl (w/v, optimum in3.0%) and at pH5.0–10.0(optimum at pH7.0). Cells were Oxidase-and Catalyse positive, could reduce nitrate to nitrite, hydrolyze casein, starch, Tween20, Tween40, Tween80and gelatin but not agar,DNA, Tween60and aesculin.It contained C16:0, summed feature2(C14:03-OH and/or iso-C16:1I), C18:1ω7c, cyclo-C19:0ω7c and C18:1ω7c11-methyl as the predominant cellular fatty acids and Q-6as themajor respiratory quinone. The polar lipids of strain SM1341Tcomprisedphosphatidylcholine (PC), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) andtwo aminolipids (AL1-AL2).Phylogenetic analysis based on nearly complete16S rRNA gene sequences revealedthat strain SM1341Tbelonged to the family Rhodobacteraceae, representing a novelspecies of the genus Oceanicella. It shared the highest16S rRNA gene sequence similaritywith type strain of Oceanicella actignis DSM22673T(94.37%) andPleomorphobacteriumxiamenenseCLWT(94.31%).The genomic DNA G+C content ofstrain SM1341Twas68.8mol%.On the basis of the polyphasic data from this study, strain SM1341Trepresents a novelspecies in the genus Oceanicella, for which the name Oceanicella nanhaiensis sp. nov. isproposed. The type strain of Oceanicella nanhaiensis is SM1341T(=CCTCC AB2013360T=KCTC32512T).