36 



Biochemical Activity of Microorganisms 



[March, 



The solvent action of enzymes is commonly apparent when 

 microorganisms are grown upon Heyden Nälirstoff-agar. This 

 medium almost invariably contains particles of protein material 

 which have passed through the cotton filters and give Petri dishes a 

 slight turbidity. Colonies of organisms usually dissolve these par- 

 ticles through the action of proteases, the diffusing enzymes acting 

 for some distance beyond the margin of the colony. More con- 

 spicuous examples of this power may be afforded by using some of 

 the following methods. 



TABLE 5 



Data pertaining to tcsts for proiease-production on fibrin-agar 



Organism Growth Dissolution of fibrin 



Phyllosticta pirina Good Rapid 



Helminthosporium turcicum Excellent Very rapid 



Aspergillus sp Good Rapid 



Aspergillus niger Good Slow 



B. pyocyaneus Very slight Very slight 



Sarcina lutea Excellent Good 



Diplococcus sp None 



B. hartlebii Slight if any Slight if any 



B. lactis ccrogcncs Slight if any Slight if any 



B. fiuorescens liquifacicns Slight if any Slight if any 



M. citricus Excellent Good 



B. subtilis Excellent Slight 



B. megatherium Excellent Good 



Bact. lactis acidi Fair Slight 



B. prodigiosus Good Good 



B. campestris Good Good 



B. mycoides Good Good 



B. putidum Slight if any Slight if any 



B. cyanogcnus Slight if any Slight if any 



Bacteria of ropy milk Fair Fair 



B. butyricus Excellent Excellent 



B. amylovorus None 



Microspira tyrogena Slight if any Slight if any 



B. vulgaris Slight Slight 



Bact. denitrificans Slight Slight 



B. coli Slight Slight 



Bact. tumcfacicns Slight Slight 



B. radiatum Fair Slight 



Streptothrix sp Excellent Fair 



Oidium lactis Poor Slight 



Fibrin-agar. Some blood fibrin is pulverized in a mortar and 

 added to the stock agar to the amount of i percent. Agglutination 

 of the fibrin takes place and although it is almost impossible to 

 get it evenly distributed through the medium, many fungi thrive on 

 it satisfactorily and dissolve fibrin. Some bacteria show marked 

 action on the fibrin but produce no distinct halo; others grow poorly 



