All ETDs from UAB

Advisory Committee Chair

Janet Yother

Advisory Committee Members

William H Benjamin, Jr

David E Briles

Kevin F Dybvig

Mark Walter

Document Type

Dissertation

Date of Award

2012

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Biosynthesis of capsule polysaccharide in the Gram-positive pathogen Streptococcus pneumoniae is regulated in part through the action of a phosphoregulatory system comprised of the products of the capsule biosynthetic operon genes cpsBCD. CpsC and CpsD together comprise an autophosphorylating tyrosine kinase whose homologs are implicated in chain length regulation in other systems in both Gram-positive and Gram-negative organisms. CpsB is the cognate phosphatase for the system. Unlike Gram-negative organisms, which use a low molecular weight phosphotyrosine phosphatase in phosphoregulation of capsule synthesis, Gram-positive organisms utilize a polymerase and histidinol phosphatase (PHP) superfamily phosphatase. Deletion of cpsB has resulted in conflicting reports concerning the CPS production of the resulting strains. Regulation of capsule is critical for bacterial survival in environmental niches within the host. During colonization some capsule is required, but inappropriately high expression results in rapid clearance. In invasive disease, increased amounts of capsule are required to resist opsonophagocytic killing by masking surface-deposited complement and surface antigens. The organism must respond to environmental cues in order to adapt. One such cue is oxygen, which is available at near-atmospheric levels in the nasopharynx but can become limited in sites of infection. In this dissertation, additional insight into underlying factors of the differing ∆cpsB phenotypes is presented. In addition, CpsB is demonstrated to be essential for aeration-mediated alterations in capsule. Mutagenesis of cps2B confirms the importance of one non-PHP motif residue and one unconserved PHP motif residue suggested by crystal structures to be involved in CpsB catalysis. Use of strains with cpsB mutations representing a spectrum of CpsB impairment gives insight into phosphoregulation of pneumococcal CPS and suggests the existence of a non-CpsD target for CpsB.

Share

COinS