Consistent Occurrence of Hydrocarbonoclastic Marinobacter Strains in Various Cultures of Picocyanobacteria from the Arabian Gulf: Promising Associations for Biodegradation of Marine Oil Pollution

Fifteen nonaxenic cultures of picocyanobacteria were isolated from the Arabian Gulf, from which 122 heterotrophic bacterial strains were obtained. Based on their 16S rRNA gene sequences, those strains were affiliated with 22 different species, 82.8% of which belonged to the genus Marinobacter, known to comprise hydrocarbonoclastic strains. The remaining species belonged to the genera Alcanivorax, Bacillus, Halomonas, Mesorhizobium, and Paenibacillus, and a Bacteriodetes bacterium also known to comprise hydrocarbonoclastic strains. All the picocyanobacterial cultures harbored one or more strains of Marinobacter. Marinobacter in addition to Alcanivorax and other genera isolated from those picocyanobacteria grew on Tween 80, crude oil, and pure hydrocarbons as sole sources of carbon and energy, i.e. they are related to the obligate hydrocarbonoclastic bacteria group. They consumed crude oil, n-octadecane, and phenanthrene in batch cultures. The results indicated that Marinobacter isolates seemed to grow better and consume more oil in the presence of their host picocyanobacteria than in their absence. Such natural microbial associations assumingly play a role in bioremediation of spilled hydrocarbons in the Arabian Gulf. Similar associations probably occur in other marine environments as well and are active in oil spill removal.