Characterization of multiple chlorobenzoic acid-degrading organisms from pristine and contaminated systems: Mineralization of 2,4-dichlorobenzoic acid

Multiple bacterial strains with CBA metabolic properties were isolated using a simple selective strategy. Phylogenetic analysis of the 165 rRNA gene sequences grouped them into two main clusters consisting of four bacterial phyla and belonging to 17 genera. Whereas growth was more frequent with 2-CBA (similar to 68%), 50% grew on 4-CBA and similar to 7% utilized 3-CBA. One third of the strains exhibited 2,4-dichlorobenzoic acid (2,4-diCBA) catabolic function and were mainly representatives of alpha-, beta- and gamma-Proteobacteria. In batch experiments, growth was concomitant with substrate disappearance and near-stoichiometric release of chloride. Doubling times for 2,4-diCBA degradation doubled those determined for mono-substituted CBAs. Out of the six 2,4-diCBA degraders submitted for enzyme assays, significant induction of catechol 1,2-dioxygenase types I and II activities in cell-free extracts were found in four while protocatechuate 3,4-dioxygenase activity was detected in the remaining two. Activities in CBA-grown cells were 20 orders-of-magnitude higher than those grown on benzoic acid. (C) 2010 Elsevier Ltd. All rights reserved.