Diversity of culturable heterotrophic bacteria from sediments of the Mariana Trench and their ability to degrade dimethylsulfoniopropionate (DMSP)

Abstract:

[Objective] The Mariana Trench is the deepest trench on earth. It has the characteristics of ultra-high hydrostatic pressure, low temperature and lack of light and contains unique microbial resources. Dimethylsulfoniopropionate (DMSP) is one of the marine's most abundant organosulfur molecules. Marine heterotrophic microorganisms can cleave DMSP and release “cooling gas” dimethyl sulfide (DMS), which plays an important role in driving global sulfur cycling and regulating global climate change. The heterotrophic bacteria from sediments of the Mariana Trench were isolated and identified and their ability to degrade DMSP was studied. Our study provides unique microbial resources for elucidating the life process of abyssal microorganisms. [Methods] Our study collected the sediments from five stations of the Mariana Trench as subject, using three kinds of conventional heterotrophic bacteria culture media (2216E, R2A and TCBS) and two kinds of heterotrophic bacteria enrichment culture media (TCBS broth and alkaline peptone water) for isolation and cultivation of bacteria at 4 ℃, 16 ℃ and 28 ℃, respectively. [Results] A total of 1057 strains were isolated and identified. And these isolates belonged to four phyla, seven classes and 76 genera. Gammaproteobacteria was the most abundant class, accounting for 61.4% of the total isolates. Pseudomonas and Halomonas were the most abundant genera; Proteobacteria was dominated in samples of all layers of sediments. The relative abundance of deep layer of Firmicutes was higher than that of the surface layer; The alkaline peptone water (AP) medium were found to have a better selectivity to Actinobacteria, and the TCBS broth medium were found to have a better selectivity to Bacilli; 101 strains were potential novel taxa of bacteria; In this study, the ability to degrade DMSP of 134 representative heterotrophic bacteria were tested, and 52 strains were found to have the ability to cleave DMSP and release DMS, accounting for 38.8% of the tested strains. [Conclusion] These results indicate that there is a high diversity of culturable bacteria and strains that have the ability to degrade DMSP from sediments of the Mariana Trench. Our research provides valuable microbial resources for further research on the life process of abyssal microorganisms.