A streptolysin S homologue is essential for β-haemolytic Streptococcus constellatus subsp. constellatus cytotoxicity
Tabata, Atsushi and Sato, Yuji and Maya, Kentaro and Nakano, Kota and Kikuchi, Ken and Whiley, Robert A. and Ohkura, Kazuto and Tomoyasu, Toshifumi and Nagamune, Hideaki,, 160, 980-991 (2014),
doi = https://doi.org/10.1099/mic.0.075580-0,
publicationName = Microbiology Society,
issn = 1350-0872,
abstract= Streptococcus constellatus is a member of the Anginosus group streptococci (AGS) and primarily inhabits the human oral cavity. S. constellatus is composed of three subspecies: S. constellatus subsp. constellatus (SCC), S. constellatus subsp. pharyngis and the newly described subspecies S. constellatus subsp. viborgensis. Although previous studies have established that SCC contains β-haemolytic strains, the factor(s) responsible for β-haemolysis in β-haemolytic SCC (β-SCC) has yet to be clarified. Recently, we discovered that a streptolysin S (SLS) homologue is the β-haemolytic factor of β-haemolytic Streptococcus anginosus subsp. anginosus (β-SAA), another member of the AGS. Furthermore, because previous studies have suggested that other AGS species, except for Streptococcus intermedius, do not possess a haemolysin(s) belonging to the family of cholesterol-dependent cytolysins, we hypothesized that, as with β-SAA, the SLS homologue is the β-haemolytic factor of β-SCC, and therefore aimed to investigate and characterize the haemolytic factor of β-SCC in the present study. PCR amplification revealed that all of the tested β-SCC strains were positive for the sagA homologue of SCC (sagA SCC). Further investigations using β-SCC strain W277 were conducted to elucidate the relationship between sagA SCC and β-haemolysis by constructing sagA SCC deletion mutants, which completely lost β-haemolytic activity. This loss of β-haemolytic activity was restored by trans-complementation of sagA SCC. Furthermore, a co-cultivation assay established that the cytotoxicity of β-SCC was clearly dependent on the presence of sagA SCC. These results demonstrate that sagA SCC is the factor responsible for β-SCC β-haemolysis and cytotoxicity.,
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