Cell division in 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. 

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-... 

Consider first the filamentation effect. Trials of many complexes established that mainly those complexes which were neutral and had no electrically charged ions in solution, markedly inhibited cell division in bacteria. The cts-configuration was active, the trans was not. They did not inhibit growth unless the concentrations were greatly increased. They were associated in the cell primarily with nucleic acids (RNA and DNA) and with some soluble proteins. 

Cell division in bacteria and eukaryotes takes place in precisely the same manner. 

During metabolism the single cell imbibes nutrients from which it synthesises macromolecules and will therefore grow in size and eventually it must divide. The process of cell division in bacteria is well regulated the new (or daughter) cells are very uniform both dimensionally and in genetic information. 

Sulfa drugs, which are used to treat certain bacterial infections, are analogs of para-aminobenzoic acid. They prevent growth and cell division in bacteria by interfering with the synthesis of folate. Because we cannot synthesize folate, sulfa drugs do not affect human cells in this way. 

Figure 32-1 Comparison of cell division in three species of bacteria. Escherchia coli divides symmetrically after forming a septum in a plane marked by a ring of FtsZ (tubulin-like) and other cell division proteins. Caulobacter crescentus divides asymmetrically to give one flagellated swarmer cell and one stalked cell. Bacillus subtilis, under starvation conditions, divide to form a mother cell and a forespore. The latter is engulfed by the mother cell, which promotes its conversion to a resistant spore. From Shapiro and Losick.83 Courtesy of L. Shapiro.

From the complementary duplex structure of DNA described in chapter 25, it is a short intuitive hop to a model for replication that satisfies the requirement for one round of DNA duplication for every cell division. In chapter 26, DNA Replication, Repair, and Recombination, key experiments demonstrating the semiconservative mode of replication in vivo are presented. This is followed by a detailed examination of the enzymology of replication, first for how it occurs in bacteria and then for how it occurs in animal cells. Also included in this chapter are select aspects of the metabolism of DNA repair and recombination. The novel process of DNA synthesis using RNA-directed DNA polymerases is also considered. First discovered as part of the mechanisms for the replication of nucleic acids in certain RNA viruses, this mode of DNA synthesis is now recognized as occurring in the cell for certain movable genetic segments and as the means whereby the ends of linear chromosomes in eukaryotes are synthesized. 

Second, chemistry is an intellectual enterprise, a way of explaining our material world. When Rosenberg and his coworkers saw that cell division in the bacteria had ceased, they systematically looked for the chemical substance that caused it to cease. They sought a chemical explanation for the occurrence. 

Studies carried out with microorganisms exposed to PAHs showed that the majority of these compounds, when present in small concentrations (5 to 100 ppb) in the environment, can stimulate or inhibit the cell division of bacteria and algae. In higher concentrations (0.2 to 10 ppm) these chemicals interfere, negatively, on the cell division of these organisms being capable of even leading them to death (Albers, 2002). 

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. 

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