Effects of Clupein and of its Degradation Products on a Rhizobium Bacteriophage, on its Host Bacterium and on the Interaction between the two

RESP-357

The behaviour of Rhizobium bacteriophages during and after exposure to ultraviolet radiation

SUMMARY: After inactivation by ultraviolet radiation, particles of two Rhizobium bacteriophages interfered temporarily with the multiplication of active particles of the homologous phage, in liquid cultures of their respective host bacteria. Inactivated particles did not affect the number of plaques produced by active particles in bacterial cultures on agar. No evidence was found that particles that were inactive singly became active when two or more of them infected the same bacterial cell. The rate of inactivation approximated closely to that of a first-order reaction. Exposing infected bacteria to visible light increased the residual activities of irradiated phage preparations by amounts equivalent to decreasing the doses of ultraviolet irradiation by a constant factor. Exposing either the irradiated phage preparations or the bacterial cultures separately to visible light had no effect. Those ultraviolet irradiated phage particles which remained active were so altered that they became relatively unstable

The ability of single phage particles to form plaques and to multiply in liquid cultures

SUMMARY: The results of testing a bacteriophage to a strain of clover nodule bacteria using young (1 day) and old ( 5 days) bacterial cultures both fit to the hypothesis that phage multiplication can be initiated by single phage particles. As the same phage preparations gave more plaques on solid media and higher proportions of liquid cultures in which phage multiplication could be detected, with young than with old bacterial cultures, the fit to the hypothesis is not an evidence that every single phage particle will multiply. It may be so when young bacterial cultures are used, although there is no positive evidence for it. With older bacterial cultures definitely only a proportion of viable phage particles succeed in starting phage multiplication, the proportion decreasing with the increasing age of bacterial cultures used for testing

A study of the mechanism of inhibition of bacteriophage multiplication by chymotrypsin

RESP-331

The Effect of Infection with Bacteriophage on the Electrokinetic Potential of Rhizobium leguminosarum

SUMMARY: Infection with bacteriophage increased the electrophoretic mobility of pea nodule bacteria (Rhizobium leguminosarum) at pH 7, suggesting an alteration of the bacterial surface. This seemed to occur at about the middle of the latent period

Effect of Specific Polysaccharides from the Host Bacteria and of Ribonuclease on the Multiplication of Rhizobium Phages

SUMMARY: Two serologically unrelated strains of nodule bacteria produced two different polysaccharides, only one of which precipitated with antiserum to its parent bacterium. Both polysaccharides interfered with the multiplication of two bacteriophages in liquid cultures of the two bacterial strains, each of which was susceptible to only one of the two bacteriophages. One polysaccharide was slightly more effective than the other in interfering with multiplication of both bacteriophages: one phage was much more susceptible than the other to the interfering action of both polysaccharides. Crystallized pancreatic ribonuclease interfered with multiplication of bacteriophages much more strongly than did the polysaccharides. Neither the polysaccharides nor ribonuclease destroyed the phage particles

A study of phage-resistant mutants of Rhizobium trifolii

RESP-291

Mutations in symbiotic effectiveness in Rhizobium trifolii caused by transforming DNA and other agents

RESP-528

Improving epidemic control strategies by extended detection

The majority of epidemics eradication programs work in a preventive responsive way. The lack of exact information about the epidemiological status of individuals makes responsive actions less efficient. Here, we demonstrate that additional tests can significantly increase the efficiency of “blind” treatment (vaccination or culling). Eradication strategy consisting of “blind” treatment in very limited local neighbourhood supplemented by extra tests in a little bit larger neighbourhood is able to prevent invasion of even highly infectious diseases and to achieve this at a cost lower than for the “blind” strategy. The effectiveness of the extended strategy depends on such parameters as the test efficiency and test cost

A study of some mutations in a strain of Rhizobium trifolii

RESP-459