Envelope protein changes, autoagglutination, sensitivity to hydrophobic agents and a conditional division lesion in Escherichia coli strains carrying ColV virulence plasmids.

The presence of the virulence plasmids ColV,I-K94 or ColV-K30 in Escherichia coli produces a number of cell membrane and envelope changes. The most striking of these are (1) the presence of the 33K VmpA outer membrane protein and (2) the ColV-associated occurrence of autoagglutination. The VmpA protein is a plasmid-encoded outer membrane protein which is synthesized from a larger precursor. It is distinct from the chromosomally-encoded OmpA protein but resembles it in a few respects. The VmpA protein does not appear to be involved in colicin synthesis or immunity, or in plasmid transfer. This protein was found in 6 out of 8 new ColV+ isolates, but not in 2 ColIa+ strains. ColV-induced autoagglutination occurred for strains grown in static culture at 37 but not at 25 degrees C. Detergents prevented agglutination, as did the presence in a ColV+ strain of a fi+ plasmid, ColB. Autoagglutination may be a virulence phenotype. Associated with the ability of ColV+ bacteria to agglutinate was inhibition of motility. ColV+ bacteria also showed changes in envelope permeability indicated by inhibitor sensitivity and by a ColV-associated suppression of the lac Y lesion. Some ColV,I-K94+ strains showed a mucoid colonial phenotype and this ability to form mucoid colonies was efficiently transferred with ColV but apparently not without it. The mucoid ColV+ strains resembled lon mutants in UV-sensitivity, division behaviour and sensitivity to lambda phage.