In a ground-breaking discovery released by the journal Science, researchers have revealed microhabitats of metabolically active, thriving microbes living in the world’s largest asphalt lake, Pitch Lake, on the island of Trinidad in the Caribbean. Asphalt lakes are large reservoirs of a sticky, black, viscous hydrocarbons (known as asphalt, bitumen or pitch) where no life was expected to be found.
The international team discovered the microbes in tiny water droplets recovered from the lake in 2011. Each sample, measuring only one to three microliters, has the equivalent volume of approximately 1/50 of a conventional “drop” of water.
The team’s only United States-based researcher, Dirk Schulze-Makuch, is a professor at Washington University School of the Environment. Using advanced sequencing technologies, the team extracted all the DNA of all organisms in each droplet simultaneously. Reading through 12 microdroplets, they found 21 species of bacteria and archaebacteria.
Professor Schulze-Makuch explained that each water droplet seems representative of an entire ecosystem because of the observed diversity in bacteria and archaea. Moreover, remarkably there was very little measurable ammonia or phosphates, both ingredients thought to be essential for life.
These microbes, the researchers report, are actively degrading oils in the lake, most likely to exploit it as a source of bioenergy. One bioengineering implication of this discovery is to use these active microbes to clean up oil spills with as little impact to the environment as possible.
The water droplets also had an unusually high salt content. By studying the isotope composition of droplets from Pitch Lake, the team was able to say that the microbes did not originate from surface waters that are part of the hydrologic cycle, but rather from much deeper, for example ancient underground seawater or another deep source of brine.
Professor Schulze-Makuch went on to explain that these microbes could mean life on other planets as well. One well-known example is Saturn’s moon, Titan. Its surface is characterized as being saturated with hydrocarbons, in liquid lakes on the ground and also in vapor form and liquid rain in the atmosphere. Schulze-Makuch explains that this discovery has implications for astrobiology, the study of life on other planets.