An ffh mutant of Streptococcus mutans is viable and able to physiologically adapt to low pH in continuous culture.
Previously, we described in Streptococcus mutans strain NG8 a 5-gene operon (sat) that includes ffh, the bacterial homologue of the eukaryotic signal recognition particle (SRP) protein, SR54. A mutation in ffh resulted in acid sensitivity but not loss of viability. In the present study, chemostat-grown cells of the ffh mutant were shown to possess only 26% and 39% of the parental membrane F-ATPase activity and 55% and 75% of parental glucose-phosphotransferase (PTS) activity when pH-7 and pH-5-grown cells, respectively, were assayed. Two-dimensional-gel electrophoretic analyses revealed significant differences in protein profiles between parent and ffh-mutant strains at both pH 5 and pH 7. It appears that the loss of active SRP (Ffh) function, while not lethal, results in substantial alterations in cellular physiology that includes acid tolerance.
Crowley
Paula J
PJ
Department of Oral Biology, University of Florida, P.O. Box 100424, Gainesville, FL 32610, USA. crowley@dental.ufl.edu
Svensäter
Gunnel
G
Snoep
Jacky L
JL
Bleiweis
Arnold S
AS
Brady
L Jeannine
LJ
D000064:Acclimatization; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009876:Operon / Q000235:genetics*; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism; D018271:Signal Recognition Particle / Q000235:genetics / Q000378:metabolism; D013295:Streptococcus mutans / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D013379:Substrate Specificity
D001426:Bacterial Proteins; D018271:Signal Recognition Particle; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D006180:Proton-Translocating ATPases