Gally D, Bray K, Cooper S
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109-0620.
J Bacteriol. 1993 May;175(10):3121-30. doi: 10.1128/jb.175.10.3121-3130.1993.
A modified procedure for determining the pattern of peptidoglycan synthesis during the division cycle has allowed the measurement of the rate of side wall synthesis during the division cycle without the contribution due to pole formation. As predicted by a model proposing that the surface growth of the cell is regulated by mass increase, we find a decrease in side wall synthesis in the latter half of the division cycle. This supports the proposal that, upon invagination, pole growth accommodates a significant proportion of the increasing cell mass and that residual side wall growth occurs in response to the residual mass increase not accommodated by pole volume. The observed side wall synthesis patterns support the proposal that mass increase is a major, and possibly sole, regulator of bacterial surface increase. Membrane synthesis during the division cycle of the gram-negative, rod-shaped bacteria Escherichia coli and Salmonella typhimurium has also been measured with similar methods. The rate of membrane synthesis--measured by incorporation of radioactive glycerol or palmitate relative to simultaneous labeling with radioactive leucine--exhibits the same pattern as peptidoglycan synthesis. The results are compatible with a model of cell surface growth containing the following elements. (i) During the period of the division cycle prior to invagination, growth of the cell occurs predominantly in the side wall and the cell grows only in length. (ii) When invagination begins, pole growth accommodates some cytoplasmic increase, leading to a concomitant decrease in side wall synthesis. (iii) Surface synthesis increases relative to mass synthesis during the last part of the division cycle because of pole formation. It is proposed here that membrane synthesis passively follows the pattern of peptidoglycan synthesis during the division cycle.
一种用于确定分裂周期中肽聚糖合成模式的改良方法，能够测量分裂周期中侧壁合成的速率，而不包括极形成所带来的影响。正如一个提出细胞表面生长受质量增加调节的模型所预测的那样，我们发现在分裂周期的后半段侧壁合成减少。这支持了以下观点：内陷时，极生长容纳了相当一部分增加的细胞质量，而残余的侧壁生长是对极体积无法容纳的残余质量增加做出的反应。观察到的侧壁合成模式支持了质量增加是细菌表面增加的主要（可能也是唯一）调节因子这一观点。革兰氏阴性杆状细菌大肠杆菌和鼠伤寒沙门氏菌在分裂周期中的膜合成也用类似方法进行了测量。通过放射性甘油或棕榈酸的掺入相对于同时用放射性亮氨酸标记来测量的膜合成速率，呈现出与肽聚糖合成相同的模式。结果与包含以下要素的细胞表面生长模型相符。(i) 在分裂周期的内陷之前，细胞主要在侧壁生长，且细胞仅在长度上生长。(ii) 当内陷开始时，极生长容纳了一些细胞质的增加，导致侧壁合成随之减少。(iii) 由于极的形成，在分裂周期的最后阶段表面合成相对于质量合成增加。本文提出，在分裂周期中膜合成被动地遵循肽聚糖合成的模式。
