The galEp3 (galE490∗)mutation represents a 1.3 kb IS2 insertion in the gal leader region (between the promoter and structural genes of the galETKM operon). The mutation causes transcriptional polarity on the structural genes due to rho dependent transcription termination within IS2. In this assay, the gal operon expression in a galEp3mutant or its derivatives was monitored by one of two means. In the first, MacConkey galactose indicator plates (with 1% galactose) were used, where Gal+ colonies are red, and Gal− colonies are white. Therefore, the depth of color serves as an indicator of relative levels of gal expression. In the second method, growth of strains on minimal-galactose (0.2%) was used as a test for Gal+ phenotype