84 CARBON NUTRITION 



medium, the white rot fungi forming a colored zone (the "oxidase 

 reaction"). Numerous studies on this reaction, summarized by Gott- 

 lieb and Pelczar (72), indicate that the enzyme responsible is a poly- 

 phenol oxidase (Chapter 6), generally present in but not limited to 

 the lignin-utilizing fungi. The separation into brown and white rots, 

 although useful, is not absolute — most white rot fungi use cellulose 

 at one stage or another of the decomposition process (31, 81). The 

 brown rot fungi, however, do not attack lignin appreciably (35) except 

 perhaps in the advanced stages of wood decomposition (169). 



In considering the utilization of lignin as the sole source of carbon, 

 i.e., apart from other plant materials, we are reminded of the de- 

 pendence of nutritional studies on adequate knowledge of the chemis- 

 try of the substrate. Most of the early work, reviewed by Waksman 

 and Hutchings (226), is of doubtful validity, since it appears that the 

 lignin used was contaminated with carbohydrates and protein deg- 

 radation products (21, 72). A more recent method of preparation, 

 employing mild procedures, is believed to yield an uncontaminated 

 lignin (20). Studies on this material indicate that white rot fungi can 

 utilize it (149, 220); other wood-destroying fungi may require a period 

 of "training," i.e., a long incubation period in contact with the sub- 

 strate, before they can utilize it (49, 71). 



Although lignosulfonic acid disappears from media in which fungi 

 are growing (1), it seems from other studies that lignosulfonate forms a 

 complex with the mycelium and that the utilization, therefore, is only 

 apparent (48). 



Keratin, the insoluble protein of wool, hair, and feathers, has been 

 implicated as a possible substrate for fungus growth since the observa- 

 tions of Ward (229) on Onygena equina. Jensen (97) reported growth 

 and ammonia liberation by Streptomyces spp. in sand culture with 

 keratin as the sole source of carbon and nitrogen. In a survey of 

 keratin utilization (237), it was found that untreated wool is not 

 attacked by common saprophytic fungi; actively keratinolytic forms 

 are all dermatophytes, especially species of Trichophyton and Micro- 

 sporum. The action of Microsporum gypseum on keratin and collagen 

 is analyzed by Stahl et al. (191). 



The success of keratin-containing materials as bait for chytrids (101, 

 102) and the ability of Polychytrium aggregatum to make visible 

 growth on keratin (2) suggest that these fungi, which are not isolated by 

 conventional procedures of soil and fabric microbiology, are worth 

 study as possible agents of keratin destruction in nature. 



Purified rubber is attacked by both fungi and actinomycetes (247); 



