Liu Yaling, Hu Tao, Jiang Dan, Zhang Jingyi, Zhou Xuedong
FEMS Microbiol Lett. 2008 Jan;278(2):157-63. doi: 10.1111/j.1574-6968.2007.00959.x. Epub 2007 Nov 21.
The metabolism of urea by urease enzymes of oral bacteria has a profound influence on oral biofilm pH homeostasis and oral microbial ecology, and Actinomyces naeslundii is an important ureolytic organism in the oral cavity. To gain an insight into the regulation of urease gene expression in cells of A. naeslundii growing in biofilms under different environmental conditions, the behavior of A. naeslundii ATCC12104 was examined in in vitro biofilms. The strain was grown in a chemostat biofilm reactor, and at a quasi-steady state, the urease activity of biofilm cells was measured and transcription of ureC gene was detected with Taqman quantitative PCR. The effect of environmental changes on urease expression was examined by varying the environmental pH, dilution rate, carbohydrate and nitrogen availability of the fluid phase of the culture. The results showed that the conditions of neutral pH, fast dilution rate, increased carbohydrate supply or low nitrogen supply in the medium all resulted in enhancement of urease activity in biofilm cells. But only low nitrogen availability and a fast dilution rate were observed to lead to an increase in ureC mRNA levels. This suggests that nitrogen availability and dilution rate can influence the urease activity of A. naeslundii by modulating ureC gene transcription.
口腔细菌脲酶对尿素的代谢对口腔生物膜pH稳态和口腔微生物生态具有深远影响，内氏放线菌是口腔中一种重要的尿素分解菌。为深入了解在不同环境条件下生长于生物膜中的内氏放线菌细胞中脲酶基因表达的调控情况，对体外生物膜中的内氏放线菌ATCC12104的行为进行了研究。该菌株在恒化器生物膜反应器中培养，在准稳态下，测定生物膜细胞的脲酶活性，并用Taqman定量PCR检测ureC基因的转录情况。通过改变培养液相的环境pH、稀释率、碳水化合物和氮的可利用性，研究环境变化对脲酶表达的影响。结果表明，中性pH、快速稀释率、增加培养基中碳水化合物供应或低氮供应条件均导致生物膜细胞中脲酶活性增强。但仅观察到低氮可利用性和快速稀释率会导致ureC mRNA水平升高。这表明氮的可利用性和稀释率可通过调节ureC基因转录来影响内氏放线菌的脲酶活性。
