196 



THE ACTINOMYCETES, Vol. I 



upon the growth of swine has been presented 

 by Brande et al., and a detailed analysis of 

 the nature of the growth promoting effect of 

 antibiotics upon animals has been made by 

 Porter (1957). Porter summarized the evi- 

 dence that their use results in appreciable 

 benefit to growing livestock. Early fears that 

 their use for breeding stock might lead to the 

 establishment of resistant strains of patho- 

 genic bacteria have been found to be ground- 

 less. The feeding of antibiotics to animals 

 was found to result in a healthier environ- 

 ment. 



The mechanism by which the antibiotics 

 produce this favorable effect on growth of 

 the animals may be due to their action on 

 the tissues, or primarily upon bacteria. This 

 may depend partly on the state of health of 

 the animals. Conditions of poor health can 

 lead to a state of disease, making it difficult 

 to draw a distinguishing line between the 

 therapeutic effect of antibiotics and their 

 nutritional action. Antibiotics may exert a 

 direct antibacterial action on pathogenic 

 bacteria in the gut or animal tissues. Their 

 presence in small quantities in both the gut 

 and tissues may also act as a prophylactic. 

 Even in the absence of a state of disease 

 there is a definite relationship between the 

 effect of antibiotics on growth and the effect 

 on the microbial flora. There is little or no 

 evidence of consistent changes in the types 

 and numbers of the microorganisms in the 

 gut, possibly because present techniques are 

 not sufficiently developed to detect changes 

 in the gut population. Such changes may not 

 take place and the antibiotics may act by 

 altering the metabolism Init not the mor- 

 phology of the microorganisms. J\jrter postu- 

 lated that such alteration may result either 

 ill an increased microbial synthesis of known 

 or unidentified nutrients or in a lessened 

 competition by the microorganisms for nu- 

 trients, the host benefiting from l)oth. 



Stimulating Effect of Products of Ac- 

 tinoniycetes upon Plants and Bac- 

 teria 



Koaze demonstrated that the culture fil- 

 trate of a streptomyces had a strong pro- 

 moting effect on the germination of rice 

 plants, in a dilution of 10~^ to 10~^ A crys- 

 talline substance was obtained by ethyl 

 acetate extraction and chromatography on 

 aluminum oxide which was active in con- 

 centration of 0.1 mg/ml. It was a neutral 

 substance, soluble in alcohol, benzene, 

 chloroform, and water. On analysis it gave 

 C10H16X2O2 . It was found to be L-prolyl-L- 

 valine anhydride (diketopiperazine). The 

 substance had no antibiotic activity. 



In a study of the effect of antibiotics upon 

 plant growth Koaze et al. (1957) found that 

 certain antibiotics showed a similar promot- 

 ing effect; neomycin B and sarkomycin had 

 a marked effect on the growth of broad 

 beans. 



IVIention may also be made of the growth- 

 promoting effect of certain actinomycetes 

 upon cellulose-decomposing and nitrogen- 

 fixing bacteria (Sanborn, 192G). The mech- 

 anism of this action is still insufficienth' 

 understood. 



Ciferri and Machado noted, during the 

 isolation of an antibiotic produced by a cul- 

 ture of a streptomyces belonging to the S. 

 griseiis group, a considerable yellow-green 

 fluorescence of the metabolic liquids. The 

 riboflavin potency of such liquids was as- 

 sayed with mutant strains of Lactobacillus 

 casci and Leuconostoc mesenteroidcs, gi\'ing an 

 activity corresponding to a ribofla\'in con- 

 tent of 0.9 to 1.2 tig/n\\. The fluorescent 

 pigments could be easily extracted with n- 

 butanol and purified by absorption on char- 

 coal and elution with aqueous pyridine. 

 Paper chromatography of such preparations 

 and of the original broths showed at least 

 four spots characterized by fluorescence 

 under Wood's light but none could be identi- 



