DESULFOVIBRIO-PROFUNDUS SP-NOV, A NOVEL BAROPHILIC SULFATE-REDUCING BACTERIUM FROM DEEP SEDIMENT LAYERS IN THE JAPAN SEA

Several strains of a strictly anaerobic, vibrio-shaped or sigmoid, sul fate-reducing bacterium were isolated from deep marine sediments (dept h, 80 and 500 m) obtained from the Japan Sea (Ocean Drilling Program L eg 128, site 798B), This bacterium was identified as a member of the g enus Desulfovibrio on the basis of the presence of desulfoviridin and characteristic phospholipid fatty acids (iso 17:1 omega 7 and iso 15:0 ), the small number of growth substrates utilized (lactate, pyruvate, and hydrogen), and 16S rRNA gene sequence analysis data, Based on data for 16S rRNA sequences (1,369 bp), all of the Japan Sea strains were identical to each other and were most closely related to Desulfovibrio salexigens and less closely related to Desulfovibrio desulfuricans (l evels of similarity, 91 and 89.6%, respectively). There were, however, considerable phenotypic differences (in temperatures, pressures, and salinities tolerated, growth substrates, and electron donors) between the Japan Sea isolates and the type strains of previously described de sulfovibrios, as well as important differences among the Japan Sea iso lates, The Japan Sea isolates were active (with sulfide production) ov er a wide temperature range (15 to 65 degrees C) and a wide sodium chl oride concentration range (0.2 to 10%) (moderate halophile), and they were barophiles that were active at pressures up to about 40 MPa (400 atm), The optimum pressures for activity corresponded to the calculate d pressures at the depths from which the organisms were isolated (for isolates obtained at depths of 80 and 500 m the optimum activities occ urred at 10 and 15 MPa, respectively [100 and 150 atm, respectively]), This confirms that the organisms came from deep sediments and indicat es that they are well-adapted for deep sediment conditions, which is c onsistent with other characteristics (utilization of hydrogen, ferment ation, and utilization of ferric iron and organic sulfonates as electr on accepters), We propose that Japan Sea isolate 500-1 is the type str ain of a new species, Desulfovibrio profundus.