170 



BREAKDOWN OF NITROGENOUS MATERIAL 



The distribution of the amino-acid decarboxylases amongst 

 bacteria appears to be haphazard (see Table XIV). Esch. coli 

 may have the decarboxylases specific for arginine, lysine, 

 ornithine, histidine, glutamic acid, and very occasionally 

 tyrosine, but wide strain variations are found as some strains 

 may have five of these enzymes while others may have two, 

 one, or none. Many Streptococci possess tyrosine decarboxy- 

 lase, but strains differ widely in the activity of the enzyme. 

 Clostridia again show wide differences; CI. welchii may 

 possess both histidine and glutamic acid decarboxylases, CI. 

 septicmn ornithine decarboxylase only, and many other 

 species have no decarboxylases. Aspartic acid decarboxylase 

 has been found in the symbiotic nitrogen-fixing organisms 

 Rhizohia. 



TABLE XIV 



DlSTRIBTTTION OF AmINO-ACID DECARBOXYLASES 



Organism 



Esch. coli ... 



S. haemolyticus 



Proteus vulgaris . . . 



Gl. welchii ... 



CI. septicum 



CI. aerofoetidum ... 



CI. sporogenes 



Ehizobium legum- 

 inosarum 



Decarboxylase Substrate : 



+ 



