This is Deep Lake, home to a host of "promiscuous" bacteria. Photo: University of New South Wales
Over the past several years, a host of scientists have discovered that life not only exists in some of Antarctica's lakes, but actually thrives there. Now, we're learning how: "Promiscuous" bacteria share DNA not just among species, but across genera as well.
Located in East Antarctica's Vestfold Hills, the imaginatively named "Deep Lake" reaches depths of 118 feet and its waters remain liquid in temperatures as low as -4 degrees Fahreinheit because of its extreme salinity. It's the saltiest known lake in Antarctica. Despite these, a host of "haloarchaea"—bacteria that love salty environments—live there.
According to a new study published in Proceedings of the National Academy of Sciences, despite the fact that several different genera of haloarchaea live there, they all share large swaths of the same DNA that may have allowed them to adapt to live in the lake.
"Our research shows these ones swap much more genetic material with each other than has been observed in the natural environment before," Rick Cavicchioli, lead author of the study, said. "Long stretches of virtually identical DNA are exchanged between different genera, not just species."
In the study, Cavicchioli and his team took water samples from depths of 5, 13, 24, and 36 meters. They then sequenced the DNA of everything living in each sample. Roughly 85 percent of the DNA of all of the life living in the lake is identical.
Though many of the bacteria living in the lake share identical stretches of DNA, they have evolved to differ slightly to consume different resources in the lake, which are severely lacking. According to the researchers, Deep Lake is "the least productive lake ever recorded." Some species, for example, consume free proteins in the water, others consume sugars present in the water from algae that live on the surface.
In such a harsh environment, energy is at a premium. Uniformly, the haloarchaea in the lake get around this problem by reproducing at an extremely slow rate: Cavicchioli believes that only six generations are produced each year. In a lab, some species of bacteria divide every couple minutes.
Besides learning more about how life functions in seemingly ridiculous environments, Cavicchioli thinks his study might have some applications in laboratory settings.
"Enzymes from cold-adapted microbes could have significant value. Their high activity in cold temperatures could provide reduced energy costs for processes that would otherwise require heating, such as cleaning, or which must be carried out at cold temperatures, such as food production or bioremediation of cold, contaminated sites," he said.