Related Experiment Videos
Frequency of IS1-mediated molecular events in different members of the family Enterobacteriaceae
J A Bustos-Martinez1, M C Gomez-Eichelmann
1Departamento de Biologia Molecular, Universidad Nacional Autonoma de Mexico, Mexico City, D.F.
Abstract:
The numbers of chromosomal copies of the insertion sequence IS1 in strains of Salmonella typhimurium (0 to 8 copies), Shigella sonnei (56 copies), and Shigella flexneri (41 copies) isolated in Mexico City, Mexico, were similar to those reported for these genera isolated in other countries. Of the 11 Shigella strains studied, all carried several small plasmids; however, in only one of these strains did a small plasmid contain IS1, IS1 recombination, cointegrate formation mediated by IS1 or by the IS1-flanked transposon Tn9, and transposition of Tn9 occurred at a higher frequency in S. typhimurium than in either Escherichia coli or S. sonnei strains. The frequencies of IS1 recombination in S. typhimurium strains containing either zero or eight copies of IS1 were similar.
Insights
This study investigated the insertion sequence IS1 in Salmonella and Shigella strains from Mexico City. IS1 copy numbers and transposition frequencies were analyzed, revealing similarities to global data and higher transposition in S. typhimurium.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- The insertion sequence IS1 is a mobile genetic element found in bacterial genomes.
- IS1 plays a role in genome evolution and the acquisition of antibiotic resistance.
- Understanding IS1 dynamics is crucial for tracking bacterial adaptation and spread.
Purpose of the Study:
- To quantify chromosomal copy numbers of IS1 in Salmonella typhimurium and Shigella species isolated in Mexico City.
- To investigate the occurrence of IS1-mediated genetic events, including recombination and transposition, in these strains.
- To compare IS1 transposition frequencies across different bacterial species and relate them to IS1 copy numbers.
Main Methods:
- Bacterial strains (Salmonella typhimurium, Shigella sonnei, Shigella flexneri) isolated in Mexico City were analyzed.
- Chromosomal copy numbers of IS1 were determined.
- The presence of IS1 on plasmids and IS1-mediated events (recombination, cointegrate formation, Tn9 transposition) were assessed.
- Transposition frequencies of IS1 and Tn9 were measured in different bacterial species (S. typhimurium, Escherichia coli, S. sonnei).
Main Results:
- Chromosomal IS1 copy numbers in Mexican isolates were comparable to international reports (S. typhimurium: 0-8 copies; S. sonnei: 56 copies; S. flexneri: 41 copies).
- IS1 was found on a small plasmid in one Shigella strain, alongside IS1 recombination and cointegrate formation.
- Transposition of IS1 and the IS1-flanked transposon Tn9 occurred at a higher frequency in S. typhimurium compared to E. coli and S. sonnei.
- IS1 recombination frequencies were similar in S. typhimurium strains with zero or eight IS1 copies.
Conclusions:
- IS1 copy numbers in Mexican Salmonella and Shigella strains are consistent with global patterns.
- IS1-mediated genetic rearrangements and Tn9 transposition are active in these bacterial populations.
- S. typhimurium exhibits a higher capacity for IS1 and Tn9 transposition than E. coli and S. sonnei, irrespective of IS1 copy number.