Genome sequence of a Streptococcus dysgalactiae subsp. equisimilis, possessing the group A carbohydrate cell wall antigen, and its comparative genomics
Zusammenfassung der Projektergebnisse
Objectives: Information on the genomes of S. dysgalactiae subsp. equisimilis (SDSE) is highly desirable since this pathogen causes a spectrum of infections similar to those caused by S. pyogenes. Two genomes of SDSE (serological group G) were recently published. Here we report on the complete genome sequence of SDSE strain AC-2713 possessing a group A Lancefield antigen and compare it to other streptococcal genomes. Methods: SDSE strain AC-2713 originated from a blood culture of an adult (without STSS). Pyrosequencing (Roche/454 method, shot-gun and an 8 kb paired-end library, combined 59-fold coverage) was applied. Gap closure was achieved by Sanger sequencing of PCR products. Assembly and finishing was obtained by applying different bioinformatics tools. Annotation was performed by combining results of the “GenDB”, “RAST”, and “BASys” servers and manual curation. For comparisons different bioinformatics tools were applied. Results: The AC-2713 genome consists of one circular chromosome of 2,179,445 bp coding for 2,181 proteins, 15 rRNAs, and 57 tRNAs. The G+C content is 39.5%. Two phage-related chromosomal islands (PRCIs) were identified that did not contain any of the phage-encoded virulence factors of S. pyogenes. Other orthologs of virulence factor genes of S. pyogenes including determinants for an M- protein (emm stG485.0), pili, streptokinase, hemolysins (SLO, SLS), NADase, matrix-protein binding surface proteins, etc. were detected. Spegg4 was found as the only superantigen gene. Comparative analyses revealed a high degree of homology and colinearity with the published S. dysgalactiae genomes and closer relationships to S. pyogenes (based on available genomes) than to other betahemolytic streptococci including groups C and G streptococci of animal origin. Conclusion: AC-2713, an SDSE possessing Lancefield’s group A antigen is highly homologous to other S. dysgalactiae and more closely related to S. pyogenes than to other streptococcal species, including groups C and G streptococci of animal origin.
