Biogeochemistry represents the several billion-year-old relationship between microbes and rock, between the living and the nonliving world. As a marine microbial ecologist, I study the metabolic capability and activity of microbial populations in order to better understand the mechanisms that drive this relationship. My research utilizes a combination of molecular biology and biochemistry tools to examine the microbial community as a functional whole, not a collection of species but a collection of functional genes and metabolic processes- a super-metabolism or meta-metabolism, combining the metabolic networks of multiple players.
North Pond, Mid-Atlantic Ridge
Mid-ocean ridge flanks are composed of geologically young (1-65 million year old) rock and make up 75% of the ocean floor. Ocean crustal fluid (water circulating through ocean crust) accounts for 1-2% of the total ocean volume, or about 1.35-27 million trillion liters of water. North Pond is an isolated sediment pond on the western flank of the Mid-Atlantic Ridge, underlain by basaltic rock and a cold, oxygenated aquifer that chemically resembles seawater. The microbial populations that inhabit this crustal fluid, however, are distinct from those in the ocean above. My work in North Pond involves using DNA and RNA sequencing techniques (metagenomics and metatranscriptomics) to describe the metabolic capabilities and activities of these crustal fluid microbial communities, in order to discern whether they serve as a carbon source or carbon sink in the deep ocean.
Coast Range Ophiolite Microbial Observatory (CROMO), California, USA
The Coast Range Ophiolite was formed by the obduction of oceanic crust onto continental crust during the Jurassic period. Metamorphosed peridotite in the form of serpentine rock characterizes this formation. This rock is formed by a low temperature geochemical reaction in which the minerals olivine and pyroxene (found in ultramafic rock in the lower crust and upper mantle) chemically react with water. This reaction results in the release of hydrogen gas, the production of methane and small-chain hydrocarbons, and the precipitation of insoluble minerals. The reducing power supplied by serpentinizing environments, when mixed with oxidants from surface and subsurface sources, creates chemical disequilibria that provide a strong thermodynamic drive that microbial populations can harness. CROMO is a subsurface observatory funded by the NASA Astrobiology Institute (NAI), the Sloan Foundation, and the Deep Carbon Observatory, consisting of a series of eight wells drilled at strategic locations and depths into the ophiolite. My work at CROMO uses a combination of cultivation, molecular techniques, and metabolomics approaches to study microbial and organic carbon samples obtained from the wells. This combined approach assesses microbial activity in action, by identifying the metabolites consumed and produced by these microbial communities in conjunction with genetic potential.
Semail Ophiolite, Oman
The Semail Ophiolite, like the Coast Range Ophiolite, is composed of oceanic crust and upper mantle that was overthrust onto continental crust, during the late Cretaceous period, and is characterized by actively serpentinizing rock. It is located on the eastern corner of the Arabian Peninsula and, at 100,000 km2, is the largest and most extensively studied ophiolite in the world. The Oman Drilling Project (http://www.omandrilling.ac.uk/) has been taking core samples and sampling groundwater from the Semail Ophiolite for the last several years. I took part in an expedition to Oman in February 2017 to characterize the dissolved organic matter in the ophiolite groundwater, to better understand the metabolism of the microbes living there. The data from this project is currently being prepared for publication.
The Origin of Life; Europa, Enceladus, and Ganymede
In collaboration with Laurie Barge at the NASA Jet Propulsion Laboratory, I am developing culturing platforms that support conditions resembling those hypothesized to exist at the origin of life, and which may support life on icy moons in our solar system. This project will utilize custom-made flow reactors mimicking early mineral catalytic systems in hydrothermal chimneys/sediments to compare biogenic and abiogenic outputs from these systems, and uses molecular/organic geochemical techniques to characterize the metabolic processes that occur in this environment in relation to abiotic reactions occurring in tandem. The project represents a novel system for culturing microbes with ancient metabolisms, in order to observe microbial populations and the products and kinetics of biochemical and geochemical pathways in an early life scenario.