Identification and characterization of novel genes belonging to microbial
aromatic biodegradation pathway is of great importance as they have been
proven versatile biocatalysts. In this study, the selection of 19
environmental bacterial isolates capable to degrade a wide range of aromatic
compounds has been screened for the presence of five genes from the lower and
the upper aromatic biodegradation pathway using PCR methodology. In the case
of 4-oxalocrotonate tautomerase and toluene dioxygenases, although present in
the most of environmental isolates, very limited diversity of the genes has
been encountered. Highly conserved sequences of these genes in environmental
samples revealed high homology with gene sequences of the characterized
corresponding genes from Pseudomonas putida species. The screen using
degenerate primers based on known catechol-and naphthalene dioxygenases
sequences resulted in a limited number of amplified fragments. Only two
catechol 2,3-dioxygenase from two Bacillus isolates were amplified and showed
no significant similarities with dioxygenases from characterized organisms,
but 80-90% identities with partial catechol 2,3-dioxygenase sequences from
uncultured organisms. Potentially three novel catechol 1,2-dioxygenases were
identified from Bacillus sp. TN102, Gordonia sp. TN103 and Rhodococcus sp.
TN112. Highly homologous tautomerase and toluene dioxygenases amongst
environmental samples isolated from the contaminated environment suggested
horizontal gene transfer while limited success in PCR detection of the other
three genes indicates that these isolates may still be a source of novel
genes.