Sources of pollution such as fuel oil spills have the potential to devastate local populations of many marine birds, fish and mammals. Recent historical events such as the Deepwater Horizon spill in the Mexican Gulf and the Prestige oil spill off the north-western coast of Spain have highlighted the impact of these man-made natural disasters. Microbial populations, on the other hand, have become a source of interest for many marine microbiologists due to the ability of many marine bacteria to survive and degrade these toxic chemicals. The authors collected specimens of spilled oil from the rocks and sand on the Costa da Morte, North-Western Spain 12 months after the Prestige oil spill with non-soiled samples taken from an adjacent site to act as a control. These samples were taken and grown on growth media containing different hydrocarbons (alkanes and aromatics) to assess the ability of the bacterial communities present to biodegrade these chemicals. Positive isolates were then taken from these cultures after incubation, genotyped and sequences from interesting strains compared to a clone library. DNA was also extracted directly from the environmental samples, sequenced and compared again to the clone library.
Results showed that bacterial communities present in the samples contaminated with Prestige oil observed a higher population diversity than samples originating from unpolluted beaches. Previous studies by these authors from immediately after the oil spill agree with these findings where, after a couple of months, diversity was dramatically reduced but recovered over the following months to create a new community with a completely different structure than before pollution. When species were compared to the clone library, species of bacteria such as Rhodococcus and Chromatiales spp. showed high homology with species found on geographically separate beaches that had all been affected by the same spill.
Many of the isolates that were cultured, such as Rhodococcus and Mycobacterium, belong to a distinct group of gram-positive bacteria under the sub-order of Corynebacteria. Compared to other gram-positive bacteria this group is fairly unique in containing an outer permeability barrier which confers resistance to toxic chemicals such as fuel oil and allows these species to play a role in bioremediation. Therefore, the addition of mycolic acids (key constituents promoting growth of this group of bacteria) could be added to polluted sea water and costal environments to provide biodegradation and allow effective treatment of the oil spill at a microscopic level. This would be an advantage compared to treating coastlines with bioremediating bacterial communities that are not indigenous to the area. Once fully treated with additives such as mycolic acid the local bacterial species should allow a bacterial community diversity similar to the one present before the event.
A review of : Alonso-Gutierrez, J, Figueras, A, Albaiges, J, Jiminez, N, Vinas, M, Solanas, A.M, Novoa, B; 2009; Bacterial Communities from Shoreline Environments (Costa da Morte, Northwestern Spain) Affected by the Prestige Oil Spill; App. & Env. Micro.; June 2009; pp.3407-18.
5 comments:
This is an interesting article. I reviewed a paper which investigated the ability of an exotic bacterium to degrade crude oil in saline conditions. Although the bacteria did work well in the conditions against most types of crude oil it makes sense to promote the growth of a species already present.
A study comparing the two species ability to degrade crude oil would be interesting.
Hi Theo
Interesting review. I can see that this method of treating an oil spill should be better and maybe more effective. Boosting a population of native species should be easier too, rather than using non-native species which could have unforeseen consequences.
I was just wondering however, you mentioned about adding mycolic acid to promote growth of this group of bacteria. Am I right in saying it is a type of fatty acid? Is it needed as a fuel source or is it needed for anabolic processes, like membrane synthesis? Do they mention any other side affects this molecule could have in the environment where its spread?
Hi Matt,
Interestingly, Dave Flynn just posted a review on a paper exploring the advantages and disadvantages of using exotic species as opposed to indigenous species for bioremediation (Indigenous vs. Exotic: Biodegradation faceoff, 7th April 2012).
The authors of that paper conclude that all species of bacteria tested degrade oil to a similar level and, therefore, the use of indigenous species for bioremediation should be seen as a viable treatment.
Happy Easter!
Theo
Hi Lee,
Mycolic acid is indeed a fatty acid and, as the authors of this paper suggest, is a major constituent in the bacterial permeability layer that provides tolerance to toxic chemicals. It can also be assumed that the addition of mycolic acid en masse to a marine environment would promote the growth of Corynebacteria spp. throughout the environment. The issue of any side effects would therefore lie in the application of the treatment, i.e. whether the concentrations of mycolic acid used locally would affect bacterial communities further afield that may not have been affected by the original pollutant.
Happy Easter!
Theo
Thanks, I just read that post. I noticed the exotic bacteria were still all marine bacteria though and that there was no comparison between those marine bacteria and another species that is known to be good at degrading crude oil, especially one that is able to work as well as (or better than)these marine bacteria species.
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