The capsule biosynthesis locus of Haemophilus influenzae shows conspicuous similarity to the corresponding locus in Haemophilus sputorum and may have been recruited from this species by horizontal gene transfer

Nielsen, Signe Maria; Gier, Camilla de; Dimopoulou, Chrysoula; Gupta, Vikas; Hansen, Lars; Nørskov‐Lauritsen, Niels

doi:10.1099/mic.0.000081

Cited by 10 publications

(10 citation statements)

References 33 publications

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“…The sheer diversity of polysaccharide antigens in some species – much greater than expected based on the rest of the genome 4 , 6 , 50 – undoubtedly suggests the role of diversifying selection in generating new structures. The existence of such selection is also supported by the fact that polysaccharide synthesis loci are genetic variability hotspots between close bacterial species in the human gut [51] , and they are often recombination hotspots, for which we have direct 41 , 42 , 52 , 53 , 54 , 55 , 56 , 57 and indirect evidence 4 , 35 , 58 , 59 , 60 , 61 . Finally, bacterial polysaccharides often involve synthesis of rare sugars, like l -rhamnose or l -fucose, which are not typically found in animal cells [62] .…”

Section: Factors Shaping the Diversity Of Polysaccharide Antigensmentioning

confidence: 84%

“…Importantly, phylogenetic and phylodynamic analyses revealed that these recombinants emerged prior to the introduction of the vaccine 39 , 54 , implying that the polysaccharide capsule diversity evolves over time and that selection acts on this diversity. This process could be enhanced by interactions with closely related commensal bacteria, as we have seen that capsule genes are often shared between pathogens and commensals in all three bacterial species 59 , 60 , 61 . Furthermore, in the pneumococcus there is evidence that commensals can act as a source of horizontally acquired capsule diversity 56 , 120 .…”

Section: Medical Implicationsmentioning

confidence: 99%

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Diversity-Generating Machines: Genetics of Bacterial Sugar-Coating

Mostowy

Holt

2018

Trends in Microbiology

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Bacterial pathogens and commensals are surrounded by diverse surface polysaccharides which include capsules and lipopolysaccharides. These carbohydrates play a vital role in bacterial ecology and interactions with the environment. Here, we review recent rapid advancements in this field, which have improved our understanding of the roles, structures, and genetics of bacterial polysaccharide antigens. Genetic loci encoding the biosynthesis of these antigens may have evolved as bacterial diversity-generating machines, driven by selection from a variety of forces, including host immunity, bacteriophages, and cell–cell interactions. We argue that the high adaptive potential of polysaccharide antigens should be taken into account in the design of polysaccharide-targeting medical interventions like conjugate vaccines and phage-based therapies.

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Section: Factors Shaping the Diversity Of Polysaccharide Antigensmentioning

confidence: 84%

Section: Medical Implicationsmentioning

confidence: 99%

Diversity-Generating Machines: Genetics of Bacterial Sugar-Coating

Mostowy

Holt

2018

Trends in Microbiology

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“…The existence of the H. influenzae capsule has also invoked HGT from another species. Similarly to Nme , H. influenzae consists of variants both with and without a capsule; the capsule locus cap was proposed to have been donated by HGT from Haemophilus sputorum , although H. sputorum may actually be a member of another genus from the Pasteurellacae family 50 . The low GC content of region A of the capsule locus has also been cited as evidence that the capsule may have been acquired by HGT 8, 51 , but this has also been observed in the capsule synthesis region of other Neisseria species 15 , as well as E. coli , H. sputorum and A. pleuropneumoniae 52– 54 .…”

Section: Discussionmentioning

confidence: 99%

Neisseria meningitidis has acquired sequences within the capsule locus by horizontal genetic transfer

