Growth Medium-Dependent Glycine Incorporation into the Peptidoglycan of Caulobacter crescentus
Growth Medium-Dependent Glycine Incorporation into the Peptidoglycan of Caulobacter crescentus
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DOI：
10.1371/journal.pone.0057579
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发表时间：
2013-02-28
期刊：
影响因子：
3.7
通讯作者：
Jacobs-Wagner, Christine
中科院分区：
文献类型：
--
作者：
Takacs, Constantin N.;Hocking, Jason;Jacobs-Wagner, Christine
肽聚糖（PG）是细菌细胞壁的大分子成分，可维持细胞的形状和完整性。与许多其他革兰氏阴性细菌不同，新月柄杆菌的 PG 已多次被证明含有大量的甘氨酸。这种成分的特殊性被认为是该物种的固有特征。通过高效液相色谱 (HPLC) 和质谱 (MS) 对 C. crescentus PG 进行全面的定性和定量分析，我们在此表明甘氨酸掺入 C. crescentus PG 取决于生长培养基中外源甘氨酸的存在。在复合实验室培养基 PYE 或单独补充酪蛋白氨基酸或甘氨酸的确定成分培养基 (M2G) 中生长的新月形细胞中分离出的 PG 肽侧链的第五个位置检测到高水平的甘氨酸。相反，当细胞在缺乏甘氨酸的 M2G 培养基中生长时，检测不到甘氨酸的掺入。值得注意的是，即使在低毫摩尔至亚毫摩尔浓度的游离甘氨酸存在的情况下，甘氨酸也会掺入新月杆菌肽聚糖中。 PG中的高甘氨酸含量对生长速率、PG掺入方式或细胞形态没有明显影响。因此，尽管其组成发生了显着变化，新月形藻 PG 仍能够保留其在细胞生长和形态发生中的生理功能，我们认为这是前所未有的可塑性。
The peptidoglycan (PG) is a macromolecular component of the bacterial cell wall that maintains the shape and integrity of the cell. The PG of Caulobacter crescentus, unlike that of many other Gram-negative bacteria, has repeatedly been shown to contain significant amounts of glycine. This compositional peculiarity has been deemed an intrinsic characteristic of this species. By performing a comprehensive qualitative and quantitative analysis of the C. crescentus PG by high-performance liquid chromatography (HPLC) and mass spectrometry (MS), we show here that glycine incorporation into the C. crescentus PG depends on the presence of exogenous glycine in the growth medium. High levels of glycine were detected at the fifth position of the peptide side chains of PG isolated from C. crescentus cells grown in the complex laboratory medium PYE or in defined medium (M2G) supplemented with casamino acids or glycine alone. In contrast, glycine incorporation was undetectable when cells were grown in M2G medium lacking glycine. Remarkably, glycine incorporation into C. crescentus peptidoglycan occurred even in the presence of low millimolar to sub-millimolar concentrations of free glycine. High glycine content in the PG had no obvious effects on growth rates, mode of PG incorporation or cell morphology. Hence, the C. crescentus PG is able to retain its physiological functions in cell growth and morphogenesis despite significant alterations in its composition, in what we deem to be unprecedented plasticity.