Our current research interests are directed to two main aspects of microbial physiology - the physiology of oral pathogens and the molecular basis for resistance of bacterial spores to heat and oxidative agents.
Work with oral pathogens includes studies of bacteria involved in dental caries and in periodontal diseases. Research on cariogenic bacteria is focused primarily on the acid-base physiology of the major pathogen Streptococcus mutans, especially on the roles of the proton-translocating F-ATPases in acid tolerance. Other projects include study of acid-stress responses involved in adaptation of oral bacteria to acid environments and study of the functions of the arginine deiminase system in protecting non-cariogenic bacteria against acid damage.
The major research on periodontal pathogens involves the oral spirochete Treponema denticola, its oxygen metabolism, production of enzymes protective against oxygen radicals, and resistance to oxidative killing. Projects on spore resistance include identification of targets for heat damage and the roles of mineralization and dehydration in preventing protein denaturation. We also are attempting to determine mechanisms of spore damage by oxidative agents such as H2O2 and by organic hydroperoxides. Damage by these agents involves formation of highly reactive radicals.
Phan TN, Marquis RE "Triclosan inhibition of membrane enzymes and glycolysis of Streptococcus mutans in suspensions and biofilms." Can J Microbiol. 2006 Oct;52(10):977-83
Sheng J, Marquis RE "Enhanced acid resistance of oral streptococci at lethal pH values associated with acid-tolerant catabolism and with ATP synthase activity." FEMS Microbiol Lett. 2006 Sep;262(1):93-98
Sheng J, Nguyen PT, Baldeck JD, Olsson J, Marquis RE "Antimicrobial actions of benzimidazoles against the oral anaerobes Fusobacterium nucleatum and Prevotella intermedia." Arch Oral Biol. 2006 Jun 23
Koo H, Sheng J, Nguyen PT, Marquis RE. "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. 2006 Jan;254(1):134-40.
Barboza-Silva E, Castro AC, Marquis RE. "Mechanisms of inhibition by fluoride of urease activities of cell suspensions and biofilms of Staphylococcus epidermidis, Streptococcus salivarius, Actinomyces naeslundii and of dental plaque." Oral Microbiol Immunol. 2005 Dec;20(6):323-32.
Duarte, S., P. L. Rosalen, et al. "The influence of a novel propolis on mutans streptococci biofilms and caries development in rats." Arch Oral Biol. 2005.
Nguyen, P. T., J. D. Baldeck, et al. "Antimicrobial actions of benzimidazoles against oral streptococci." Oral Microbiol Immunol 20(2): 93-100, 2005.
Sheng, J., P. T. Nguyen, et al. "Multi-target antimicrobial actions of zinc against oral anaerobes." Arch Oral Biol 50(8): 747-57, 2005.
Marquis, R. E. "Applied and ecological aspects of oxidative-stress damage to bacterial spores and to oral microbes." Sci Prog 87(Pt 3): 153-77. 2004
Phan TN, Buckner T, Sheng J, Baldeck JD, Marquis RE. Physiologic actions of zinc related to inhibition of acid and alkali production by oral streptococci in suspensions and biofilms. Oral Microbiol Immunol. 19:31-8, 2004.