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FEMS Microbiol Lett. 2004 May 15;234(2):315-24.

An ffh mutant of Streptococcus mutans is viable and able to physiologically adapt to low pH in continuous culture.

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Department of Oral Biology, University of Florida, P.O. Box 100424, Gainesville, FL 32610, USA.

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  • FEMS Microbiol Lett. 2004 Jul 1;236(1):161.


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.

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