title: Capsule loss or death: the position of mutations among capsule genes sways the destiny of Streptococcus suis.
abstract: Streptococcus suis, an emerging zoonotic pathogen, is responsible for various diseases in swine and humans. Most S. suis strains from clinical cases possess a group of capsular polysaccharide synthesis (cps) genes and phenotypically express capsular polysaccharides (CPs). Although CPs are considered to be an important virulence factor, our previous study showed that many S. suis isolates from porcine endocarditis lost their CPs, and some of these unencapsulated isolates had large insertions or deletions in the cps gene clusters. We further investigated 25 endocarditis isolates with no obvious genetic alterations to elucidate the unencapsulation mechanisms and found that a single-nucleotide substitution and frameshift mutation in two glycosyltransferase genes (cps2E and cps2F) were the main causes of the capsule loss. Moreover, mutations in the genes involved in side-chain formation (cps2J and cps2N), polymerase (cps2I), and flippase (cps2O) appeared to be lethal; however, these lethal effects were relieved by mutations in the cps2EF region. As unencapsulation and even the death of individual cells have recently been suggested to be beneficial to the pathogenesis of infections, the results of the present study provide a further insight into understanding the biological significance of cps mutations during the course of S. suis infections.
authors.affiliation: Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Nattakan
authors.initials: N
authors.lastname: Lakkitjaroen
authors.forename: Daisuke
authors.initials: D
authors.lastname: Takamatsu
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Okura
authors.forename: Masumi
authors.initials: M
authors.lastname: Sato
authors.forename: Makoto
authors.initials: M
authors.lastname: Osaki
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Sekizaki
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004696:Endocarditis / Q000382:microbiology / Q000662:veterinary*; D008969:Molecular Sequence Data; D017384:Sequence Deletion; D013290:Streptococcal Infections / Q000382:microbiology / Q000662:veterinary*; D017011:Streptococcus suis / Q000235:genetics / Q000378:metabolism*; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins
keywords: capsular polysaccharide; capsule synthesis; endocarditis; porcine