All ETDs from UAB

Advisory Committee Chair

Janet L Yother

Advisory Committee Members

William H Benjamin, Jr

Kevin F Dybvig

Patrick Higgins

Hui Wu

Document Type

Dissertation

Date of Award

2013

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Streptococcus pneumoniae is a major human pathogen that can reside asymptomatically in the nasopharynx before causing invasive disease by entering systemic sites. This involves regulation of colonization and virulence factors including capsule. cps2A, the first gene of the capsule (cps) locus has been proposed to regulate capsule, however its exact role and mechanism is not well understood. A complete deletion of cps2A resulted in enhanced capsule levels, with no alteration in the transcription levels of cps genes. Complementation of Cps2A restored wild type levels of capsule. Expression of the C-terminal tail alone was able to partially complement the deletion strain, suggesting its important role in the regulation of capsule. δcps2A exhibited increase in the activity of Cps2E, initiating glycosyltransferase in the capsule synthesis and did not respond to aeration. Despite increased capsule, δcps2A strain showed significant attenuation in intraperitoneally infected mice, suggesting that cps2A was critical for in vivo infection. These results show that cps2A is a negative regulator of capsule synthesis. Alteration of capsule and colonization factors can also be triggered by changes in the bacterial environment. Glucose availability, which differs in these sites, modulates the expression of genes involved in host interactions, in part through the global regulator catabolite control protein A (CcpA). Colonization factors such as the exoglycosidases, ß- galactosidase (BgaA), neuraminidase (NanA), and N-acetylglucosaminidase (StrH) are repressed by glucose, whereas capsule production is enhanced. Critical levels of glucose required for repression differed for each exoglycosidases, as reflected in enzyme activity levels and gene expression. CcpA acted as a repressor for BgaA and NanA, but as an activator for StrH and capsule. CcpA bound to a regulatory element (cre) located upstream of the strH promoter, explaining its function as an activator. However, CcpA failed to bind to the putative cre of nanA. In the cps operon, CcpA bound to a putative cre located upstream of the promoter, a cre located within the start site of the first cps gene and to multiple other cre within the capsule locus, indicative of multiple levels of CcpA-mediated regulation. These results further demonstrate a link between metabolism and virulence expression.

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