.mixi:h.\i, mi:i\\H()I.ism 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 0.01 to 

 0.1 ;ug ml, but not at higher levels. (See 

 also Burton and I.ochhead, 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 

 effects upon the gi-owth of actinomycetes. 

 Hickey and Tresner reported that the addi- 

 tion of 2 mg of CoChi-filljO to a modified 

 Bennett's medium gi'eatly laN'ored the rate 

 and extent of sporulation of S. Jradiav and 

 of a number of other streptomycetes. Sj)oru- 

 lation was suppressed when the cobalt was 



