Strain and plasmid list.

a<p>All strains are isogenic with MG1655 with the genotype F-<i>rph</i>-1.</p>b<p>The <i>dam</i> gene was cloned using the Gateway Cloning Technology and methods provided by the manufacturer (Invitrogen). The <i>dam</i> gene was amplified by PCR with Triplemaster (Eppendorf), primers 5′-GGGGACAAGT TTGTACAAAA AAGCAGGCTT CACAGCCGGA GAAGGTGTAA TTAGTTAGTC AGCATGAAGA AAAA and 5′-GGGGACCACT TTGTACAAGA AAGCTGGGTT TATTTTTTCG CGGGTGAAAC GACT and the chromosomal template DNA derived from <i>E. coli</i> K-12 MG1655 (Masterpure DNA purification kit, Epicentre). After purification (Qiagen PCR purification kit), the <i>dam</i> gene was inserted into vector pDONR201 and subcloned from this plasmid into the destination vector pSTL360 <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1000300#pgen.1000300-Dutra1" target="_blank">[64]</a>, a derivative of pBAD18 <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1000300#pgen.1000300-Guzman1" target="_blank">[65]</a> with an arabinose-regulated promoter. Plasmids were recovered by transformation into <i>E. coli</i> K-12 strain DH5α. The presence of intact <i>dam</i> in these plasmids was confirmed by DNA sequence analysis.