Degradation of Aroclor 1221 by microbial populations of the Lagos lagoon

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 showedslight 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 isolatesnamely, 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 1221concomitant 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 theself-purification processes occurring in the lagoon, and this could be exploited for decontamination of PCB polluted aquatic ecosystems

Microbial population changes in tropical agricultural soil experimentally contaminated with crude petroleum

Impacts of crude petroleum pollution on the soil environment and microbial population dynamics as well as recovery rates of an abandoned farmland was monitored for seven months spanning the twomajor seasons in Nigeria with a view to establishing process conditions necessary for development of effective strategies for bioremediation. The physico-chemistry of the control and contaminated soilsdiffered just significantly (P < 0.05). Whereas these factors were relatively stable over the period of investigation for the control site, a downward trend was observed for the experimental. The pollutedsoil showed significant diversity in structure and number of flora .There was an initial drop in microbial population densities at the onset of pollution but, a gradual increase was observed thereafter. Highercounts of microflora were obtained for April, May, June and July samples which coincided with the onset and peak of wet season. A rapid and significant reduction in residual oil concentration wasobserved during this period. Overall, nearly 100% of the crude oil pollutant was degraded within the 28-week study period. The residual oil concentration gave a high but negative correlation coefficient (r = -0.84 to -0.90) with total heterotrophic and hydrocarbon-utilizing populations. On application of data generated to model equations, approximately 60.5 weeks would elapse before the contaminated soilcould recover from the impact of the oil. Our results show that a natural population readily able to degrade crude oil is present in the soil chosen for this study. However, it may be necessary to monitor the level of inorganic nutrients and adjust some appropriately to enhance biodegradation of the organic pollutant