Payie K G, Rather P N, Clarke A J
Department of Microbiology, University of Guelph, Ontario, Canada.
J Bacteriol. 1995 Aug;177(15):4303-10. doi: 10.1128/jb.177.15.4303-4310.1995.
A collection of Providencia stuartii mutants which either underexpress or overexpress aac(2')-Ia, the chromosomal gene coding for gentamicin 2'-N-acetyltransferase (EC 2.3.1.59), have been characterized phenotypically as possessing either lower or higher levels of peptidoglycan O acetylation, respectively, than the wild type. These mutants were subjected to both negative-staining and thin-section electron microscopy. P. stuartii PR100, with 42% O acetylation of peptidoglycan compared with 52% O acetylation in the wild type, appeared as irregular rods. In direct contrast, P. stuartii strains PR50.LM3 and PR51, with increased levels of peptidoglycan O acetylation (65 and 63%, respectively), appeared as coccobacilli and chain formers, respectively. Membrane blebbing was also observed with the chain-forming strain PR51. Thin sectioning of this mutant indicated that it was capable of proper constriction and separation. P. stuartii PM1, when grown to mid-exponential phase, did not have altered peptidoglycan O-acetylation levels, and cellular morphology remained similar to that of wild-type strains. However, continued growth into stationary phase resulted in a 15% increase in peptidoglycan O acetylation concomitant with a change of some cells from a rod-shaped to a coccobacillus-shaped morphology. The fact that these apparent morphological changes were directly related to levels of O acetylation support the view that this modification plays a role in the maintenance of peptidoglycan structure, presumably through the control of autolytic activity.
斯氏普罗威登斯菌（Providencia stuartii）的一系列突变体，这些突变体对编码庆大霉素2'-N-乙酰基转移酶（EC 2.3.1.59）的染色体基因aac(2')-Ia的表达要么不足要么过度表达，经表型鉴定，与野生型相比，它们分别具有较低或较高水平的肽聚糖O-乙酰化。对这些突变体进行了负染色和超薄切片电子显微镜观察。斯氏普罗威登斯菌PR100的肽聚糖O-乙酰化率为42%，而野生型为52%，其形态呈不规则杆状。与之形成直接对比的是，肽聚糖O-乙酰化水平升高的斯氏普罗威登斯菌菌株PR50.LM3和PR51（分别为65%和63%），其形态分别为球杆菌状和链状。在形成链状的菌株PR51中还观察到了膜泡形成。对该突变体的超薄切片显示它能够正常缢缩和分离。斯氏普罗威登斯菌PM1在生长至指数中期时，肽聚糖O-乙酰化水平没有改变，细胞形态与野生型菌株相似。然而，持续生长至稳定期会导致肽聚糖O-乙酰化增加15%，同时一些细胞从杆状变为球杆菌状。这些明显的形态变化与O-乙酰化水平直接相关，这一事实支持了这样一种观点，即这种修饰在维持肽聚糖结构中起作用，大概是通过控制自溶活性来实现的。
