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Date of Award

Spring 2012

Document Type

Restricted Thesis: Campus only access

Degree Name

Bachelor of Science

Department

Biochemistry & Molecular Biol.

First Advisor

Dr. Laura Runyen-Janecky

Abstract

Sodalis glossinidius is a facultative, extra- and intracellular midgut symbiont of the tsetse fly, endemic to Sub-Saharan Africa. Because almost all bacteria require iron for growth and iron is not freely available, many bacteria utilize high affinity iron capturing molecules called siderophores to scavenge iron. Sodalis has a putative achromobactin siderophore iron acquisition system made up of twelve genes on the pSG1 plasmid. Wildtype Sodalis produced detectable siderophore in CAS plate assays, while a mutant with a null mutation in the putative biosynthesis gene acsD lost all siderophore production. The reduced growth of the siderophore synthesis mutant was able to be reconstituted by addition of exogenous achromobactin, suggesting the strain retains a functional siderophore transport system; however, reduced growth of a Sodalis mutant with a null mutation in acr, the ferric-siderophore outer membrane receptor, was not reconstituted by exogenous siderophore due to its defective transport system. RNA analysis revealed that the achromobactin operon is transcribed as a single polycistronic molecule and expression levels were inversely dependent on environmental iron availability. Repression of achromobactin operon expression in iron replete conditions was lost in Fur null strains and Fur titration assays suggest that the achromobactin promoter is regulated by direct Fur binding.

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