Sunday, August 12, 2012
Columbia Hall, Terrace Level (Washington Hilton)
Geobacter metallireducens strain GS 15 is one of the dominant iron-reducing micro-organism present in anoxic environments capable of detoxifying heavy metals and reported to be present in several DOE sites including Uranium Contaminated Rifle site in Colorado, and Chromium contaminated Hanford 100H area in Washington. We performed a detailed study of the response of this organism to increased salt, nitrate and temperature. Fluctuations of temperature, salinity and nitrate concentrations are expected stressors microbes encounter in the real environment. Our results indicate that while the metal reducing capacity of the organism decreased along with reduced growth, cells are able to overcome these stressors without fatal consequences. Unlike other dominant metal reducing microbes (namely, Shewanella and Deulfovibrio spp), the minimum inhibitory concentration of NaCl on this organism was determined to be 100mM and that of nitrate was 20mM. In general, during nitrate stress, proteins involved in Energy production, Amino acid transport and metabolism, Coenzyme transport and metabolism and Nucleotide transport and metabolism were upregulated. Downregulated genes encoded for proteins involved in defense mechanism, signal transduction mechanism, transcription and some whose function were unknown. Under salt stress, transcriptomic analysis revealed that several proteins involved in the process of chemotaxis, flagellar motor and assembly along with several histidine kinases and response regulators were down-regulated.