Conjugative Transfer of the Integrative Conjugative Elements ICESt1 and ICESt3 from Streptococcus thermophilus
Résumé
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.
Domaines
Sciences du Vivant [q-bio]
Origine : Fichiers éditeurs autorisés sur une archive ouverte
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