Novel Two-Component System of Streptococcus sanguinis Affecting Functions Associated with Viability in Saliva and Biofilm Formation

Author(s)

Camargo, Tarsila M. ^[1] ; Stipp, Rafael N. ^[1] ; Alves, Livia A. ^[1] ; Harth-Chu, Erika N. ^[1] ; Hofling, Jose F. ^[1] ; Mattos-Graner, Renata O. ^[1]

Affiliation

^[1] Univ Estadual Campinas, UNICAMP, Piracicaba Dent Sch, Dept Oral Diag, Campinas, SP - Brazil

• Document type: Journal article
• Source: Infection and Immunity; v. 86, n. 4 APR 2018.
• Web of Science Citations: 7

Abstract

Streptococcus sanguinis is a pioneer species of teeth and a common opportunistic pathogen of infective endocarditis. In this study, we identified a two-component system, S. sanguinis SptRS (SptRS(Ss)), affecting S. sanguinis survival in saliva and biofilm formation. Isogenic mutants of sptR(Ss) (SKsptR) and sptS(Ss) (SKsptS) showed reduced cell counts in ex vivo assays of viability in saliva compared to those of parent strain SK36 and complemented mutants. Reduced counts of the mutants in saliva were associated with reduced growth rates in nutrient-poor medium (RPMI) and increased susceptibility to the deposition of C3b and the membrane attach complex (MAC) of the complement system, a defense component of saliva and serum. Conversely, sptR(Ss) and sptS(Ss) mutants showed increased biofilm formation associated with higher levels of production of H2O2 and extracellular DNA. Reverse transcription-quantitative PCR (RT-qPCR) comparisons of strains indicated a global role of SptRS(Ss) in repressing genes for H2O2 production (2.5- to 15-fold upregulation of spxB, spxR, vicR, tpk, and ackA in sptR(Ss) and sptS(Ss) mutants), biofilm formation, and/or evasion of host immunity (2.1- to 11.4-fold upregulation of srtA, pcsB, cwdP, iga, and nt5e). Compatible with the homology of SptR(Ss) with AraC-type regulators, duplicate to multiple conserved repeats were identified in 1,000-bp regulatory regions of downstream genes, suggesting that SptR(Ss) regulates transcription by DNA looping. Significant transcriptional changes in the regulatory genes vicR, spxR, comE, comX, and mecA in the sptR(Ss) and sptS(Ss) mutants further indicated that SptRS(Ss) is part of a regulatory network that coordinates cell wall homeostasis, H2O2 production, and competence. This study reveals that SptRS(Ss) is involved in the regulation of crucial functions for S. sanguinis persistence in the oral cavity. (AU)

• FAPESP's process: 15/12940-3 - Identification of surface proteins of Streptococcus mutans involved in evasion of opsonization by the complement system
• Grantee: Renata de Oliveira Mattos Graner
• Support type: Regular Research Grants
• FAPESP's process: 09/50547-0 - Characterization of GbpB/PcsB homologues in commensal species of oral streptococci
• Grantee: Erika Nikitza Shiauha Harth Chu
• Support type: Scholarships in Brazil - Post-Doctorate
• FAPESP's process: 15/07237-1 - Identification of surface proteins of Streptococcus mutans involved in the scape to opsonization by the complement system
• Grantee: Lívia Araújo Alves
• Support type: Scholarships in Brazil - Doctorate
• FAPESP's process: 12/51832-3 - Analysis of a new Two Component System possibly involved in the adaptation of Streptococcus mutans and Streptococcus sanguinis to human saliva.
• Grantee: Renata de Oliveira Mattos Graner
• Support type: Regular Research Grants
• FAPESP's process: 12/04222-5 - Analysis of the roles of the transcriptional regulators VicRK and CovR in the susceptibility of Streptococcus mutans to opsonization by the complement system.
• Grantee: Lívia Araújo Alves
• Support type: Scholarships in Brazil - Master