Chopp D L, Kirisits M J, Moran B, Parsek M R
Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208-3125, USA.
Bull Math Biol. 2003 Nov;65(6):1053-79. doi: 10.1016/S0092-8240(03)00057-0.
In a process called quorum sensing, bacteria monitor their population density via extracellular signaling molecules and modulate gene expression accordingly. In this paper, a one-dimensional model of a growing Pseudomonas aeruginosa biofilm is examined. Quorum sensing has been included in the model through equations describing the production, degradation, and diffusion of the signaling molecules, acyl-homoserine lactones, in the biofilm. From this model, we are able to make some important observations about quorum sensing. First, in order for quorum sensing to initiate near the substratum, in accordance with experimental observations, the model suggests that cells in oxygen-deficient regions of the biofilm must still be synthesizing the signal compound. Second, the induction of quorum sensing is related to a critical biofilm depth; once the biofilm grows to the critical depth, quorum sensing is induced. Third, the critical biofilm depth varies with the pH of the surrounding fluid. Of particular interest is the prediction of a critical pH threshold, above which quorum sensing is not possible at any depth. These results highlight the importance of careful study of the relationship among metabolic activity of the bacterium, signal synthesis, and the chemistry of the surrounding environment.
在一种称为群体感应的过程中，细菌通过细胞外信号分子监测其种群密度，并相应地调节基因表达。在本文中，研究了一个生长中的铜绿假单胞菌生物膜的一维模型。通过描述生物膜中信号分子酰基高丝氨酸内酯的产生、降解和扩散的方程，群体感应已被纳入该模型。从这个模型中，我们能够对群体感应做出一些重要的观察。首先，为了使群体感应在靠近基质处启动，根据实验观察，该模型表明生物膜缺氧区域的细胞仍必须合成信号化合物。其次，群体感应的诱导与一个关键的生物膜深度有关；一旦生物膜生长到关键深度，群体感应就会被诱导。第三，关键的生物膜深度随周围流体的pH值而变化。特别值得关注的是对一个关键pH阈值的预测，高于该阈值，在任何深度都不可能发生群体感应。这些结果突出了仔细研究细菌代谢活性、信号合成和周围环境化学之间关系的重要性。
