Samples obtained from three locations in the Lagos lagoon were studied for the effect of Aroclor 1221 on their population dynamics. In all three cases, both control and experimental microcosms showed slight increases between day 5 and day 10 with the highest value of 4 × 1010 cfu/ml in control and 1.2 × 1011, 8 × 1010 and 9 × 1010 cfu/ml for Iddo, Apapa and Tin Can samples respectively. Three isolates namely, Bacillus subtilis, Alcaligenes eutrophus and Pseudomona aeruginosa were obtained from the microcosms after successive enrichment. All the isolates grew readily on 100 ppm of Aroclor 1221 concomitant with production of yellow metabolites in mineral salts medium. Whereas maximal growth was observed at day 12 on biphenyl, that of the polychlorinated biphenyl (PCB) mixture was on day 15. Generally, growth dynamics were similar irrespective of the substrate while typical generation times, with the exception of B. subtilis on Aroclor 1221, ranged insignificantly (P < 0.05) from 6.86 to 8.35 day, thus, suggesting that chlorine substitution has little or no effect on catabolic potentials of the organisms. The degradative capability of these strains suggest that they contribute immensely to the self-purification processes occurring in the lagoon, and this could be exploited for decontamination of PCB polluted aquatic ecosystems.
Key words: Aroclor 1221; biodegradation; polychlorinated biphenyls (PCBs); Lagos lagoon, bacterial strains.
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