Abstract
To analyze microbial communities in environmental samples, this study combined Denaturing Gradient Gel Electrophoresis of amplified 16S rRNA‐genes in total genomic DNA extracts from those samples with gene sequencing. The environmental samples studied were oily seawater and soil samples, that had been bioaugmented with natural materials rich in hydrocarbonoclastic bacteria. This molecular approach revealed much more diverse bacterial taxa than the culture‐dependent method we had used in an earlier study for the analysis of the same samples. The study described the dynamics of bacterial communities during bioremediation. The main limitation associated with this molecular approach, namely of not distinguishing hydrocarbonoclastic taxa from others, was overcome by consulting the literature for the hydrocarbonoclastic potential of taxa related to those identified in this study. By doing so, it was concluded that the hydrocarbonoclastic bacterial taxa were much more diverse than those captured by the culture‐dependent approach. The molecular analysis also revealed the frequent occurrence of nifH‐genes in the total genomic DNA extracts of all the studied environmental samples, which reflects a nitrogen‐fixation potential. Nitrogen fertilization is long known to enhance microbial oil‐bioremediation. The study revealed that bioaugmentation using plant rhizospheres or soil with long history of oil‐pollution was more effective in oil‐removal in the desert soil than in seawater microcosms.
Highlights
About 0.08% to 0.4% of the crude oil produced and used on our planet is spilled as pollutants in the marine ecosystem (National Research Council, 1989)
The major objective of this study is to complement a recent work (Ali et al, 2016), in which we investigated the feasibility of autochthonous bioaugmentation for bench-scale bioremediation of oil- contaminated samples
The DGGE gels carrying the resolved 16S rRNA-gene bands, that have been amplified in total genomic DNA extracts from the three studied seawater samples (Figure 2) revealed that the amplicon numbers in each sample were relatively high
Summary
About 0.08% to 0.4% of the crude oil produced and used on our planet is spilled as pollutants in the marine ecosystem (National Research Council, 1989). Today, those estimates undoubtedly must have increased dramatically. Terrestrial and atmospheric ecosystems are suffering from hydrocarbon pollution This problem is acute in oil-producing countries such as those in the Arabian/Persian Gulf region. Based on their relatively slow biodegradability, oil-pollutants persist long in the environment (Andreoni & Gianfreda, 2007).
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