Date Approved

11-15-2011

Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department or School

Biology

Committee Member

James L. VandenBosch, Phd, Chair

Committee Member

Daniel Clemans, Phd

Committee Member

David Kass, Phd

Abstract

Salmonella typhimurium is a leading cause of infectious human gastroenteritis and systemic disease when it escapes into the bloodstream. The human serum complement system is central in fighting systemic bacterial infections. S. typhimurium exhibits resistance to killing by complement (serum-resistance), a trait conferred by several known virulence genes. This study investigates a potential chromosomal complement-resistance gene in S. typhimurium tagged by TnphoA insertional transposon mutagenesis. S. typhimurium strain EM876 has a chromosomal TnphoA insertion and reduced serum-resistance. Inverse PCR and subsequent DNA sequence analysis reveal the insertion to be in the gene glpQ. glpQ codes for a periplasmic glycerophosphodiester phosphodiesterase involved in glycerol degradation. Complementation assays using a clone of glpQ on a multicopy plasmid are consistent with a role for glpQ in serum-resistance. glpQ is preferentially expressed at 37°C versus 30°C. This is similar to traT and suggests that multiple temperature-regulated genes may contribute to serum-resistance in S. typhimurium.

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