Figure 2.

Bacteriophage P1 transduction of methylated and unmethylated DNA sequences. Symbols are defined in Figure 1. (A) Schematic of experimental workflow. Asterisks indicate DNA adenine methylation. All genes are chromosomal except cfp, which is on a plasmid. Recipient cells also contained a chromosomal copy of yfp that was constitutively transcribed (not shown). Note: OxyR and Dam proteins shown in transduced cells are from the recipient cell and are not transmitted from the donor cell via phage. Donor strains are HL23 (Δdam) and HL24 (ΔoxyR). Recipient strains are HL5786 (wild-type), HL6712 (Δdam), HL6794 (ΔoxyR) and HL6713 (ΔdamΔoxyR). (B) Fluorescence and brightfield (with phase condenser annulus 3) microscopy of colonies. Scale bar is 500 μm. Red arrow indicates the location of the OFF colony. (C) Percentage of OFF, ON and mixed colonies. Error bars are the standard error of the mean (SEM) of 15 biological replicates. § OFF expression could not be distinguished from the partial level of expression expected in ΔdamΔoxyR strains (11) by fluorescence microscopy.