58 MICROBIAL CELL WALLS 



wall structures of the alga Chlorella pyrenoidosa,^ Neuro- 

 spora crassa/ and yeast.^ Cellulases and chitinases in the 

 snail-gut enzymes are generally believed to be active in cell- 

 wall digestion, but most investigators have used unfrac- 

 tionated preparations undoubtedly rich in a variety of 

 enzymes. Indeed, Myers and Northcote ^ reported that the 

 snail enzyme preparations contained active lipases and car- 

 bohydrases, including cellulase, xylanase, and mannanase. 

 Only weak proteolytic activity was found in their extracts. 

 Several microorganisms isolated on selective media contain- 

 ing yeast cell walls have been found to produce enzymes 

 digesting the yeast wall structures. 5' <^ The enzymes used 

 for degrading the walls of Chlorella, Neurospora, and yeasts 

 have not resulted in complete digestion. The most effec- 

 tive enzyme so far reported is that prepared from the bac- 

 terium isolated by Masschelein.^ He observed a decrease 

 of 84% in the turbidity of isolated yeast walls incubated 

 with the enzyme preparations. ^ Nor has the nature of the 

 products released by enzymic degradation of these microbial 

 walls been determined in any detail. Northcote, Goulding, 

 and Home ^ reported the release of 70% of the total a-cel- 

 lulose and 43% of the lipid of the wall of Chlorella pyre- 

 noidosa. A mannan-protein complex was released from 

 yeast walls treated with papain. ^ Thus at present there is 

 no indication of the nature of the linkages attacked by the 

 various enzymes used in degrading the walls of these micro- 

 organisms. 



Baciena. Lysis of bacterial cells and breakdown of the 

 wall has received a great deal of attention, and a variety of 

 enzyme systems is available for various bacterial species. ^-^° 

 Of all the wall-degrading enzymes so far investigated, more 

 is now known about the mode of action of egg-white lyso- 

 zyme than any other system. ^^ The only other enzymes 

 obtained in a purified form and well characterized are the 



