Characterization and Potentials of Indigenous Oil-Degrading Bacteria Inhabiting the Rhizosphere of Wild Oat (Avena Fatua L.) in South West of Iran.

Abstract

Background: The contamination of ecosystem with petroleum and its derivatives is con‌sidered as one of the most crucial environmental threat in Iran. Application of micro‌organisms has been demonstrated as an appropriate and more practical alternative to clean-up petroleum hydrocarbons in the contaminated environments. Objectives: The objectives of this study were isolating rhizosphere-inhabiting indig‌enous oil-degrading bacteria in wild oat grown in petroleum-polluted areas and in vitro evaluating the efficiency of oil biodegradability by microbial isolates. Materials and Methods: Bacteria were isolated from rhizosphere of wild oat grown on contaminated sites in Khuzestan and were identified based on 16S rRNA gene sequenc‌ing. The catabolic genes were detected using PCR and hybridization analysis. Hydrocar‌bon degradation in liquid culture was evaluated by gas chromatography-mass spec‌trometry (GC-MS). Results: 23 indigenous oil-degrading bacterial strains were isolated from the wild oat rhizosphere, grown in severely oil contaminated soil in Khuzestan. Based on 16S rRNA gene sequence analyses, isolated strains were classified to Genera Acinetobacter, Pseudo‌monas, Enterobacter, Stenotrophomonas, Bacillus, Achromobacter, Ochrobactrum, Paenibacil‌lus, Microbacterium, Curtobacterium and Sphingobacterium. Catabolic genes alkM, alkB and xylE, responsible for biodegradation of the alkanes and aromatic petrochemical com‌pounds were detected in bacterial community inhabiting rhizosphere of the wild oat. The GC-MS analysis indicated that consortium of these bacteria was capable of reducing crude petroleum in the liquid culture by 40.5%, after 10 days. The results of the present study revealed the adaptability of microbes to the rhizospheric area and subsequently their great potential to be exploited for cleaning up hydrocarbon contaminated sites. Conclusions: This study might be an important step towards the development of a phy‌toremediation strategy in the South of Iran.