Molds as MefaboUc Models 93 



conic acid from the oxidation of glucose. Perhaps worthy 

 of note here is the recorded oxidation by fungi of other 

 hexoses, and also pentoses, to the corresponding hexonic 

 and pentonic acids (7, 8). It is not unreasonable to sup- 

 pose that these may represent intermediate stages analogous 

 to gluconic acid in direct oxidative pathways. Lastly in 

 this particular respect are what appear to be some long- 

 recorded manifestations of current evidence for initial 

 stages in new oxidation pathways. These relate to the 

 demonstration that the hexose molecule may undergo 

 novel changes in the oxidation of certain carbons, with- 

 out prior rupture of the carbon skeleton. I refer here to 

 the rather substantial yields of glucosone obtained from 

 carbohydrates by Walker (14), using species of Asper- 

 gilluSj and the recent isotopic evidence of Arnstein and 

 Bentley (1) and of Denison and Carson (5) that kojic acid 

 formation by Aspergillus flavus represents intramolecular 

 oxidation and dehydration of the glucose molecule, with- 

 out rupture of the six-carbon chain. 



We could turn the spotlight on numerous other 

 neglected or unheeded contributions that might have 

 heralded the great developments made later in other bio- 

 logical systems, but that is like watching the stations go 

 by while riding backward on a train. If we reverse our 

 seating position and exercise good vision, we should be 

 able to spot and evaluate the stations as we approach them, 

 before they recede from our view. The discussion of or- 

 ganic acid accumulation by fungi points up a modus 

 operandi which, although habitual with investigators of 

 mold metabolism, appears not to have been widely adopted 

 in metabolic studies with other microorganisms, the bac- 

 teria in particular. From studies too numerous to cite in 

 detail, it has become well established that ordinarily a 

 fungus in culture converts the bulk of its substrate to cell 

 material and carbon dioxide. Products of incomplete oxi- 

 dation, that is, the intermediates in the combustion proc- 



