The explosion of the Deepwater Horizon oil rig, in the Gulf of Mexico, in April 2010, resulted in the release of approximately 4.9 million barrels of light crude oil over a period of three months. Much of the oil was transported to the shoreline, and a significant proportion still remains within coastal ecosystems. The marine sands of the Gulf are covered with microbial biofilms, and much of the oil hydrocarbon entering marine systems is degraded by indigenous microorganisms. The aim of this study was to identify and characterise predominant oil-degrading taxa which could be used as model hydrocarbon degraders or indicators of contamination, and to investigate the in situ response of indigenous bacterial communities to oil contamination.
Sediment cores were taken from beach sands of Pensacola Beach, Florida, an area which was exposed to heavy oil contamination in June 2010 as a result of the Deep Horizon oil spill. Samples were collected in July and September 2010. Chemical analysis revealed concentrations of petroleum hydrocarbon (C8 to C40) ranging from 3.1 to 4500 mg kg-1. The abundance of bacterial rRNA gene sequences was approximately ten times higher in oiled sand than clean sand from a control area. Sequence libraries from the contaminated sands showed high sequence identity (up to 99%) to characterized oil-degrading isolates. A total of 24 bacterial strains from 14 genera were isolated and confirmed as oil-degrading microorganisms, with Gammaproteobacteria (Alcanivorax, Marinobacter) and Alphaproteobacteria (Rhodobacteraceae) dominating. Community analysis showed an increase in abundance of rRNA gene sequences from the genus Alcanivorax, in contaminated samples, indicating a response to oil contamination.
The findings suggest that oil contamination can influence the abundance and community composition of indigenous bacteria in the Gulf beach sands. The authors also hypothesise that Alcanivorax spp. can act as indicators of early stage oil degradation, and members of Alphaproteobacteria and Gram-positive groups can act as indicators of later stages of degradation, and suggest work to further investigate this.
This paper is fairly easy to read, it sets out the aims very clearly and although quite lengthy, the methods and results are presented in a logical order, with the discussion clearly addressing the key questions. The findings are important because oil spills can have severe ecological and economic consequences, and the authors point out that whilst technologies for oil drilling have advanced rapidly, the strategies employed to respond to and assess the impacts of oil spills are trailing behind. In order to manage oil spills and their clean-up more effectively, more must be known and understood about those microbial communities which are not only affected, but also play a key role in biodegradation. This is one of the few studies to investigate bacteria in situ, rather than under laboratory conditions.
A review of: Kostka, J.E. et al. (2011) Hydrocarbon-degrading bacteria and the bacterial community response in Gulf of Mexico beach sands impacted by the Deepwater Horizon oil spill. Applied and Environmental Microbiology, 77 (22): 7962.
4 comments:
Hi Helen
The findings of this paper are really interesting! Do the authors mention anything about harnessing the microbe's biodegrading powers to help clean up oil spills? Do you think it could be possible to perhaps culture them and apply large numbers to oil affected areas to help degrade the oil faster? Or perhaps to other substrates?
Tasha
Interesting indeed. I have read other papers which are investigating your suggested approach by looking at isolating and culturing a successful degrading bacterium.
Degradation has been suggested to involve specific enymatic activity which has seen attention from researchers in order to engineer bacteria with this specicic trait - in an attempt to create a more effective process of bioremediation. This has occured in bacteria isolated from an unpolluted environment with the possibility of applying them in a contaminated site. However, implications surrounding their response to other processes such as weathering is yet to be ascertained as well as the inevitable ethical issues surrounding their application.
maybe the active enzymes and chemicals that the bacteria produce could be harness and poured over the oil to get rid of it, however what the oil is broken down into may be an issue. What would be good is to find an organism that collects and retains the oil which then could be harvested to use the oil and not waste it!
Hi Tasha
The authors didn't address that issue, they focused more on the selective response of indigenous communities, investigating shifts that occurred as a result of the presence of oil.
They did mention that metabolism of oil could be limited by temperature, oxygen and nutrient availability, hydrocarbon content and weathering of the oil, so I guess if the isolated bacteria were to be 'applied' to oil spills, the success of the bioremediation would also depend on where the oil spill takes place and whether the bacteria can survive.
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