A novel lactic acid bacterium, strain MIC1-18(T), was isolated from crude oil collected at an oil-water well in Akita, Japan. Cells of strain MIC1-18(T) were found to be facultatively anaerobic, mesophilic, neutrophilic, Gram-negative, non-sporulating, motile by means of peritrichous flagella and oval rods, 1.8-2.5 mum long. Optimum growth was observed at 30 degrees C, pH 7.0 and 3 % (w/v) NaCl. Strain MIC1-18(T) produced acid from l-arabinose, ribose, glucose, fructose, mannose, N-acetylglucosamine, amygdalin, arbutin, salicin, cellobiose, maltose, sucrose, trehalose, gentiobiose and 5-ketogluconate. l-Lactic acid was the major end product from glucose. The major cellular fatty acid was C(16 : 1)omega7c. The cell-wall murein type was A4alpha containing Lys-Glu. The G+C content of the genomic DNA was 37.8 mol%. Phylogenetic analysis based on the 16S rRNA gene revealed that strain MIC1-18(T) was accommodated as a member of the lactic acid bacteria of the low-G+C content Gram-positive bacteria; the closest neighbour of this organism was Atopococcus tabaci CCUG 48253(T), with only 90.0 % sequence similarity. On the basis of the phenotypic features and phylogenetic position, a novel genus and species, Lacticigenium naphtae gen. nov., sp. nov., are proposed for strain MIC1-18(T) (=NBRC 101988(T)=DSM 19658(T)).