Molecular Biotechnology, Institute of Biology, Leiden University, Leiden, The Netherlands.
Division of Analytical Biosciences, Leiden Academic Center for Drug Research, Leiden University, Leiden, The Netherlands.
J Bacteriol. 2018 Sep 24;200(20). doi: 10.1128/JB.00290-18. Print 2018 Oct 15.
The bacterial cell wall maintains cell shape and protects against bursting by turgor. A major constituent of the cell wall is peptidoglycan (PG), which is continuously modified to enable cell growth and differentiation through the concerted activity of biosynthetic and hydrolytic enzymes. Streptomycetes are Gram-positive bacteria with a complex multicellular life style alternating between mycelial growth and the formation of reproductive spores. This involves cell wall remodeling at apical sites of the hyphae during cell elongation and autolytic degradation of the vegetative mycelium during the onset of development and antibiotic production. Here, we show that there are distinct differences in the cross-linking and maturation of the PGs between exponentially growing vegetative hyphae and the aerial hyphae that undergo sporulation. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis identified over 80 different muropeptides, revealing that major PG hydrolysis takes place over the course of mycelial growth. Half of the dimers lacked one of the disaccharide units in transition-phase cells, most likely due to autolytic activity. The deacetylation of MurNAc to MurN was particularly pronounced in spores and strongly reduced in sporulation mutants with a deletion of or , suggesting that MurN is developmentally regulated. Altogether, our work highlights the dynamic and growth phase-dependent changes in the composition of the PG in Streptomycetes are bacteria with a complex lifestyle and are model organisms for bacterial multicellularity. From a single spore, a large multigenomic multicellular mycelium is formed, which differentiates to form spores. Programmed cell death is an important event during the onset of morphological differentiation. In this work, we provide new insights into the changes in the peptidoglycan composition and over time, highlighting changes over the course of development and between growing mycelia and spores. This revealed dynamic changes in the peptidoglycan when the mycelia aged, with extensive peptidoglycan hydrolysis and, in particular, an increase in the proportion of 3-3 cross-links. Additionally, we identified a muropeptide that accumulates predominantly in the spores and may provide clues toward spore development.
细菌细胞壁维持细胞形状并防止因膨胀而破裂。细胞壁的主要成分是肽聚糖 (PG)，它通过生物合成和水解酶的协同作用不断修饰，以促进细胞生长和分化。链霉菌是革兰氏阳性细菌，具有复杂的多细胞生活方式，在菌丝生长和生殖孢子形成之间交替。这涉及到菌丝伸长过程中顶端部位细胞壁的重塑，以及发育和抗生素产生开始时营养菌丝的自溶降解。在这里，我们表明，在指数生长期的营养菌丝和进行孢子形成的气生菌丝之间，PG 的交联和成熟存在明显差异。液相色谱-串联质谱 (LC-MS/MS) 分析鉴定了 80 多种不同的肽聚糖，表明主要的 PG 水解发生在菌丝生长过程中。有一半的二聚体在过渡阶段的细胞中缺少一个二糖单元，这很可能是由于自溶活性。MurNAc 脱乙酰化为 MurN 在孢子中尤为明显，在缺失 或 的孢子形成突变体中强烈减少，表明 MurN 是发育调控的。总的来说，我们的工作强调了 PG 组成在链霉菌中的动态变化和生长阶段依赖性。链霉菌是一种生活方式复杂的细菌，是细菌多细胞性的模式生物。从一个单一的孢子开始，形成一个大的多基因组多细胞菌丝体，然后分化形成孢子。程序性细胞死亡是形态分化开始时的一个重要事件。在这项工作中，我们提供了关于肽聚糖组成变化的新见解，随着时间的推移，突出了发育过程中的变化以及生长菌丝和孢子之间的变化。这揭示了随着菌丝老化，肽聚糖发生动态变化，肽聚糖水解广泛，特别是 3-3 交联比例增加。此外，我们还鉴定了一种主要在孢子中积累的肽聚糖，可能为孢子发育提供线索。
