Evolutionary paths of streptococcal and staphylococcal superantigens

BMC Genomics

Research Article

Tohru Miyoshi-Akiyama¹  Yumi Shimomura¹  Teruo Kirikae¹  Kayo Okumura²  Junji Yagi³  Kimiko Ubukata⁴  Somay Yamagata Murayama⁵ 

[1] Department of Infectious Diseases, National Center for Global Health and Medicine, 1-21-1, Shinjuku-ku, 162-8655, Tokyo, Japan;Department of Infectious Diseases, National Center for Global Health and Medicine, 1-21-1, Shinjuku-ku, 162-8655, Tokyo, Japan;Department of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, 080-8555, Obihiro, Hokkaido, Japan;Department of Microbiology and Immunology, Tokyo Women’s Medical University, 8-1 Kawada-cho, Shinjuku-ku, 162-8666, Tokyo, Japan;Graduate School of Infection Control Science, Kitasato University, 5-9-1, Shirokane, Minato-ku, 108–8641, Tokyo, Japan;Graduate School of Infection Control Science, Kitasato University, 5-9-1, Shirokane, Minato-ku, 108–8641, Tokyo, Japan;College of Pharmacy, Nihon University, Narashinodai, Funabashi, 274-8555, Chiba, Japan;

关键词: Superantigen;    Streptococcus;    Staphylococcus;    Fenome comparison;    Bayes MCMC;   

DOI  :  10.1186/1471-2164-13-404

 received in 2012-04-03, accepted in 2012-06-30,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundStreptococcus pyogenes (GAS) harbors several superantigens (SAgs) in the prophage region of its genome, although speG and smez are not located in this region. The diversity of SAgs is thought to arise during horizontal transfer, but their evolutionary pathways have not yet been determined. We recently completed sequencing the entire genome of S. dysgalactiae subsp. equisimilis (SDSE), the closest relative of GAS. Although speG is the only SAg gene of SDSE, speG was present in only 50% of clinical SDSE strains and smez in none. In this study, we analyzed the evolutionary paths of streptococcal and staphylococcal SAgs.ResultsWe compared the sequences of the 12–60 kb speG regions of nine SDSE strains, five speG+ and four speG–. We found that the synteny of this region was highly conserved, whether or not the speG gene was present. Synteny analyses based on genome-wide comparisons of GAS and SDSE indicated that speG is the direct descendant of a common ancestor of streptococcal SAgs, whereas smez was deleted from SDSE after SDSE and GAS split from a common ancestor. Cumulative nucleotide skew analysis of SDSE genomes suggested that speG was located outside segments of steeper slopes than the stable region in the genome, whereas the region flanking smez was unstable, as expected from the results of GAS. We also detected a previously undescribed staphylococcal SAg gene, selW, and a staphylococcal SAg -like gene, ssl, in the core genomes of all Staphylococcus aureus strains sequenced. Amino acid substitution analyses, based on dN/dS window analysis of the products encoded by speG, selW and ssl suggested that all three genes have been subjected to strong positive selection. Evolutionary analysis based on the Bayesian Markov chain Monte Carlo method showed that each clade included at least one direct descendant.ConclusionsOur findings reveal a plausible model for the comprehensive evolutionary pathway of streptococcal and staphylococcal SAgs.

【 授权许可】

Unknown   
© Okumura et al.; licensee BioMed Central Ltd. 2012. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.