Biofilms are thin, slimy films of microbes like bacteria and archaea that adhere to fracture surfaces at DeMMO. Living in a biofilm has lots of potential advantages in the deep subsurface, such as making it easier to access nutrients, exchange DNA with other microbes nearby, or getting closer to a tasty mineral in the rock.
We deploy in situ cultivation experiments at DeMMO boreholes to target the growth of biofilm communities. These ongoing experiments will shed light on which microbes can eat minerals in the rocks at DeMMO. Minerals are likely an important source of energy for life in the rocky subsurface on Earth, and could also be an energy source in extraterrestrial rocky subsurface environments. Understanding the role that minerals play in subsurface habitability at DeMMO will inform our understanding of habitability on other planets like Mars.
The image below is a scanning electron micrograph of a DeMMO biofilm on a mineral surface. The cells are about 1 micron in diameter.