NATURE OF BACTEKIAL TOXINS l95 



yet been identified. The ^-toxin is active only in a reduced 

 state and can be completely inactivated by oxidation; the 

 nature of effective oxidising and reducing agents suggests 

 that the group which is oxidised in the toxin molecule is 

 — SH, oxidation to — SS — ■ leading to inactivation. 



We have attempted in this way to explain the toxicity 

 of CI. welchii by analysing the various factors which act 

 biochemically in a way that we might expect would explain 

 the toxic action. In the same way we endeavour to explain 

 the oxidations carried out by bacteria in terms of the activity 

 of isolated enzyme systems. When we come to integrate 

 our findings with isolated enzyme systems in terms of the 

 activities of the intact cells, we find that the interplay of 

 various environmental factors, etc., complicate the reactions 

 established in vitro. In the same way we find that we cannot 

 explain the complete pathological picture found in gas gangrene 

 in terms of the activities of the separate factors we have 

 discussed. The exact importance of the role played by toxins 

 in the clinical picture is not yet clear, and it has been suggested 

 that some part may be played by substances released from 

 muscle cells and necrotic tissues on disruption. There are 

 almost certainly some factors brought into play by the inter- 

 action of the infecting organism and the infected host which 

 have not yet been revealed by studies in vitro. 



THE NATURE OF BACTERIAL TOXINS 



The a-toxin of CI. welchii is probably an enzyme whose 

 substrate is an essential structural unit in the cells of the 

 host. The pathogenicity of this organism depends largely 

 upon its power to excrete certain enzymes which attack the 

 tissues of the host as substrate. It does not, of course, follow 

 that all toxins are necessarily enzymes, but such a hypothesis 

 fits in with what is known of the nature of many of them We 

 must now expect that work will be intensified with a view to 

 estabHshing the enzymatic nature of other toxins and the 

 identity of their substrates. The work is difficult as there is 

 often no clue as to the possible nature of the substrate ; with 



