ENERGY SUPPLY OF THE CELL 101 



within the cell of Bad. coli drop to —0.4 volts in order that hydrogen 

 can be formed from sugar ? If not, then the low reduction potential of 

 Bad. coli does not really indicate that it has strongly reducing powers, 

 but it is low because the bacteria form hydrogen, and the reduction 

 electrode is simply changed to a hydrogen electrode by the gas formed. 

 Or the potential —0.06 simply indicates that cysteine has been 

 formed by the bacterium under test. There seems to be some reason 

 for doubt as to what is the cause, and what, the effect. 



The introduction of oxidation-reduction potentials, 

 though not quite clear as yet in all its aspects, will 

 influence quite considerably our conceptions of the 

 mechanism of life, and of biological oxidations. It will 

 prove useful to explain many reactions hitherto difficult 

 to account for. It will tell us why certain reactions take 

 place in the cells, and our conception of microbial activity 

 will be shifted to a somewhat different basis. 



(/) SUMMARY 



The common culture media made from meat extract 

 have a reduction potential of about +0.2 to +0.3 volt 

 taking the normal hydrogen electrode potential as zero. 

 Milk has a similar potential. 



If these media are deaerated by vacuum or by a neutral 

 gas, the potential drops below zero. They contain 

 reducing compounds which come into play if the dissolved 

 oxygen is removed from the medium. They will then 

 decolorize methylene blue. 



This reducing property of our common media might be 

 caused by traces of glutathione, cysteine or similar com- 

 pounds in the meat extract or milk. 



Bacterial cultures will usually bring about a decrease 

 in potential. There is not sufficient material on hand 

 to say whether all bacteria will produce a potential 

 lower than that of the deaerated sterile medium. 



