Peptidoglycan Synthesis in Cocci and Rods of a pH-Dependent, Morphologically Conditional Mutant of Klebsiella pneumoniae

Cell division of Escherichia coli K-12 strain PA3092 was inhibited by the addition of adenosine 3',5'-phosphate (cAMP), and the cellular morphology was changed from rods into flaments. Nucleoids in the filaments were regularly distributed and septum formation was perfectly inhibited. This inhibition of cell division by cAMP was reversed by the addition of guanosine 3',5'-monophosphate. To examine whether the inhibitory effect of cAMP on cell division in E. coli PA3092 was specific, its effect in several parental strains was investigated. Induction of cell filamentation by cAMP was observed in E. coli PA309 and P678, but not in E. coli W595, Wl, Y10, or the wild-type strain. This result suggests that filamentation by cAMP in E. coli PA3092, PA309, and P678 was due to the mutagenesis by which E. coli P678 was derived from E. coli W595.Cyclic AMP (cAMP) exerts its effect in Escherichia coli primarily by stimulating the synthesis of a number of proteins (19). The most important example is the control of the synthesis of ,B-galactosidase, the gene of which is transcribed at a significant rate in the presence of cAMP and cAMP receptor protein (CRP). In addition to controlling the synthesis of these proteins positively (positive control), cAMP has been found to regulate the synthesis of glutamate synthase, glutaminase A (18), and the outer membrane protein III (15) negatively (negative control).On the other hand, it has been reported that adenylate cyclase-deficient (cya) mutants and CRP-deficient (crp) mutants show cocci or short rod morphology (11,13), and the increase in intracellular cAMP concentration precedes the observed change in cellular morphology from cocci to rods in Arthrobacter crystallopoites (10). Furthermore, Aono et al. reported that synthesis of several envelope proteins in E. coli is regulated by cAMP and CRP (2). These results suggest that there is some correlation between cAMP and cell morphology.Recently, we found that in E. coli PA3092, rods were changed into filaments upon the addition of cAMP. There have been many reports about filamentation in E. coli (7-9, 12, 23-26), but filamentation by cAMP has not been reported yet. It is important if cell division is controlled by cAMP, which is a regulatory molecule in transcription. Several temperature-sen-sitive cell division mutants have been isolated (17) and used to investigate cell division in E. coli, but the control mechanism of cell division is poorly understood. Studies with E. coli PA3092 should provide useful information regarding the cell division process in E. coli. This report presents characteristics of the inhibition of cell division and the morphological change in E. coli caused by cAMP and suggests the control mechanism of filamentation involving this molecule.

Section: Discussionsupporting

confidence: 63%

Inhibitory effect of adenosine 3',5'-phosphate on cell division of Escherichia coli K-12 mutant derivatives

Utsumi¹,

Tanabe²,

Nakamoto³

et al. 1981

“…Interestingly, Klebsiellapneumoniae Mir M7, a pH conditional morphology mutant with a round shape at pH 7 (13), was observed to undergo morphogenic changes similar to those in LS1 when treated with cephalexin, a ,B-lactam antibiotic acting on PBP-3 (G. Botta et al, Abstr. XII, Int.…”

mentioning

confidence: 99%

Effects of furazlocillin, a beta-lactam antibiotic which binds selectively to penicillin-binding protein 3, on Escherichia coli mutants deficient in other penicillin-binding proteins

Schmidt¹,

Botta²,

Park³

1981

Furazlocillin binds selectively to penicillin-binding protein 3 (PBP-3), prevents septation of Escherichia coli, and allows the cells to form long fiaments without lysis. The effect offurazlocillin on the morphology, autolysis, and murein synthesis of E. coli mutants deficient in either PBP-1A, PBP-lBs, or PBP-2 was studied. The results reveal that PBP-1A and PBP-lBs functions are not equivalent since furazlocillin affects the morphology, autolysis, and murein synthesis of PBP1Amutants quite differently from that of PBP-lBs mutants. Different "PBP-2-" mutants were found to respond to furazlocillin in dramatically different ways: strain LS-1 cells formed elongated rods with a central bulge which eventually lysed, whereas SP6 cells formed stable "barbells" in which the two daughter cells were well separated but remained connnected by a thick central region.At least nine penicillin-binding proteins (PBPs), located in the cytoplasmic membrane of Escherichia coli, can be detected with radiolabeled benzylpenicillin by a sodium. dodecyl sul-

“…Evidence has recently been presented that two competing sites for peptidoglycan assembly exist in rod-shaped bacteria: one responsible for lateral wall synthesis, and the other responsible for septal wall synthesis (30,33). This suggests that rods have a more complex cellular organization than cocci and represent more highly evolved organisms (7).…”

mentioning

confidence: 99%

“…To investigate these problems, we are using strain MirM7, a pH-conditional morphology mutant of Klebsiella pneumoniae (a species closely related both genetically and physiologically to Escherichia coli [21]), isolated by Meloni and Monti-Bragadin (23) and characterized in some detail by others (9,29,30,32). Among the morphology mutants so far described in E. coli (2,11,13,14,20,22,24,34,36) and other bacterial species (3,5,10,27), strain MirM7 shows several properties that make it particularly interesting.…”

mentioning

confidence: 99%

Control of cell septation by lateral wall extension in a pH-conditional morphology mutant of Klebsiella pneumoniae

Satta¹,

Canepari²,

Botta³

et al. 1980

The pH-conditional morphology mutant of Klebsiella pneumoniae strain MirM7 grows as cocci at pH 7 and as rods at pH 5.8. The mutant has a high-level mecillinam resistance (50% lethal dose > 200 ,ug/ml) in both forms. When broth cultures of the rod-shaped mutant were grown with 0.7 ,ug of mecillinam per ml, cells assumed a round shape and continued to divide at a higher rate than the untreated control. A MirM7 rod-shaped revertant (MirA12), when treated with the same antibiotic concentration, changed to coccal shape and stopped dividing. The penicillin-binding proteins (PBPs) of strains MirA12 and MirM7 were analyzed. K. pneumoniae had six major PBPs quite similar to those of Escherichia coli. No differences were seen in the PBPs of MirM7 cocci and rods and MirA12 cells. In particular, PBP2 was found to be prepent and similar in MirM7 rods and cocci and MirA12 cells. We suggest that in gram-negative rods, a control mechanism exists which prevents further septation in the absence of lateral cell wall elongation. The unique behavior of MirM7 is due to the fact that the control mechanism is not active in this strain. This model allows us to explain the preservation of shape in bacterial rods under various conditions of growth and the mechanism of bacterial killing by mecillinam.