On the basis of phenotypical characteristics and analysis of 16S rRNA sequence, a new species belonging to a new genus is described, and the name Marinobacter hydrocarbonoclasticus is proposed. This organism, isolated from Mediterranean seawater near a petroleum refinery, is a gram-negative, aerobic, rod-shaped bacterium. It grows at NaCl concentrations of 0.08 to 3.5 M and uses various hydrocarbons as the sole source of carbon and energy. Its DNA has a guanine-plus-cytosine content of 52.7 mol%. The 16S rRNA analysis shows a clear affiliation between M. hydrocarbonoclasticus and the gamma group of the phylum Proteobacteria. A close phylogenetic relationship appears among the species Marinomonas vaga, Oceanospirillum linum, Halomonas elongata, and Pseudomonas aeruginosa. Because of the impossibility of finding a single most closely related species, we suggest that this bacterium be assigned to a new genus, at least temporarily. The possibility of a revision of this status when new data appear is, however, not excluded. The type strain is M. hydrocarbonoclasticus SP.17 (=ATCC 49840).

A novel Gram-positive, anaerobic and thermophilic bacterium, strain MET79^T, was isolated from an oil well located in the Gulf of Mexico. Cells were straight rods, motile by a subpolar flagellum. Spores were formed in old cultures. Inner gas vacuoles swelled the cells when exposed to air. The optimum growth conditions were 55 °C, pH 7·5 and 1 % NaCl. Yeast extract was required for growth. Strain MET79^T fermented several sugars, some organic acids and Casamino acids. Glucose was fermented into lactate, acetate, butyrate, H₂ and CO₂. Strain MET79^T reduced thiosulfate to hydrogen sulfide and nitrate to ammonium. The DNA G+C content was 30·9 mol%. The closest phylogenetic relative of strain MET79^T was Caloranaerobacter azorensis (88·7 % 16S rDNA sequence similarity). As strain MET79^T (=DSM 15102^T=CIP 107615^T) was physiologically and phylogenetically different from its closest relatives, it is assigned as the type strain of a novel species of a new genus, Garciella nitratireducens gen. nov., sp. nov.