Measurement of pcrtS copy number by qPCR

The copy number was approximated by measuring the relative marker frequency of the kanamycin resistance gene, kanR2, present in pcrtS, to ori1 on the chromosome. An aliquot of cell culture grown similarly as for time-lapse microscopy was diluted 1:100 in H₂O, heated at 95 °C for 10 mins and frozen at -20 °C prior to being used directly as template for qPCR, which was performed as described previously [12]. The ratios were normalized to the ratio obtained from the DNA of CVC3013, which contains a kanR2 inserted into lacZ, thus possessing a kanR2/ori1 marker frequency ratio of ~1. Data represents mean ± standard deviation and was averaged from two biological replicates analyzed in duplicate.