. The actinomycetes. Actinomycetales. .mixi:h.\i, mi:i\\H() and i'.kkixt of s.\i/rs ox cHowi'if 143. CONTROL 4 DAYS Figure 68. Effect on streptomyces mycelial gruwth produced by various concentrations of compost soil extract (Reproduced from: Spicher, G. Zentr. Bakteriol., Abt. 2, 108: 579, 1955). to mediti from which cohaU was omitted. Levels of 1 to 2 parts pei- milhon cobalt yielded maximum results; levels of 20 to 50 parts per million were toxic. Colialt has since been used routinely in culture media for screening and for production of vitamin Bi-> . The form of cobalt and the conc
. The actinomycetes. Actinomycetales. .mixi:h.\i, mi:i\\H() and i'.kkixt of s.\i/rs ox cHowi'if 143. CONTROL 4 DAYS Figure 68. Effect on streptomyces mycelial gruwth produced by various concentrations of compost soil extract (Reproduced from: Spicher, G. Zentr. Bakteriol., Abt. 2, 108: 579, 1955). to mediti from which cohaU was omitted. Levels of 1 to 2 parts pei- milhon cobalt yielded maximum results; levels of 20 to 50 parts per million were toxic. Colialt has since been used routinely in culture media for screening and for production of vitamin Bi-> . The form of cobalt and the concenti'a- tion varied according to the indi\'i(lual in- vestigator and the media used. A cobalt-tol- erant culture of Saccknromijces cercvimie, developed l)y Perlman and O'Brien, added to a soybean meal-glucose mediimi inocu- lated with *S. griscus could be utilized as a source of cobalt for ^•itamin B]-.) production more efficiently than inorganic cobalt added as the nitrate. The increased efficiency was noted over a concentiation range of to ;ug ml, but not at higher levels. (See also Burton and , C'harney, Du- lancy and Williams, Kojima and Matsuki, Principe and Thoriiberry, Smith ct ai). Radioactive vitamin B12 was produced l)y S. griseus from cobalt^" (Chariet et al.). The necessity for col)alt to gi\'e increased yields of vitamin B12 by S. olivaceus and other organisms is now well established (Hall et al.). Coppei', at concentrations of 82 parts per million, almost completely inhibits vita- min B12 synthesis; at concentrations of 133 parts per million, it permits only slight growth of the organism. Xo effect on growth or vitamin production was observed at con- centi'ations of oO parts per million. Strips of metallic copper in the medium inhibited vitamin B12 synthesis. Strips of stainless steel, tin, aluminum, iron, or lead placed in the medium showed no effect. In addition to its effect upon the produc- tion of \itamin B12 , cobalt exerts other eff
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