Oxygenase systems in an oligotrophic bacterial community of a subsurface water polluted by btex

Molecular probes were designed to detect genes coding for various oxygenase systems. PCR amplifications were carried out either on DNA extracted directly from water samples or from isolates. In the DNA from water samples, genes for toluene-benzene monoxygenase (tbmA), for toluene dioxygenase (todCl), for catechol 2,3-dioxygenase (xylE), and for catechol 1,2-dioxygenase (catA) were present. Among 100 strains isolated to check the presence of hydrocarbon-degrading bacteria, 11 grew on aromatic substrates and most of them attacked aromatics through monoxygenase enzymatic systems. In strains able to grow on benzene, the nucleotide sequence of the 580 bp PCR fragment showed 78% homology to the bmoB gene for benzene monoxygenase of Pseudomonas aeruginosa JI104. In strains able to grow on m-xylene and p-xylene, the PCR fragment showed 66% homology to the pheB gene for phenol hydroxylase of Ralstonia eutropha JMP134. Degradation patterns of isolates monitored by HPLC analysis were in accord with the presence of these degradative enzymes. The probes developed in the present study enlarge the detection of degradative systems in the environment.