Cell-Biological Studies of Osmotic Shock Response in Streptomyces spp.
Cell-Biological Studies of Osmotic Shock Response in Streptomyces spp.
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DOI：
10.1128/jb.00465-16
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发表时间：
2017-01-01
影响因子：
3.2
通讯作者：
Ausmees, Nora
中科院分区：
文献类型：
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作者：
Fuchino, Katsuya;Flardh, Klas;Ausmees, Nora
大多数细菌都可能面临渗透性的挑战，但关于这种环境变化如何影响细菌细胞的结构，还有很多东西需要了解。在这里，我们报告的模式生物链霉菌属，这是放线菌生长在一个高度极化的方式，形成分支菌丝的细胞生物学研究。链霉菌菌丝的特征性顶端生长是由蛋白质组装体（称为极化体，polarisomes）协调的，所述蛋白质组装体包含卷曲螺旋蛋白DivIVA和Scy，并将细胞壁合成复合物和FilP的应力承受细胞骨架募集到菌丝的顶端区域。我们监测细胞的生长和细胞结构的变化，通过延时显微镜在渗透上调实验。高渗休克引起生长停滞、膨压丧失和染色体高度浓缩。恢复期延长，可能是由于细胞质的脱水状态，菌丝才能恢复肿胀并开始再次生长。在大多数菌丝中，这种再生长并不发生在原来的菌丝顶端。相反，细胞极性被重新编程，极性体被重新分配到新的位置，导致出现多个侧枝，从中生长。已知调节链霉菌菌丝分支模式的因子，如丝氨酸/苏氨酸激酶AfsK和Scy，不参与细胞极性的重编程，表明不同的机制可能在不同的环境条件下起作用以控制菌丝分支。我们的观察菌丝形态在应力响应表明，膨压和足够的水化的细胞质是所需的链霉菌尖端growth.IMPORTANCE极性增长是一个复杂的增长方式，为实现一个复杂的形态，广泛的生物界的生命。链霉菌菌丝的顶端延伸是细菌中极性生长的最明显的例子之一。膨胀的细胞壁的顶端延伸被认为是由膨压促进，但它是未知的外部渗透变化如何影响链霉菌尖端生长。我们在这里报告说，严重的高渗胁迫导致停止生长，随后通过细胞极性的重新编程和生长区的重排，以促进侧菌丝分支。这一现象可能是菌丝生物避免生长中菌丝顶端所遇到的渗透胁迫的一种策略。
Most bacteria are likely to face osmotic challenges, but there is yet much to learn about how such environmental changes affect the architecture of bacterial cells. Here, we report a cell-biological study in model organisms of the genus Streptomyces, which are actinobacteria that grow in a highly polarized fashion to form branching hyphae. The characteristic apical growth of Streptomyces hyphae is orchestrated by protein assemblies, called polarisomes, which contain coiled-coil proteins DivIVA and Scy, and recruit cell wall synthesis complexes and the stres-sbearing cytoskeleton of FilP to the tip regions of the hyphae. We monitored cell growth and cell-architectural changes by time-lapse microscopy in osmotic upshift experiments. Hyperosmotic shock caused arrest of growth, loss of turgor, and hyper-condensation of chromosomes. The recovery period was protracted, presumably due to the dehydrated state of the cytoplasm, before hyphae could restore their turgor and start to grow again. In most hyphae, this regrowth did not take place at the original hyphal tips. Instead, cell polarity was reprogrammed, and polarisomes were redistributed to new sites, leading to the emergence of multiple lateral branches from which growth occurred. Factors known to regulate the branching pattern of Streptomyces hyphae, such as the serine/threonine kinase AfsK and Scy, were not involved in reprogramming of cell polarity, indicating that different mechanisms may act under different environmental conditions to control hyphal branching. Our observations of hyphal morphology during the stress response indicate that turgor and sufficient hydration of cytoplasm are required for Streptomyces tip growth.IMPORTANCE Polar growth is an intricate manner of growth for accomplishing a complicated morphology, employed by a wide range of organisms across the kingdoms of life. The tip extension of Streptomyces hyphae is one of the most pronounced examples of polar growth among bacteria. The expansion of the cell wall by tip extension is thought to be facilitated by the turgor pressure, but it was unknown how external osmotic change influences Streptomyces tip growth. We report here that severe hyperosmotic stress causes cessation of growth, followed by reprogramming of cell polarity and rearrangement of growth zones to promote lateral hyphal branching. This phenomenon may represent a strategy of hyphal organisms to avoid osmotic stress encountered by the growing hyphal tip.