Pinette M F, Koch A L
Biology Department, Indiana University, Bloomington 47405.
J Bacteriol. 1987 Oct;169(10):4737-42. doi: 10.1128/jb.169.10.4737-4742.1987.
Cells of Ancylobacter aquaticus were observed under phase microscopy in a chamber to which a measured pressure could be applied. The initial collapse pressure (Ca), i.e., the lowest pressure needed to collapse the most pressure-sensitive gas vesicles, was measured for 69 cells. The cells were taken from cultures in low-density balanced exponential growth, and the experiments were performed quickly so that the bacteria were in a uniform physiological state at the time of measurement. The turgor pressure, Pt, is the difference between the pressure, C, that would cause collapse of vesicles when removed from the cell and Ca. In this paper we focus on the variability of Pt from cell to cell. Part of the observed variability of Ca was due to the variability of the collapse pressure of individual vesicles (standard deviation [SD] = 90 kPa), but because there were about 100 vesicles per cell and because a change in refracted light after the fifth vesicle (approximately) collapsed probably could be detected by the human eye, the pressure would only have an SD of 18.6 kPa due to this type of sampling error. The observed SD of Pt was 42 kPa, indicating that turgor pressure did vary considerably from cell to cell. However, the turgor pressure was independent of cell size. Statistical analysis showed that Pt would decrease 6.9 kPa over a cell cycle, but with too large an SD (19.9 kPa) to be significant. This implies that the observed change in Pt over the cell cycle is not statistically significant.
在一个可以施加测量压力的小室中，利用相差显微镜观察水生弯曲杆菌细胞。对69个细胞测量了初始塌陷压力（Ca），即塌陷最敏感气体囊泡所需的最低压力。细胞取自低密度平衡指数生长的培养物，并且实验进行得很快，以便在测量时细菌处于均匀的生理状态。膨压Pt是当从细胞中取出时会导致囊泡塌陷的压力C与Ca之间的差值。在本文中，我们关注细胞间Pt的变异性。观察到的Ca变异性部分归因于单个囊泡塌陷压力的变异性（标准差[SD]=90kPa），但由于每个细胞约有100个囊泡，并且由于在第五个囊泡（大约）塌陷后折射光的变化可能可以被人眼检测到，由于这种类型的采样误差，压力的标准差仅为18.6kPa。观察到的Pt标准差为42kPa，表明膨压在细胞间确实有很大差异。然而，膨压与细胞大小无关。统计分析表明，在一个细胞周期内Pt会降低6.9kPa，但标准差太大（19.9kPa）以至于不显著。这意味着在细胞周期内观察到的Pt变化在统计学上不显著。
