Microbial biogeochemistry in Hawaiian lava tubes
Metabolically active microbial communities are detected in ever more extreme environments, such as subsurface basalt aquifers, granite batholiths and the oceanic crust. Understanding how these communities thrive under what are generally highly oligotrophic conditions is a new frontier. New work in this field is being enabled by both novel techniques and new approaches with extant technology. By determining how single cells and communities interact at the molecular level with each other, with their environment, and with potential sources of energy, we and our collaborators aim to bring new insights into the environmental control of microbial diversity and physiology, and help interpret the fossil record and exobiology.
We aim to identify and understand processes through which microorganisms derive energy by interacting with metals and minerals. For example, chemolithoautotrophy is important where labile carbon may be in short supply, e.g., deep-sea hydrothermal vents, terrestrial geothermal features, and high altitude, xeric settings. In this respect, volcanic materials are among the most ubiquitous rock types on the Earth's surface, yet how microbes interact with a volcano per se, particularly on fresh or moderately weathered lava, has been largely overlooked. Hawai'i Volcanoes National Park (HVNP) is an excellent terrestrial site in which to investigate microbial community structure under highly nutrient limited conditions. Along with fumaroles, gases and rain, the scene is reminiscent of conditions that prevailed on much of early Earth. We hypothesize that members of the microbial community here derive energy by oxidizing elements in lava, such as Fe and Mn, and that they require nutrients from the dissolution of primary minerals, e.g., P, Mo and V. The mechanisms they use to colonize and alter host rocks may be specific to terrestrial chemolithoautotrophs, or may be cosmopolitan.
Lava caves in Kilauea are an attractive habitat type in which to investigate microbial interactions with the environment. The rock substrates are very young, UV-exposure variable, and water availability may be low. How these factors might affect hypogean (cave) microbial communities in terms of phylogeny, physiology, gene expression, growth rates, nutrient cycling and lithoautotrophic alteration of basalt substrates, are some of the questions we propose to investigate here. By examining natural microbial communities, as well as the colonization of substrates in situ and in the laboratory, we anticipate discovering novel microbes (and new biogeochemical functions for previously known microbes) through cell-specific and oligotrophic culturing techniques.
Collaborators
Alexis Templeton, University of Colorado
Greg Ravizza, Department of Geology and Geophysics, University of Hawai'i at Manoa
Jamie Foster, University of Florida, Kennedy Space Center
Hubert Staudigel, Scripps Institution of Oceanography, University of California, San Diego
Stephan Kempe Technical University of Darmstadt, Darmstadt, Germany