Conjugative mobilization of the cloned M6 protein gene from Streptococcus pneumoniae to Streptococcus pyogenes
Oggioni, M.R.; Pozzi, G.
Microbiologica 13(4): 273-281
1990
ISSN/ISBN: 0391-5352 PMID: 1965005 Document Number: 351787
The host-vector system .OMEGA.6001-pDP36 was used to transfer the M6 protein gene (emm-6.1) of Streptococcus pyogenes to other S. pyogenes strains, isogenic and nonisogenic to D471, the strain from which emm-6.1 was originally cloned. The first step was to subclone emm-6.1 into the insertion vector pDP36. The resulting plasmid, pRMB20, was used as donor in transformation to insert emm-6.1 into the conjugative transposon .OMEGA.6001. Streptococcus pneumoniae DP1322, carrying .OMEGA.6001 integrated into the chromosome, was the recipient in the transformation experiment. .OMEGA.6001 containing emm-6.1 was then transferred by conjugation from S. pneumoniae to the chromosomes of M+ and M- S. pyogenes strains. S. pyogenes transconjugants contained one intact copy of emm-6.1 integrated into the chromosome, but no expression of M6 protein could be detected by Western blot analysis. We found no evidence of the positive transacting regulation of emm gene expression postulated by other authors. In fact, the cloned emm-6.1 was not expressed in three strains expressing their own M proteins (M5, M17 and a shorter M6). In these partial diploids M protein genes were expressed only when present in the original chromosomal locus.