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Capsule Type of Streptococcus pneumoniae Determines Growth Phenotype

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Hathaway, Lucy J., Brugger, Silvio D., Morand, Brigitte, Bangert, Mathieu, Rotzetter, Jeannine U., Hauser, Christoph, Graber, Werner A., Gore, Suzanna, Kadioglu, Aras and Mühlemann, Kathrin (2012) 'Capsule Type of Streptococcus pneumoniae Determines Growth Phenotype'. PLoS Pathogens, Vol 8, Issue 3, e1002574.

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Abstract

The polysaccharide capsule of Streptococcus pneumoniae defines over ninety serotypes, which differ in their carriage prevalence and invasiveness for poorly understood reasons. Recently, an inverse correlation between carriage prevalence and oligosaccharide structure of a given capsule has been described. Our previous work suggested a link between serotype and growth in vitro. Here we investigate whether capsule production interferes with growth in vitro and whether this predicts carriage prevalence in vivo. Eighty-one capsule switch mutants were constructed representing nine different serotypes, five of low (4, 7F, 14, 15, 18C) and four of high carriage prevalence (6B, 9V, 19F, 23F). Growth (length of lag phase, maximum optical density) of wildtype strains, nontypeable mutants and capsule switch mutants was studied in nutrient-restricted Lacks medium (MLM) and in rich undefined brain heart infusion broth supplemented with 5% foetal calf serum (BHI+FCS). In MLM growth phenotype depended on, and was transferred with, capsule operon type. Colonization efficiency of mouse nasopharynx also depended on, and was transferred with, capsule operon type. Capsule production interfered with growth, which correlated inversely with serotype-specific carriage prevalence. Serotypes with better growth and higher carriage prevalence produced thicker capsules (by electron microscopy, FITC-dextran exclusion assays and HPLC) than serotypes with delayed growth and low carriage prevalence. However, expression of cpsA, the first capsule gene, (by quantitative RT-PCR) correlated inversely with capsule thickness. Energy spent for capsule production (incorporation of H3-glucose) relative to amount of capsule produced was higher for serotypes with low carriage prevalence. Experiments in BHI+FCS showed overall better bacterial growth and more capsule production than growth in MLM and differences between serotypes were no longer apparent. Production of polysaccharide capsule in S. pneumoniae interferes with growth in nutrient-limiting conditions probably by competition for energy against the central metabolism. Serotype-specific nasopharyngeal carriage prevalence in vivo is predicted by the growth phenotype.

Item Type: Article
Subjects: QW Microbiology and Immunology > Viruses > QW 160 Viruses (General). Virology
QW Microbiology and Immunology > QW 51 Morphology and variability of microorganisms. Microbial genetics.
WC Communicable Diseases > Infection. Bacterial Infections > Bacterial Infections > WC 210 Streptococcal infections (General or not elsewhere classified)
Faculty: Department: Groups (2002 - 2012) > Clinical Group
Digital Object Identifer (DOI): https://doi.org/10.1371/journal.ppat.1002574
Depositing User: Lynn Roberts-Maloney
Date Deposited: 14 Jan 2015 11:05
Last Modified: 06 Feb 2018 13:08
URI: https://archive.lstmed.ac.uk/id/eprint/4733

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