Scientists from the J. Craig Venter Institute (JCVI), along with collaborators from the Univ. of Southern California (USC) and Delft Univ. in the Netherlands, have published results from a three-year study outlining the microbial diversity in The Cedars, a high-pH, ultrareducing, low-salinity systems of springs located in Northern California. The research, led by first author and postdoctoral fellow at JCVI, Shino Suzuki Ishii, PhD, has been published in an online, early edition of PNAS.

This unique spring system is an active terrestrial serpentinization site. Serpentinization is a process whereby water reacts with certain types of minerals in the ground to produce other kinds of minerals, as well as hydrogen, methane and highly alkaline fluids. These sites are common in the deep ocean where tectonic plates meet, but are very rare elsewhere.

For three years the JCVI, USC and Delft Univ. team took multiple samples in three springs at The Cedars and isolated the microbes using sequencing technologies as opposed to culturing them. Each spring was fed by unique groundwater, one by deep groundwater only and the other two by a mixture of deep and shallow groundwater. The team found that the microbial communities remained constant in each spring but that each one had unique microbes which were determined by the type of groundwater by which they were fed.

The microbes in the deep groundwater fed spring were distinct from any other microbial communities found in other terrestrial serpentinizing sites. The most abundant of these microbes are members of the Chloroflexi, Clostridia and candidate division OD1, followed by some Euryarchaeota. The microbes found in the mixture of shallow and deep groundwater fed sites appear to be similar to other microbial communities isolated from other terrestrial sites. The most abundant of these microbes were Betaproteobacteria.

The team concludes that because of the pristine yet harsh nature of The Cedars environment, the microbes found there could be crucial to understanding the origins of life on Earth and in understanding the key survival mechanism used by these hearty microbes.

Kenneth Nealson, PhD, sr. author, JCVI Distinguished Prof., Dept. of Microbial and Environmental Genomics; and Wrigley Chair in Environmental Studies and Prof. of Earth Sciences and Biological Sciences at USC, stated, “This combination of water chemistries in The Cedars springs is very challenging for life. While there is plenty to “eat” (i.e., electron donors) in the form of hydrogen and methane produced by serpentinization there, there is nothing obvious to “breathe” (i.e., electron acceptors). There are also low levels of sodium to be used for establishing a membrane potential. However, the challenge of sustaining life has been met, as evidenced in this study, by the stable microbial populations seen in each spring. We believe these communities have the potential to yield important insights into survival mechanisms in these challenging, early-Earth analog environments.”

Source: J. Craig Venter Institute