title: Streptococcus oligofermentans Inhibits Streptococcus mutans in Biofilms at Both Neutral pH and Cariogenic Conditions.
abstract: Homeostasis of oral microbiota can be maintained through microbial interactions. Previous studies showed that Streptococcus oligofermentans, a non-mutans streptococci frequently isolated from caries-free subjects, inhibited the cariogenic Streptococcus mutans by the production of hydrogen peroxide (HP). Since pH is a critical factor in caries formation, we aimed to study the influence of pH on the competition between S. oligofermentans and S. mutans in biofilms. To this end, S. mutans and S. oligofermentans were inoculated alone or mixed at 1:1 ratio in buffered biofilm medium in a 96-well active attachment model. The single- and dual-species biofilms were grown under either constantly neutral pH or pH-cycling conditions. The latter includes two cycles of 8 h neutral pH and 16 h pH 5.5, used to mimic cariogenic condition. The 48 h biofilms were analysed for the viable cell counts, lactate and HP production. The last two measurements were carried out after incubating the 48 h biofilms in buffers supplemented with 1% glucose (pH 7.0) for 4 h. The results showed that S. oligofermentans inhibited the growth of S. mutans in dual-species biofilms under both tested pH conditions. The lactic acid production of dual-species biofilms was significantly lower than that of single-species S. mutans biofilms. Moreover, dual-species and single-species S. oligofermentans biofilms grown under pH-cycling conditions (with a 16 h low pH period) produced a significantly higher amount of HP than those grown under constantly neutral pH. In conclusion, S. oligofermentans inhibited S. mutans in biofilms not only under neutral pH, but also under pH-cycling conditions, likely through HP production. S. oligofermentans may be a compelling probiotic candidate against caries.
authors.affiliation: Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology, Beijing, China; Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Xudong
authors.initials: X
authors.lastname: Bao
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Johannes Jacob
authors.initials: JJ
authors.lastname: de Soet
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Huichun
authors.initials: H
authors.lastname: Tong
authors.affiliation: Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology, Beijing, China.
authors.forename: Xuejun
authors.initials: X
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Libang
authors.initials: L
authors.lastname: He
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Cor
authors.initials: C
authors.lastname: van Loveren
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Dong Mei
authors.initials: DM
authors.lastname: Deng
mesh_terms: D018441:Biofilms / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D013291:Streptococcus / Q000378:metabolism; D013295:Streptococcus mutans / Q000187:drug effects*
chemical_list: D006861:Hydrogen Peroxide