PDF(Pubmed)
Abstract：
Bacteria require membrane fission for both cell division and endospore formation. In Bacillus subtilis, sporulation initiates with an asymmetric division that generates a large mother cell and a smaller forespore that contains only a quarter of its genome. As the mother cell membranes engulf the forespore, a DNA translocase pumps the rest of the chromosome into the small forespore compartment, inflating it due to increased turgor. When the engulfing membrane undergoes fission, the forespore is released into the mother cell cytoplasm. The B. subtilis protein FisB catalyzes membrane fission during sporulation, but the molecular basis is unclear. Here, we show that forespore inflation and FisB accumulation are both required for an efficient membrane fission. Forespore inflation leads to higher membrane tension in the engulfment membrane than in the mother cell membrane, causing the membrane to flow through the neck connecting the two membrane compartments. Thus, the mother cell supplies some of the membrane required for the growth of the membranes surrounding the forespore. The oligomerization of FisB at the membrane neck slows the equilibration of membrane tension by impeding the membrane flow. This leads to a further increase in the tension of the engulfment membrane, promoting its fission through lysis. Collectively, our data indicate that DNA translocation has a previously unappreciated second function in energizing the FisB-mediated membrane fission under energy-limited conditions.
摘要：
细菌需要膜裂变以进行细胞分裂和内生孢子形成。在枯草芽孢杆菌中,孢子形成始于不对称分裂，产生一个大的母细胞和一个只包含其基因组四分之一的较小的前孢子。当母细胞膜吞没前孢子时，DNA转位酶将染色体的其余部分泵入小的前孢子室，由于膨胀增加。当吞噬的膜经历裂变时，前孢子被释放到母细胞的细胞质中。枯草芽孢杆菌蛋白FisB在孢子形成过程中催化膜裂变，但是分子基础不清楚。这里,我们表明，前生膨胀和FisB积累都是有效的膜裂变所必需的。前孢子膨胀导致吞噬膜的膜张力高于母细胞膜，使膜流过连接两个膜隔室的颈部。因此，母细胞提供一些膜生长所需的膜周围的膜。FisB在膜颈处的低聚通过阻碍膜流动来减慢膜张力的平衡。这导致吞噬膜的张力进一步增加，通过裂解促进其裂变。总的来说，我们的数据表明，在能量受限的条件下，DNA易位在激发FisB介导的膜裂变方面具有先前未被理解的第二功能。
