Oil-loving Microbes Could Gobble Up Slicks And Spills

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Oil-loving Microbes Could Gobble Up Slicks And Spills

Spills of crude oil that devastate huge areas of the oceanic environment could be cleaned up by naturally occurring microorganisms.

It's one application of new research into how bacteria break down oil, which could also help oil companies assess the quality of new reserves.

In 2010, the Deepwater Horizon oil spill released around 5 million barrels into the Gulf of Mexico, becoming the largest oil spill in US history. In such a case, some of the oil can be cleaned up by skimming it from the surface, while detergents added to the water together with wave action can cause much of the oil to disperse as droplets.

While this breaks up the slick, the oil droplets spread far and wide, becoming difficult to treat and creating pollution in wide areas of ocean. Now, researchers believe it may be possible to counteract this issue with the help of ocean bacteria which have evolved to consume naturally-emerging oil from underwater seeps.

In an EU-funded project called OILY MICROCOSM, a team at the Technical University of Crete, Greece, are investigating how the bacteria help to break down oil in these droplets.

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There can be 100 billion bacteria (bright dots) per ml of oil droplet (red) in water (green). Image credit - Prof. Rainer Meckenstock

‘About 40% of the oil that ends up in the sea is from natural seeps,’ said Dr George Kapellos, who works on the project. ‘So microbial species have evolved to degrade it.’

Problems arise when the concentration of the oil is very high and when microdroplets spread far and wide through the action of ocean currents.

‘We are trying to track the fate of the microdroplets when they are degraded by the microbes,’ said Dr Kapellos, who is cooperating with scientists at the Massachusetts Institute of Technology.

Although in its early stages - the project only began in November last year - he has already identified three potential mechanisms that allow the bacteria to break down the oil.

The first involves the droplets dissolving in the water column and being consumed by the microbes as they do so. A second is that the microbes attach to the surface of the oil droplet and consume the oil without it needing to be dissolved. The third potential mechanism involves the formation around the oil of colonies of bacteria known as biofilms.

‘The first two mechanisms are quite well known, but the third is less well understood,’ said Dr Kapellos, who is presenting his initial findings at the GoMRI Conference in New Orleans in the US  which runs until 7 February. ‘One might think, the thicker a biofilm is (with a high number of) microbes, the faster the degradation of the oil droplet would be,’ he said. ‘But this is not necessarily the case, as biofilms also act as diffusive barriers that impede the dissolution of the droplet.'

‘A biofilm that covers a microdroplet and grows thicker over time will accelerate the droplet shrinking rate only if oil is more soluble and mobile in the biofilm than in the seawater,' he said. This could raise the prospect of exploiting these oleophilic (oil-loving) biofilms to help break down oil spills faster.

Toxic microdroplets

The modelling work undertaken by Dr Kapellos demonstrates that, when oil microdroplets descend on the sea bed, they concentrate in a way that affects how microbes will break them down.

‘Just now there is no method for handling the dispersal of droplets in deep waters below 300 metres,' he said. 'It is important, as microdroplets are known to be more toxic to fish, sea mammals and invertebrates, and spills can have major impacts on local economies that rely upon them.

‘We are hoping that the fundamental work we are doing will have a positive impact on developing methods that combat oil spills in the sea,’ he said.

Yet, although microorganisms that eat oil could help to clean it up in places where it is not welcome, they can also create a major headache for the oil industry.

Recent research by scientists in Germany shows that microbes appear to live within oil reservoirs themselves - suspended within microscopic droplets of water, hundreds of metres beneath the sea floor.

Professor Rainer Meckenstock, a microbiologist at the University of Duisburg-Essen, believes these complex microbial communities became trapped with the water in the oil long ago and thrive inside the water droplets as miniature ecosystems. It is an extraordinary discovery, as many scientists doubted life could survive in such a toxic, hostile environment.

Read full article: Horizon Magazine

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