1 64 CARBON METABOLISM III 



related classes, the polyenynes and the polyenes (406). The polyenynes, 

 characterized by a system of conjugated triple bonds, include, among 

 compounds of known structure, diatetrynes 1 and 2 of Clitocybe 

 diatreta (10), agrocybin of Agrocybe dura (305, 312), and mycomycin, 

 produced by Nocardia acidophilus (113). Some have nitrogenous 

 substituents, e.g., diatetryne 2: 



HOOC— CH = C H— C^C— Ce=C— C=N 



Mycomycin, on the other hand, is an acid containing no nitrogen: 



HC=C— C=C— CH=C=CH— CHrrCH- CH=CH— CH 2 — COOH 



Acetylenic compounds are also known in higher plants and in other 

 fungi than those named here (9, 11, 97). In an unidentified basidio- 

 mycete, the formation of polyacetylenes early in the culture cycle is 

 followed by their disappearance; this may be interpreted as a re- 

 utilization of the compounds (98). 



The conjugated polyenes include a number of antibiotics the 

 complete structure of which is not known; the polyene structure is 

 inferred from their ultraviolet absorption spectra (28a, 530, 534, 558). 

 All are fungistatic agents. The polyenynes, except for mycomycin, 

 have been found only among basidiomycetes; the known polyene 

 antibiotics, on the other hand, are produced primarily by actino- 

 mycetes. Grifolin, formed by Grifola confluens (275), is a substituted 

 hydrocarbon with one pair of conjugated double bonds. 



Species of Corticium produce two yellow pigments, both containing 

 a system of conjugated double bonds comparable to that of the 

 carotenoid pigments (183, 246); other aspects of their structure, how- 

 ever, relate them to atromentin and thelephoric acid, considered later 

 with the aromatic compounds. 



The sporophore of Lactarius spp., and probably the ascocarp of 

 Peziza sp., contain a rubberlike polymer, a as-polyisoprene (491). 



3. THE METABOLISM OF AROMATIC COMPOUNDS 



Aromatic Compounds of Fungi. The fungi resemble the higher 

 plants and differ from the bacteria in that many species convert 

 carbohydrate to aromatic compounds not known to be essential metab- 

 olites. These compounds have been reviewed in detail by Birkin- 

 shaw (63), by Raistrick (430), and, in lichens, by Asahina and Shibata 

 (24). Any classification of them must of necessity be based on their 

 chemical structure and may unintentionally obscure physiological and 

 biosynthetic relations. Thus, a substituted benzene and the quinone 



