Inactivation of haemolysin production in Escherichia coli by transposon insertion results in loss of virulence.

A haemolytic E. coli strain is nephropathogenic for mice. Mutagenesis by transposon insertion resulted in mutants with altered haemolytic activity. Reduction or elimination of the haemolytic activity is accompanied with loss of virulence. It is shown that this loss of virulence is due to altered haemolytic activity and not caused by the transposon insertion itself.