Thesis subject

Transposons guide to hitchhiking in the microbial world

Transposons are small genetic elements, with the ability to integrate themselves into the genome and later excise them self and jump to another place in the genome. In addition to this does some transposons, called conjugative transposons, contain genes enabling them to transfer themselves from one cell to another. In this way genes can spread from one species to another.

Transposons can vary in size from very small transposons that only contain the information necessary for integrating in to the genome to larger transposons that contain both the genesnecessary for transposition and additional genes. Some of these transposons do have catabolic genes, providing their host with the ability to grow on new substrates (4).

A transposon containing the genes PCEABCT have recently been described (2, 3). These genes enables the bacteria to grow on PCE, which is widely recognised as one of the mostprominent groundwater contaminants in the Netherlands. The mechanism and dynamics of spreading of these genes of are great interest due to their possible application in bioremediation.

Interestingly almost the same sequence have been found in five different bacteria indicating that it have been transferred horizontally.Since this transposon does not contain the genes necessary for transferring itself from one cell to another it must have been dependent on the gene transfer machinery encoded by other mobile elements for its transfer.

Since transposons are able to “jump” from one piece of DNA to another, they are also able to jump into genetic elements like plasmids or phages, and subsequently be transferred withthem into other cells (1)”hitchhiking”

The aim of this project will be to test the transposon hitchhiking theory.

Key elements will be:

  • Find and introduce mobile elements into bacteria containing catabolic transposons
  • Transfer the mobile elements to new bacteria known not to degrade chlorinated compounds
  • Check for hitchhiking transposons, by a combination of growth/DNA based methods

Interested?

Contact Thomas Kruse at Thomas.kruse(at)wur.nl

References

1. Frost, L. S., R. Leplae, A. O. Summers, and A. Toussaint. 2005. Mobile genetic elements: The agents of open source evolution. Nature Reviews Microbiology 3:722-732.

2. Futagami, T., Y. Tsuboi, A. Suyama, M. Goto, and K. Furukawa. 2006. Emergence of two types of nondechlorinating variants in the tetrachloroethene-halorespiring Desulfitobacterium sp strain Y51. Applied Microbiology And Biotechnology 70:720-728.

3. Maillard, J., C. Regeard, and C. Holliger. 2005. Isolation and characterization of Tn-Dha1, a transposon containing the tetrachloroethene reductive dehalogenase of Desulfitobacterium hafniense strain TCE1. Environmental Microbiology 7:107-117.

4. Tan, H. M. 1999. Bacterial catabolic transposons. Applied Microbiology and Biotechnology 51:1-12.