Chapter II — 4 1 — Important Types 



autolysis of the mycelium but is due to cell nutrition or to cell synthesis. 

 This renders the mechanism of the production of this substance distinct 

 from that of tyrothricin, for example, which is a result of autolysis of 

 the bacterial cells, or of penicillin, which is produced at a much later 

 stage of growth of the organism, that is, when it reaches an alkaline 

 reaction. 



The efficiency of utilization of carbon and nitrogen by S. lavendulae 

 is very high. At the maximum growth stage, 65 per cent of the nitro- 

 gen in the glycine added to the medium was found to be converted into 

 actinomyces cell substance. Since as much as 330-350 mg. of mycelial 

 growth was obtained from 1 gm. of raw starch, the efficiency of utiliza- 

 tion of the carbon, considering the carbon content of the starch as well 

 as of the glycine, is about 40 per cent. 



Strepto-myces veneznelae Ehrlich, Gottlieb, Burkholder, 

 Anderson and Pridham 



S. veneziielae, the organism that produces Chloromycetin (chloram- 

 phenicol) was isolated from two different soils, one a mulched field near 

 Caracas, Venezuela, and the other a compost soil at Urbana, Illinois 

 (103, 103a). 



Primary mycelium growing in agar substrates is thin-walled, colorless, 

 hyaline, monopodially branched. Mature vegetative hyphae vary in 

 diameter from 0.9 to 1.8[j, and the branches grow to about iSOji. in 

 length. Sometimes the substratal mycelium forms oval spores by frag- 

 mentation. The aerial mycelium is lavender under the microscope, 

 thick-walled, generally not much branched, straight or slightly and irreg- 

 ularly curved, not forming spirals, having individual filaments that ap- 

 pear stiff, and arising frequently from the primary mycelium at the 

 surface of the substrate. Individual filaments are rarely septate, are 

 1.0 to 1.8[j- in diameter, and vary in length up to about 350[ji.. In young 

 colonies, the aerial hyphae project outward radially over the surface 

 of the colony and show a lavender color when examined microscopi- 

 cally. The color of colonies when viewed on agar without magnifica- 

 tion is gray to light tan or pink, but not lavender. Distal portions of 

 the aerial hyphae commonly subdivide into unbranched oidial spore 

 chains, which are readily fragmented into small groups or individual 

 spores. 



The spores are oval to oblong. Mature spores range from about 

 0.4 to Q.% in diameter and from 0.7 to 1.6[x in length. The spores 

 formed by fragmentation of hyphae in the substrate are generally 

 smaller than those formed from the aerial hyphae. Individual spores 

 arCf colorless at maturity but in mass appear tan to gray when viewed 

 without magnification. They may be stained readily with crystal violet 



