Koch A L, Woeste S
Department of Biology, Indiana University, Bloomington 47405.
J Bacteriol. 1992 Jul;174(14):4811-9. doi: 10.1128/jb.174.14.4811-4819.1992.
Preparations of purified peptidoglycan of Escherichia coli (i.e., sacculi) were studied by low-angle laser light scattering. Control experiments and theoretical calculations based on the Rayleigh-Gans theory showed that the mean sacculus surface area could be accurately inferred from measurements with our apparatus by using computer routines developed previously. Large changes in the mean saccular surface area resulted from alterations in the stress caused by varying the net charge on the sacculi. The net charge was affected by altering the suspending medium pH, causing carboxyl and amino groups in the peptidoglycan to gain or lose protons, or by acetylation or succinylation of the amino groups. A preponderance of either plus or minus charges caused an expansion of the mean sacculus surface area. The largest increase in area probably represents the elastic limit of the peptidoglycan and was 300% above the area of isoionic sacculi. This degree of expansion is consistent with possible conformations of the intact peptidoglycan structure without necessitating rupture of the wall fabric. Our findings concerning saccular elasticity provide support for the surface stress theory. It provides a mechanism so that bacteria can grow and divide while maintaining turgor pressure, without the necessity of having and using proteins to do the mechanical work.
利用低角度激光光散射对大肠杆菌纯化肽聚糖制剂（即细胞壁）进行了研究。对照实验以及基于瑞利 - 甘斯理论的理论计算表明，通过使用先前开发的计算机程序，利用我们的仪器测量可以准确推断出平均细胞壁表面积。平均细胞壁表面积的巨大变化是由改变细胞壁净电荷所引起的应力变化导致的。净电荷受以下因素影响：改变悬浮介质的pH值，使肽聚糖中的羧基和氨基获得或失去质子；或者通过氨基的乙酰化或琥珀酰化。正电荷或负电荷的优势都会导致平均细胞壁表面积的扩大。面积的最大增加可能代表肽聚糖的弹性极限，比等离子强度细胞壁的面积高出300%。这种膨胀程度与完整肽聚糖结构的可能构象一致，而无需细胞壁结构破裂。我们关于细胞壁弹性的研究结果为表面应力理论提供了支持。它提供了一种机制，使细菌能够在维持膨压的同时生长和分裂，而无需拥有和使用蛋白质来完成机械工作。
