Isolation and characterization of Pseudomonas aeruginosa PAO mutant that produces altered elastase

Pseudomonas aeruginosa PAO mutants defective in elastase were isolated by plate assays of nitrosoguanidine-mutagenized clones. A total of 75 elastase mutants were isolated from 43,000 mutagenized clones. One mutant (PAO-E64) was apparently identical to the parental strain except for its deficiency in elastase activity. This mutant produced an enzyme which was antigenically indistinguishable from parental elastase. Furthermore, equal levels of elastase antigen were produced by this mutant and its parental strain. The mutant elastase, however, had greatly reduced enzymatic activity. Mutant PAO-E64 is presumed to have a mutation in the structural gene for elastase. We have designated the genotype of the mutation in PAO-E64 as lasA1.