Comparison of cell-to-cell transformation with artificial transformation.

<p>Strain names: CAG, CAG18439; HB, HB101; and MC, MC4100. Cell-to-cell transformation (A) was performed with three combinations including donor cells harbouring pHSG299. Artificial transformations by the CaCl₂ method (B) and PEG method (C) was performed as described in Methods. In artificial transformation, plasmid (pHSG299) was used in a semi-saturating amount (500 ng/sample) or the roughly estimated amount of leaked plasmid DNA in co-culture [CAG: 2×10^–10; HB: 1×10^–8; MC: 1×10^–9 ng per recipient ( = competent) cells]. The latter values were calculated on the assumptions that free plasmid DNA was supplied from dead donor cells (maximum 5% of total population) to co-existing recipient cells in each corresponding co-culture of cell-to-cell transformation, and that the pHSG299 copy number is ∼200 per cell <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0016355#pone.0016355-Hong1" target="_blank">[38]</a>. Transformation frequency and transformation efficiency were calculated as described in Methods. Data are presented as mean and S.D. (<i>n</i> = 3).