Unique molecules from bacteria help them digest petroleum, vegetable oil, and coal.

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Bacteria come from some of the planet’s most ancient forms of life. Often, bacteria have impressive abilities that are rare in other creatures. Some bacteria, for instance, can actually eat fossil fuels, like petroleum (used to make gasoline) or coal. This ability enables bacteria to survive in places that many other species can’t.

Like all species, including humans, bacteria need water to help them break down or digest food. But bacteria can also break down fossil fuels, which are oils, and oil and water don’t mix together. So how do these bacteria manage to use water to help them digest oils anyway?

Normally, water molecules like to stick together, which results in oil being pushed out, keeping the two liquids separated. This happens because the structure of a water molecule gives it a negative charge on one side and a positive charge on the other. (This is what is known as a “polar” molecule.) That means one water molecule’s positive end likes to stick to the neighboring molecule’s negative end, making water cling together like a pack of weak magnets. As a result, oil (a non-polar molecule) gets pushed out and stays separated from water.

Some bacteria make special molecules called surfactants that help them pry water molecules apart, so that water can mix more easily with other substances. These special molecules have one end that is attracted to water (also known as hydrophilic, or “water-loving”) and one end that is repelled by water (hydrophobic, or “water-fearing”). So, while one end of a surfactant molecule attaches to a water molecule, the other end of the surfactant pushes other water molecules away. The result is that water no longer sticks together as well. This enables other substances like oil to fill in the spaces and come in closer contact with water. Two liquids which previously didn’t mix all of a sudden can mix together. Once mixed together in water, bacteria can begin to digest or break down the oil  into simpler molecules and atoms, like hydrogen and carbon (the component parts of oils).

The actinobacteria are a large class of bacteria that includes 54 known families. They are able to make many different kinds of surfactants. Actinobacteria produce surfactant molecules having different shapes, sizes, and chemical behaviors. All of these different qualities make these surfactants behave slightly differently and enable the actinobacteria to digest many different oil-based food sources. Molecular methods of changing how oil is distributed can help people clean up wildlife and the environment in the case of oil spills. Bacterial surfactants were used to help clean up the Exxon Valdez oil spill, for example, and have been shown to clean shorelines contaminated with spilled oil. These surfactants are not only effective at breaking down oil, but are also biodegradable themselves, becoming a harmless part of the environment after use.

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References

The combinations of different types of hydrophilic and hydrophobic moieties within surfactants are innumerable and highly biodiverse. Due to their amphiphillic structures, surfactants act as emulsifying agents, resulting in low surface tensions of interphases. Often, microorganisms produce them when growing on hydrophobic carbon sources or when exposed to growth limiting conditions. It is hypothesized, that biosurfactants play a role in the uptake of various hydrophobic carbon sources thus making nutrients bioavailable” (Kugler et al. 2015:1)

Journal article
Surfactants tailored by the class ActinobacteriaFrontiers in Microbiology, 6(212): 1-23March 19, 2015
Kügler JH, Le Roes-Hill M, Syldatk C, Hausmann R

“Many prokaryotic and eukaryotic microorganisms can grow on compounds that are poorly soluble in aqueous media. The growth on such substrates, like hydrocarbons, is often associated with the production of surface-active compounds. Surface-active molecules contain hydrophilic and hydrophobic moieties which enable them to concentrate at interfaces and to reduce the surface tensions of aqueous media.” (Christova et al. 2004:70)

Journal article
Rhamnolipid Biosurfactants Produced by Renibacterium salmoninarum 27BN During Growth on n-HexadecaneZeitschrift für Naturforschung C, 59(1-2): 70–74February 1, 2004
Christova N, Tuleva B, Lalchev Z, Jordanova A, Jordanov B

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ActinobacteriaActinobacteriaPhylum


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