70 THE FORMATION OF ENZYMES IN BACTERIA 



and histidine, can only take place if energy is provided by 

 some metabolic activity such as glucose fermentation. Some 

 Gram-positive organisms also differ from many of the Gram- 

 negative species in that they are unable to synthesise glutamic 

 acid, etc., from ammonia, whereas many Gram-negative 

 species can synthesise all their amino-acid requirements from 

 ammonia. Yeasts again synthesise their amino-acids from 

 ammonia, but cannot assimilate ammonia unless fermentation 

 is occurring simultaneously. Further research is necessary 

 to clarify the relation of these various findings, but there is a 

 suggestion that the presence of glucose during growth may 

 alter the assimilatory processes of the cells, and this, in turn, 

 may be reflected in an alteration of the enzyme constitution, 

 especially with regard to those enzymes concerned with the 

 breakdown of amino-acids to ammonia. 



Further examples of substances, other than the specific 

 substrate, having an effect on enzyme formation, are found in 

 the case of certain growth factors (see Chap. V) which act 

 as coenzymes. For instance, Haemophilus parainjluenzae is 

 unable to synthesise coenzyme I, and is unable to grow in 

 its absence. If, however, sub-optimal amounts of coenzyme 

 are provided in the growth medium, then we find that the 

 organisms grow, but are unable to oxidise at a normal rate 

 those substances forming the substrates of coenzyme I 

 dehydrogenase systems. The deficient organisms can oxidise 

 L-malic acid slowly, but if coenzyme is added to a suspension 

 of these organisms they can then oxidise malic acid at the 

 normal rate. This means that the organism has synthesised 

 its normal complement of enzyme-protein, but has been unable 

 to saturate it with coenzyme due to its inability to synthesise 

 this substance. 



PHYSICO-CHEMICAL CONDITIONS OF GROWTH 

 Aerobiosis or anaerobiosis 



Facultative anaerobes can grow under strictly aerobic or 

 strictly anaerobic conditions and develop a different enzyme 

 constitution in each case. When we examine the activities 



