MRC Centre for Molecular Bacteriology and Infection, Department of Medicine, Imperial College, London, United Kingdom.
PLoS One. 2012;7(9):e44582. doi: 10.1371/journal.pone.0044582. Epub 2012 Sep 10.
Mycobacteria are members of the actinomycetes that grow by tip extension and lack apparent homologues of the known cell division regulators found in other rod-shaped bacteria. Previous work using static microscopy on dividing mycobacteria led to the hypothesis that these cells can grow and divide asymmetrically, and at a wide range of sizes, in contrast to the cell growth and division patterns observed in the model rod-shaped organisms. In this study, we test this hypothesis using live-cell time-lapse imaging of dividing Mycobacterium smegmatis labelled with fluorescent PBP1a, to probe peptidoglycan synthesis and label the cell septum. We demonstrate that the new septum is placed accurately at mid-cell, and that the asymmetric division observed is a result of differential growth from the cell tips, with a more than 2-fold difference in growth rate between fast and slow growing poles. We also show that the division site is not selected at a characteristic cell length, suggesting this is not an important cue during the mycobacterial cell cycle.
分枝杆菌是放线菌的成员，通过尖端延伸生长，缺乏与其他杆状细菌中已知细胞分裂调节剂明显同源的物质。以前使用静态显微镜对正在分裂的分枝杆菌进行的研究提出了这样的假设，即这些细胞可以不对称地生长和分裂，并且可以在很宽的范围内生长，这与在模型杆状生物中观察到的细胞生长和分裂模式形成对比。在这项研究中，我们使用荧光标记的 PBP1a 对标记的分枝杆菌进行活细胞延时成像，以探测肽聚糖的合成并标记细胞隔膜，从而验证了这一假设。我们证明新的隔膜准确地位于细胞中部，并且观察到的不对称分裂是细胞尖端的差异生长的结果，快速生长的极和缓慢生长的极之间的生长速率差异超过 2 倍。我们还表明，分裂位点不是在特征细胞长度处选择的，这表明这不是分枝杆菌细胞周期中的重要线索。
