This application is for support of a project focused on the acid-base physiology of plaque bacteria, especially the mutans streptococci, but also Lactobacillus casei and arginine-deiminase positive streptococci. The proposed work arises from previous studies the acid tolerance with particular attention on proton-translocating F-ATPases. A basic hypothesis is that the more acid-tolerant bacteria in plaque are also the more cariogenic. To be cariogenic, a bacterium must be able to colonize plaque, become a significant part of the flora, and produce acid. However, since the challenge to the tooth is exponentially related to the extent of acidification of plaque, those organisms which can lower the plaque pH to values as low as .4 are particularly damaging. The results of our prior work indicated two adaptations in F-ATPases for acid tolerance. More tolerant organisms have higher F-ATPase activities per unit of cell weight, and the enzymes have lower pH optima for activity. Plans are to extend these results with other organisms, especially the acid-tolerant, non-mutants, plaque streptococci. The proposed work will now consider proton-translocating efficiencies of the enzymes in terms of coupling ratios i.e., how many protons are transported per ATP hydrolyzed, means to inhibit the enzyme and to affect the efficiency of coupling, and the possible involvement of lactate transport in proton currents. Membrane vesicles isolated from Streptococcus mutans GS-5 will be used extensively for the proposed work, as will bacteria grown in biofilms under a variety of conditions. In addition, isolated genes for the atp operon of S. mutans will be used for studies of regulation of F-ATPase synthesis. In the overall acid-base cycles of plaque, ammonia production by arginine-deiminase-positive bacteria is considered important for protecting less acid-tolerant bacteria against acid damage and for reducing cariogenicity. Studies are proposed on regulation of the arginine deiminase system (ADS) by redox potential in S. sanguis and S. rattus, on ADS-negative mutants, on cells grown in biofilms and on transmembrane transport of arginine peptides. The results of our previous work and that of others has indicated overlap in the adaptations of plaque streptococci for protection against acid damage and against oxidative damage caused, for example, by hydroperoxides. We proposed to define in more detail the nature of acid damage, especially to the glycolytic system, and the relationship between acid damage and oxidative damage. A major objective will be to develop means, for example, with enhancers of oxidative damage, to reduce acid tolerance and cariogenicity.

National Institute of Health (NIH)
National Institute of Dental & Craniofacial Research (NIDCR)
Research Project (R01)
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Oral Biology and Medicine Subcommittee 1 (OBM)
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University of Rochester
Schools of Dentistry
United States
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Nguyen, Phuong T M; Marquis, Robert E (2011) Antimicrobial actions of ?-mangostin against oral streptococci. Can J Microbiol 57:217-25
Lemos, Jose A; Abranches, Jacqueline; Koo, Hyun et al. (2010) Protocols to study the physiology of oral biofilms. Methods Mol Biol 666:87-102
Sheng, Jiangyun; Baldeck, Jeremiah D; Nguyen, Phuong T M et al. (2010) Alkali production associated with malolactic fermentation by oral streptococci and protection against acid, oxidative, or starvation damage. Can J Microbiol 56:539-47
Barboza-Silva, E; Castro, A C D; Marquis, R E (2009) Fluoride, triclosan and organic weak acids as modulators of the arginine deiminase system in biofilms and suspension cells of oral streptococci. Oral Microbiol Immunol 24:265-71
Baldeck, Jeremiah D; Marquis, Robert E (2008) Targets for hydrogen-peroxide-induced damage to suspension and biofilm cells of Streptococcus mutans. Can J Microbiol 54:868-75
Sheng, Jiangyun; Marquis, Robert E (2007) Malolactic fermentation by Streptococcus mutans. FEMS Microbiol Lett 272:196-201
Sheng, Jiangyun; Nguyen, Phuong T M; Baldeck, Jeremiah D et al. (2006) Antimicrobial actions of benzimidazoles against the oral anaerobes Fusobacterium nucleatum and Prevotella intermedia. Arch Oral Biol 51:1015-23
Koo, Hyun; Sheng, Jiangyun; Nguyen, Phuong T M et al. (2006) Co-operative inhibition by fluoride and zinc of glucosyl transferase production and polysaccharide synthesis by mutans streptococci in suspension cultures and biofilms. FEMS Microbiol Lett 254:134-40
Sheng, Jiangyun; Marquis, Robert E (2006) Enhanced acid resistance of oral streptococci at lethal pH values associated with acid-tolerant catabolism and with ATP synthase activity. FEMS Microbiol Lett 262:93-8
Phan, Tuan-Nghia; Marquis, Robert E (2006) Triclosan inhibition of membrane enzymes and glycolysis of Streptococcus mutans in suspensions and biofilms. Can J Microbiol 52:977-83

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