Grover N B, Eidelstein E, Koppes L J H
Hubert H. Humphrey Center for Experimental Medicine and Cancer Research, The Hebrew University Faculty of Medicine, PO Box 12272, Jerusalem 91120, Israel.
J Theor Biol. 2004 Apr 21;227(4):547-59. doi: 10.1016/j.jtbi.2003.11.028.
In this article, we examine a large number of combinations of growth models, with separate attention to cell volume, cylindrical surface-area, polar caps, nascent poles, onset of constriction, precision of cell division and interdivision-time dispersion, for Escherichia coli cells growing in steady state at various doubling times. Our main conclusion is striking, and quite general: exponential cylindrical surface-area growth is not possible, irrespective of the behaviour of cell volume, the polar regions, the nascent poles, or any other feature of cell growth-such cells never reach steady state. The same is true of linear cylindrical surface-area growth, regardless of when during the cell cycle the doubling in growth rate takes place. Only after the introduction of feedback into the surface-area growth law, do the cultures attain steady state, all of them. The other components of the models contribute only marginally to the properties of the steady state. Thus, whether the feedback applies just to the cylindrical portion of the cell or to its entire surface area affects only the coefficient of variation of cell radius and the radius-volume correlation. The dynamics of old-pole maintenance, constant area or constant shape, influences the radius-length and radius-volume correlations and, to a much lesser extent, the coefficients of variation of cell radius and length; how the nascent poles grow, whether linearly or exponentially, does not seem to matter at all. The absolute dimensions of the cells are set by the growth rate of the culture and have almost no effect when the feedback is taken to apply to the entire cell surface area; when it is limited to the cylindrical portion of the cell, however, both radius-length and radius-volume correlations increase with increasing doubling time. Comparison with published values was inconclusive. The nature of cell surface-area growth has therefore been settled, but whether the volume increases by simple-exponential or by pseudo-exponential growth, or whether the old poles maintain a constant shape or a constant area during the cell cycle, can be determined only with more precise experimental data. The form of nascent-pole growth is not resolvable by present techniques.
在本文中，我们研究了大量生长模型的组合，分别关注了处于不同倍增时间下稳态生长的大肠杆菌细胞的细胞体积、圆柱表面积、极帽、新生极、缢缩起始、细胞分裂精度和分裂间期离散度。我们的主要结论引人注目且相当普遍：无论细胞体积、极区、新生极或细胞生长的任何其他特征如何，指数形式的圆柱表面积生长都是不可能的——这样的细胞永远不会达到稳态。线性圆柱表面积生长也是如此，无论生长速率的倍增发生在细胞周期的何时。只有在将反馈引入表面积生长规律后，培养物才能达到稳态，所有培养物均是如此。模型的其他组成部分对稳态性质的贡献很小。因此，反馈是仅应用于细胞的圆柱部分还是整个表面积，仅影响细胞半径的变异系数和半径 - 体积相关性。旧极维持的动态过程，即恒定面积或恒定形状，会影响半径 - 长度和半径 - 体积相关性，并且在较小程度上影响细胞半径和长度的变异系数；新生极是线性生长还是指数生长似乎根本无关紧要。细胞的绝对尺寸由培养物的生长速率设定，当反馈应用于整个细胞表面积时几乎没有影响；然而，当反馈仅限于细胞的圆柱部分时，半径 - 长度和半径 - 体积相关性都会随着倍增时间的增加而增加。与已发表值的比较尚无定论。因此，细胞表面积生长的性质已经确定，但细胞体积是通过简单指数生长还是伪指数生长增加，或者旧极在细胞周期中是保持恒定形状还是恒定面积，只能通过更精确的实验数据来确定。目前的技术无法分辨新生极生长的形式。
