Biogeochemistry and the Subsurface Biosphere
Our laboratory undertakes a number of studies of natural and built environments using genomic tools to describe microbial community functions, and geochemistry approaches to measure their consequences.
Serpentinite Biogeochemistry
Serpentinites represent a vector for the transport of deeply sourced carbon and reducing power from the mantle into the biosphere. Our ongoing work is tracking the composition and source of carbon-bearing compounds in marine and terrestrial serpentinizing environments, and the ways in which microbial populations impact the flux of these compounds. Recently, we have also examined sulfur biogeochemistry in serpentinites, as the transport of sulfur (and paleo-seawater) during the weather of oceanic crust and its' accretion onto the continents represents a mechanism connecting marine and terrestrial environments.
Biology meets Subduction
An international team of researchers, using seed funding from the Deep Carbon Observatory has studied the flux of volatiles (H2O, CO2, etc) from above subduction zones. Work in Central America showed that a substantial proportion of carbon previously assumed to be buried in the deep Earth was actually "trapped" in the forearc region. Ongoing work is investigating the links between volatiles and the deep biosphere in Central and South America.
Image Source: Deep Carbon Observatory, Deep Life
Evolutionary Ecology in Extreme Environments
Extreme environments challenge microbial physiology by shaping adaptations to cope with variations in energy flow, nutrient acquisition, cell survival, and biomolecular repair. We investigate microbial adaptations to environmental extremes (pH, pressure, temperature) by studying naturally occurring extreme environments. We study how microbial interactions within these communities, including horizontal gene transfer shape genome composition and evolution. Further, we compare biotic and abiotic processes in these systems to develop reliable biosignatures to apply to both terrestrial (modern and early Earth) and extraterrestrial environments.
Extremophile-Geared Astrobiology
Extremophiles adapt to conditions in extreme environments on Earth, some of which are analog environments for places scientists and astrobiologists are looking for life elsewhere (i.e. Icy Ocean Worlds, Mars, various exoplanetary systems, etc.). One specific extreme environment we study in the lab is hydrothermal vent systems, with specialized research focusing on the parameter of high hydrostatic pressure. Hydrothermal vent systems on Earth are proposed to have similar conditions to the Icy Ocean Worlds of Saturn and Jupiter, where oceans persist under thick icy crusts that surround the moons on the surface. Maridesulfovibrio hydrothermalis is a novel piezophilic (‘pressure-loving’) sulfate reducing bacterium that is grown in pressure experiments to understand it’s physiologies under high pressure. M. hydrothermalis’s adaptation of biofilm construction and the intricacies of its proteome could provide insight into detectable biosignatures that can hopefully lead future astrobiologists to find life in Icy Ocean World environments.
Biofilm Composition
One of the mechanisms used by microorganisms to survive against environmental stresses such as high pH, is the formation of biofilms. Biofilms are important in understanding microbial survival and growth in extremes because they offer resistance against different conditions including UV radiation, extreme temperature and pH, high salinity, desiccation, among others. A biofilm is an organized aggregate of microorganisms living within a self-produced matrix of Extracellular Polymeric Substances (EPS) that is attached to a biotic or abiotic surface. Although the main biofilm matrix component is water (up to 97%), it contains several biopolymers including proteins, exopolysaccharides, nucleic acids (RNA and extracellular DNA), and lipids. Some of the components of EPS are quite refractory to degradation, such as certain proteins, peptides, and lipids ,which may serve as potential biosignatures for identifying extraterrestrial life. Besides their potential as biosignatures, EPS have strong implications for habitability, as it has been shown that they are capable of physically altering sea ice, can enhance aggregation of soil particles, which retains the moisture and traps nutrients, have the ability to stabilize sediments (biostabilization) which become more resistant to erosion and represent an excellent substratum for biofilm growth. Consequently, EPS-producers serve as “ecosystem engineers”, improving environmental habitability and survivability of microorganisms.
Groundwater Microbiology and Environmental Health
Extreme environments challenge microbial physiology by shaping adaptations to cope with variations in energy flow, nutrient acquisition, cell survival, and biomolecular repair. We investigate microbial adaptations to environmental extremes (pH, pressure, temperature) by studying naturally occurring extreme environments. We study how microbial interactions within these communities, including horizontal gene transfer shaping genome composition and evolution.
Saginaw Bay Septics
In rural areas, septic systems are a major mechanism of on-site wastewater treatment. However, in Michigan, there is no unified state-wide septic code and therefore these systems exist in various states of upkeep and regulation. The signatures of failing septic systems can overlap with our sources of environmental contamination such as agriculture, industry, and municipal wastewater overflow. Our work will combine high resolution microbiology and geochemical studies with detailed maps of septic systems in Bay County, MI to develop novel, high-fidelity indicators of septic field contamination. We will also study how septic field inputs impact local groundwater ecosystems.
Environmental Change and the Groundwater Microbiome
Groundwater flow pathways where water is exchanged between the Earth's surface and subsurface span from days to millennia. Microbial communities in groundwater adapt to both in situ conditions such as pressure, temperature, and oxidation-reduction potential (ORP) as well as perturbations at the Earth's surface such as contamination and land use changes. We are investigating the composition and function of groundwater microbial communities along shallow and deep flow pathways to explore how surface signals propagate and persist into the subsurface. The work will intensively sample aquifers of various depth of mid-Central Michigan to to explore these hypotheses.
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