CTnscr94, a conjugative transposon found in enterobacteria

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Conjugative transposons are key drivers of horizontal gene transfer (HGT) in bacteria.
• While prevalent in many bacterial groups, conjugative transposons were previously unreported in enteric bacteria.
• Salmonella senftenberg 5494-57 harbors genes for sucrose fermentation on a mobile element.

Purpose of the Study:

• To characterize the mobile genetic element responsible for sucrose fermentation gene transfer in Salmonella senftenberg.
• To determine the nature and integration mechanism of this element in enteric bacteria.
• To identify the first conjugative transposon in the enteric bacterial group.

Main Methods:

• Bacterial conjugation experiments using Salmonella senftenberg and Escherichia coli K-12 strains.
• Molecular cloning and characterization of the mobile DNA element.
• DNA sequencing to analyze the element's ends and integration site.
• RecA-dependent and independent integration assays.

Main Results:

• A large (approx. 100 kb) conjugative transposon, designated CTnscr94, was identified.
• CTnscr94 carries genes for a phosphoenolpyruvate-dependent sucrose phosphotransferase system and sucrose metabolism.
• CTnscr94 integrates into the E. coli chromosome at two specific sites, one within the pheV tRNA gene, in a RecA-independent manner.
• Integration preserves the integrity of the pheV gene.

Conclusions:

• CTnscr94 is the first described conjugative transposon in enteric bacteria.
• This element facilitates HGT of sucrose metabolism genes within enteric bacteria.
• The RecA-independent integration mechanism and preservation of the target gene highlight its unique characteristics.