Biochemical and genetic studies on degradation of chlorobenzoates by Pseudomonas

The chlorobenzoates constitute an important class of recalcitrant compounds polluting this biosphere. Two bacterial strains B16 (Pseudomonas aeruginosa) and DT4 (Pseudomonas sp.) isolated by enrichment technique were found to utilize 2-chlorobenzoic acid (2-Cba) and 4-chlorobenzoic acid (4-Cba) respectively as sole source of carbon and energy. 2-Cba and 4-Cba were supplemented in synthetic medium at 1500 micrograms/ml and 1000 micrograms/ml (w/v) respectively. Addition of 100 micrograms/ml (w/v) yeast extract stimulated growth of cultures. Degradation studies revealed that substrates were degraded without release of chloride ion with possible accumulation of respective chlorophenols. Respiration studies revealed inducible nature of enzymes for break down of 2-Cba, 4-Cba benzoic acid, 4-hydroxybenzoic acid and catechol. Extraction of plasmid DNA from parent strains showed presence of plasmid of same size in both strains. Cured strains showed absence of corresponding plasmid DNA bands thus indicating plasmid-borne genes for degradation of chlorobenzoates.