)|SI'KIIU"I"1()\ l\ N AITHI'] 



45 



lioiicycoinl), and otluM' stoinaclis of niini- 

 iiants, and in llic rectum; lie su<;<;cst('(l that 

 th('si> ()rj>;anisnis uiv ohlijiiatc inhabitants of 

 the intestinal system ol' animals. I'mther 

 studi(^s on tlu> aetinomyeetes ol' the intesti- 

 nal population of hoises are found in the 

 woi'k of IlolTe, and of man in the woik of 

 Breit. 



X'arious aetinomyeetes are fre(|uently 

 found in organs of (-(Mtain insects. An organ- 

 ism desijiiiated as Xocardia rhodnii, isolated 

 from the reduvid bug, Rhodniiis prolixus 

 (Erikson, 1935), is said to he taken up by 

 the young nympli from tlu^ eontaminatcHl 

 surface of the egg or to be transmitted to the 

 insect by the dry excreta of the insects. 

 When the insect is freed of the actinomycete 

 by sterilizing the surface of the egg and by 

 feeding the adult with suita})le precautions, 

 sterile insects are produced. These grow and 

 moult normally only for a certain period, but 

 they are usually incapable of reproduction. 

 When the insects are reinoculated with the 

 actinomycete cultures, normal growth, 

 moulting, and egg production will result. 



The occurrence and isolation of aetino- 

 myeetes from animal diseases ha^'e already 

 been mentioned (Chapter 1) and will lie dis- 

 cussed in greater detail later (Chapter 17). 

 Mau}^ of the organisms repoi'ted to have been 

 isolated from disease conditions, beginning 

 with those of Bostroem and ending with 

 those of Erikson (1935), may not be the caus- 

 ative agents of the disease, since only few 

 animal experiments were carried out, in most 

 cases, to confirm this assumption. 



Aetinomyeetes and Geologic Forma- 

 tions 



The role played by aetinomyeetes in geo- 

 logic formations is not yet sufficiently clear, 

 although .some evidence has been submitted 

 on the question, as will l)e shown later 

 (Chapter 9). 



Iiilcrrrlalionsliips am<»iig Microorgan- 

 isms ill Natural Substrates 



The remarkable progress made in I'ecent 

 years on the production of antibiotics by 

 soil microorganisms, especially acrtinomy- 

 celes, has aroused considerable interest in 

 the po.ssible effect of such antibiotics on the 

 microbiological population of the soil. Some 

 investigators, notably Krassilnikov, were in- 

 clined to see in these antil)iotics mechanisms 

 that the soil microorganisms use in competi- 

 tion for existence. Waksman considered 

 these concepts as purely speculative in na- 

 ture. In support of this conclusion, the fol- 

 lowing evidence was submitted. 



1. Aetinomyeetes occur in the complex 

 natural substrate in a mixed microbiological 

 population. This population consists of nu- 

 merous groups of microbes, which range from 

 the ultramicroscopic forms, through the 

 bacteria, aetinomyeetes, and filamentous 

 fungi, to the complex mycelium of the higher 

 or mushroom fungi, the protozoa, and vari- 

 ous small invertebrates. Each of these groups 

 is represented in nature, especially in the soil 

 and in water basins, by many species and 

 \arieties, which have the capacity to bring 

 about many complex chemical reactions. 

 The ability to produce antibiotics is only 

 one such property and is limited to certain 

 kinds of microbes, when these are grown in 

 a pure state, in an artificial (Mi\-iromnent, 

 and in a special medium. 



2. For the formation of antibiotics in sig- 

 nificant concentrations in such an artificial 

 medium, certain nutrients, characteristic for 

 each organism and comprising largely pro- 

 teins or amino acids, sugars and other com- 

 pounds, must be present. Such nutrients are 

 seldom found in the soil in sufficient concen- 

 trations to enable even the antibiotic-pro- 

 ducing organisms to dominate the environ- 

 ment or to produce measurable quantities of 

 the antibiotics. 



3. All the experimental e\-idence so far 



