Isolation and Characterization of Hydrocarbon-Degrading Bacteria from Polluted Terrestrial and Aquatic Environments in Tunisia

This study aimed to isolate and characterize hydrocarbon-degrading bacteria from polluted environmental samples in Tunisia. Fifteen bacterial strains were isolated from soils (petroleum station and refinery) and marine environment samples (Teboulba harbor) after enrichment in BHMS medium with Zarzatine crude oil (ZCO) as the only carbon source. The most represented genera were Bacillus and Proteus from sediment, Staphylococcus, Enterococcus and Citrobacter from seawater, Pseudomonas, Staphylococcus and Arthrobacter from soil. The results indicated that the majority of isolates showed a high ability to utilize crude oil as growth substrate and a substantial growth on several aliphatic, aromatic and complex hydrocarbons. In addition, a molecular screening of the key genes involved in petroleum hydrocarbon biodegradation showed that five strains were positive for at least one of alkB, ndoB, cat23 and xylA genes. Furthermore, slime, biofilm, and biosurfactant production were investigated to characterize the hydrocarbon-degrading strains. Six bacterial strains namely P. aeruginosa K7, Staphylococcus aureus R1, Pseudomonas stutzeri R5, Arthrobacter creatinolyticus R6, Pseudomonas stutzeri R13 and Proteus mirabilis S7 were considered as highly-biofilm-producing isolates, while only the P. aeruginosa K7 strain was characterized as a potent biosurfactant producer species. Overall results suggest that the selected bacterial isolates may be used in bioremediation and for further biotechnological applications.