Chemical Engineering Department, University Politehnica of Bucharest, 011061 Polizu 1-7, Bucharest, Romania.
J Theor Biol. 2010 May 7;264(1):45-54. doi: 10.1016/j.jtbi.2010.01.020. Epub 2010 Jan 25.
A new model is presented that describes microbial population dynamics that emerge from complex interactions among birth, growth and death as oriented, discrete events. Specifically, birth and death act as structuring operators for individual organisms within the population, which become synchronised as age clusters (called cell generations that are structured in age classes) that are born at the same time and die in concert; a pattern very consistent with recent experimental data that show bacterial group death correlates with temporal population dynamics in chemostats operating at carrying capacity. Although the model only assumes "natural death" (i.e., no death from predation or antimicrobial exposure), it indicates that short-term non-linear dynamic behaviour can exist in a bacterial population growing under longer term pseudo-steady-state conditions (a confined dynamic equilibrium). After summarizing traditional assumptions about bacterial aging, simulations of batch, continuous-flow, and bioreactors with recycle are used to show how population dynamics vary as function of hydraulic retention time, microbial kinetics, substrate level, and other factors that cause differential changes in the distribution of living and dead cells within the system. In summary, we show that population structures induced by birth and death (as discrete and delayed events) intrinsically create a non-linear dynamic system, implying that a true steady state can never exist in growing bacterial populations. This conclusion is discussed within the context of process stability in biotechnology.
提出了一个新模型，用于描述由出生、生长和死亡等定向离散事件之间的复杂相互作用所产生的微生物种群动态。具体而言，出生和死亡作为种群中个体生物的结构操作算子，当它们同时出生并协调死亡时，会形成同步的年龄簇（称为细胞世代，它们按年龄分类结构）；这种模式与最近的实验数据非常吻合，实验表明细菌群体死亡与恒化器中在承载能力下运行的种群动态相关。尽管该模型仅假设“自然死亡”（即，没有捕食或抗微生物暴露引起的死亡），但它表明在长期假稳态条件下（受限动态平衡）生长的细菌种群中可能存在短期非线性动态行为。在总结了关于细菌老化的传统假设之后，使用批处理、连续流动和带有循环的生物反应器的模拟来展示种群动态如何随水力停留时间、微生物动力学、基质水平以及其他导致系统内活细胞和死细胞分布差异变化的因素而变化。总之，我们表明，出生和死亡（作为离散和延迟事件）引起的种群结构内在地创建了一个非线性动态系统，这意味着在生长的细菌种群中永远不可能存在真正的稳态。这一结论在生物技术中的过程稳定性背景下进行了讨论。
