Identity and Dynamics of the Microbial Community Responsible for Carbon Monoxide Oxidation in Marine Environments

John Tolli, Ph.D., 2003
Craig Taylor, Advisor

Carbon monoxide is produced in the ocean as a photolytic product of colored dissolved organic matter (CDOM). The ocean surface water is saturated with respect to CO, and is thus a source of CO to the atmosphere. An important sink for CO in seawater is the biological oxidation of CO to CO2 by marine microorganisms. In this study we identify component members of the coastal microbial community responsible for the oxidation of CO through recent microbiological and molecular approaches, and estimate their contributions to total in situ CO bio-oxidation. Specific CO-oxidation activity is determined for selected strains with a time-series 14CO-oxidation method. Molecular phylogeny is based on 16S-rDNA sequences of CO-oxidizing bacteria that result from our cultivation program. Isolates with greatest CO oxidizing activities are related to Roseobacter and Paracoccus genera of the alpha-proteobacteria, collectively known as the "marine alpha group". Other isolates with environmentally relevant CO oxidation rates are beta- and gamma-proteobacteria, and one strain is within the Cytophaga-Flavobacterium-Bacteroides group. Abundances of CO-oxidizing marine alpha group organisms were resolved microscopically by microautoradiography in combination with DAPI and fluorescent-labeled oligonucleotide probes. Marine alpha group organisms were a major component of total cell numbers (45.7%) at the time of sampling (March 2003), and CO-oxidizing members of the marine alpha group contributed up to 40.7% of total CO oxidation occurring in coastal waters.