%0 Journal Article %A Binepal, Gursonika %A Wenderska, Iwona B %A Crowley, Paula %A Besingi, Richard N %A Senadheera, Dilani B %A Jeannine Brady, L %A Cvitkovitch, Dennis G %T K+ modulates genetic competence and the stress regulon of Streptococcus mutans %D 2017 %J Microbiology, %V 163 %N 5 %P 719-730 %@ 1465-2080 %R https://doi.org/10.1099/mic.0.000458 %K Trk2 %K Streptococcus mutans %K Genetic transformation %K stress response %K K+ %I Microbiology Society, %X Potassium (K+) is the most abundant cation in dental plaque fluid. Previously, we reported the link between K+ transport via Trk2 in Streptococcus mutans and its two critical virulence attributes: acid tolerance and surface adhesion. Herein, we build further on the intimate link between K+ levels and S. mutans biology. High (>25 mM) versus low (≤5 mM) K+ concentrations in the growth medium affected conformational epitopes of cell surface-localized adhesin P1. At low K+, the expression of stress response elements gcrR and codY, cell-adhesion-associated genes such as spaP and metabolism-associated genes such as bglP was induced at stationary phase (P<0.05), suggesting that K+-mediated regulation is growth phase-dependent and stress-sensitive. Production of the newly discovered secretory protein encoded by SMU_63 c was strongly dependent on the availability of K+ and growth phase. This protein is a newly discovered regulator of genetic competence and biofilm cell density. Thus, the influence of K+ on DNA transformation efficiency was also examined. Compared with 25 mM K+ concentration, the presence of low K+ reduced the transformation frequency by 100-fold. Genetic transformation was abolished in a strain lacking a Trk2 system under all K+ concentrations tested. Consistent with these findings, repression of competence-associated genes, comS and comX, was observed under low environmental K+ conditions and in the strain lacking Trk2. Taken together, these results highlight a pivotal role for environmental K+ as a regulatory cation that modulates stress responses and genetic transformation in S. mutans. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.000458