The Enrichment of Iron-Oxidizing Bacteria from Catalina Harbor using Environmental Incubation and Electrochemical Techniques

Monday, 15 December 2014
Taylor Ryan Strumwasser1, Bonita R Lam2, Annette R Rowe2 and Kenneth H Nealson2, (1)California Institute of Technology, Pasadena, CA, United States, (2)University of Southern California, Los Angeles, CA, United States
In the last two decades, bacteria capable of extracellular electron transport have been discovered. These bacteria transfer electrons to or from insoluble substrates outside of the cellular membrane. An organism can benefit from extracellular electron transfer when a substrate is capable of causing oxidative stress to internal organelles or is incapable of being brought into the cell due to insolubility. This research looked deeper into the growing conditions of bacteria using elemental iron as their electron donor. Specifically, this experiment observed the growth and community of iron-oxidizing bacteria in Catalina Harbor sediment. The resulting ferric and ferrous iron concentrations were measured through a ferrozine assay (Jan Riemer et al., 2004) on a weekly basis, while temperature, pH, and dissolved oxygen were measured six to seven times during the month. Additionally, bacteria from Catalina Harbor sediment were used to generate a current in a sediment battery (Reimers et al., 2001). Sediment samples showed consistent ferric iron concentrations over the month. However, the iron coupons demonstrated a drastic increase in ferric iron concentrations, implying the presence of iron-oxidizing bacteria. While none of the sediment batteries showed a consistent trend in average power density, the average power densities stayed within one order of magnitude of each other. This would imply the presence of stable communities of electrochemically active bacteria. Furthermore, because these bacteria were found in the sediment in Catalina Harbor, there is a good chance that some of these bacteria may be iron-oxidizing bacteria.