Subsurface Associations of Acaryochloris -Related Picocyanobacteria with Oil-Utilizing Bacteria in the Arabian Gulf Wate
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MICROBIOLOGY OF AQUATIC SYSTEMS
Subsurface Associations of Acaryochloris-Related Picocyanobacteria with Oil-Utilizing Bacteria in the Arabian Gulf Water Body: Promising Consortia in Oil Sediment Bioremediation Dhia Al-Bader & Mohamed Eliyas & Rihab Rayan & Samir Radwan
Received: 12 June 2012 / Accepted: 9 December 2012 / Published online: 21 December 2012 # Springer Science+Business Media New York 2012
Abstract Two picocyanobacterial strains related to Acaryochloris were isolated from the Arabian Gulf, 3 m below the water surface, one from the north shore and the other from the south shore of Kuwait. Both strains were morphologically, ultrastructurally, and albeit to a less extend, phylogenetically similar to Acaryochloris. However, both isolates lacked chlorophyll d and produced instead chlorophyll a, as the major photosynthetic pigment. Both picocyanobacterial isolates were associated with oilutilizing bacteria in the magnitude of 10 5 cells g−1. According to their 16S rRNA gene sequences, bacteria associated with the isolate from the north were affiliated to Paenibacillus sp., Bacillus pumilus, and Marinobacter aquaeolei, but those associated with the isolate from the south were affiliated to Bacillus asahii and Alcanivorax jadensis. These bacterial differences were probably due to environmental variations. In batch cultures, the bacterial consortia in the nonaxenic biomass as well as the pure bacterial isolates effectively consumed crude oil and pure aliphatic and aromatic hydrocarbons, including very highmolecular-weight compounds. Water and diethylether extracts from the phototrophic biomass enhanced growth of individual bacterial isolates and their hydrocarbonconsumption potential in batch cultures. It was concluded that these consortia could be promising in bioremediation of hydrocarbon pollutants, especially heavy sediments in the marine ecosystem. D. Al-Bader : M. Eliyas : R. Rayan : S. Radwan (*) Department of Biological Sciences, Faculty of Science, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait e-mail: [email protected]
Introduction Since our pioneer finding of the association of hydrocarbonutilizing bacteria with coastal cyanobacterial mats [27], many similar associations were described in the marine environment worldwide, including those in which the phototrophic partners were picocynobacteria [19]. Such associations are effective in freeing seawater from hydrocarbon pollutants via the direct activities of the bacterial partners [20]. The cyanobacterial partners play an indirect but important role by offering attachment surfaces to the bacteria, as well as through providing them with molecular oxygen produced during photosynthesis, and growth factors [1]. Oxygen is needed by bacteria in the initial step of attack on the hydrocarbon molecules using oxygenases, also called hydroxylases [21, 22]. So far, these associations were described only in coastal and planktonic environments. Since, however, oil sediments usually reach considerable depths in the seawater column, it would be ecologica
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