Presence of a Prophage Determines Temperature-Dependent Capsule Production in Streptococcus pyogenes.
A hyaluronic acid capsule is a major virulence factor in the pathogenesis of Streptococcus pyogenes. It acts as an anti-phagocytic agent and adhesin to keratinocytes. The expression of the capsule is primarily regulated at the transcriptional level by the two-component regulatory system CovRS, in which CovR acts as a transcriptional repressor. The covRS genes are frequently mutated in many invasive strains, and a subset of the invasive CovRS mutants does not produce a detectable level of the capsule at 37 °C, but produces a significant amount of the capsule at sub-body temperatures. Here, we report that a prophage has a crucial role in this capsule thermoregulation. Passaging CovR-null strains showing capsule thermoregulation using a lab medium produced spontaneous mutants producing a significant amount of the capsule regardless of incubation temperature and this phenotypic change was caused by curing of a particular prophage. The lab strain HSC5 contains three prophages on the chromosome, and only ΦHSC5.3 was cured in all spontaneous mutants. This result indicates that the prophage ΦHSC5.3 plays a crucial role in capsule thermoregulation, most likely by repressing capsule production at 37 °C.
Department of Biology, Indiana State University, Terre Haute, IN 47809, USA. lesliejobrown@gmail.com.
Leslie
L
Brown
Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Science, Washington, DC 20037, USA. jh_kim@email.gwu.edu.
Jeong-Ho
JH
Kim
Department of Biology, Indiana State University, Terre Haute, IN 47809, USA. kyuhong.cho@indstate.edu.
Kyu Hong
KH
Cho
Capsule thermoregulation; CovRS; Hyaluronic acid capsule; Prophages; Streptococcus pyogenes
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