Detection of meta- and ortho-cleavage dioxygenases in bacterial phenol-degraders

In the last five years, in our lab, several bacterial genera capable of degrading phenol as sole carbon source were isolated from different Egyptian ecosystems. Phenol mineralization using these isolates was ranged from 55% to 0.4%. In the present work, randomly chosen representative strains; W-17, DF4 (Acinetobacter), Sea-8 (Stenotrophomonas), W-6 (Klebsiella), S-5 (Bacillus) and W-15 (Ralstonia) were analyzed for the type of ring-cleavage (ortho or meta) dioxygenase physiologically induced during growth in the presence of phenol as a sole carbon and energy source. The specific activities of the phenol-degrading enzymes phenol hydroxylase, catechol-1,2-dioxygenase and catechol-2,3-dioxygenase were investigated. In addition, whole-cell dioxygenases activities of the examined isolates were determined. Out of the results, only the Acinetobacter strains W-17 and DF-4 showed activity with the enzymes phenol hydroxylase and catechol-1,2-dioxygenase, which responsible for phenol degradation through ortho-cleavage pathway. In contrast, isolates S-5, Sea-8, W-6, W-15 and Pla-1 showed activity with the enzyme catalyzing the second step in the phenol degradation meta-cleavage pathway, catechol-2,3-dioxygenase. On the basis of our previous and present analysis, the investigated isolates are considered to have a good potential for application in remediation of phenol contaminated environments and industrial wastewater.