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Tn1545: a conjugative shuttle transposon
Abstract:
Tn1545, from Streptococcus pneumoniae BM4200, confers resistance to kanamycin (aphA-3), erythromycin (ermAM) and tetracycline (tetM). The 25.3 kb element is self-transferable to various Gram-positive bacterial genera where it transposes. Tn1545 was cloned in its entirety in the recombination deficient Escherichia coli HB101 where it was unstable. The three resistance genes aphA-3, ermAM and tetM were expressed but were not transferable to other E. coli cells. Tn1545 transposed from the hybrid plasmid to multiple sites of the chromosome of its new host. The element re-transposed, at a frequency of 5 X 10(-9), from the chromosome to various sites of a conjugative plasmid where it could be lost by apparently clean excision. The element transformed and transposed to the chromosome of Bacillus subtilis. The properties of the conjugative shuttle transposon Tn1545 may account for the recent emergence of genes from Gram-positive bacteria in Gram-negative organisms.
Insights
The conjugative shuttle transposon Tn1545, carrying antibiotic resistance genes, can transfer between bacteria. This element
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Tn1545 is a 25.3 kb element from Streptococcus pneumoniae BM4200.
- It confers resistance to kanamycin (aphA-3), erythromycin (ermAM), and tetracycline (tetM).
Purpose of the Study:
- To investigate the transferability and transposition properties of Tn1545.
- To understand its behavior in different bacterial hosts, including Gram-negative bacteria.
Main Methods:
- Cloning Tn1545 into a recombination-deficient Escherichia coli host.
- Assessing gene expression and transferability in E. coli.
- Observing transposition from plasmid to chromosome and vice versa.
- Evaluating transformation and transposition in Bacillus subtilis.
Main Results:
- Tn1545 was unstable when cloned in E. coli.
- Resistance genes were expressed but not transferable between E. coli cells.
- Tn1545 transposed to the E. coli chromosome and subsequently to a conjugative plasmid.
- The element could be excised cleanly from the plasmid.
- Tn1545 successfully transformed and transposed within Bacillus subtilis.
Conclusions:
- Tn1545 exhibits self-transferable and transposing capabilities across different bacterial genera.
- Its properties as a conjugative shuttle transposon may explain the spread of Gram-positive genes into Gram-negative organisms.