One　sulfur-oxidizing　bacterium　Thioclava　sp.　M1-LQ-LJL-11　was　isolated　from　the　gill　of　Chrysomallon　squamiferum　collected　from　2700　m　deep　hydrothermal　named　Longqi　on　the　southwest　Indian　Ocean　ridge.　In　order　to　understand　its　survival　mechanism　in　hydrothermal　extreme　environment　and　symbiotic　relationship　with　its　host,　the　complete　genome　of　strain　M1-LQ-LJL-11　was　sequenced　and　analyzed.　A　total　of　6117　Mb　of　valid　data　was　obtained,　including　4096　coding　genes,　61　non　coding　genes,　including　9　rRNAs　(among　them,　there　are　3　in　23S　rRNA,　3　in　5S　rRNA,　and　3　in　16S　rRNA.),　52　tRNAs　and　35　genomic　islands.　Strain　M1-LQ-LJL-11　contains　one　chromosome　and　two　plasmids.　In　the　genome　annotation　information　of　the　strain,　we　found　28　genes　including　cys　sox,　sor,　sqr,　tst　related　to　sulfur　metabolism　and　17　metal　resistance　genes.　Interestingly,　a　pair　of　quorum　sensing　system　which　probably　regulating　biofilm　formation　located　in　chromosome　was　found.　These　genes　are　critical　for　self-adaptation　against　severe　environment　as　well　as　host　survival.　This　study　provides　a　basis　understanding　for　the　adaptive　strategies　of　deep-sea　hydrothermal　bacteria　and　symbiotic　relationship　with　its　host　in　extreme　environments　through　gene　level.　©　2023　Elsevier　B.V.