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首页> 外文期刊>Journal of bacteriology >Alterations in peptidoglycan chemical composition associated with rod-to-sphere transition in a conditional mutant of Klebsiella pneumoniae.
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Alterations in peptidoglycan chemical composition associated with rod-to-sphere transition in a conditional mutant of Klebsiella pneumoniae.

机译：在肺炎克雷伯菌的条件突变体中，与杆-球过渡有关的肽聚糖化学组成的变化。

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Klebsiella pneumoniae Mir M7 is a spontaneous parentless morphology mutant which grows as cocci at pH 7 and as rods at pH 5.8. This strain has been characterized as defective in lateral wall formation (at pH7). Data suggest that the cell wall is mainly made up of poles of the rods (G. Satta, R. Fontana, P. Canepari, and G. Botta, J. Bacteriol. 137:727--734, 1979). In this work the isolation and the biochemical properties of the peptidoglycan of both Mir M7 rods and cocci and a nonconditional rod-shaped Mir M7 revertant (strain Mir A12) are described. The peptidoglycan of Mir M7 (both rods and cocci) and Mir A12 strains carried covalently bound proteins which could be easily removed by pronase treatment in Mir M7 rods and Mir A12 cells, but not in Mir M7 round cells. However, when the sodium dodecyl sulfate-insoluble residues of Mir M7 cocci were pretreated with ethylenediaminetetraacetic acid (EDTA), pronase digestion removed the covalently bound proteins, and pure peptidoglycan was obtained. EDTA treatment of the rigid layer of Mir M7 cocci removed amounts of Mg2+ and Ca2+, which were 10- and 50-fold higher, respectively, than the amount liberated from the rigid layer of Mir M7 rods and Mir A12 cells. Amino acid composition was qualitatively similar in both strains, but Mir M7 cocci contained a higher amount of alanine and glucosamine. Mir M7 cocci contained approximately 50% less peptidoglycan than rods. Under electron microscopy, the rigid layer of the Mir M7 rods and Mir A12 cells appeared to be rod-shaped and their shape remained unchanged after EDTA and pronase treatment. On the contrary, the Mir M7 cocci rigid layer appeared to be round, and after EDTA treatment it collapsed and lost any definite morphology. In spite of these alterations, the peptidoglycan of Mir M7 cocci still appeared able to determine the shape of the cell and protect it from osmotic shock and mechanical damages. The accumluation of divalent cations appeared necessary for the peptidoglycan to acquire sufficient rigidity for shape determination and cell protection. We concluded that the coccal shape in Mir M7 cells is not due to loss of cell wall rigidity but is a consequence of the formation of a round peptidoglycan molecule. The possibility that the alterations found in the Mir M7 cocci rigid layer may reflect natural differences in the biochemical composition of the septa and lateral wall of normally shaped bacteria is discussed.
机译：肺炎克雷伯氏菌Mir M7是一种自发的无父母形态突变体，在pH 7时呈球菌生长，在pH 5.8时呈杆状生长。该菌株的特征是侧壁形成缺陷（在pH7下）。数据表明，细胞壁主要由杆的两极组成（G.Satta，R.Fontana，P.Canepari和G.Botta，J.Bacteriol.137：727--734，1979）。在这项工作中，描述了Mir M7杆和球菌和无条件杆状Mir M7还原剂（Mir A12菌株）的肽聚糖的分离和生化特性。 Mir M7的肽聚糖（杆和球菌）和Mir A12菌株均带有共价结合的蛋白，可以通过链霉蛋白酶处理在Mir M7杆和Mir A12细胞中容易地去除它们，但在Mir M7圆形细胞中则不能。然而，当用乙二胺四乙酸（EDTA）预处理Mir M7球菌的十二烷基硫酸钠不溶性残基时，链霉蛋白酶消化去除了共价结合的蛋白质，从而获得了纯的肽聚糖。 EDTA处理的Mir M7球菌的刚性层去除了Mg2 +和Ca2 +的量，分别比从Mir M7棒和Mir A12细胞的刚性层释放的量高10倍和50倍。两种菌株的氨基酸组成在质量上相似，但Mir M7球菌含有更高含量的丙氨酸和葡糖胺。 Mir M7球菌所含肽聚糖比棒状糖少约50％。在电子显微镜下，Mir M7杆和Mir A12细胞的刚性层似乎呈棒状，并且在EDTA和链霉蛋白酶处理后其形状保持不变。相反，Mir M7球菌刚性层似乎是圆形的，在EDTA处理后，它塌陷并失去了任何确定的形态。尽管有这些改变，但Mir M7球菌的肽聚糖仍然能够确定细胞的形状并保护其免受渗透压和机械损伤。二价阳离子的积累似乎是肽聚糖获得足够的刚度以进行形状确定和细胞保护所必需的。我们得出的结论是，Mir M7细胞中的球菌形状不是由于细胞壁刚性的丧失，而是圆形肽聚糖分子形成的结果。讨论了在Mir M7球菌硬质层中发现的变化可能反映正常形状细菌的隔膜和侧壁的生化成分中自然差异的可能性。

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