Transformation Efficiency Assay Protocol

Transformation assays were performed as previously described (35 (link)) except that then bacterial suspensions of the recipient strain were mixed with an equal volume of either genomic DNA extracted from the donor strain (concentration, 200 ng/μL), a bacterial suspension of the donor strain at an OD₆₀₀ of 0.01 for mixed culture, or a filtered spent medium. DNase I treatment was performed at a final concentration of 0.3 U/μL (Sigma). All the transformation assays were performed on at least two separate occasions with three independent transformation reactions (three different bacterial cultures). All the independent data points are plotted. For kinetics of transformation, bacteria were recovered at indicated times points with bacteria harvested from an independent sample and plated as previously described.