Genomic Structure of Capsular Determinants
The production of an extracellular polysaccharide capsule is a common feature of many bacteria (Whitfield and Valvano 1993). The capsule, which often constitutes the outermost layer of the cell, mediates the interaction between the bacterium and its immed
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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
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The Diversity of E. coli Capsules . . . . . . . . . . . . . . . . The Genetics of E. coli Group 1 and 4 Capsules . . . . . . . The Genetics of E. coli Group 2 Capsules . . . . . . . . . . . The Genetics of E. coli Group 3 Capsules . . . . . . . . . . . Localisation of the Group 2 and 3 Capsule Gene Clusters on
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Capsule Gene Clusters in Neisseria meningitidis . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
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138 140 142 144 145
4 Capsule Diversity in Streptococcus pneumoniae . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 4.1 Capsule Gene Clusters in Streptococcus pneumoniae . . . . . . . . . . . . . . . . . . . . . . . . 149 4.2 The Role of Transposition and Recombination in the Emergence of S. pneumoniae Capsule Gene Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 5
Capsule Gene Clusters in Other Gram-Positive Pathogens . . . . . . . . . . . . . . . . . . . . . 151
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Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
1 Introduction The production of an extracellular polysaccharide capsule is a common feature of many bacteria (WHITFIELD and VALVANO 1993). The capsule, which often constitutes the outermost layer of the cell, mediates the interaction between the bacterium and its immediate environment and plays a crucial role in the survival of bacteria in hostile environments. One such environment is the human host, where interactions between the capsule and the host's immune system may be vital in deciding the outcome of an infection (MOXON and KROLL 1990). In the absence of speci®c antibody, a capsule oers protection against the nonspeci®c arm of the host's immune system by conferring increased resistance to complement-mediated killing and complement-mediated opsonophagocytosis (MICHALEK et al. 1988; MOXON and KROLL 1990). A small set of capsular polysaccharides which resemble poly-
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J. Hacker et al. (eds.), Pathogenicity Islands and the Evolution of Pathogenic Microbes © Springer-Verlag Berlin Heidelberg 2002
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B. Barrett et al.
saccharide moieties present in host tissue are poorly immunogenic (FINNE 1982; LINDAHL et al. 1994). The Escherichia coli K1 and Neisseria meningitidis serogroup B capsules, both of which contain N-acetyl-neuraminic acid and the heparin-like E. coli K5 capsule, all elicit a poor antibody response in infected individuals (JENNINGS 1990) and confer some measure of resistance to the host's adaptive humoral response. Aside from d
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