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[Effect of R plasmids on the DNA content of Escherichia coli]
Abstract:
The morphological properties, cell cycle and DNA content in rifampicin- and nalidixic acid-resistant mutants of E. coli M without plasmids and with R plasmids R6K and pKMR200 were studied. It was shown that the cells of the strains both containing the plasmids and containing no plasmids had elongated bacteria in their populations. Such bacteria were found to be nonseparated rods, 2-4 in number. The plasmids had an effect on the cell cycle period and DNA content: the presence of either R6K or pKMR200 induced lowering of the generation time and DNA content as compared to those in the strains without plasmids.
Insights
Rifampicin-resistant E. coli mutants with R plasmids showed elongated cells and altered DNA content. Plasmids R6K and pKMR200 reduced generation time and DNA levels in these resistant bacterial strains.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- E. coli resistance to antibiotics like rifampicin and nalidixic acid is a growing concern.
- R plasmids can influence bacterial physiology and genetics.
- Understanding these changes is crucial for combating antibiotic resistance.
Purpose of the Study:
- To investigate the impact of R plasmids (R6K and pKMR200) on the morphology, cell cycle, and DNA content of rifampicin- and nalidixic acid-resistant E. coli mutants.
- To compare these properties in strains with and without plasmids.
Main Methods:
- Culturing E. coli M strains with and without R plasmids.
- Inducing resistance to rifampicin and nalidixic acid.
- Analyzing cell morphology and counting non-separated rods.
- Measuring cell cycle duration and DNA content.
Main Results:
- Both plasmid-containing and plasmid-free resistant E. coli strains exhibited elongated bacterial cells, appearing as non-separated rods (2-4 per cell).
- The presence of R plasmids R6K or pKMR200 significantly decreased the cell cycle generation time compared to strains lacking plasmids.
- R plasmids also led to a reduction in the overall DNA content per cell.
Conclusions:
- R plasmids R6K and pKMR200 modulate the cell cycle and DNA content in resistant E. coli.
- The observed morphological changes (elongated, non-separated rods) are associated with plasmid presence in these resistant strains.
- These findings contribute to understanding the complex interactions between antibiotic resistance, plasmids, and bacterial physiology.