An Escherichia coli Mutant That Makes Exceptionally Long Cells

Abstract

Although Escherichia coli is a very small (1-to 2-m) rod-shaped cell, here we describe an E. coli mutant that forms enormously long cells in rich media such as Luria broth, as long indeed as 750 m. These extremely elongated (eel) cells are as long as the longest bacteria known and have no internal subdivisions. They are metabolically competent, elongate rapidly, synthesize DNA, and distribute cell contents along this length. They lack only the ability to divide. The concentration of the essential cell division protein FtsZ is reduced in these eel cells, and increasing this concentration restores division. IMPORTANCEEscherichia coli is usually a very small bacterium, 1 to 2 m long. We have isolated a mutant that forms enormously long cells, 700 times longer than the usual E. coli cell. E. coli filaments that form under other conditions usually die within a few hours, whereas our mutant is fully viable even when it reaches such lengths. This mutant provides a useful tool for the study of aspects of E. coli physiology that are difficult to investigate with small cells. We think of bacterial cells as small organisms. Cells in a growing Escherichia coli culture look like rigid rods 0.5 m wide by 2 m long. Each rod elongates to twice its original length by making new peptidoglycan in many disperse areas by using an enzyme complex including penicillin-binding protein 2 (PBP2). The organism then localizes peptidoglycan synthesis to midcell by using a different enzyme complex, based on PBP3. This changes the direction of cell wall synthesis; the cell wall invaginates from both sides, thus forming two identical daughter cells (1, 2, 3).E. coli cells are small because their division controls are set accordingly (4). However, they can be much longer if a shift to PBP3 cannot be made but conditions still permit PBP2 function. This occurs under many circumstances. Mutants with conditional temperature-sensitive mutations in the gene coding for the essential cell division protein FtsZ have been isolated. These mutations result in the inhibition of division, accompanied by elongation into short-lived filaments, when cells are shifted from 37°C to 42°C (5).Filaments also form when the SOS response is triggered under conditions of DNA damage (6) or when the cells are treated with the antibiotic aztreonam, which blocks division irreversibly by inhibiting the FtsI protein, involved in the formation of the septal ring (7). The filaments formed under these conditions, and others, are not viable and lyse within a few hours. As a result, it was largely believed that E. coli could not sustain a large cell size.However, in this paper, we describe a mutant that forms very long viable (i.e., colony-forming) cells. This strain was derived from our earlier mutant carrying a deletion in metK, which codes for S-adenosylmethionine (SAM) synthetase; SAM is the major donor of methyl groups (8, 9). Our metK deletion mutant, MEW649, had to be exogenously provided with both SAM and methionine in order to grow, as well as with a SAM transporte...

Chromosome-free bacterial cells are safe and programmable platforms for synthetic biology

“…However, the SOS response is subsequently silenced after attempted DNA repair (47,48). Other studies have observed that when FtsZ is downregulated or mutated in parent cells, cells can reach up to 750 μm in length and are still metabolically competent and will synthesize DNA (49). This preservation of functionality is also supported by our results as the longer SimCells could still produce mCherry (Figs.…”

Imaging Bacterial Colonies and Phage–Bacterium Interaction at Sub‐Nanometer Resolution Using Helium‐Ion Microscopy

“…Phage infection is much rarer; however, some ongoing infections are still visible. There is also an exceptionally long E. coli cell shown in Figure , which is only recently described …”

Regulation of Growth, Cell Shape, Cell Division, and Gene Expression by Second Messengers (p)ppGpp and Cyclic Di-GMP in Mycobacterium smegmatis

“…Similarly, qRT-PCR analysis of MSMEG_4712 and MSMEG_5779, genes involved in cell-wallrelated processes, and MSMEG_3112 and MSMEG_4963, genes involved in intermediary metabolism and respiration, correlated well with microarray data. We also selected the principal bacterial cell division gene, ftsZ, for qRT-PCR analysis, as downregulation of this gene is known to make bacterial cells elongated, even though microarray data showed no significant differences in its expression level (41). The qRT-PCR analysis showed that in the knockout strains, the levels of ftsZ were significantly downregulated (see Fig.…”

“…Since depletion of ftsZ has been linked to a filamentous phenotype in bacteria (41,47), and the ⌬rel Msm and ⌬dcpA strains exhibited the filamentous phenotype, we checked expression of the principal cell division control gene ftsZ. The qRT-PCR analysis showed that it was downregulated in both the knockout strains, thus explaining the filamentous phenotype shown by ⌬rel Msm and ⌬dcpA strains (see Fig.…”