Physical analysis of the conjugative shuttle transposon Tn1545
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Abstract:
The conjugative shuttle transposon Tn1545 from Streptococcus pneumoniae 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 is also capable of transposition, but not of conjugation, after cloningoff Escherichia coli. Analysis of the element by restriction endonucleases, molecular cloning, electron microscopy of heteroduplexes, DNA hybridization, and sequencing allowed us to establish a physical map of Tn1545, localize the resistance genes, determine their direction of transcription, and compare them with other characterized resistance determinants, and show that Tn1545 is not flanked by large terminal repeated sequences in opposite orientation.
Insights
The conjugative shuttle transposon Tn1545 confers antibiotic resistance. This 25.3-kb element from Streptococcus pneumoniae can transfer and transpose in various bacteria, with resistance genes aphA-3, ermAM, and tetM characterized.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The conjugative shuttle transposon Tn1545, isolated from Streptococcus pneumoniae, is known to confer resistance to multiple antibiotics.
- Understanding the genetic makeup and transfer mechanisms of such elements is crucial for tracking and combating antibiotic resistance.
Purpose of the Study:
- To characterize the physical and genetic properties of the Tn1545 transposon.
- To determine the location and transcriptional orientation of antibiotic resistance genes within Tn1545.
- To investigate the transferability and transposition capabilities of Tn1545 in different bacterial hosts.
Main Methods:
- Restriction endonuclease digestion and physical mapping.
- Molecular cloning and DNA hybridization techniques.
- DNA sequencing and heteroduplex analysis via electron microscopy.
Main Results:
- A detailed physical map of the 25.3-kb Tn1545 element was established.
- The aphA-3 (kanamycin), ermAM (erythromycin), and tetM (tetracycline) resistance genes were localized and their transcriptional directions determined.
- Tn1545 demonstrated self-transfer and transposition in various gram-positive bacteria, and transposition (but not conjugation) in Escherichia coli.
- Tn1545 was found not to be flanked by large terminal inverted repeat sequences.
Conclusions:
- Tn1545 is a versatile conjugative shuttle transposon with a well-defined genetic structure conferring resistance to kanamycin, erythromycin, and tetracycline.
- Its ability to transpose and conjugate across different bacterial genera highlights its significance in the dissemination of antibiotic resistance.
- The absence of terminal inverted repeats suggests a unique transposition mechanism compared to other characterized transposons.