@article{mbs:/content/journal/micro/10.1099/mic.0.075580-0, author = "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", title = "A streptolysin S homologue is essential for β-haemolytic Streptococcus constellatus subsp. constellatus cytotoxicity", journal= "Microbiology", year = "2014", volume = "160", number = "5", pages = "980-991", doi = "https://doi.org/10.1099/mic.0.075580-0", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.075580-0", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", 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.", }