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SBI 2009 Summer Workshop
July 23-24, 2009 -- La Sells Stewart Center, Corvallis, Oregon
About 40 scientists gathered at La Sells Stewart Center for the Subsurface Biosphere Initiative’s fourth annual workshop. The meeting was a chance for faculty and students from four OSU colleges to share their work with each other and meet with invited experts. Over the day and half meeting, researchers discussed the biology and environmental functions of microbial communities living in diverse environments – from soils and aquifers to deep sea sediments. While the researchers work in many different settings, the talks and posters illustrated some of the common themes of subsurface biosphere research:
Many subsurface environments are a frontier – researchers are just now discovering what organisms are present. Their work is aided by new DNA techniques that make it possible to identify organisms that can’t currently be cultured or isolated in a lab. The talks by Radu Popa, a professor at Portland State University, and Brandon Briggs, a PhD student in marine geology and physics (OSU-COAS), illustrated this theme. Radu’s team is using DNA techniques to identify microbes living kilometers under the sea bed. They inserted rock samples into flow-through chambers in deep sea drill holes and looked at the types of bacteria that colonized mineral surfaces over several years. Brandon is also using DNA techniques to identify bacteria removed from the deep sea – he is studying clusters of cells called biofilms that form in sub-seafloor methane deposits. Rich Cooley, a PhD student in biochemistry and biophysics (OSU-Botany and Plant Pathology), described the metabolic capabilities of bacteria that use organic chemicals called alkanes as an energy source and have recently been found living near deep sea methane deposits.
Even when subsurface microbes have been identified and cultured in a lab, there are still many unknowns about their basic biology. Talks by PhD students Gaurav Saini and Nizar Mustafa (OSU-Environmental Engineering) illustrated this theme. Gaurav is creating nanometer-scale images to better understand how bacteria attach to surfaces and to one another in biofilms. Nizar described lab experiments and modeling efforts to understand the kinetics of the chemical reactions triggered by microbes that consume groundwater contaminants. Understanding these reactions is one step toward effectively using microbes to clean up contaminated aquifers.
It takes both lab and field studies to learn about subsurface microbes. Many of the talks described both field experiments or collections and careful lab work. For example, Anne Taylor (OSU-Crop and Soil Science) and Naraja Vajrla (OSU-Molecular and Cellular Biology, Botany and Plant Pathology) described experiments with both pure cultures and field-collected samples. They are using multiple approaches to separate the roles of bacteria and archaea - two groups of soil organisms that oxidize ammonia, a key step in the nitrogen cycle.
Subsurface microbes are both an influence on and influenced by the chemistry of their surroundings. Professor Brad Tebo (OHSU Environmental and Biomolecular Systems) described bacteria that can cause deposits of the mineral manganese to form in many environments, from the ocean to water pipes. Julie Pett-Ridge, a new OSU assistant professor (Crop and Soil Science), spoke about her field research to measure the amount of wind-blown dust from Africa in a Puerto Rican forest. The dust is a source of micronutrients for the soil microbial community in that environment.
Subsurface microbes can be used as a tool. PhD student Ellen Swogger (OSU-Environmental Engineering) is part of an OSU team studying microbes that could one day increase the efficiency of wastewater treatment plants. Her experiments tested the response of the microbes to contaminants when they were free floating and when they were clustered in a biofilm. Professor Roy Haggerty (OSU-Geosciences) spoke about his efforts to develop a nontoxic stream tracer to measure the flow rate of water moving underneath and adjacent to streams. He described lab and field experiments testing the potential of the compound resazurin to detect subsurface microbiological activity.
Subsurface microbes play a role in global change - they influence how carbon, nitrogen and other nutrients cycle between the atmosphere and the biosphere. Assistant professor Rich Phillips (Indiana University) and Kate Lajtha (OSU-Botany and Plant Pathology) spoke about the role of forests in the carbon cycle. Rich described large experiments at the Duke Forest FACE site where sections of forest were artificially exposed to high concentrations of atmospheric carbon dioxide. Rich’s work focuses on the fine scale of tree roots and soil microbes and the role they play in cycling and storing carbon and other nutrients below ground. Kate gave an overview of the Detrital Input and Removal Treatment (DIRT) project in the Andrew’s Experimental Forest. The 10-year study is investigating the role of forest litter on storing and removing carbon from soils.
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