Palacios P, Vicente M, Sánchez M
Departamento de Biología Celular y del Desarrollo, Cousejo Superior de Investigaciones Científicas, Velázquez, Madrid, Spain.
Mol Microbiol. 1996 Jun;20(5):1093-8. doi: 10.1111/j.1365-2958.1996.tb02549.x.
Expression of ftsZ in strain VIP205 is dissociated from its natural promoters, and is under the control of an inducible tac promoter. This abolishes the oscillation in ftsZ transcription observed in the wild type, allowing different levels of ftsZ expression. We demonstrate that this construction does not affect the expression of other genes, and has no effects on replication or nucleoid segregation. A shift in IPTG from 30 microM, that supports division at wild-type sizes, to lower (6 microM) or higher (100 microM) concentrations, indicates that VIP205 cells can divide within a broad range of FtsZ concentrations. Analysis of the morphological parameters during the transition from one IPTG concentration to another suggests that the correct timing of ftsZ expression, and the correct FtsZ concentration, are required for division to occur at normal cell sizes. After a transient division delay during the transition to lower IPTG concentrations, cells in which ftsZ is expressed continuously (yielding 80% of the wild-type FtsZ levels) divide with the same division time as the wild type, but at the expense of becoming 1.5 times larger. A precise control of ftsZ expression is required for normal division, but the existence of additional regulators to maintain the correct timing during the cell cycle cannot be ruled out.
ftsZ在菌株VIP205中的表达与其天然启动子解离，并受诱导型tac启动子的控制。这消除了在野生型中观察到的ftsZ转录振荡，允许ftsZ表达处于不同水平。我们证明这种构建不影响其他基因的表达，并且对复制或类核分离没有影响。将IPTG从支持野生型大小分裂的30微摩尔转移到较低（6微摩尔）或较高（100微摩尔）浓度，表明VIP205细胞可以在广泛的FtsZ浓度范围内分裂。在从一种IPTG浓度转变为另一种浓度的过程中对形态学参数的分析表明，为了在正常细胞大小下发生分裂，需要ftsZ表达的正确时间和正确的FtsZ浓度。在向较低IPTG浓度转变期间有一个短暂的分裂延迟后，ftsZ持续表达（产生80%的野生型FtsZ水平）的细胞以与野生型相同的分裂时间分裂，但代价是细胞大小变为野生型的1.5倍。正常分裂需要对ftsZ表达进行精确控制，但不能排除存在额外的调节因子以维持细胞周期中正确时间的可能性。
