A Study On The Environmental And Symbiont Microbial Communities In Okinawa Trough Hydrothermal Vent Fields

Microbial diversity is an important research part in microbial ecology. The study for microbial diversity and structure in one certain region contributed to our understanding the function of microbes inside it. The deep-sea hydrothermal vents were considered as one area of the most hostile environtment on earth. However, there are a large amount of microorganisms with versatile metabolic pathways living in the hydrothermal ecosystems, which have drawn a great deal of attention of microbiologists all over the world. In 2014, we obtained sediments and some shrimps sampled from the Okinawa Trough hydrothermal field during the “Okinawa Trough hydrothermal fields” cruise of the vessel KEXUE. Microbial diveristiy in sediments and shrimps were analyzed via culture-dependent and culture-independent methods, respectively. Further, we detected some bioactivity characteristics of the culturable bacteria; performed polyphasic taxonomy studies of two potential novel bacterial species; explored the carbon metabolic pathway of the shrimp-associated microbial community.A total of 213 strains were isolated from two hydrothermal fields(HV1 and HV2) of Okinawa Trough. Of these isolates, 128 were from HV1 and 85 were from HV2. Based on near full-length 16 S rRNA gene sequence analysis, the 213 isolates obtained from HV1 and HV2 belonged to 4 phyla, 5 classes, 12 orders, 22 families, 33 genera, and 96 species. Gammaproteobacteria were the most abundant, followed by bacilli, and Alphapreobacteria and Flavobacteria were minor groups in two hydrothermal fields; Actinobacteria was occurred only in HV1. Bioactivity analysis revealed that 25 isolates belonging to 9 different genera exhibited extracellular protease activities, 21 isolates from 11 genera exhibited extracellular lipase activities, and 13 isolates of 8 genera displayed antimicrobial activities. This is the first observation of a large population of bacteria with extracellular bioactivities existing in deep-sea hydrothermal vents.A novel Gram-positive bacterium, designated as strain S6 T, isolated from the deep sea sediment in Okinawa Trough. Phylogenetic analysis based on 16 S rRNA gene sequence indicated that strain S6 T belonged to the genus Domibacillus. The closest phylogenetic neighbors of strain S6 T were D robiginosus(98.6%), D. indicus(97.6%), D. enclensis(97.6%), and D. tundrae(97.6%). The identities between strain S6 T and other close members were below 96%. The values of DNA–DNA relatedness between strain S6 T and its closest relatives in genus Domibacillus were well below 70%. Phylogenetic, physiological, biochemical, and morphological analyses suggest that this strain represents a novel species of genus Domibacillus, and the name Domibacillus iocasae sp. nov. is proposed with the type species S6T(= DSM 29979 T = CCTCC AB 2015183T). A novel Gram-negative bacterium, designated as strain S61 T, isolated from the deep sea sediment in Okinawa Trough. Phylogenetic analysis based on 16 S rRNA gene sequence indicated that strain S61 T belonged to the genus Algoriphagus. The closest phylogenetic neighbors of strain S6 T were A. lutimaris(98.12%), A. halophila(98.12%), A. chungangensis(97.95%) and A.aestuarii(97.35%). The identities between strain S6 T and other close members were below 97%. The values of DNA–DNA relatedness between strain S6 T and its closest relatives in genus Algoriphagus were well below 70 %. Phylogenetic, physiological, biochemical, and morphological analyses suggest that this strain represents a novel species of genus Algoriphagus, and the name Algoriphagus iocasae sp. nov. is proposed with the type species S61 T.Alvinocaris longirostris is a species of shrimp existing in the hydrothermal fields of Okinawa Trough. To date the structure and function of the microbial community associated with A. longirostris are essentially unknown. In this study, by employment of the techniques of high through-put sequencing and clone library construction and analysis, we compared for the first time the community structures and metabolic profiles of microbes associated with the gill and gut of A. longirostris in a hydrothermal field of Okinawa Trough. Fourteen phyla were detected in the gill and gut communities, of which 11 phyla were shared by both tissues. Proteobacteria made up a substantial proportion in both tissues, while Firmicutes was abundant only in gut. Although gill and gut communities were similar in bacterial diversities, the bacterial community structures in these two tissues were significantly different. Further, we discovered for the first time the existence in the gill and gut communities of the genes encoding the key enzymes of Calvin-Benson-Bassham(CBB) cycle and the reductive tricarboxylic acid(rTCA) cycle, and that both CBB- and rTCA-associated genes were significantly more abundant in gill than in gut. Taken together, these results provide the first evidence that at least two carbon fixation pathways are present in both the gill and gut communities of A. longirostris, and that the communities in different tissues likely differ in autotrophic productivity.