Waksman — 84 — Actinomycetes 



sium, and magnesium are usually required in varying concentrations; 

 the need for sulfur, calcium, and iron is often questioned, although 

 there is no doubt that certain organisms, such as the grisein-producing 

 types, benefit considerably from the presence of iron. Traces of other 

 elements, such as zinc are frequently found to have a marked effect 

 upon the growth of certain organisms. 



Although actinomycetes are found only seldom in salt water basins 

 (522), their sensitivity to higher concentrations of different ions may be 

 of interest. 



KoBER (226) reported that some actinomycetes are able to withstand 

 a high salt concentration, 0.5 to 0.6 molar solutions giving the largest 

 sized colonies, although the smallest number, pointing to the selective 

 action of the salt. He also found, that although MgSOj is not essential 



Table 12: Metabolic changes and efficiency of carbon utilization of 

 S. lavendulae in aerated cultures (517): — 



Tryptone Glycine 



medium medium 



Mycelium, dry weight, 7ng 



Glucose consumed, mg 



NH3-N liberated, mg 



Nitrogen compounds deaminated, 77ig 



Lactic acid produced, mg 



Volatile acid as acetic, mg 



Conversion of glucose to lactic acid, pr cent 



Conversion of glycine to acetic acid, pr cent 



Efficiency of carbon utilization, ^er cent 



for growth, it has a favorable effect in fairly high concentrations. Cal- 

 cium is not essential for growth, but its lack in the medium has an in- 

 jurious effect unless magnesium is present. Potassium is injurious in 

 concentrations of 0.5 per cent KCl, which can be neutralized, however, 

 by high concentrations of MgS04. 



Growth and Cell Synthesis of Aerobic Actinomycetes:— In ordi- 

 nary stationary cultures, actinomycetes produce on the surface of the 

 medium a compact pellicle which may be continuous or which may 

 consist of discontinuous masses of growth or even of individual colonies. 

 Occasionally, growth takes the form of a surface ring along the wall of 

 the vessel. Many species give rise to masses of growth only on the bot- 

 tom of the vessel or in the form of flakes or colonies throughout the 

 medium and on the bottom. This type of growth is greatly influenced 

 by the nature of the spores, the amount of air admitted, and the agita- 

 tion of the cultures, which results in breaking up of the mycelium or of 

 the spores, thus initiating fresh growth. 



In a submerged state, growth of actinomycetes is usually in the form 



