DETHIOSULFOVIBRIO PEPTIDOVORANS GEN-NOV, SP-NOV, A NEW ANAEROBIC, SLIGHTLY HALOPHILIC, THIOSULFATE-REDUCING BACTERIUM FROM CORRODING OFFSHORE OIL-WELLS

A strictly anaerobic thiosulfate-reducing bacterium was isolated from a corroding offshore oil well in Congo and was designated strain SEER 4207(T). Pure culture of the strain induced a very active pitting corr osion of mild steel, with penetration rates of up to 4 mm per year. Th is constitutes the first experimental evidence of the involvement of t hiosulfate reduction in microbial corrosion of steel. Strain SEER 4207 (T) cells were vibrios (3 to 5 by 1 mu m), stained gram negative, and possessed lateral flagella. Spores were not detected. Optimum growth o ccurred in the presence of 3% NaCl at pH 7.0 and 42 degrees C. Strain SEER 4207(T) utilized peptides and amino acids, but not sugars or fatt y acids. It fermented serine, histidine, and Casamino Acids, whereas a rginine, glutamate, leucine, isoleucine, alanine, valine, methionine, and asparagine were only used in the presence of thiosulfate. Peptides were fermented to acetate, isobutyrate, isovalerate, 2-methylbutyrate , H-2, and CO2. The addition of either thiosulfate or sulfur but not s ulfate increased peptide utilization, growth rate, and biomass; during growth, H2S was produced and a concomitant decrease in H-2 was observ ed, The addition of either thiosulfate or sulfur also reversed H-2 inh ibition. 16S rRNA sequence analysis indicates that strain SEER 4207(T) is distantly related to members of the genus Thermoanaerobacter (83% similarity). Because the phenotypic and phylogenetic characteristics c annot be assigned to any described genus, strain SEER 4207(T) is desig nated as a new species of a new genus, Dethiosulfovibrio peptidovorans gen. nov., sp. nov. Strain SEER 4207(T) has been deposited in the Deu tsche Sammlung von Mikroorganismen and zellkulturen GmbH (= DSM 11002) .