Electrotransformation of Streptococcus pneumoniae: evidence for restriction of the DNA on entry.
Electrotransformation is a method generally used in biotechnology to introduce recombinant DNA into a wide range of bacteria. However the mechanism of DNA entry is poorly understood. We report that in Streptococcus pneumoniae, a naturally transformable species, electrotransformation efficiently introduces a plasmid replicon. DNA is strongly restricted by the restriction-modification systems DpnI and DpnII which degrade methylated and nonmethylated DNA respectively at GATC sequences. This suggests that in electrotransformation double-strand DNA penetrates into these bacteria without a single-strand step in contrast to natural transformation. Single-strand DNA by itself is able to electrotransform very weakly and linearized double-stranded plasmid DNA yields barely detectable levels of transformants.
LeFrançois
J
J
Laboratoire de Microbiologie et Génétique Moléculaire du C.N.R.S., Toulouse, France.
Gasc
A M
AM
Sicard
M
M
D019175:DNA Methylation; D004269:DNA, Bacterial / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism; D009691:Nucleic Acid Denaturation; D010957:Plasmids / Q000235:genetics; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000378:metabolism; D014169:Transformation, Bacterial / Q000235:genetics*
D004269:DNA, Bacterial; D004277:DNA, Single-Stranded