A Study On The Ureolysis In Dental Biofilms And Urease Gene Expression

Urea are secreted from saliva and gingival crevicular fluid continuously and rapidly broken down by urease enzymes of oral microflora to ammonia and carbonhydrate. Alkali production from ureolysis could neutralize acid end products to stabilize pH homotasis in dental biofilms, so be helpful to stabilize microflora balance, inhibit enamel demineralization and promote mineral deposition. Thus, ureolysis is considered to be an important factor to prevent dental caries. High level of specific urease activity was detected in dental plaque, but understanding of the molecular characteristics of the urease enzymes of oral bacteria and the critical role that ureolysis play in ecological balance of dental biofilms are very limited. In this study, firsty, we concentrated on the examination of ureolytic bacteria in dental biofilms and compare the biochemical characteristics of the enzyme from different strains. Based on the result of the first part, we took Actinomyces neaslundii as research objective to study the physiological characteristics of ureolysis and effects of envirometal factors and growth state on the urease expression. Methods Continuous culture chemostat system was used to establish a nono-specie biofilms of A. neaslundii to study the effect of enviromental factors on the urease gene expression. In this part, biochemical methods and Real-time PCR techniques were used to detect the urease specific activity and urease mRNA levels as a function of pH, dilution rate, carbohydrate and nitrogen availability in fluid phase of culture medium. At the same time, the...