It is well-established that FtsZ drives peptidoglycan synthesis at the division site in walled bacteria. However, the function and conservation of FtsZ in wall-less prokaryotes such as mycoplasmas are less clear. In the genome-reduced bacterium Mycoplasma genitalium, the cell division gene cluster is limited to four genes: mraZ, mraW, MG_223, and ftsZ. In a previous study, we demonstrated that ftsZ was dispensable for growth of M. genitalium under laboratory culture conditions. Herein, we show that the entire cell division gene cluster of M. genitalium is non-essential for growth in vitro. Our analyses indicate that loss of the mraZ gene alone is more detrimental for growth of M. genitalium than deletion of ftsZ or the entire cell division gene cluster. Transcriptional analysis revealed a marked upregulation of ftsZ in the mraZ mutant. Stable isotope labeling by amino acids in cell culture (SILAC)-based proteomics confirmed the overexpression of FtsZ in MraZ-deprived cells. Of note, we found that ftsZ expression was upregulated in non-adherent cells of M. genitalium, which arise spontaneously at relatively high rates. Single cell analysis using fluorescent markers showed that FtsZ localization varied throughout the cell cycle of M. genitalium in a coordinated manner with the chromosome and the terminal organelle (TMO). In addition, our results indicate a possible role for the RNA methyltransferase MraW in the regulation of FtsZ expression at the post-transcriptional level. Altogether, this study provides an extensive characterization of the cell division gene cluster of M. genitalium and demonstrates the existence of regulatory elements controlling FtsZ expression at the temporal and spatial level in mycoplasmas.

众所周知，FtsZ 驱动有壁细菌分裂位点的肽聚糖合成。然而，FtsZ 在无壁原核生物（如支原体）中的功能和保守性尚不清楚。在基因组减少的细菌中生殖支原体，细胞分裂基因簇仅限于四个基因：米拉兹,兆瓦、MG_223 和ftsZ 。在之前的一项研究中，我们证明了ftsZ对于成长来说是可有可无的生殖支原体在实验室培养条件下。在这里，我们展示了整个细胞分裂基因簇生殖支原体对于增长来说不是必需的体外。我们的分析表明，损失米拉兹单独的基因对生长更不利生殖支原体比删除ftsZ或整个细胞分裂基因簇。转录分析显示显着上调ftsZ在米拉兹突变体。基于细胞培养 (SILAC) 的蛋白质组学中氨基酸的稳定同位素标记证实了 MraZ 缺失细胞中 FtsZ 的过度表达。值得注意的是，我们发现ftsZ在非贴壁细胞中表达上调生殖支原体，它们以相对较高的比率自发出现。使用荧光标记的单细胞分析表明，FtsZ 定位在整个细胞周期中发生变化。生殖支原体以与染色体和末端细胞器（TMO）协调的方式。 此外，我们的结果表明 RNA 甲基转移酶 MraW 在转录后水平调节 FtsZ 表达中可能发挥作用。总而言之，这项研究提供了细胞分裂基因簇的广泛表征。生殖支原体并证明了支原体中在时间和空间水平上控制 FtsZ 表达的调控元件的存在。