Plasmid Involvement In Biodegradation Of Polycyclic Aromatic Hydrocarbons By Bacteria Isolated From Nigeria

Abstract

Six Gram‐negative bacteria isolates designated PYR 1, FLU 1, FLU 2, FLU 3, FLU 4 and FLU 5 capable of utilizing fluoranthene, pyrene and phenanthrene as sole source of carbon and energy were isolated from diesel‐oil contaminated soil in Nigeria and evaluated for the role of plasmid in biodegradation of polycyclic aromatic hydrocarbons (PAHs). 97% degradation of fluoranthene and pyrene (100mg/L) were observed for all the isolates whereas phenanthrene (100mg/L) was degraded to undetectable level by HPLC analysis within 8days. Co‐metabolizing of fluoranthene and pyrene in the presence of phenanthrene showed statistical significant difference (p<0.05) in degradation and total viable cell count compared to degradation of fluoranthene and pyrene. Large plasmids (>500bp) were detected in isolates; PYR 1 (880.24bp), FLU 2 (1521.42bp and 880.24bp), FLU 3 (1521.42bp and 880.24bp), FLU 4 (1521.42bp and 880.24bp) and FLU 5 (34693.65bp, 1521.42bp and 880.24bp) while FLU 1 had no plasmid under the condition of assay. SDS‐curing of the isolates lead to complete loss of plasmid and PAHs degradation activity. This study suggests that these mega plasmids could be responsible for the isolates degradation of PAHs.