Cell division, bacteria

Binary fission- Division of one cell into two cells by the formation of a septum. It is the most common form of cell division in bacteria. 

The mode of action of starch capped copper nanoparticles (SCuNPs) was compared with that of the well-known antibiotic amphicillin (Fig. 9). There was a drastic decrease in the optical density of compounds containing SCuNPs and ampicillin, ultimately reaching almost zero suggesting that there were no more bacteria present in the culture. AmpiciUin at a concentration of 100 pg/ml has the ability to lyse E.coli almost immediately [29]. The same effect was produced by SCuNPs at 365 ng/ml concentration. The cell lysis occurs at the expense of the fact that at the point of cell division there occurs a deformation of the cell envelope. The decrease in optical density is possibly associated with the cell-envelope deformation occurring at the point of cell division [30]. 

The methylation of deoxyuridine monophosphate (dUMP) to thymidine monophosphate (TMP), catalyzed by thymidylate synthase, is essential for the synthesis of DNA. The one-carbon fragment of methy-lene-tetrahydrofolate is reduced to a methyl group with release of dihydrofolate, which is then reduced back to tetrahydrofolate by dihydrofolate reductase. Thymidylate synthase and dihydrofolate reductase are especially active in tissues with a high rate of cell division. Methotrexate, an analog of 10-methyl-tetrahydrofolate, inhibits dihydrofolate reductase and has been exploited as an anticancer drug. The dihydrofolate reductases of some bacteria and parasites differ from the human enzyme inhibitors of these enzymes can be used as antibacterial drugs, eg, trimethoprim, and anti-malarial drugs, eg, pyrimethamine. 

Plasmids have the ability to transfer within and between species and can therefore be acquired from other bacteria as well as a consequence of cell division. This property makes plasmid-acquired resistance much more threatening in terms ofthe spread of antibiotic resistance than resistance acquired due to chromosomal mutation. Plasmids also harbour transposons (section 2.1.3), which enhances their ability to transfer antibiotic resistance genes. 

Nasmyth There is a classic experiment to address whether there is size control. That is to transiently delay the cell cycle so that you produce abnormally large cells. Then you look at the cell division time of subsequent cycles. If these experiments are done with bacteria or yeast, the subsequent cycles are greatly accelerated. These experiments could be done by Bruce Edgar and his imaginal discs. They are technically harder, but they could be done. 

The effect of platinum in a bacterial cell is to act in a very selective way — on cell division or causing lysis of lysogenic bacteria. It is likely that these changes are due to site specific attack on particular proteins or on particular bases in RNA or in DNA. It is necessary now to describe this attack in detail and to develop new probes for following the site in vivo. This exercise can be followed by a parallel examination of how cis- [Pt (NH3) 2CI2] acts as an anti-tumour agent. Here we only point to some interesting observations. 

Some or all of the events of this sequence are readily thrown out of balance, or even completely inhibited. Thus bacteria, particularly the rod-shaped organisms, may be induced to elongate into filaments by various treatments which apparently inhibit cell division but which do not inhibit growth. Such an effect is produced by various chemical substances, by sub-bacteriostatic concentration of certain antibacterial agents, as, for example, methyl violet, sulfonamides, /w-cresol, penicillin, irradiation, and higher temperatures of incubation. 

Variation in the magnesium (Mg) content of the medium may exert a marked effect on cell division of some bacteria. In a Mg-deficient medium, Gram-positive rods grow in the form of long filaments. Such filaments revert to normal forms when transferred to the same medium supplemented with suitable concentrations of Mg. Filament formation is enhanced by the addition of zinc and cobalt. Inhibition of cell division occurs also in media supplemented with an excess of Mg. 

Bacteria Unicellular prokaryotic microorganisms which generally possess rigid cell walls, multiply by cell division, and exhibit three prindpal forms round or coccal, rodlike or badllary, and spiral or spirochetal. [NIH]... 

This pyrimidine inhibits cell division in bacteria and yeast [319], as well as cell growth in tissue culture [320]. For example, 5-diazouracil possesses signifi-... 

Animal cells add a significant layer of complexity to the system due to their dependence on cell-matrix and cell-cell signaling pathways. Unicellular species such as bacteria and yeasts tend to grow and proliferate as fast as nutrients can be supplied. In fact, their growth rates are typically proportional to the amounts of nutrients available. By contrast, however, cells from multicellular organisms must develop mechanisms that include both nutrient supplies and signal pathways that control cell division. Thus, while nutrients are necessary for an animal cell to proliferate, the cell must receive stimulatory chemical signals from other, usually adjacent, cells. 

---