Diversity and sulfur oxidation characteristics of culturable sulfur-oxidizing bacteria associated with benthic organisms in deep-sea hydrothermal area

Abstract:

[Background] Microbes in deep-sea hydrothermal vents use the extensive H₂S and sulfides in the environment to form a close symbiotic relationship with macrofauna. For example, sulfur-oxidizing bacteria use their unique metabolic system to help their hosts better adapt to the extreme conditions in hydrothermal vents. However, there is still no study on the identification and functional analysis of these symbionts of vent fauna. [Objective] To investigate the diversity and sulfur oxidation characteristics of culturable sulfur-oxidizing bacteria in hydrothermal benthos, and explore the symbiosis between sulfur-oxidizing bacteria and their animal hosts. [Methods] We used three culture media (M1, SPG, SOB) to isolate sulfur-oxidizing bacteria associated with hydrothermal benthos from different areas in the deep-sea hydrothermal vents. 16S rRNA gene sequences were used for phylogenetic analysis. The iodometric method was used to measure the sulfur oxidation activity. [Results] In the experiment, we obtained 169 strains of sulfur-oxidizing bacteria, which belong to Actinobacteria and Proteobacteria. Among them, the genus Halomonas was dominant, accounting for 73%. Three isolates showed higher sulfur oxidation activities:Thioclava nitratireducens M1-LQ-LJL-11 (70.4%), Qipengyuania vulgaris M1-TC-YB-4 (77.7%), and Dietzia cercidiphylli M1-TC-01-YL-6 (69.8%). [Conclusion] The diversity of culturable sulfur-oxidizing bacteria in hydrothermal benthos was reported for the first time. It was found that Gammaproteobacteria was the dominant, which had high sulfur oxidation ability and could detoxificate H₂S for their hosts in the hydrothermal fluids.