Fig. 1

a Phylogenetic tree illustrating the separation of S. mitis NCTC12261^T and SK321 in different branches (adapted from [20]). b Kinetics of transformation in the S. mitis type strain and strain SK321. Pre-cultures at OD600 0.5 were diluted 1:100 in C + Y_YB medium and grown until OD600 0.04 at 37 °C in 5% CO₂. Cultures were treated with 300 nM cognate CSP and distributed into 200 μL aliquots that were further exposed to 1 μg ml^− 1 recombinant plasmid pVA838 at indicated times. 20 U ml^− 1 DNase I were added after 30 min of exposure to DNA and the culture was incubated in air at 37 °C for additional 30 min. Transformants were recovered in blood agar plates supplemented with Erythromycin. Each line represents results of a single experiment