258 A SYMPOSIUM ON RESPIRATORY ENZYMES 



stable isotopes are much more favored for quantitative studies than 

 the radioactive elements. 



The application of isotopes to problems involving respiratory en- 

 zymes has not been extensive. The metabolism of lactic acid and the 

 assimilation of carbon dioxide have been traced with stable and 

 radioactive carbon isotopes. The use of radioactive P^^ in the study 

 of the role of phosphorus in respiration has attracted a number of 

 investigators. In the near future, undoubtedly, isotopes will be em- 

 ployed in many other studies of this nature. 



MECHANISMS FOR THE COMPLETE OXIDATION OF 

 CARBOHYDRATES BY AEROBIC BACTERIA 

 C. H. Werkman, Iowa State College: 



This topic is a broad one that has not been exhaustively inves- 

 tigated because it offers serious technical diflBculties. Bacteria 

 seem to possess a distinct and quite troublesome cell wall whose 

 behavior as regards changes in permeability is far from clear. Realiz- 

 ing the danger of drawing conclusions from the use of unnatural 

 systems, we have attempted, by correlating the results obtained 

 with juices and whole cells, to circumvent the pitfall. But to do so 

 would apparently require an uncanny ability, since neither the work 

 with juices nor the cell suspension could be accepted as portraying 

 processes that occur in the living, reproducing organism. In the face 

 of this difficulty of preparing juices or cell suspensions that behave 

 naturally, the task of elucidating the natural processes in bacterial 

 respiration is laden with danger. Our present purpose is to encour- 

 age a free discussion of the possibilities in bacterial respiration and 

 to outline a working hypothesis. 



There is abundant evidence that phosphorus plays an important, 

 if not essential, role in bacterial respiration. Early workers, including 

 Virtanen, have shown the ability of bacteria to form phosphorylated 

 esters. Wiggert in our laboratory showed an uptake of phosphorus 

 by living bacteria. That the principles of the Embden-Meyerhof 

 scheme of glucolysis operate in bacterial metabolism was first given 

 substantial support in 1936, when the characteristic intermediate of 

 that scheme, phosphoglyceric acid, was isolated from representa- 

 tive types of bacteria, both aerobic as well as anaerobic (Werkman 

 et al., Stone and Werkman). Utter in our laboratory has shown the 

 occurrence of the aldolase reaction by means of bacterial juices. In 

 this reaction hexosediphosphate is converted into phosphoglyceralde- 

 hyde and dihydroxyacetone phosphate. Furthermore, he has estab- 



