A Study On Two Bacteria From The Deep-sea Hydrothermal Vents In Okinawa

Extreme environmental conditions support a variety of microbes which are characterized with unique physiological and biochemical properties and energy metabolisms.These microbes are not only huge reservoirs for novel functional genes and bioactive substances,but of vital importance in deep-sea biogeochemical process.Therefore,it's necessary to do researches on deep-sea hydrothermal microbes.Studies on microbial adaption mechanisms to deep-sea hydrothermal vent environments are rare.In this study,we studied a bacteria strain,named Exiguobacterium sp.HVEsp1,isolated from an active hydrothermal vent at Okinawa Trough.HVEsp1 grew at 50 °C and exhibited a strong swimming capacity and resistance against multiple heavy metals and antibiotics.The high-quality draft genome sequence indicated that the genome of HVEsp1 is 2838499 bp with an average G+C content of 48.2% and contains 2948 predicted coding sequences.The genome is abundant with genes associated with cell motility,heavy metal resistance,drug resistance and thermo-tolerance.By comparing with the genome of its closest relative Exiguobacterium sp.AT1 b,HVEsp1 was found to possess large amounts of mobile elements,which can enable the bacteria to gain favorable genes by horizontal gene transfer.These results shed light on the mechanism of bacterial adaption to the extreme environment in deep-sea hydrothermal vent.In the second part of this study,we screened a pathogenic strain Bacillus sp.SR-52 from bacteria isolated from deep-sea hydrothermal vent samples.The results showed that SR-52 could induce mortality in turbot(Scophthalmus maximus)and mice(Mus musculus).When incubated with turbot and mouse sera,SR-52 exhibited high survival rates(96.15% and 72.05 %,respectively).SR-52-incubated turbot serum exhibited significance reduced hemolytic activity and bactericidal activity.These results indicated that SR-52 could activate the complement in turbot serum,but it could also resist the killing effect of the serum.In vivo infection experiment showed that SR-52 could disseminate and colonized in liver,spleen and kidney of turbots.These results provided a basis for further study of the pathogenicity of deep-sea bacterial pathogens.