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Date of Award

Spring 2013

Document Type

Restricted Thesis: Campus only access

Degree Name

Bachelor of Science

Department

Biology

First Advisor

Dr. Laura Runyen-Janecky

Second Advisor

Dr. Omar Quintero

Abstract

Sodalis glossindius is a facultative intracellular symbiont of the tsetse fly (Glossina). Sodalis is one of the few bacterial symbionts that can be cultured outside its host, therefore understanding the biological process in Sodalis, would yield valuable knowledge towards understanding nonpathogenic symbiosis between insect hosts and its microbial symbionts. Sodalis must acquire iron for growth. Due to low amounts of free iron available to bacteria in hosts, high affinity iron acquisition systems are needed to permit bacteria to colonize in such challenging environments. Sodalis genomic investigations have shown that the species has putative genes for the transport of heme via the HemR/HemTUV transport system. In this study, we found that an E. coli strain unable to use heme as an iron source can be stimulated to grow when heme is provided in low iron conditions, when it possessed Sodalis hemR/hemTUV genes. In addition, a Sodalis mutant possessing a deficient achromobactin gene, which renders the bacteria unable to produce its own siderophores, had growth stimulated by the addition of heme to the iron deficient media. These results suggest a possible functionality of hemR/hemTUV in conferring to heme utilization capacity in Sodalis. Iron levels fluctuates in the varying tissues that a bacterium may colonize, therefore the expression of these energetically expensive high affinity acquisition systems seem plausible in Sodalis. In this study, we found that transcription of hemR, which encodes for an outer membrane heme receptor, is increased when free iron is low. Similarly we found evidence to support that iron-mediated repression of hemR transcription is Fur regulated.

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