title: Characterization of the Actinomyces naeslundii ureolysis and its role in bacterial aciduricity and capacity to modulate pH homeostasis.
abstract: Ammonia production from urea by ureolytic oral bacteria is believed to have a significant impact on oral health and ecological balance of oral microbial populations. Actinomyces naeslundii is an important ureolytic organism in the oral cavity. In this study, we aimed to investigate the substrate affinity and pH optimum for ureolysis of A. naeslundii (ATCC12104), and expression of urease under different environmental factors. In addition, in vitro acid killing and pH drop experiments were used to detect the role of ureolysis in bacterial aciduricity and capacity to modulate pH homeostasis. We observed the K(s) value of the ureolytic activity was 7.5mM and a pH optimum near 6.5. Urease expression by A. naeslundii (ATCC12104) was affected by multiple factors, including environmental pH, glucose and nitrogen availability. The cells could be protected against acid killing through hydrolysis of physiologically relevant concentrations of urea. A. naeslundii (ATCC12104) demonstrated a significant capacity to temper glycolytic acidification in vitro at urea concentrations normally found in the oral cavity.
authors.affiliation: Key Laboratory for Oral Biomedical Engineering Ministry of Education, Chengdu City, PR China.
authors.forename: Yaling
authors.initials: Y
authors.lastname: Liu
authors.forename: Liu
authors.initials: L
authors.lastname: Yaling
authors.forename: Tao
authors.initials: T
authors.lastname: Hu
authors.forename: Hu
authors.initials: H
authors.lastname: Tao
authors.forename: Jingyi
authors.initials: J
authors.lastname: Zhang
authors.forename: Zhang
authors.initials: Z
authors.lastname: Jingyi
authors.forename: Xuedong
authors.initials: X
authors.lastname: Zhou
authors.forename: Zhou
authors.initials: Z
authors.lastname: Xuedong
mesh_terms: D000190:Actinomyces / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic; D006706:Homeostasis / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D014158:Transcription, Genetic; D014510:Urease / Q000235:genetics / Q000502:physiology*
chemical_list: D014510:Urease