132 



THE ACTl.NOMYCETES, Vol. I 



tivity. According to Erikson, they do not 

 attack egg or blood serum; they do not clot 

 or hydrolyze milk; they seldom grow on 

 gelatin; they have little or no hemolytic 

 action on blood agar. Certain strains iso- 

 lated from human infec^tions have been 

 found to show a slight degree of hemolysis 

 on blood-agar plates at different times, but 

 not consistent^. They do not produce 

 soluble pigments on protein media or in- 

 soluble pigments in their cells. 



The growth of .4. hoiis on sugars is not 

 accompanied by gas formation. Glucose is 

 the most readily available source of energy; 

 acid is formed. Maltose, lactose, and sucrose 

 are also utilized by all strains. Positive or 

 negative reactions with salicin and mannitol 

 have been found of value in differentiating 

 strains, such as human ve7'sus bovine. A. 

 hovis was found by Rosebury to have a 

 limited tolerance for oxygen, which varies, 

 however, among strains. 



The introduction of synthetic media for 

 the growth of actinomyces (Howell and 

 Pine) made possible the study of the ability 

 of these organisms to produce lactic acid. 

 According to Erikson and Porteous (1953), 

 A. Israeli has the capacity to convert as 

 much as 30 to 60 per cent of the glucose 

 utilized to lactic acid, imder suitable condi- 

 tions of growth. 



Like aerobic actinomycetes, A. hovis is 

 killed by heating at 62 to 64° C for 3 to 10 

 minutes, but it apparently survives drying 

 for a long time, particularly when kept at 

 low temperatures. Lieske, however, re- 

 ported that anaerobic forms are highly sensi- 

 tive to drying, being unable to survive even 

 for one day. 



Influence of Temperature 



The range of temperature within which 

 many microbes are able to develop is com- 

 paratively wide. Most microbes begin to 



8 



k- 



/ 



/ 



/ 



..•' r' •' 



NO GLUCOSE 



0.1* 



0.5* 



I* 



2* 



2 4 6 8 10 



DAYS 



Figure 64. Effect of glucose concentration on pH (Reproduced from: Knissilnikov, X. A. 1950, p. 

 206). 



