The potential of Burkholderia cepacia strain RQ1 in the biodegradation of heavy crude oil (Maya) was assessed to develop an active indigenous bacterial consortium for the bioremediation of crude oil-polluted systems in Nigeria. The heavy crude oil (Maya) was utilized as sole source of carbon, attaining maximum cell densities of 10 8 cfu ml ±1 from an initial 10 5 cfu ml ±1 in 15 days. Biomass also increased with oil concentrations up to 0.8% (w/v). Growth rates ranged from 0.028 h ±1 to 0.036 h ±1 and degradation rates decreased with increasing concentrations of oil from 0.009 day ±1 to 0.004 day ±1 . The quantity of oil metabolized increased signi®cantly (P<0.05) with increasing concentrations of oil. However, the growth of the bacterium was inhibited at crude oil concentrations beyond 6% (w/v). The pH of the culture media also dropped signi®cantly (P<0.05) during the 15-day test period, while the non-asphaltic fractions of the oil were signi®cantly reduced (by about 89%) during the same period. The bacterium harbours a plasmid of about 10 kb that lacks restriction sites for the endonucleases Asp718, BamHI and PstI.

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Two bacterial species isolated using enrichment culture techniques from the topsoil of a main refuse dumpsite in Nigeria were assessed for their dehalogenation potentials. The bacterial isolates were identified as belonging to the Bacillus and Pseudomonas genera. Axenic cultures of the isolates utilized monochloroacetic acid (MCA), trichloroacetic acid (TCA), trichloromethane (CHCl3) and tetrachloromethane (CCl4) as the sole source of carbon for growth up to a final substrate concentration of 0.1% (w/v). The mean generation times of the isolates in all the growth media ranged significantly (P<0.05) from 2.41 to 10.04 h and were generally higher than that observed in glucose medium (1.46-1.51 h). The numbers of the chloride atoms in the different organochlorides were negatively correlated with the ability of the organisms to degrade the compounds. Dehalogenase specific activities of the cell-mediated cultures ranged from 0.1 to 0.96 microg ml(-1) chloride release (mg protein)(-1) h(-1) and were significantly (P<0.05) higher than that of the cell-free extract [0.09-0.8 microg ml(-1) chloride release (mg protein)(-1) h(-1)]. The optimal pH of the dehalogenase activity was found to be 8.0, and the optimal temperature was between 30 and 35 degrees C.