AbstractSerpentinization is the process in which ultramafic rocks, characteristic of the upper mantle, react with water liberating mantle carbon and reducing power to potenially support chemosynthetic microbial communities. These communities may be important mediators of carbon and energy exchange between the deep Earth and the surface biosphere. Our work focuses on the Coast Range Ophiolite Microbial Observatory (CROMO) in Northern California where subsurface fluids are accessible through a series of wells. Preliminary analyses indicate that the highly basic fluids (pH 9-12) have low microbial diversity, but there is limited knowledge about the metabolic capabilities of these communties. Metagenomic data from similar serpentine environments  have identified Betaproteobacteria belonging to the order Burkholderiales and Gram-positive bacteria from the phylum Clostridiales, as key components of the serpentine microbiome. In an effort to better characterize the microbial community, metabolism, and geochemistry at CROMO, fluids from two representative wells (N08B and CSWold) were sampled during a recent field campaign. The wells selected can be differentiated in that N08B had cell counts ranging from 105 -106 cells mL-1 of fluid, and abundance of the Betaproteobacterium Hydrogenophaga. In contrast, fluids from CSWold have lower cell counts (~103 cells mL-1 ) and an abundance of Dethiobacter, a taxon within the phylum Clostridiales. Geochemical characterization of the fluids includes measurements of dissolved gases (H2, CO, CH4), dissolved inorganic and organic carbon, volatile fatty acids, and nutrients. Microcosm experiments were conducted with the purpose of monitoring carbon fixation and metabolism of small organic compounds, such as acetate, while tracing changes in fluid chemistry and microbial community composition. These experiments are expected to provide insight into the biogeochemical dynamics of the serpentinite subsurface at CROMO and represent a first step for developing RNA based Stable Isotope Probing (RNA-SIP) experiments to trace microbial activity at this site.
AbstractSince the days of Darwin, scientists have used the framework of the theory of evolution to explore the interconnectedness of life on Earth and adaptation of organisms to the ever-changing environment. The advent of molecular biology has advanced and accelerated the study of evolution by allowing direct examination of the genetic material that ultimately determines the phenotypes upon which selection acts. The study of evolution has been furthered through examination of microbial evolution, with large population numbers, short generation times, and easily extractable DNA. Such work has spawned the study of microbial biogeography, with the realization that concepts developed in population genetics may be applicable to microbial genomes (Martiny et al., 2006; Manhes and Velicer, 2011). Microbial biogeography and adaptation has been examined in many different environments. Here we argue that the deep biosphere is a unique environment for the study of evolution and list specific factors that can be considered and where the studies may be performed. This publication is the result of the NSF-funded Center for Dark Energy Biosphere Investigations (C-DEBI) theme team on Evolution (www.darkenergybiosphere.org).
I presented a poster at the GRS and GRC titled “Metagenomic evidence for primary production fueled by serpentinization” that summarizes my ongoing work to identify autotrophic organisms in serpentinite-hosted subsurface ecosystems. The particular focus of this poster was to identify intriguing connections between several marine and continental sites of serpentinization in order to gain greater insight into biogeochemical process in ultramafic subseafloor habitats, which are currently inaccessible to the large-scale metagenomic techniques we are employing. This conference represented an opportunity to share my research with a community of researchers who are mostly unaware of our work but share common interests. In addition to the many techniques that we have in common, the questions of microbial biogeography that are inherent to our research direction also drive the work by many other marine microbial ecologists who do not necessarily study the subseafloor.