Proposal of Vibrionimonas magnilacihabitans gen. nov., sp. nov., a curved Gram-stain-negative bacterium isolated from lake water.

A mesophilic bacterium appearing as curved rod-shaped cells was isolated from Lake Michigan water. It exhibited highest similarities with Sediminibacterium ginsengisoli DCY13(T) (94.4%); Sediminibacterium salmoneum NJ-44(T) (93.6%) and Hydrotalea flava CCUG 51397 (T) (93.1%) while similarities with other recognized species were <92.0%. The primary polar lipid was phosphatidylethanolamine, with moderate amounts of two unidentified glycolipids, three unknown polar lipids, one unknown aminophospholipid and one aminolipid. The primary respiratory quinone was MK-7 and sym-homospermidine was the primary polyamine. The major cellular fatty acids were iso-C(15 : 1)G, iso-C(15 : 0), iso-C(16 : 0) 3-OH and iso-C(17 : 0) 3-OH, with moderate amounts of iso-C(16 : 0). The presence of glycolipids differentiated the novel strains from related genera. The DNA mol% G+C content of the type strain MU-2(T) was 45.2. Results for other phenotypic and molecular analyses indicated that strain MU-2(T) is a representative of a novel genus and species for which the name Vibrionimonas magnilacihabitans is proposed. The type strain is MU-2(T) ( = NRRL B-59231 = DSM 22423).

Desulfotomaculum and Methanobacterium spp. dominate a 4- to 5-kilometer-deep fault.

Alkaline, sulfidic, 54 to 60 degrees C, 4 to 53 million-year-old meteoric water emanating from a borehole intersecting quartzite-hosted fractures >3.3 km beneath the surface supported a microbial community dominated by a bacterial species affiliated with Desulfotomaculum spp. and an archaeal species related to Methanobacterium spp. The geochemical homogeneity over the 650-m length of the borehole, the lack of dividing cells, and the absence of these microorganisms in mine service water support an indigenous origin for the microbial community. The coexistence of these two microorganisms is consistent with a limiting flux of inorganic carbon and SO4(2-) in the presence of high pH, high concentrations of H2 and CH4, and minimal free energy for autotrophic methanogenesis. Sulfide isotopic compositions were highly enriched, consistent with microbial SO4(2-) reduction under hydrologic isolation. An analogous microbial couple and similar abiogenic gas chemistry have been reported recently for hydrothermal carbonate vents of the Lost City near the Mid-Atlantic Ridge (D. S. Kelly et al., Science 307:1428-1434, 2005), suggesting that these features may be common to deep subsurface habitats (continental and marine) bearing this geochemical signature. The geochemical setting and microbial communities described here are notably different from microbial ecosystems reported for shallower continental subsurface environments.