Capsulation gene loss and 'rescue' mutations during the Cap+ to Cap- transition in Haemophilus influenzae type b

Brophy, L. N.; Kroll, J. Simon; Ferguson, David; Moxon, E. Richard

doi:10.1099/00221287-137-11-2571

Cited by 13 publications

(2 citation statements)

References 12 publications

(7 reference statements)

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“…Thus, cells could alternate between periods of capsule expression and low transfer and periods where they lack a capsule and favour genetic transfer. Alternatively, some cells in the population may lack a capsule, either because it is subject to phase variation [58, 59], gene loss [60, 61], or to stochastic phenotypic heterogeneity at the cellular level [62], and these cells may account for a large fraction of genetic exchanges. Such switching phenotypes emerge easily as a response to fluctuating environments and allow faster adaptation whilst minimizing capsule cost [63].…”

Section: Discussionmentioning

confidence: 99%

Genetic exchanges are more frequent in bacteria encoding capsules

et al. 2018

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Capsules allow bacteria to colonize novel environments, to withstand numerous stresses, and to resist antibiotics. Yet, even though genetic exchanges with other cells should be adaptive under such circumstances, it has been suggested that capsules lower the rates of homologous recombination and horizontal gene transfer. We analysed over one hundred pan-genomes and thousands of bacterial genomes for the evidence of an association between genetic exchanges (or lack thereof) and the presence of a capsule system. We found that bacteria encoding capsules have larger pan-genomes, higher rates of horizontal gene transfer, and higher rates of homologous recombination in their core genomes. Accordingly, genomes encoding capsules have more plasmids, conjugative elements, transposases, prophages, and integrons. Furthermore, capsular loci are frequent in plasmids, and can be found in prophages. These results are valid for Bacteria, independently of their ability to be naturally transformable. Since we have shown previously that capsules are commonly present in nosocomial pathogens, we analysed their co-occurrence with antibiotic resistance genes. Genomes encoding capsules have more antibiotic resistance genes, especially those encoding efflux pumps, and they constitute the majority of the most worrisome nosocomial bacteria. We conclude that bacteria with capsule systems are more genetically diverse and have fast-evolving gene repertoires, which may further contribute to their success in colonizing novel niches such as humans under antibiotic therapy.

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Section: Discussionmentioning

confidence: 99%

Genetic exchanges are more frequent in bacteria encoding capsules

et al. 2018

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“…Export of the type b capsule of H. influenzae is not a stable genetic trait. With in vitro passage, type b strains can lose bexA present in the bridging portion of the type b capsule gene cluster (4). This results in an isolate which fails to agglutinate with anti-b antisera and is classified as nontypeable.…”

Section: Methodsmentioning

confidence: 99%

Serum Resistance in an Invasive, NontypeableHaemophilus influenzaeStrain

et al. 2001

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A common feature of many different organisms causing bacteremia is the ability to avoid the bactericidal effects of normal human serum. In Haemophilus influenzae encapsulated strains are particularly serum resistant; however, we found that a nonencapsulated strain (R2866) isolated from the blood of an immunocompetent child with meningitis who had been successfully immunized with H. influenzae type b conjugate vaccine was serum resistant. Since serum resistance usually involves circumventing the action of the complement system, we defined the deposition of various complement components on the surfaces of this H. influenzae strain (R2866), a nonencapsulated avirulent laboratory strain (Rd), and a virulent type b encapsulated strain (Eagan). Membrane attack complex (MAC) accumulation correlated with the loss of bacterial viability; correspondingly, the rates of MAC deposition on the serum-sensitive strain Rd and the serum-resistant strains differed. Analysis of cell-associated immunoglobulin G (IgG), C1q, C3b, and C5b indicated that serumresistant H. influenzae prevents MAC accumulation by delaying the synthesis of C3b through the classical pathway. Among the initiators of the classical pathway, IgG deposition contributes most of the C3 convertase activity necessary to start the cascade ending with MAC deposition. Despite similar IgG binding, strain R2866 delays C3 convertase activity compared to strain Rd. We conclude that strain R2866 can persist in the bloodstream, in part by inhibiting or delaying C3 deposition on the cell surface, escaping complement mediated killing.

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Intraclonal Polymorphism in Bacteria

Rainey

Thompson

Moxon

1993

Advances in Microbial Ecology

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Before the invention of pure culture methods, bacteria were believed to be fantastically variable-indeed, all the different types observed were thought by some biologists (the pleomorphists) to represent different stages in the life cycles of a few kinds of microbe. Koch's demonstration that each type of bacterium breeds true when grown in pure culture caused the pendulum to swing the other way; it became the majority opinion that bacteria were monomorphic. At the beginning of the twentieth century, however, it became recognized that even the most impeccably pure cultures were able to change, and many bacteriologists began to study the mechanism of such variations.Stanier, Dourdoroff, and Adelberg (1958)

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Capsulation gene loss and 'rescue' mutations during the Cap+ to Cap- transition in Haemophilus influenzae type b

Cited by 13 publications

References 12 publications

Genetic exchanges are more frequent in bacteria encoding capsules

Genetic exchanges are more frequent in bacteria encoding capsules

Serum Resistance in an Invasive, NontypeableHaemophilus influenzaeStrain

Intraclonal Polymorphism in Bacteria

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