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C W Douglas

Publications and source records attributed to C W Douglas.

63 records · Page 4Linked to original sources
PubMed1983

The binding of human salivary alpha-amylase by oral strains of streptococcal bacteria.

The ability of various oral streptococci to bind salivary alpha-amylase to their cell surfaces was investigated. Samples of cells were mixed with whole cleared saliva and the alpha-amylase remaining after removal of the cells was assayed by radial diffusion in starch-containing agarose. Seventy-five per cent of Streptococcus sanguis strains bound the enzyme but strains of Streptococcus mutans and Streptococcus mitior did not. SDS-polyacrylamide gel electrophoretic analysis of Strep. sanguis cells which had been mixed with saliva showed that alpha-amylase is bound to the surface of the cells and can be recovered from them intact. The ability of Strep. sanguis strains to bind the enzyme did not correlate with biotype, IPS production or ability to adhere to saliva-coated hydroxyapatite. The cell-surface receptor responsible for the binding of alpha-amylase to Strep. sanguis (NCTC 7865) is a heat-stable component, possibly protein in nature, which is closely associated with the cell wall.

Humans↗
PubMed1983

Fructosyltransferase activity of a glucan-binding protein from Streptococcus mutans.

Streptococcus mutans serotype c produces several extracellular proteins which bind to affinity columns of immobilized glucans. The proteins are three distinct glucosyltransferases and another glucan-binding protein (molecular weight 74000) which is now shown to be a fructosyltransferase. This enzyme is antigenically distinct and genetically independent of two other fructosyltransferases produced by the same organism. A mutant is described which lacks the glucan binding fructosyltransferase and has defective ability to form adherent colonies in the presence of sucrose. Although the production of glucans from sucrose results in the glucan binding protein becoming bound to the bacterial surface, and hence perhaps contributing to adherence, the fructans synthesized by the enzyme do not appear to contribute to this phenomenon.

Carrier Proteins↗
PubMed1982

Effect of specific antisera on adherence properties of the oral bacterium Streptococcus mutans.

Antisera to Strep. mutans antigens B, glucosyltransferase (GTF) and a glucan-binding protein (GBP) reduced the build-up of this bacterium on glass surfaces in vitro; antiserum to antigen A and a control non-immune serum were without significant effect. The same sera were used to study the involvement of these antigens in cell-cell aggregation mediated by sucrose or water-soluble Dextran 2000. Antiserum to GTF and antigen B inhibited sucrose-dependent cell-cell aggregation of the organism by approximately 50 per cent; none of the antisera tested had any effect upon dextran-mediated aggregation. In the presence of sucrose, GTF and GBP became cell associated while the distribution of antigens A and B between culture supernatant and cell surface remained unchanged. Cells incubated in the presence of Dextran 2000 showed no change in the distribution of any of these antigens. It is concluded that the aggregation of Strep. mutans induced by sucrose or by dextran involves different cellular components. Consideration of these in-vitro results in relation to data from experiments in which macaque monkeys were immunized with purified Strep. mutans antigens suggests that inhibition of sucrose-dependent adherence is not the basis for protection against dental caries.

Adhesiveness↗
PubMed1979

Measurement of Proteus cell motility during swarming.

The motilities of Proteus long forms during swarming on agar were measured on cells transferred to liquid suspension. During concentric-ring formation on solid medium, when the edge of the swarm was advancing slowly or had stopped, the velocity of long-form motility was low. When the colony was spreading rapidly, long-form velocitywas relatively high. This periodic variation in cell velocity, which determines the zones formed during swarming, cannot adequately be explained by negative chemotaxis.

Bacteriological Techniques↗
PubMed1976

A continuous study of morphological phase in the swarm of Proteus.

Continuous study, at intervals of 1 h, on the advancing edge of the swarm of Proteus vulgaris confirms that this is almost permanently composed of elongated swarmers, and that short, non-swarming forms arise in the interior of the culture where motion has already ceased. Previous errors have probably arisen from inaccurate sampling.

Movement↗
PubMed1976

Development of concentric zones in the Proteus swarm colony.

Two main mechanisms of concentric ring formation in cultures of Proteus species are described. One of these is the classically accepted method, wherein rings are produced as the advance of the swarm stops and recommences. In the other, the ring is produced as a fold inside the colony. These are considered to be extremes of a spectrum of growth types, the common feature being that rings are formed by piling-up of growth, and this process is not always directly correlated with morphological change in the individual bacteria, or with cessation of advance of the swarm. The validity of the presently accepted theories of ring formation and swarming in general are thus called into question.

Models, Biological↗