Brussels, 31 Jul 2006
A team of European researchers has decoded the genome of a key oil-degrading bacterium, Alcanivorax borkumensis. They hope that their new understanding of the biochemistry of the micro-organism will lead to the development of new, effective, environmentally friendly methods to clean up oil-contaminated waters.
Every year several million tonnes of oil are discharged into the oceans, mostly as a result of human activities. These oil spills have serious environmental and economic consequences; thousands of birds and other creatures are killed or injured, and coastal and marine habitats can take years to recover. The costs of cleaning up the oil alone are immense. Fishermen also suffer as their catch is contaminated and cannot be sold, and tourism suffers when beaches are covered in oil.
However, there exist organisms which positively thrive in an oily environment, and A. borkumensis is one of these. While it is rare in clean waters, in oil-polluted water this bacterium makes up a large percentage of the oil-degrading microbial community. Now researchers have decoded the genome of this remarkable organism and found out what makes it so special.
'We already know of a number of marine oil-degrading bacteria,' said Dr Peter Golyshin of the Helmholtz Centre for Infection Research, Germany. 'However, several studies have shown that Alcanivorax borkumensis is one of the most important worldwide. And after genome sequencing we know why: these bacteria produce a whole arsenal of very effective oil-degrading enzymes.'
According to the research, which is published in the latest edition of Nature Biotechnology, A. borkumensis' most distinctive features is its ability to grow efficiently and almost exclusively on the hydrocarbons found in crude oil. Furthermore, it is able to degrade an extremely wide range of hydrocarbons, something which gives it a competitive advantage over other oil-degrading microbes. A. borkumensis also produces biosurfactants, which help to emulsify the oil and so increase the rate of degradation.
The marine environment is often low in nutrients, and in fact a lack of nutrients, in particular nitrogen and phosphorus, often limits the degradation of otherwise biodegradable components of crude oil. However, A. borkumensis' genome provides a range of systems for the uptake of these scarce nutrients, giving it another advantage over other microbes in oily, low nutrient waters.
Finally the genome of this fascinating bacterium ensures it is able to cope with the stresses of its environment. Living as it does in the upper layers of the ocean, it has a number of genes which help to protect it from the damaging effects of ultraviolet radiation. It is also able to detoxify compounds like arsenate, mercury, copper and other heavy metals.
Put together, these properties have made A. borkumensis a very successful species, and it is found in marine and coastal waters around the world, including in the Mediterranean, the Pacific and the Arctic Sea. 'The ubiquity of A. borkumensis reflects its highly developed ability to adapt to the varying conditions it faces in different unpolluted and polluted environments,' states the paper. The researchers now plan to see how the bacterium behaves in a range of hydrocarbon-relevant situations, to further increase their understanding of marine hydrocarbon degradation.
While the researchers see the main applications of their work in the mitigation of damages caused by oil spills, it could also have implications for research into infectious diseases.
'Oil degrading bacteria form so-called biofilms on the interface between oil and water,' explained Professor Kenneth Timmis of the Helmholtz Centre for Infection Research. 'Since microbial biofilms are the principal lifestyle of both beneficial and disease-causing microbes on and in the human body, a deeper understanding of these processes will certainly benefit efforts to improve human health and control microbial infections.'