2004 Annual Science Report
Marine Biological Laboratory Reporting | JUL 2003 – JUN 2004
Iron Oxidation - Shaping the Past and Present Environments
The principal objective of our project is to develop a better understanding of the fundamental biology of microbial iron (Fe) oxidation at neutral pH. Though the capacity for Fe oxidation is likely an ancient metabolic pathway, it is to date the least well understood among the major microbial metabolisms
The principal objective of our project is to develop a better understanding of the fundamental biology of microbial iron (Fe) oxidation at neutral pH. Though the capacity for Fe oxidation is likely an ancient metabolic pathway, it is to date the least well understood among the major microbial metabolisms. We secondarily wish to explore the potential for Fe oxidation among eukaryotes, using the acid mine drainage system “Rio Tinto” and the eukaryotic culture collection as a model system.
Toward our first objective, we have identified an ideal model bacterium that we have focused most of our efforts on in the past year. Our deep-sea Fe-oxidizing culture collection consists entirely of obligate Fe-oxidizing autotrophs. Many of these are gamma Proteobacteria that are closely related to the common marine heterotrophs Marinobacter and Halomonas . In testing available cultures of these bacteria, we found that many of them are facultative autotrophs and/or mixotrophs that are capable of oxidizing Fe. We have developed one of them, Marinobacter aquaeoloi , as a model bacterium for studying Fe oxidation, because of its advantageous growth characteristics. Using SDS-PAGE gel electrophoresis of cell extracts we have determined that a 35 kDa protein is up regulated with increasing Fe(II) content in medium. We have also developed a plate-based screening assay for the detection of Fe oxidation. This plate-based method is being used to develop a genetic system in M. aquaeoloi, which we have determined to be competent, and are in the process of optimizing conditions for transposon mutagenesis. This plate screen will also be used for our second objective with eukarya. Finally, we are working towards genome sequencing of M. Aquaeoloi and toward this end have extracted high-molecular-weight DNA and sized the genome, which is 2.555 -2.595 kb. Large insert libraries have also been made (Fosmid).
PROJECT INVESTIGATORS:Katrina Edwards
RELATED OBJECTIVES:Objective 4.1
Earth's early biosphere