262 A SYMPOSIUM ON RESPIRATORY ENZYMES 



E. S. GuzMAPf Barron, University of Chicago: 



Until a few years ago seme investigators in the field of oxidation- 

 reductions tended to devote their efforts exclusively to animal, plant, 

 or bacterial oxidations. Many papers published recently showing the 

 variety of oxidation mechanisms, even in the oxidations involving 

 simply an electron transfer, have demonstrated the necessity of in- 

 tegrating the facts obtained with these different kinds of living be- 

 ings. For such comparative studies, work with bacteria has been 

 fruitful not only because it is possible to obtain suspensions or ex- 

 tracts with which quantitative studies can be perfoiTned but also 

 because in a single species, say hemolytic streptococci, a variety of 

 oxidation mechanisms may be found in different strains. 



If we take the component of oxidation enzyme systems closest to 

 molecular oxygen, the iron porphyrins, we may divide bacteria into 

 two groups: cytochrome-containing bacteria (including most of the 

 so-called aerobic bacteria) and cytochrome-lacking bacteria (the so- 

 called anaerobic bacteria). Species of the two groups may produce 

 identical oxidations. They may oxidize, for example, lactate or 

 glycerol. The rxidation of lactate and glycerol by cytochrome-con- 

 taining bacteria (Staphylococcus) is completely inhibited by cyanide, 

 whereas the same oxidations by cytochrome-lacking bacteria are 

 cyanide-insensitive. Obviously iron porphyrins take part in the 

 oxidation of lactate and glycerol by cytochrome-containing bacteria, 

 whereas in cytochrome-lacking bacteria the oxidation proceeds 

 through different channels (flavin nucleotides). 



In the field of phosphorylative oxidations the laboratory of Werk- 

 man has demonstrated that there exist in bacteria the different 

 phosphorylations observed in the breakdown of carbohydrate by 

 muscle or yeast extracts. In our laboratory it has been found that 

 the oxidation of glycerol by hemolytic streptococci does not take 

 place in the absence of phosphates. This does not mean that phos- 

 phorylation is essential for glucose oxidation; it is known that the 

 breakdown of carbohydrate by molds proceeds without phosphoryla- 

 tion. 



It is assumed that in animal tissues carbohydrate metabolism starts 

 with the fermentation process ending in lactate, whereas in yeast it 

 ends in the fonnation of alcohol. In bacteria the fermentation process 

 may end in the formation of either lactate or of alcohol or in the 

 formation of both end products, as Friedemann has shown. Fermen- 

 tation may be absent altogether, as in glucose-non-fermenting bac- 



