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Stable Isotope Probing - A Tool for Assessing the Potential Activity and Stability of Hydrocarbonoclastic Communities in Contaminated Seawater

Petra J Sheppard, Eric M Adetutu, Alexandra Young, Mike Manefield, Paul D Morrison and Andrew S Ball

To optimize bioremediation strategies, knowledge of which bacterial groups are actually degrading specific hydrocarbon fractions is required. In this study, we monitored the utilization rate of unlabeled ( 12 C) and labeled ( 13 C) substrates, benzene (0.559 μL L -1 h -1 ) and hexadecane (0.330 μL L -1 h -1 ) in seawater pre-exposed to hydrocarbons over 72 h in laboratory based microcosms. Microbial community analysis by RNA-SIP DGGE showed substantial differences between the banding pattern of 12 C and 13 C communities. Cluster analysis of the microbial community profiles showed that the labeled bacterial population was ~25% similar to the original community in the unlabeled microcosms. This suggested that only a subset of the original bacterial community appeared to have utilized the labeled substrates. Sequence analysis of 16S rRNA gene sequences revealed the presence of known hydrocarbon degraders including Alcanivorax , Acinetobacter , Pseudomonas and Roseobacter . The presences of a number of Firmicutes in both sets of mesocosms suggest that these species were able to utilize both benzene and hexadecane. This study highlights the benefits of incorporating RNA-SIP in remediation studies to enhance the understanding of microbial communities in contaminated seawater.