Date of Award

Spring 2001

Project Type


Program or Major


Degree Name

Doctor of Philosophy

First Advisor

Louis S Tisa


Shewanella algae BrY is a Gram negative, facultative anaerobe isolated from the Great Bay Estuary of New Hampshire. This member of the gamma Proteobacteria demonstrates extensive versatility in the variety of terminal electron acceptors it uses for anaerobic respiration. Since the natural habitat of this non-fermenting organism is the oxiclanoxic interface of sediments, the ability to utilize various terminal electron acceptors contributes to its survival and growth. Among the terminal electron acceptors used by S. algae BrY are insoluble iron minerals. The transfer of electrons from a bacterial cell to an insoluble compound presents a strategic challenge for this organism. This dissertation focuses on understanding the mechanism of electron transfer from S. algae BrY to insoluble iron minerals and characterizing the component used in bacterial-mineral electron transfer. Here I show that S. algae BrY produces the quinone rich heteropolymer, melanin, when grown with tyrosine. The redox-cycling capabilities of melanin provide it with the ability to serve as a terminal electron acceptor and soluble electron shuttle for iron mineral reduction. When melanin is associated with the cell surface, it accelerates the rate of electron transfer from the cell membrane to iron minerals.