GENETICS AND VIRULENCE OF PNEUMOCOCCAL CAPSULAR TYPES

Summary

Principal Investigator: JANET L YOTHER
Abstract: DESCRIPTION (provided by applicant): Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide, resulting in 1 to 2 million deaths annually. Serious infection and death result primarily from the ability of S. pneumoniae to cause pneumonia in the elderly, young children, and those with underlying conditions. Essential to the ability to cause disease are the capsular polysaccharides. Although 91 distinct capsular serotypes have been identified, all perform similar functions. In systemic infections, high levels of capsule production are necessary for resistance to complement-mediated opsonophagocytosis. In contrast, low levels of capsule are sufficient to sustain colonization in the nasopharynx, as factors necessary for adherence are unmasked as capsule is reduced. The ability to alter capsule production is critical to the survival of S. pneumoniae. For 89 of the 91 S. pneumoniae capsular serotypes, the polymer is assembled by the Wzy-dependent mechanism, which is also used in the assembly of most capsules and exopolysaccharides produced by Gram-positive bacteria, and many capsules and lipopolysaccharide O-antigens of Gram-negative bacteria. Although a general picture for Wzy-dependent synthesis in Gram-positive bacteria has emerged, much remains to be learned about specific aspects of this process. As a model system, we have used the S. pneumoniae serotype 2 capsule, in which the repeat unit contains a backbone of glucose-rhamnose-rhamnose-rhamnose and a side chain of glucose- glucuronic acid. During polymer assembly, repeat units synthesized on the inner face of the cytoplasmic membrane are transported to the outer face of the membrane and then polymerized by the Wzy-polymerase into long chain polymer. In S. pneumoniae, the polymer remains largely cell-associated via linkages to the membrane and peptidoglycan. Modulation of capsule chain length and amount occurs, at least in part, through the action of a phosphoregulatory system. This research proposal focuses on further defining the complex mechanisms involved in Wzy-dependent capsule assembly and control in S. pneumoniae. The specific aims for this proposal are to: 1) characterize the functions of the initiating glycosyltransferase Cps2E and the effects of cps2E mutations;2) identify glycosyltransferases catalyzing type 2 repeat unit synthesis;3) characterize mechanisms involved in retention of the capsule on the bacterial cell;and 4) characterize protein-protein interactions between capsule-related proteins. The results of these studies could have broad relevance for understanding mechanisms involved in synthesis and modulation of similar polymers produced by other pathogenic bacteria. Streptococcus pneumoniae is responsible for more than 50,000 deaths annually in the United States and 1 to 2 million worldwide due primarily to its ability to cause pneumonia in the elderly and young children. The proposed studies will further our understanding of how the bacterium synthesizes its major virulence determinant, the capsular polysaccharide. By understanding the mechanisms involved in this process, we may be better able to develop means for treating and preventing these infections.
Funding Period: -----------------198 - ----------------2013
more information: NIH RePORT

Top Publications

  1. ncbi Control of capsular polysaccharide chain length by UDP-sugar substrate concentrations in Streptococcus pneumoniae
    Christy L Ventura
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
    Mol Microbiol 61:723-33. 2006
  2. pmc Mutations blocking side chain assembly, polymerization, or transport of a Wzy-dependent Streptococcus pneumoniae capsule are lethal in the absence of suppressor mutations and can affect polymer transfer to the cell wall
    Bobbi Xayarath
    Department of Microbiology, 845 19th Street South, BBRB 661 12, Birmingham, AL 35294 2170, USA
    J Bacteriol 189:3369-81. 2007
  3. pmc CcpA-dependent and -independent control of beta-galactosidase expression in Streptococcus pneumoniae occurs via regulation of an upstream phosphotransferase system-encoding operon
    Greer E Kaufman
    Department of Microbiology, Univerisity of Alabama at Birmingham, Birmingham, AL 35294 2170, USA
    J Bacteriol 189:5183-92. 2007
  4. pmc Biochemical, genetic, and serological characterization of two capsule subtypes among Streptococcus pneumoniae Serotype 20 strains: discovery of a new pneumococcal serotype
    Juan J Calix
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
    J Biol Chem 287:27885-94. 2012
  5. pmc Genetic and biochemical characterizations of enzymes involved in Streptococcus pneumoniae serotype 2 capsule synthesis demonstrate that Cps2T (WchF) catalyzes the committed step by addition of β1-4 rhamnose, the second sugar residue in the repeat unit
    David B A James
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
    J Bacteriol 194:6479-89. 2012
  6. pmc Streptococcus pneumoniae serotype 11D has a bispecific glycosyltransferase and expresses two different capsular polysaccharide repeating units
    Melissa B Oliver
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294 2170, USA
    J Biol Chem 288:21945-54. 2013
  7. pmc Biochemical activities of Streptococcus pneumoniae serotype 2 capsular glycosyltransferases and significance of suppressor mutations affecting the initiating glycosyltransferase Cps2E
    David B A James
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
    J Bacteriol 195:5469-78. 2013
  8. pmc Streptococcus pneumoniae phosphotyrosine phosphatase CpsB and alterations in capsule production resulting from changes in oxygen availability
    K Aaron Geno
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
    J Bacteriol 196:1992-2003. 2014
  9. ncbi Capsules of Streptococcus pneumoniae and other bacteria: paradigms for polysaccharide biosynthesis and regulation
    Janet Yother
    Department of Microbiology, University of Alabama, Birmingham, Alabama 35294 2170, USA
    Annu Rev Microbiol 65:563-81. 2011

