It doesn’t take much to keep oil-consuming microbes happy and working. Researchers have discovered communities of microorganisms that live in the tiniest droplets of water suspended in natural tar lakes, where they actively break down oil from the inside out. These thriving microhabitats need very little water to support them, and they could be harnessed for cleaning up disastrous spills. The findings also open up the possibilities of life in harsh and extraterrestrial worlds. The work was published in Science this week.
Researchers previously assumed that natural microbial oil degradation only occurred at the interface where water and oil meet: such as at the bottom of a tar pit where oil mixes with groundwater or at natural oil flows in the ocean (where oil flows up through networks of cracks). Not so, according to an international team led by Rainer Meckenstock from Helmholtz Zentrum München. Tiny ecosystems that biodegrade petroleum are scattered in water droplets trapped throughout oil.
The team discovered these microbial communities in water sampled from Trinidad and Tobago’s 100-acre Pitch Lake -- the world’s largest natural asphalt lake. After sequencing DNA extracted from the water, they found a huge diversity of bacteria and single-celled organisms called archaea active in droplets as small as a microliter -- about one-fiftieth a drop of water.
The chemical compositions of the microdroplets were distinct from control samples of lake oil mixed with distilled water, Nature reports, indicating that the organisms were eating and processing the oil -- degrading it into a variety of organic molecules. An analysis of the water droplets’ isotopic signatures and salt content showed that the droplets themselves came from within the oil deposit, and not through infiltration by rain or groundwater. Their source was likely ancient sea water or a brine deep underground.
Biodegradation reduces the quality (and worth) of the oil by changing its composition and turning it into oil sands, Meckenstock explains in a news release. To the right, you can see the sort of solidified oil that’s being mined at Pitch Lake. However, the process can be harnessed for new ways to clean up contaminated groundwater and oil spills -- from within the oil itself.
The findings also add a new, microscopic level of detail to how life can exist in such a toxic, harsh environment. "For me, the cool thing is I got into it from an astrobiology viewpoint, as an analog to Saturn's moon, Titan, where we have hydrocarbon lakes on the surface," says Dirk Schulze-Makuch from Washington State in a university statement. “We discovered that there are additional habitats where we have not looked at where life can occur and thrive.”
Images: Rainer Meckenstock