 For example, pyelonephritis-associated pili (PAP) phase variation in uropathogenic "E. coli" is controlled by Dam through the methylation of the two GATC sites proximal and distal to the PAP promoter.Given its role of protein regulation in "E. coli", the Dam methylase gene is nonessential as a knockout of the gene still leaves the bacteria viable.The retainment of viability despite a "dam" gene knockout is also seen in Salmonella and Aggregatibacter actinomycetemcomitans.