Attempts to construct an E.coli strain that secretes singe stranded DNA (ssDNA)

by Birgit Koch

16:00 (40 min) in Daysh G.07

Type IV secretion systems (T4SS) are multi-protein complexes that can translocate DNA and protein substrates across the cell envelope of Gram-negative and Gram-positive bacteria. Three types of T4SS have been described: conjugation systems, defined as machines that translocate DNA to other bacteria by a contact-dependent process; effector translocator systems, functioning to deliver proteins or other effector molecules to eukaryotic target cells; and DNA release or uptake systems that translocate DNA to or from the extracellular milieu. As the only bacterium Neisseria gonorrhoeae uses a T4SS to secrete single stranded DNA into the medium. The aim of my project is to transfer the Neisseria gonorrhoeae T4SS to E. coli in order to construct an ssDNA secreting E. coli strain. I will give an introduction to T4SS and present some lab data. Using a ssDNA specific PCR method I can detect ssDNA in a cell free supernatant obtained from 2 different E. coli strains that carry both the F-plasmid T4SS and the Neisseria gonorrhoeae T4SS. It is however unclear if the ssDNA is secreted by a T4SS and if so whether it could be a chimeric T4SS. Basically I will try to give a clear presentation based on data I don’t really understand (yet). Interesting challenge.