Conjugative Transfer of the Integrative Conjugative Elements ICESt1 and ICESt3 from Streptococcus thermophilus

Xavier Bellanger (1) , Adam P Roberts (2) , Catherine Morel (1) , Frédéric Choulet (1) , Guillaume Pavlovic (1) , Peter Mullany (2) , Bernard Decaris (1) , G. Guedon (1)

1 LGM - Laboratoire de génétique et microbiologie
2 UCL - University College of London [London]

Integrative and conjugative elements (ICEs), also called conjugative transposons, are genomic islands that excise, self-transfer by conjugation, and integrate in the genome of the recipient bacterium. The current investigation shows the intraspecies conjugative transfer of the first described ICEs in Streptococcus thermophilus, ICESt1 and ICESt3. Mitomycin C, a DNA-damaging agent, derepresses ICESt3 conjugative transfer almost 25-fold. The ICESt3 host range was determined using various members of the Firmicutes as recipients. Whereas numerous ICESt3 transconjugants of Streptococcus pyogenes and Enterococcus faecalis were recovered, only one transconjugant of Lactococcus lactis was obtained. The newly incoming ICEs, except the one from L. lactis, are site-specifically integrated into the 3 end of the fda gene and are still able to excise in these transconjugants. Furthermore, ICESt3 was retransferred from E. faecalis to S. thermophilus. Recombinant plasmids carrying different parts of the ICESt1 recombination module were used to show that the integrase gene is required for the site-specific integration and excision of the ICEs, whereas the excisionase gene is required for the site-specific excision only.

Mots clés: INTEGRATIVE AND CONJUGATIVE ELEMENT

Mots clés: GENETIQUE

Domaines: Sciences du Vivant [q-bio]

Xavier Bellanger, Adam P Roberts, Catherine Morel, Frédéric Choulet, Guillaume Pavlovic, et al.. Conjugative Transfer of the Integrative Conjugative Elements ICESt1 and ICESt3 from Streptococcus thermophilus. Journal of Bacteriology, 2009, 191 (8), pp.2764 - 2775. ⟨10.1128/JB.01412-08⟩. ⟨hal-01659303⟩