Isolation and Identification of Oil-Degrading Bacteria from Oil-Polluted Soils and Assessment of Their Growth in the Presence of Gas Oil

Oil contamination in Iran due to high application of oil compounds, is one of the most dangerous pollution factors. Bioremediation is a prime strategy for remediation, by which the pollutants can be removed by making use of microorganism or any biological process that employes microorganisms or their enzymes to rehabilitate the environment altered by the contaminants. With regards to the importance of this method, screening and isolation of oil-degrading bacteria from contaminated site of Bushehr province were done in Carbon Free Minimal Medium enriched by gas oil. In this study 19 isolates of bacteria (PDB 1-19) were isolated, and the molecular and kit identifications showed different genus and species such as Stenotrophomonas maltophilia, Ralstonia sp., Vibrio sp., Sphingobacterium sp., Zymomonas sp., Pseudomonas aeruginosa, Paracoccus sp., Pantoea sp., Achromobacter xylosoxidans, Acinetobacter johnsonii, Serattia odorifera, Pseudomonas alcaligenes, Entrobacter cloacae, Pseudomonas stutzeri and Chryseobacterium sp.. In order to determine the efficiency of these bacteria in hydrocarbondegradation an inoculum of pure culture of bacteria containing 108 cfu/ml was used in liquid assay, which was performed in factorial experiment based on completely randomized design with 2 replications. Utilization of hydrocarbon sources was again detected in CFMM broth supplemented with 2% gas oil where the growth turbidity (OD600nm) as an indicator for utilization of hydrocarbon and bacterial growth was measured at different times of 0, 48, 168, 216 and 312hr. Results showed that in CFMM broth assay all main factors including bacteria and time as well as their interaction were significant (p<0.01). These bacteria were effectively able to mineralize gas oil and among bacteria, best results was achieved by Chryseobacterium sp.. The ability of bacterial isolates for degradation of oil-compounds increased by increasing time of incubation.