Desulfovibrio profundus sp. nov., a Novel Barophilic Sulfate-Reducing Bacterium from Deep Sediment Layers in the Japan Sea

Abstract

Several strains of a strictly anaerobic, vibrio-shaped or sigmoid, sulfate-reducing bacterium were isolated from deep marine sediments (depth, 80 and 500 m) obtained from the Japan Sea (Ocean Drilling Program Leg 128, site 798B). This bacterium was identified as a member of the genus Desulfovibrio on the basis of the presence of desulfoviridin and characteristic phospholipid fatty acids (is0 17:lw7 and is0 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 Desulfuvibrio desulfuricans (levels 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 desulfovibrios, as well as important differences among the Japan Sea isolates. The Japan Sea isolates were active (with sulfide production) over a wide temperature range (15 to 65°C) and a wide sodium chloride 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 calculated pressures at the depths from which the organisms were isolated (for isolates obtained at depths of 80 and 500 m the optimum activities occurred at 10 and 15 MPa, respectively [lo0 and 150 atm, respectively]). This confirms that the organisms came from deep sediments and indicates that they are well-adapted for deep sediment conditions, which is consistent with other characteristics (utilization of hydrogen, fermentation, and utilization of ferric iron and organic sulfonates as electron acceptors). We propose that Japan Sea isolate 500-1 is the type strain of a new species, Desulfovibrio profundus.Bacterial sulfate reduction is the dominant anaerobic terminal oxidation process in marine sediments, and in coastal sediments this process can be responsible for more than 50% of the organic matter degradation (21). The importance of sulfate reduction decreases in deeper-water sediments, where the diagenetic zones are greatly extended (16,22), and as a result sulfate can be present to a depth of several hundred meters in some pelagic sediments (4). Thus, there is the potential for active sulfate reduction to continue at great depth within marine sediments. Recently, this was demonstrated for Japan Sea sediments, where sulfate reduction was shown to be present to a depth of at least 425 m together with significant bacterial populations (30). Viable sulfate-reducing bacteria were also present to a depth of 80 m, and other viable bacterial types were present at even greater depths. These findings significantly extend the environment for sulfate-reducing bacteria and are consistent with report...

Microorganisms persist at record depths in the subseafloor of the Canterbury Basin

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Sunxiuqinia faeciviva sp. nov., a facultatively anaerobic organoheterotroph of the Bacteroidetes isolated from deep subseafloor sediment

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