Interfakultäres Institut für Mikrobiologie und Infektionsmedizin Tübingen IMIT, Mikrobiologie/Biotechnologie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Deutschland.
Mol Microbiol. 2011 Mar;79(5):1367-79. doi: 10.1111/j.1365-2958.2010.07529.x. Epub 2011 Jan 18.
It is still an open question how an intracellular cytoskeleton directs the synthesis of the peptidoglycan exoskeleton. In contrast to MreB of rod-shaped bacteria, which is essential for lateral cell wall synthesis, MreB of Streptomyces coelicolor has a role in sporulation. To study the function of the S. coelicolor mre gene cluster consisting of mreB, mreC, mreD, pbp2 and sfr, we generated non-polar replacement mutants. The individual mutants were viable and growth of substrate mycelium was not affected. However, all mutants produced enlarged spores, which frequently germinated prematurely and were sensitive to heat, high osmolarity and cell wall damaging agents. Protein-protein interaction assays by bacterial two-hybrid analyses indicated that the S. coelicolor Mre proteins form a spore wall synthesizing complex, which closely resembles the lateral wall synthesizing complex of rod-shaped bacteria. Screening of a genomic library identified several novel putative components of this complex. One of them (sco2097) was deleted. The Δsco2097 mutant formed sensitive spores with an aberrant morphology, demonstrating that SCO2097 is a new player in cell morphogenesis of Streptomyces. Our results suggest that all Mre proteins cooperate with the newly identified proteins in the synthesis of the thickened spore wall required to resist detrimental environmental conditions.
细胞内细胞骨架如何指导肽聚糖外壳的合成仍是一个悬而未决的问题。与杆状细菌的必需蛋白 MreB 不同，后者是侧向细胞壁合成所必需的，链霉菌 MreB 在孢子形成中起作用。为了研究由 mreB、mreC、mreD、pbp2 和 sfr 组成的 S. coelicolor mre 基因簇的功能，我们生成了非极性替换突变体。单个突变体是有活力的，基质菌丝的生长不受影响。然而，所有突变体产生的孢子都增大了，这些孢子经常过早萌发，对热、高渗透压和细胞壁损伤剂敏感。通过细菌双杂交分析的蛋白质-蛋白质相互作用试验表明，链霉菌的 Mre 蛋白形成一个孢子壁合成复合物，与杆状细菌的侧向壁合成复合物非常相似。基因组文库的筛选鉴定出了这个复合物的几个新的假定成分。其中之一（sco2097）被删除。Δsco2097 突变体形成的孢子敏感，形态异常，表明 SCO2097 是链霉菌细胞形态发生的新参与者。我们的结果表明，所有的 Mre 蛋白都与新鉴定的蛋白合作，合成抵抗有害环境条件所需的增厚的孢子壁。
