March 31, 2016
Dr. Katrina Twing, University of Utah
Microbial diversity and metabolic potential of the serpentinite subsurface environment
Serpentinization is the hydrous alteration of mafic rocks to form serpentine minerals and magnetite. The reactions of this alteration result in elevated pH of the surrounding fluids, abiotic generation of H2, CH4 (and other organic molecules), and depletion of dissolved inorganic carbon. Thus, serpentinization has implications for the origin of life on Earth and possibly Mars and other planetary bodies with water. The Coast Range Ophiolite Microbial Observatory (CROMO), a set of wells drilled into the actively serpentinizing subsurface environment in northern California, was established in northern California to gain a better understanding of the habitability and microbial functions within the serpentinite subsurface environment. The CROMO wells represent a broad range of geochemical gradients and pH and the concentrations of carbon monoxide and methane have the strongest correlation with microbial community composition. The most extremely high pH wells were inhabited exclusively by a single operational taxonomic unit (OTU) of Betaproteobacteria and a few OTUs of Clostridia, while more moderate pH wells exhibited greater diversity. Genes involved in the metabolism of hydrogen, carbon monoxide, and carbon fixation were abundant in the extreme pH fluids, while genes for metabolizing methane were exclusively in the moderate pH wells. The subsurface environment is an amalgamation of fluids and rocks, and as such, studying fluids alone only gives half the story. CROMO represents the first drill campaign into the continental serpentinite environment and the microbial diversity of serpentinite cores to a depth of 45 meters below surface suggests that specific geological features harbor different microbial communities. Different core-enriched taxa were correlated with distinct lithostratigraphic zones within the heterogeneous cores, suggesting that mineralogy may impact community composition. These data give us a more comprehensive understanding of the inhabitants of the serpentinite subsurface environment and their geochemical surroundings.
Dr. Katrina Twing earned her B.A. in Biology from Clark University in 2007 and M.S. in Marine Biosciences at the University of Delaware in 2009. After a short stint in the US Peace Corps, where she worked on coastal resource management issues in the Philippines, she went on to earn her PhD at Michigan State University under the advisement of Dr. Matthew Schrenk. Her PhD work focused on identifying biogeochemical correlations with diversity and metabolic potential of microorganism within serpentinite fluid and core samples using next-generation sequencing methods. In Fall 2015, Dr. Twing was a ship-board scientist on IODP Expedition 357: Atlantis Massif Serpentinization and Life and her postdoctoral research at the University of Utah, under the advisement of Dr. William Brazelton, focuses on identifying the metabolic potential and activity of microbes in hard rock subseafloor cores using metagenomic and metatranscriptomic analyses.