Scientific Experts

  • JANET L YOTHER
  • David B A James
  • Juan J Calix
  • K Aaron Geno
  • Jocelyn R Hauser
  • Kanupriya Gupta
  • Melissa B Oliver
  • Thomas R Larson
  • Moon H Nahm
  • Greer E Kaufman
  • Bobbi Xayarath
  • Christy L Ventura
  • Chris Jones
  • Edward R Zartler
  • Allison M Brady
  • Richard J Porambo
  • Chitrananda Abeygunwardana
  • Robert T Cartee
  • W Thomas Forsee

Detail Information

Publications9

  1. ncbi Control of capsular polysaccharide chain length by UDP-sugar substrate concentrations in Streptococcus pneumoniae
    Christy L Ventura
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
    Mol Microbiol 61:723-33. 2006
    ..Further, they may have implications for the control of chain length in both prokaryotic and eukaryotic polymers synthesized by similar mechanisms...
  2. pmc Mutations blocking side chain assembly, polymerization, or transport of a Wzy-dependent Streptococcus pneumoniae capsule are lethal in the absence of suppressor mutations and can affect polymer transfer to the cell wall
    Bobbi Xayarath
    Department of Microbiology, 845 19th Street South, BBRB 661 12, Birmingham, AL 35294 2170, USA
    J Bacteriol 189:3369-81. 2007
    ..A central role for the initiating glycosyltransferase in controlling capsule synthesis is also suggested...
  3. pmc CcpA-dependent and -independent control of beta-galactosidase expression in Streptococcus pneumoniae occurs via regulation of an upstream phosphotransferase system-encoding operon
    Greer E Kaufman
    Department of Microbiology, Univerisity of Alabama at Birmingham, Birmingham, AL 35294 2170, USA
    J Bacteriol 189:5183-92. 2007
    ..pneumoniae adherence during colonization of the nasopharynx, a site normally devoid of glucose. CcpA and environmental glucose concentrations thus appear to play important roles in the regulation of a niche-specific virulence factor...
  4. pmc Biochemical, genetic, and serological characterization of two capsule subtypes among Streptococcus pneumoniae Serotype 20 strains: discovery of a new pneumococcal serotype
    Juan J Calix
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
    J Biol Chem 287:27885-94. 2012
    ..We propose naming bacteria that express the previously described 20α capsule structure 20A and bacteria that express the novel 20β capsule structure 20B, a new pneumococcal serotype...
  5. pmc Genetic and biochemical characterizations of enzymes involved in Streptococcus pneumoniae serotype 2 capsule synthesis demonstrate that Cps2T (WchF) catalyzes the committed step by addition of β1-4 rhamnose, the second sugar residue in the repeat unit
    David B A James
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
    J Bacteriol 194:6479-89. 2012
    ..Therefore, Cps2T is the β1-4 rhamnosyltransferase that adds the second sugar to the repeat unit and, as the committed step in type 2 repeat unit synthesis, is predicted to be an important point of capsule regulation...
  6. pmc Streptococcus pneumoniae serotype 11D has a bispecific glycosyltransferase and expresses two different capsular polysaccharide repeating units
    Melissa B Oliver
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294 2170, USA
    J Biol Chem 288:21945-54. 2013
    ..These findings demonstrate how pneumococci alter their CPS structure and their immunologic properties with a minimal genetic change. ..
  7. pmc Biochemical activities of Streptococcus pneumoniae serotype 2 capsular glycosyltransferases and significance of suppressor mutations affecting the initiating glycosyltransferase Cps2E
    David B A James
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
    J Bacteriol 195:5469-78. 2013
    ..The critical functions of these amino acids suggest a role for the Cps2E extracytoplasmic loop in initiation, and possibly regulation, of capsule synthesis. ..
  8. pmc Streptococcus pneumoniae phosphotyrosine phosphatase CpsB and alterations in capsule production resulting from changes in oxygen availability
    K Aaron Geno
    Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
    J Bacteriol 196:1992-2003. 2014
    ..Roles for factors outside the capsule locus, possible interactions between capsule regulatory proteins, and links to other cellular processes are also suggested by the results described in this study. ..
  9. ncbi Capsules of Streptococcus pneumoniae and other bacteria: paradigms for polysaccharide biosynthesis and regulation
    Janet Yother
    Department of Microbiology, University of Alabama, Birmingham, Alabama 35294 2170, USA
    Annu Rev Microbiol 65:563-81. 2011
    ..Characterization of these systems has provided novel insights that are applicable to polymers synthesized by many gram-positive and gram-negative bacteria, as well as eukaryotes...