Abortive infection by bacteriophage Me1 of Escherichia coli K12 strains bearing the plasmid ColV, I-K94.

Bacteriophage Me1 is unable to grow on Escherichia coli strains harbouring the ColV,I-K94 plasmid. The nature of this inhibition was investigated, and it was found not to be due to restriction, superinfection exclusion or receptor-mediated resistance, but to be a new example of plasmid-mediated abortive infection. Investigation of events occurring during abortive Me1 infection revealed some differences from previously described cases, especially with regard to late protein synthesis, which did occur, albeit showing abnormal amounts of some proteins. No major differences were observed in membrane permeability of productively and abortively infected cells. Phage-directed DNA synthesis was reduced in abortively infected cells. Comparative studies of Me1 and T4 revealed a striking similarity despite some minor differences.

Suppression by the ColV,I-K94 plasmid of a growth lesion in ompA mutants of Escherichia coli.

Organisms of three independently isolated ompA mutants of Escherichia coli failed to form colonies on glucose minimal agar (glucose MA) at 44 degrees C after growth in glucose minimal salts medium at 37 degrees C, although all three strains formed colonies on nutrient agar at 44 degrees C. Supplementation of the glucose MA with individual amino acids including L-methionine and/or L-cysteine did not allow colony formation at 44 degrees C, although addition of 0.1% Casamino acids was effective; replacement of glucose with other energy sources or ammonium ions with glutamate also did not allow growth at 44 degrees C. The failure to form colonies at 44 degrees C was not due to killing of the organisms, because colonies were formed if plates of the ompA mutant initially incubated at 44 degrees C were shifted to 30 degrees C after 16 h. Introduction of the ColV, I-K94 plasmid into P678-54 ompA, 1131 ompA or an ompC ompA mutant suppressed the 44 degrees C growth lesion, but other plasmids (F lac, R483ColIa, RI, ColB-K98, R124) tested in P678-54 ompA did not. Growth of the ColV, I-K94+ derivative at 44 degrees C was due to a suppressing effect of the plasmid rather than to introduction of the plasmid into a variant with normal or altered OmpA protein. An attempt was made to ascertain which component(s) encoded by ColV, I-K94 was (were) responsible for allowing growth at 44 degrees C. Transfer components appeared unlikely to be involved and plasmids which conferred individual colicins (plus the corresponding immunity component) did not suppress.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the virulence plasmid ColV, I-K94 on the sensitivity of Escherichia coli to putative environmental inhibitory agents.

Derivatives of Escherichia coli carrying the virulence plasmid, ColV, I-K94 were more resistant than the ColV- parents to phage Mel but were more sensitive to the hydrophobic inhibitors deoxycholate, erythromycin and lysozyme. The basis for these changes in sensitivity has been examined in ColV+ mutants with altered colicin or VmpA protein levels and in ColV+ strains with repressed transfer properties.

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.

Effects of the resistance plasmid R124 on the level of the OmpF outer membrane protein and on the response of Escherichia coli to environmental agents.

The introduction of the F-like resistance plasmid R124 into an ompC mutant of Escherichia coli K12 conferred altered sensitivity to a wide range of inhibitory agents. Sensitivity to ampicillin, chloramphenicol, ethionine, copper ions, deoxycholate, two fatty acids and colicins L and M was decreased by the plasmid. In contrast the plasmid-bearing ompC derivatives were more sensitive than the plasmid-free ompC mutant to erythromycin, cetyltrimethylammonium bromide and phenol. Introduction of R124 into the ompC strain also decreased the level of the OmpF protein and some (but not all) of the changed sensitivities listed above clearly resulted from this outer membrane protein deficiency. The presence in the ompC mutant of R124 (rather than the more efficient introduction of the plasmid into variants of the ompC strain) led to at least most of the changes described above because those tested were accentuated by the presence of a copy mutant of R124 and reversed by plasmid curing.