To isolate intact flagella with basal complexes from Vibrio cholerae, a rhamnolipid hemolysin from Pseudomonas aeruginosa was used to disrupt the cell envelope and flagellar sheath. The nonionic detergent, Triton X-100, provided similar results for Campylobacter fetus. Each of these basal complexes possessed, in addition to the four classical rings, concentric membrane rings (CMR's) similar to those found in Aquaspirillum serpens. Through the use of stereo imaging (which allows structures to be visualized in three dimensions) of thin sections of cells which had been sequentially treated with a number of envelope perturbants (i.e., ethylenediaminetetraacetate, lysozyme, Triton X-100, rhamnolipid hemolysin, and sodium dodecyl sulfate), we have progressively exposed the component parts of the basal organelles in V. cholerae and C. fetus. Since the action of these envelope perturbants has been well documented, we have been able to determine the associations of the exposed portions of the flagellar basal complex and the layer of the cell envelope in which they would normally reside. From our observations we have concluded that in both V. cholerae and C. fetus the L ring is embedded in the outer membrane and the P ring is associated with the peptidoglycan. The CMR's are bracketed by the L and P rings and are sandwiched between the outer membrane and the peptidoglycan. Elements of both the S and M rings appear to be associated with the plasma membrane.

Vancomycin in combination with ciprofloxacin exhibited synergy against 7 of 10 strains of Pseudomonas aeruginosa. MICs for the microbial strains used in this study ranged from 0.0325 to 3.0 micrograms/ml for ciprofloxacin and from 23.5 to > 188 micrograms/ml for vancomycin. Combinations of these antibiotics, tested in a checkerboard pattern, gave fractional inhibitory concentrations of 0.5 or less for 7 of the 10 strains tested.

Lysozyme (EC 3.2.1.17) complexes with extracted Pseudomonas aeruginosa LPS in two distinct stages. The initial stage does not produce turbidity detectable by nephelometry (measured as nephelos units (N) per time) but does permit low-speed sedimentation of the lysozyme-lipopolysaccharide (LPS) complex. This association is 100% disrupted by the action of 0.1 M Mg2+. Monovalent cations at equal ionic strength to the Mg2+ concentration used for these studies failed to alter significantly the lysozyme-LPS complex, indicating that the role of Mg2+ was not strictly an ionic one. The study of lysozyme-LPS complexes may provide a model system for investigating in vivo protein-LPS interactions.

No abstract

An alkaline phosphatase mutant of Pseudomonas aeruginosa exhibiting both regulatory and catalytic changes was isolated. Under repression conditions (i.e. high inorganic phosphate (Pi)) the mutant culture produced an alkaline phosphatase (APase) displaying significant activity against both beta-glycerol phosphate (betaGP) and p-nitrophenyl phosphate (pNPP), while the wild type displayed no activity directed towards these substrates under the same conditions. In vivo, the mutant enzyme's ratio of specific activities was 45:1 in favour of betaGP versus pNPP, whereas this ratio was reversed to 1:9 betaGP versus pNPP for the same enzyme isolated from mutant cells. In addition, the kinetic parameters and stability requirements for the mutant-derived enzyme was altered in comparison with those of the wild type. A study of lipopolysaccharide (LPS) preparations from both the mutant and wild type indicated the mutant to be deficient in the core region of its LPS. The authors propose that the modifications in the catalytic activity of the mutant enzyme, demonstrated in vivo, are due to a change in the enzyme's microenvironment.