44 ENZYMES AND ENZYM1C ACTIVITIES OF FUNGI 



called hadromase. Since then a series of studies have appeared 

 that form a basis for a better understanding of the metabolism 

 of heartwood-rotting and sapwood-rotting fungi. 



Cellulose and lignin are the most important constituents of 

 wood. Some species of fungi destroy the cellulose portions but 

 are quite unable to utilize the lignin. They constitute a group 

 called the u bro\vn-rot group," typified by Poly poms scbweinitzii. 

 Other species, which attack lignin primarily but are also able to 

 decompose cellulose, constitute the "white-rot group," typified 

 by Tonnes pint and Stereum frustulosum. The enzymic activity 

 of the brown-rot group is regarded as mainly hvdrolvtic; of the 

 white-rot group, as both hydrolytic and oxidative. 



Although this grouping may be of value to the forest patholo- 

 gist, it should be "interpreted to mean that a given species prefers 

 either cellulose or lignin but yet may be able to use both com- 

 ponents. Campbell "(1929, 1932) divided the white rots which 

 he studied into three groups. Some attack lignin in early stages, 

 and among them the incidence of attack on cellulose is delayed, 

 as occurs with Polystictus versicolor. In another group, exempli- 

 fied by Armillaria mellea, cellulose and associated pentosans are 

 first attacked, and the utilization of lignin is delayed. In the last 

 group both lignin and cellulose are utilized in varying proportions, 

 as they are by Ganoderma applanatum, Poly poms adustus, P leu- 

 rows ostreatus, and Polystictus abietimis. 



Bavendamm (1928, 1928a) devised a technique to determine the 

 ability of a given fungus to utilize lignin. He prepared agar plates 

 enriched with such substances as tannic acid, pyrogallol, hydro- 

 quinone, resorcinol, guiacol, phloroglucinol, gallic acid, or tyro- 

 sine in varying concentrations. On these media he planted 

 Merulius lacrymans, Coniophora cerebella, Trametes radiciperda, 

 and Stereiim purpureum. After 8 days' growth in the presence 

 of most of these substances, red-brown to dark-brown zones of 

 discoloration had developed in advance of the hyphal tips around 

 colonies of T. radiciperda and S. purpureum. The production 

 of these zones was ascribed to the secretion into the agar of 

 catechol-oxidative enzymes similar to those that cause the cut 

 surface of an apple or a potato to brown. These species use lignin 

 primarily and are white rots. M. lacrymans and C. cerebella, on 

 the other hand, did not develop brown pigment and hence utilize 

 cellulose and are brown rots. 



