Isolation and characterization of Xanthobacter polyaromaticivorans sp. nov. 127W that degrades polycyclic and heterocyclic aromatic compounds under extremely low oxygen conditions.

Two bacterial strains, 127W and T102, were isolated from anoxic crude oil tank sludge as effective degraders of dibenzothiophene (DBT), a model sulfur containing heterocyclic aromatic compound in crude oil. Strain 127W was more tolerant to oxygen limitation than T102 and was capable of degrading two- and three-ring polycyclic and heterocyclic aromatic compounds under both aerobic and low oxygen conditions. Strain 127W degraded 0.082, 0.055, and 0.064 mM of DBT, naphthalene, and anthracene, respectively, in one week with dissolved oxygen < or =0.2ppm (0.006 mM). Degradation by 127W cell-free extracts for DBT was increased by addition of sodium hydrogencarbonate under this oxygen concentration. Phylogenetic analysis of the 16S rRNA gene sequence and physiological characteristics indicate that the strains 127W and T102 belong to new species of the genus Xanthobacter and Pseudomonas stutzeri, respectively. We propose X. polyaromaticivorans sp. nov. 127W.