CHAPTER IV 



THE FORMATION OF ENZYMES IN BACTERIA 



The manifold chemical activities of bacteria are catalysed 

 by enzymes formed within the bacterial cell. Some bacterial 

 species can exist under widely different chemical and physical 

 environments, and require different types of enzymes in order 

 to deal with the differing external conditions. Esch. coli 

 utilises different enzymes for anaerobic existence from those 

 utilised for aerobic existence, and needs different neutralisation 

 mechanisms when growth takes place in an alkaline medium 

 from those required when growth takes place in an acid 

 medium. We find that an organism does not possess all the 

 enzymes necessary for dealing with all possible environments 

 at any one time, but that the actual enzymic constitution, 

 as opposed to the potential enzymic constitution, is determined 

 to a large extent by the external conditions holding during 

 the formation of the individual cell. Consequently the cell 

 grown aerobically is equipped with the mechanisms for 

 oxidative metabolism, while the cell grown anaerobically is 

 deficient in those mechanisms which can be utilised only 

 under aerobic conditions but possesses highly developed 

 anaerobic mechanisms. The actual enzymic constitution of 

 a cell of a given species may thus vary widely. The identifica- 

 tion of bacterial genera and species is based upon certain 

 biochemical tests, but these are always carried out under 

 standardised growth conditions and represent cross-sections 

 of the potential enzymic constitution of the organism con- 

 cerned. If an organism can ferment sucrose, then the fermen- 

 tation will occur under the test conditions of growth in a 

 fully nutrient medium containing sucrose, but it does not 

 follow that the same organism can ferment sucrose if it is 

 first grown in a medium free from sucrose or, say, nicotinamide. 



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