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1887

Microbiology Society logo - Volume 5, Issue 1, 1951

Volume 5, Issue 1

Volume 5, Issue 1, 1951

  • Article

      • Cultural and Serological Phases of

        https://doi.org/10.1099/00221287-5-1-197

        SUMMARY: Three phases of , A, B and C, are distinguishable by cellular and colonial morphology, and to some extent serologically. Phase A is the modal form of freshly-isolated strains; it has a uniform bacillary morphology, swarms intermittently on nutrient agar, and forms stable suspensions in 0·85% saline. Phase B strains, though possessing flagella, are usually non-motile, non-swarming, and highly pleomorphie; usually form unstable suspensions. Phase C strains are uniformly filamentous, motile, often swarm in a continuous film, and stability in saline varies with the strain.

        The somatic surface of phase A strains is characterized by a dominant type-specific antigen, and traces of a non-specific and a possibly strain-specific antigen. In phase B strains the type-specific antigen is largely lost, and the other two antigens dominate the surface. The antigenic surface of phase C strains does not differ markedly from that of phase A.

        The phase variations A → B and A → C are reversible. Phase B resembles a partially R form, in which the mouse-virulence is significantly less than that of the parent phase A strain.

    • Growth and Nisin Production of a Strain of

      https://doi.org/10.1099/00221287-5-1-208

      SUMMARY: Stable mutant colonies were picked from a parent strain of which gave improved yields of nisin; further improvement could not be produced by means of eolchicine or camphor.

      Nisin is stable in the culture fluid at acid pH values, but is inactivated by Seitz filtration or heating at pH 6 to 9. A ‘nisinase’ was not found.

      In the presence of sufficient glucose, growth was increased when the lactic acid formed was neutralized, the concentration of pantothenic acid becoming the limiting factor. Maximum nisin yields were obtained when, during fermentation in the presence of sufficient glucose and pantothenate at 23-30°, the pH was stabilized at c. 6, which is the pH optimum for nisin synthesis.

      Sodium lactate and nisin are only slightly inhibitory to the organism. Growth comes to an end because of the maximum limiting population density (‘M’-concentration) of cells, and is not due to the exhaustion of food or accumulation of toxic products.

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