[Isolation and preliminary characterization of mutants of Escherichia coli K-12 overproducers of 2 exported proteins: beta-lactamase and alkaline phosphatase].

: Spontaneous mutants of Escherichia coli characterized by the overproduction of two periplasmic proteins, beta-lactamase and alkaline phosphatase were isolated. Such olp (Overproduction of beta-Lactamase and alkaline Phosphatase) mutants were selected for growth in the presence of ampicillin and were identified on the basis of their increased content in alkaline phosphatase activity. Phenotypic analysis of olp mutants (resistance to bacteriophages and colicins) suggest that the organisation of their envelope has been deeply modified. Analysis of their cell envelope protein composition indicated that most mutants have a decreased content of porin proteins OmpF and OmpC. These mutations were mapped near the mtl locus, at minute 81 of the bacterial genetic map.