Increase in susceptibility to EcoRII restriction of bacteriophage lambda produced by propagation on host cells growing in 5-azacytidine: a new in-vivo method for demonstration of DNA-methylation inhibition.

The efficiency of plating on EcoRII-restricting cells of bacteriophage lambda vir propagated on an Escherichia coli K-12 dcm+ host decreased with increase in concentration of 5-azacytidine (5-azaC) in the propagating medium. This illustrates, in-vivo, the inhibition of DNA-cytosine methylation induced by 5-azaC and provides a simple system for the detection of DNA-methylation inhibitors.