Diversity Analysis Of The Dotriacontane-Degrading Microbial Community From The South Atlantic Ocean And Comparative Genomics Study Of Genus Salinisphaera

Through enrichment of the deep sea sediments in the South Atlantic Ocean by long chain alkane (dotriacontane, C32) from5different sites, this study mainly focused on diversity analysis of the corresponding microbial community.25strains of bacteria, which belong to14genera and19species, were isolated from these C32-degrading consortia. And there were2potential new species. Among these isolated bacteria, the strains were primarily Alcanivorax, Erythrobacter, Pseudoalteromonas, Pseudomonas, which constitute16%,16%,12%and12%of the total respectively. Then, by analyzing the degrading ability of C32, the stains32C-B6and32C-C3, pertained to Paracoccus and Alcanivorax, performed the best ability of degrading long chain alkane C32. Both results of16S rDNA and alkB clone libray showed that members of y-Proteobacteria (Marinobacter or Alcanivorax) played key oil-degrading roles in all sites.We also performed comparative genomics study on10stains of Salinisphaera. Their genome sizes were between3.75Mb and4.37Mb. And the range of their G+C content and coding genes were61.39%～64.13%and3366～4140respectively. Combining ANIm values and phylogenetic analysis of concatenated single copy core genes, the results showed that Salinisphaera sp. C84B14, Salinisphaera sp. S4-8and Salinisphaera sp. T5B8, Salinisphaera sp. T31B1are potential novel species. The size of the pangenome was8733genes. And the core genome included1759core genes, which account for20.14%of the pangenome. And what’s more, the genes related to metabolism are the major component of the core genome. The dispensable genome consisted of6974flexible genes. In dispensable genome, the number of strain specific-genes was3113, among which one strain had311speicial genes on average. In addition, the alkane hydroxylase related genes of10strains were also analyzed. We found that potential alkB gene existed in all these strains. All the predicted AlkB protein comprised4conserved amino acid motifs. And almost all the alkB gene clusters contained the genes related to alkane-degrading pathway. Then we used the real-time quantitative PCR techniques to confirm the predicted alkane hydroxylase genes in one of these strains, Salinisphaera sp. C84B14. Compared to the control, the alkB gene was upregulated when Salinisphaera sp. C84B14ultilized the alkane as the sole carbon source. Combining these evidences, we can conclude that the alkB is responsible for degradation of alkane in Salinisphaera.In conclusion, based on results of16S rDNA and alkB clone libray, this study mainly focused on diversity analysis of the C32-degrading microbial community enriched from five different samples of South Atlantic Ocean. And some strains of potential long chain alkane-degrading bacteria were also isolated. Those results provided us preliminary information about the constitutent of corresponding alkane-degrdaing microbial consortia in deep sea enviroment. Though comparative genomics analysis, the results also revealed the phylogenetic relationship, characteristic of pangenome and core genome related to Salinisphaera. Meanwhile, the alkane hydroxylase related gene alkB were also studied. The results contributed to understanding about the alkane-degrading molecular mechanism of Salinisphaera.