Altered osmoregulation of ompF in integration host factor mutants of Escherichia coli

Osmoregulation of the porin protein OmpF was strongly altered in integration host factor (IHF) mutants. These mutants produced approximately 15-fold more OmpF than did the parent strain when grown in media of intermediate osmolarity. At high osmolarity IHF mutants continued to produce considerable amounts of OmpF, although this protein was undetectable in the parent grown under these conditions. Experiments with an ompF-lacZ chromosomal fusion strain suggested that these changes in osmoregulation in large part involve alterations in transcriptional activity of the ompF promoter. These results add to the growing list of genes whose expression is modified in IHF mutants.