Cell division control in Escherichia coli K-12: some properties of the ftsZ84 mutation and suppression of this mutation by the product of a newly identified gene

Abstract

The Fts proteins play an important role in the control of cell division in Escherichia coli. These proteins, which possibly form a functional complex, are encoded by genes that form an operon. In this study, we examined the properties of the temperature-sensitive mutationftsZ84 harbored by low-or high-copy-number plasmids. Cells of strain AB1157, which had the ftsZ84 mutation, did not form colonies on salt-free L agar at 30°C. When a low-copy-number plasmid containing the ftsZ84 mutation was present in these mutant cells, colony formation was restored on this medium at 30°C, suggesting that FtsZ84 is probably less active than the wild-type protein and is therefore limiting in its capacity to trigger cell divisions. On the other hand, when the ftsZ84 mutation was harbored by the high-copy-number plasmid pBR325, colony formation was prevented on salt-free L agar plates whether the recipients were ftsZ84 mutant or parental cells, suggesting that, at high levels, FtsZ84 acts as a division inhibitor. The fact that colony formation was also prevented at 42°C indicates that the FtsZ84 protein is not inactivated at the nonpermissive temperature. The possibility that FtsZ84 is a more efficient division inhibitor than the wild-type FtsZ is discussed. Evidence is also presented showing that a gene adjacent to mutT codes for a product that, under certain conditions, suppresses the ftsZ84 mutation.

Role of FtsEX in Cell Division of Escherichia coli : Viability of ftsEX Mutants Is Dependent on Functional SufI or High Osmotic Strength

“…The fact that most of the point mutations in various division genes are osmoremedial and also that the occurrence of osmoremedial null mutations in genes involved in cell division reflects that perhaps the process of division itself is intrinsically sensitive to conditions of low osmotic strength. ftsZ84, the best-characterized mutation of ftsZ, is osmoremedial at a high temperature (37,39). In addition, other temperature-sensitive division mutations, such as ftsA12, ftsQ1, ftsK44, and ftsI23, are also sensitive to variations in the osmotic strength of the medium.…”

Bacterial Growth and Cell Division: a Mycobacterial Perspective

“…Maintaining assembly of the ring requires energy, as evident by the rapid depolymerization of FtsZ when ATP is depleted from the cell (356). This rapid turnover, or flux, of FtsZ may not be important for division, since a GTPase-defective mutant (FtsZ84) E. coli strain showed much slower turnover yet normal division at 30°C (316).…”

New Temperature-Sensitive Alleles of ftsZ in Escherichia coli

“…In vivo activity of FtsZ(Ts) proteins. To assess whether the novel mutant FtsZ proteins simply had reduced activity in vivo at the nonpermissive temperature (as has been demonstrated for FtsZ84 [44]), we tested the abilities of plasmids pT73Z-972, pT73Z-2066, pT73Z-2863, pT73Z-6460, and pT73Z-9124 to complement their respective temperature-sensitive isolates on LBNS agar at 42°C. Plating efficiencies were measured by comparing viability counts (36) at 30 and 42°C.…”

“…Conditional mutations in ftsZ have proven to be difficult to isolate in vivo, and of the two such mutants which exist, the ftsZ84 and ftsZ26 mutants (8), only the former is due to a single amino acid change. Furthermore, it has been demonstrated that mild overexpression of ftsZ84 provides complementation of its lethal cell division defect (44). Therefore, suppressor and complementation studies are most likely to identify previously characterized mechanisms by which ftsZ expression levels can be modified rather than novel interactions with accessory proteins (6,7,15,20,42,46,57).…”