BRC-BIO: Dispersal of deep biosphere extremophiles in seafloor sediments

Idaho State University, Pocatello ID

Investigators

Abstract

Marine sediments below seafloor globally constitute an inhospitable habitat characterized by permanent darkness and limited supply of energy. Nevertheless, this sedimentary realm hosts a large microbial biomass consisting of diverse communities with diverse metabolic capability. How biodiversity in this exclusively microbial habitat is maintained, however, remains poorly understood. This project seeks to advance the understanding of the ecological and evolutionary implications of dispersal, i.e., movement of organisms through space and time, as a driving force of community assembly and turnover in subseafloor sediments. The overarching objective of this research is to evaluate the potential of subsurface fluid discharges such as upwardly migrating hydrocarbons at marine cold seeps and warm hydrothermal fluids emanating from seamounts in transporting microorganisms from the deep biosphere to the seafloor. In addition, this project will provide both short- and long-term training for young researchers across different career stages and the required infrastructure to support a new faculty member’s research program at Idaho State University. Long-term support will be provided to two graduate students and nine undergraduate summer students. Furthermore, research activities will be integrated into two course based undergraduate research experience (CURE) lab courses and a vertically integrated project (VIP) course which will provide hands-on research experience to approximately 30 upper division undergraduate students annually. This project is jointly funded by the Building Research Capacity in Biology Program, the Established Program to Stimulate Competitive Research (EPSCoR), and the Biological Oceanography program. This project proposes to use dormant endospores of thermophilic bacteria as model organisms to study the significance of microbial dispersal in sustaining biodiversity in the deep biosphere. These bacteria are widespread in marine sediments globally and are genetically similar to bacteria inhabiting warm, deeply buried petroleum reservoirs, hydrothermal vent chimneys and crustal aquifers. Previous research focused on cold seeps in the Gulf of Mexico has provided evidence that hydrocarbon-rich fluid flow can supply viable thermophilic spores from deep to shallow sedimentary habitats. The proposed research will address a critical need to understand how laboratory incubation conditions impact the detection of endospore populations in cold seabed sediments, exposing new metabolic variation. Sediment heating at multiple temperatures followed by molecular community surveillance will be employed to identify novel subsurface bacteria in cold seep sediments from the Gulf of Mexico and Monterey Canyon, and crustal-fluid-impacted sediments from the Juan de Fuca Ridge flank off the coast of Washington, USA. A genome-centric metagenomic approach will subsequently be used to unravel metabolic traits of these organisms as an indication of subsurface provenance. The results are expected to determine whether fluid-mediated dispersal of subsurface organisms is limited to specific seafloor features or if it is a more widespread mechanism of transporting viable microbial biomass across the deep biosphere. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.