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Biomedical subjects

R J Rowbury

Publications and source records attributed to R J Rowbury.

90 records · Page 5Linked to original sources
PubMedDate not supplied

Resistance of attached Escherichia coli to acrylic acid and its significance for the survival of plasmid-bearing organisms in water.

As previously reported, free organisms of Escherichia coli are sensitive to damage and killing when exposed to acrylic acid in water. The effect of the agent was greatest in distilled water, but there was a marked effect in effluent and seawater also. The effect was temperature-dependent, with organisms exposed at 4 degrees C being much less affected than those exposed at 20 degrees C. The above sensitivity was for free organisms, but those attached to glass beads were resistant to acrylate. This resistance applied equally to attached plasmid-free and attached plasmid-bearing organisms, but is likely to be more significant for plasmid-bearing strains because some plasmids studied here stimulated bacterial attachment. The likely significance of the acrylate resistance of attached organisms for enterobacterial survival in the aquatic environment, e.g. in the vicinity of shellfish beds, is discussed.

Acrylates↗
PubMedDate not supplied

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.

Bacterial Outer Membrane Proteins↗
PubMedDate not supplied

A motility lesion in ColV+ Escherichia coli strains and its possible clinical significance.

The introduction of the ColV-K30 or ColV,I-K94 plasmid into Escherichia coli strains produced derivatives which had a motility lesion if grown without shaking at 37 degrees C. Although most ColV+ organisms from shaken cultures were motile, 80-90% of free unclumped organisms from static cultures were flagellate but non-motile. This plasmid effect was temperature-dependent with only those ColV+ organisms grown at 37 degrees C being affected; ColV+ organisms grown at 30 degrees C or below were predominantly motile. The motility lesion depended on the presence, in the ColV+ organisms, of transfer and colicin components together but not of the VmpA protein. Aside from the changed motility, there was extensive autoagglutination (clumping) of ColV+ organisms in static cultures, and the two phenomena (clumping and motility lesion) appeared to be governed by the same factors. The Flac plasmid of FI incompatibility group had a slight inhibitory effect on motility of strain 1829 and caused slight clumping, but representative plasmids of groups FII, FIII, FIV, C, H, I, K, M, N, P, W and X had no appreciable effect on either parameter. Non-motile ColV+ organisms regained motility on incubation with buffered detergent solutions, suggesting that an envelope change might be responsible for the altered motility. It can be hypothesized that ColV+ organisms in the intestine would be motile and hence able to reach the intestinal epithelium for invasion but that, once such organisms had reached the tissues and bloodstream, they would be predominantly non-motile and hence might be less susceptible to phagocytosis.

Blood↗