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Applied and Environmental Microbiology, February 2004, p. 929-936, Vol. 70, No. 2
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.2.929-936.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Shifts in the Membrane Fatty Acid Profile of Streptococcus mutans Enhance Survival in Acidic Environments

Elizabeth M. Fozo1 and Robert G. Quivey Jr.1,2*

Department of Microbiology and Immunology,1 Center for Oral Biology in the Aab Institute for Biomedical Sciences, University of Rochester, Rochester, New York 146422

Received 28 July 2003/ Accepted 30 October 2003

Acid adaptation of Streptococcus mutans UA159 involves several different mechanisms, including the ability to alter its proportion of long-chain, monounsaturated membrane fatty acids (R. G. Quivey, Jr., R. Faustoferri, K. Monahan, and R. Marquis, FEMS Microbiol. Lett. 189:89-92, 2000). In the present study, we examined the mechanism and timing of changes in fatty acid ratios and the potential benefit that an increased proportion of long-chained fatty acids has for the organism during growth at low pH. Cells taken from steady-state cultures at intermediate pH values of 6.5, 6, and 5.5 showed incremental changes from the short-chained, saturated membrane fatty acid profile normally seen in pH 7 cultures to the long-chained, monounsaturated fatty acids more typically observed in acidic cultures (pH 5). Our observations showed that the bacterium was capable of effecting the majority of changes in approximately 20 min, far less than one generation time. However, reversion to the distribution of fatty acids seen in cells growing at a pH of 7 required a minimum of 10 generations. Fatty acid composition analysis of cells taken from cultures treated with chloramphenicol suggested that the changes in fatty acid distribution did not require de novo protein synthesis. Cells treated with the fatty acid biosynthesis inhibitor cerulenin were unable to alter their membrane fatty acid profiles and were unable to survive severe acidification. Results presented here indicate that membrane fatty acid redistribution is important for low pH survival and, as such, is a component of the S. mutans acid-adaptation arsenal.

* Corresponding author. Mailing address: Center for Oral Biology, Box 611, 601 Elmwood Ave., Rochester, NY 14642. Phone: (585) 275-0382. Fax: (585) 506-0190. E-mail: Robert_Quivey{at}urmc.rochester.edu.

Applied and Environmental Microbiology, February 2004, p. 929-936, Vol. 70, No. 2
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.2.929-936.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



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