riJODlCnoN Ol' \I'I'AMINS AND (>'l'lli;i{ CKOWril FACTOUS 



197 



fiod oithor with ril)ofl:i\iii or its nucleotides 

 or decomposition pi'odiicts. ()nly spot 2 

 react (m1 with DJiiliychiii. When I he spots were 

 cut oil the chroniatoiiranis and tested in- 

 di\iduall>\ only one spot , ('liaraclei'ized by a 

 blue lluorescence, pro\{'d capable ol' sus- 

 taininji; the growtli of /.. c(ts( i. 



RubcMitsc'hik (7 al. found that \ariou.s strep- 

 toniyccs, such as »S. g)'iseus, S. c<wlicolor, and 

 »S. ylobisporus, when grown in cultures with 

 other organisms, are capable of forming 

 A()latil(> materials which stimulate the 

 growth of K. coll, B. subtilis, B. mesentericus, 

 and other bacteria. Every Streptomyces spe- 

 cies was said to exert a characteristic effect, 

 S. grisens stimulated the growth of Azoto- 

 bacter. 



Grossbard reportc^d that A'arious anti- 

 fungal substances produced by actinomy- 

 cetes exert stimulative effects upon the 

 growth of fungi, Avithin a concentric circle 

 adjoining the zone of inhibition. Pigmenta- 

 tion was intensified in cultures of Verticil ium 

 dahliac, Helminthosporium vidohae, and 

 Fusarium oxysporum. The last usually fails 

 to produce a pigment on synthetic media, 

 but in response to the metabolites of certain 



st re])tomyces cultures, a pigment was formed 

 in optimal media; a considerable intensifica- 

 tion of I he pigment (lycopersin) occiu'red. 

 ('olhlotriclmm atramcnlarium responded to 

 the same streptomyces metabolites by an 

 acceleration in the maturing and l)y a greater 

 density of stromata. Ccratostomella ulmi and 

 Streptomyces scabies responded l\y more 

 rapid sporulation. 



The favorable effect of certain strepto- 

 myces upon the sporulation of other cultures 

 of the same genus has been demonstrated by 

 Dondero and Scotti. These results led to the 

 conclusion that actinomycete metabolites 

 contain specific stimulatory substances in 

 addition to inhibitory substances, or that the 

 substances may be growth-inhibiting at one 

 concentration and growth-stimulating at an- 

 other. 



The significance of these phenomena in 

 natural processes in general and in the soil 

 in particular is still to be elucidated. This is 

 also true of the stimulating effect of actino- 

 mycin upon the growth of some strains of 

 rhizobia and its inhibiting effect upon others, 

 notably the slow growing strains (Trussell 

 and Sarles). 



