Chromosomal and plasmid mediated degradation of crude oil by Bacillus coagulans, Citrobacter koseri and Serratia ficaria isolated from the soil

Abstract

In this work, the degradative abilities of some bacteria isolated from the soil were studied. Five distinct isolates were subjected to substrate susceptibility test to determine their potential degradative abilities in the presence of different hydrocarbons. The best three crude oil degraders were selected and their identities were further established using API technique. Furthermore, the extent of each degradative ability of the three bacteria was determined using gas chromatography (GC) technique to analyze the residual crude oil after 21 days. The pH and total viable counts (TVC) were also monitored every three days for the period of the study. The three isolates were later subjected to plasmid extraction and the cured isolates were again exposed to crude oil. The initial bacteria isolated were; Pseudomonas cepacia (B1), Micrococcus luetus (B3) Bacillus coagulans (B4), Citrobacter koseri (B2) and Serratia ficaria (B5). C. koseri, S. ficaria and B. coagulans had strong growth in crude oil. B. coagulans was able to degrade 95% of the crude oil; S. ficaria degraded 92% of the crude oil, and C. koseri degraded 91% of the crude oil using it as the sole carbon source. The pH was relatively the same throughout the period and the TVC that were initially low for the three bacteria, later increased. Degradative abilities of B. coagulans and C. koseri were chromosomal mediated while S. ficaria was plasmid mediated. The biological/genetic basis of their degradative activities can be used improve their degradative abilities.   Key words: Chromosomal, crude oil, degradation, plasmid, soil.