A novel two-component system of Streptococcus sanguinis affecting functions associated with viability in saliva and biofilm formation

• Published in: Infection and immunity 2018-04, Vol.86 (4)
• Main Authors: Camargo, Tarsila M, Stipp, Rafael N, Alves, Lívia A, Harth-Chu, Erika N, Höfling, José F, Mattos-Graner, Renata O
• Format: Article
• Language: English
• Subjects: Molecular Pathogenesis
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.00942-17

is a pioneer species of teeth and a common opportunistic pathogen of infective endocarditis. In this study, we identified a two-component system, SptRS , affecting survival in saliva and biofilm formation. Isogenic mutants of (SKsptR) and (SKsptS) showed reduced cell counts in assays of viability in saliva, compared to parent strain SK36 and complemented mutants. Reduced counts of the mutants in saliva were associated with reduced growth rates in poor nutrient medium (RPMI) and increased susceptibility to deposition of C3b and MAC of the complement system, a defense component of saliva and serum. Conversely, s mutants showed increased biofilm formation associated with higher production of H O and extracellular DNA. RT-qPCR comparisons of strains indicated a global role of SptRS in repressing genes for H O production (2.5 to 15-fold up-regulation of , , , and in mutants), biofilm formation and/or evasion to host immunity (2.1 to 11.4-fold up-regulation of , , ). Compatible with SptR homology with AraC-type regulators, duplicate to multiple conserved repeats were identified in 1,000 bp regulatory regions of downstream genes, suggesting that SptR regulates transcription by DNA looping. Significant transcriptional changes in the regulatory genes , , , , and in the / mutants, further indicated that SptRS is part of a regulatory network which coordinates cell wall homeostasis, H O production, and competence. This study reveals that SptRS is involved in the regulation of crucial functions for persistence in the oral cavity.