Summary: WU235 expresses aspartase (EC when grown on aspartate or asparagine as the sole carbon source, but not on glucose or fumarate. Cells grown on glucose plus aspartate, or fumarate plus aspartate, do not express aspartase. Although these results are reminiscent of catabolite control of an inducible enzyme, induction of aspartase cannot be demonstrated in this strain. Aspartase-producing cells synthesize the enzyme after repeated subculture on glucose plus NHCl. Cells grown in glucose plus NHCl and plated onto aspartate produce different colony sizes; the larger (0·1% of the total) express aspartase, while the smaller do not. At dilutions sufficient to exclude the large aspartase-producing colonies, a single-sized, aspartase-negative colony was found initially. Such colonies later developed papillae or became cluster colonies; aspartase was produced with papillae formation. The aspartase producing strains were shown, by analysis of native plasmids and periplasmic proteins and by the use of antibiotic resistant strains, to be derived from the parental type. The data suggest that strain WU235 is unable to produce aspartase unless a mutation occurs which leads to constitutive enzyme synthesis. The significance of these observations for studies claiming catabolite repression in is discussed.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error