ABSTRACT

A large fraction of Earth?s microbial biosphere lives in the deep ocean and below the oceanic crust, under conditions of high hydrostatic pressures. However, very little is known about the contribution of these high-pressure adapted microbial communities to the Earth?s microbiome, their role in biogeochemical cycles, and their relevance for the evolution of early life on Earth. This project will investigate the adaptation mechanisms of high-pressure and high-temperature bacteria that use hydrogen as an energy source to different pressures and hydrogen concentration regimes. An innovative instrument for bacterial cultures at high pressure and temperature will be used to simulate the deep-sea physical (temperature, pressure) and chemical (hydrogen concentration) conditions. This experimental approach provides a unique opportunity to study microbial activity and functions by adjusting pressure conditions dynamically. Gene expression under different pressures and temperatures will also be monitored. Finally, since hydrogen oxidation is considered an ancient metabolic pathway, understanding hydrogen catabolism in these organisms may help to reconstruct the evolutionary history of early metabolism. The researchers will develop lessons and activities to translate the science for middle and high school aged learners. Lectures and lab demonstrations/tours will be delivered at George Mason University and Rutgers University to undergraduate/graduate students as part of graduate-level seminar series.

Culture-based studies of the physiological and metabolic adaptations of high-pressure adapted bacteria are critical to advance understanding of microbial activity and bioenergetic adaptation strategies in deep-sea ecosystems. The main objective of this study is to explore the physiology and gene expression in high-pressure and high-temperature adapted bacteria (thermopiezophiles) that have been isolated from deep-sea hydrothermal vents. One of these bacteria, Nautilia strain PV-1, thrives at elevated pressure and at a temperature of 55°C, and can live off hydrogen gas and carbon dioxide. Experiments aimed at measuring gene and protein expression will be integrated with measurements of stable hydrogen isotope compositions to understand the combined effects of pressure and hydrogen concentration of the growth of thermopiezophiles. More specifically, this project will investigate the expression of the different hydrogenases of strain PV-1 in response to pressures up to 400 atmospheres, and to limiting and non-limiting concentration of hydrogen. Further, this project will investigate how elevated pressures affect the membrane structure of strain PV-1, which is important to maintain cellular integrity and to facilitate membrane trafficking. Finally, this project will investigate the transfer of hydrogen gas from a hydrogen-producing bacterium, Marinitoga piezophila, and the hydrogen consuming Nautilia strain PV-1.

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.

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