Zhou Xiaoxue, Halladin David K, Theriot Julie A
Department of Biochemistry, Stanford University School of Medicine, Stanford, California, USA.
Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA.
mBio. 2016 Aug 30;7(4):e00952-16. doi: 10.1128/mBio.00952-16.
Dividing cells of the coccoid Gram-positive bacterium Staphylococcus aureus undergo extremely rapid (millisecond) daughter cell separation (DCS) driven by mechanical crack propagation, a strategy that is very distinct from the gradual, enzymatically driven cell wall remodeling process that has been well described in several rod-shaped model bacteria. To determine if other bacteria, especially those in the same phylum (Firmicutes) or with similar coccoid shapes as S. aureus, might use a similar mechanically driven strategy for DCS, we used high-resolution video microscopy to examine cytokinesis in a phylogenetically wide range of species with various cell shapes and sizes. We found that fast mechanically driven DCS is rather rare in the Firmicutes (low G+C Gram positives), observed only in Staphylococcus and its closest coccoid relatives in the Macrococcus genus, and we did not observe this division strategy among the Gram-negative Proteobacteria In contrast, several members of the high-G+C Gram-positive phylum Actinobacteria (Micrococcus luteus, Brachybacterium faecium, Corynebacterium glutamicum, and Mycobacterium smegmatis) with diverse shapes ranging from coccoid to rod all undergo fast mechanical DCS during cell division. Most intriguingly, similar fast mechanical DCS was also observed during the sporulation of the actinobacterium Streptomyces venezuelae
Much of our knowledge on bacterial cytokinesis comes from studying rod-shaped model organisms such as Escherichia coli and Bacillus subtilis Less is known about variations in this process among different bacterial species. While cell division in many bacteria has been characterized to some extent genetically or biochemically, few species have been examined using video microscopy to uncover the kinetics of cytokinesis and daughter cell separation (DCS). In this work, we found that fast (millisecond) DCS is exhibited by species in two independent clades of Gram-positive bacteria and is particularly prevalent among the Actinobacteria, a diverse group that includes significant pathogens as well as bacteria that generate medically important antibiotics.
球形革兰氏阳性细菌金黄色葡萄球菌的分裂细胞通过机械裂纹扩展进行极快速（毫秒级）的子细胞分离（DCS），这一策略与几种杆状模式细菌中已充分描述的渐进性、酶促驱动的细胞壁重塑过程截然不同。为了确定其他细菌，尤其是那些与金黄色葡萄球菌属于同一门（厚壁菌门）或具有相似球形形状的细菌，是否可能使用类似的机械驱动策略进行DCS，我们使用高分辨率视频显微镜检查了系统发育范围广泛、具有各种细胞形状和大小的物种的胞质分裂。我们发现，快速机械驱动的DCS在厚壁菌门（低G+C革兰氏阳性菌）中相当罕见，仅在葡萄球菌及其在巨球菌属中最接近的球形亲缘菌中观察到，而在革兰氏阴性变形菌门中未观察到这种分裂策略。相反，高G+C革兰氏阳性放线菌门的几个成员（藤黄微球菌、粪短杆菌、谷氨酸棒杆菌和耻垢分枝杆菌），形状从球形到杆状各不相同，在细胞分裂过程中都经历快速机械DCS。最有趣的是，在委内瑞拉链霉菌的孢子形成过程中也观察到了类似的快速机械DCS。
我们对细菌胞质分裂的许多了解来自对杆状模式生物如大肠杆菌和枯草芽孢杆菌的研究。对于不同细菌物种之间这一过程的变化了解较少。虽然许多细菌的细胞分裂在一定程度上已通过遗传或生化特征进行了描述，但很少有物种使用视频显微镜来揭示胞质分裂和子细胞分离（DCS）的动力学。在这项工作中，我们发现革兰氏阳性细菌的两个独立进化枝中的物种表现出快速（毫秒级）DCS，并且在放线菌门中尤为普遍，放线菌门是一个多样化的群体，包括重要病原体以及产生医学上重要抗生素的细菌。
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