2019

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Background: Expression of a capsule from one of serogroups A, B, C, W, X or Y is usually required for Neisseria meningitidis (Nme) to cause invasive meningococcal disease. The capsule is encoded by the capsule locus, cps, which is proposed to have been acquired by a formerly capsule null organism by horizontal genetic transfer (HGT) from another species. Following identification of putative capsule genes in non-pathogenic Neisseria species, this hypothesis is re-examined. Methods: Whole genome sequence data from Neisseria species, including Nme genomes from a diverse range of clonal complexes and capsule genogroups, and non-Neisseria species, were obtained from PubMLST and GenBank. Sequence alignments of genes from the meningococcal cps, and predicted orthologues in other species, were analysed using Neighbor-nets, BOOTSCANing and maximum likelihood phylogenies. Results: The meningococcal cps was highly mosaic within regions B, C and D. A subset of sequences within regions B and C were phylogenetically nested within homologous sequences belonging to N. subflava, consistent with HGT event in which N. subflava was the donor. In the cps of 23/39 isolates, the two copies of region D were highly divergent, with rfbABC’ sequences being more closely related to predicted orthologues in the proposed species N. weixii (GenBank accession number CP023429.1) than the same genes in Nme isolates lacking a capsule. There was also evidence of mosaicism in the rfbABC’ sequences of the remaining 16 isolates, as well as rfbABC from many isolates. Conclusions: Data are consistent with the en bloc acquisition of cps in meningococci from N. subflava, followed by further recombination events with other Neisseria species. Nevertheless, the data cannot refute an alternative model, in which native meningococcal capsule existed prior to undergoing HGT with N. subflava and other species. Within-genus recombination events may have given rise to the diversity of meningococcal capsule serogroups.

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“…HGT between Neisseria species has been described previously, including cross-species exchanges of pilE, another gene with links to virulence [ 21, 48 ]. Acquisition of capsule genes in H. influenzae has also been proposed to be a result of HGT from a commensal species of the same genus [ 49 ]. Interestingly, the suggested organization of the donor ancestral cps island described in the model by Bartley et al [ 22 ] matches the organization of the N. subflava cps described in the present study; however, a potential donor could alternatively be a close relative that has either not been previously isolated or since become extinct.…”

Section: Discussionmentioning

confidence: 99%

Characterization of capsule genes in non-pathogenic Neisseria species

2018

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The genus Neisseria comprises a diverse group of commensal bacteria, which typically colonize the mucosal surfaces of humans and other animals. Neisseria meningitidis, the meningococcus, is notable for its potential to cause invasive meningococcal disease (IMD) in humans; however, IMD is comparatively rare, and meningococci normally colonize the nasopharynx asymptomatically. Possession of a polysaccharide capsule has been shown to be a prerequisite for disease in almost all IMD cases, and was previously considered unique to N. meningitidis, and potentially acquired by horizontal genetic transfer (HGT). Nevertheless, the capsule must also have some role in asymptomatic colonization and/or transmission, consistent with the existence of six non-disease-associated meningococcal capsule serogroups. In this study, full complements of putative capsule genes were identified in non-pathogenic Neisseria species, including Neisseria subflava and Neisseria elongata. These species contained genes for capsule transport and translocation homologous to those of N. meningitidis, as well as novel putative capsule synthesis genes. Phylogenetic analyses were consistent with the proposal that these genes were acquired by the meningococcus through HGT. In contrast with previous evolutionary models, however, the most parsimonious explanation of these data was that capsule transport genes had been lost in the common ancestor of the meningococcus, gonococcus, and their close relatives, and then reacquired by some meningococci. The most likely donor of the meningococcal transport genes was another Neisseria species.

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The capsule biosynthesis locus of Haemophilus influenzae shows conspicuous similarity to the corresponding locus in Haemophilus sputorum and may have been recruited from this species by horizontal gene transfer

Cited by 10 publications

References 33 publications

Diversity-Generating Machines: Genetics of Bacterial Sugar-Coating

Diversity-Generating Machines: Genetics of Bacterial Sugar-Coating

Neisseria meningitidis has acquired sequences within the capsule locus by horizontal genetic transfer

Characterization of capsule genes in non-pathogenic Neisseria species

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