VARIATION OF pH RANGE WITH MEDIA 151 



the isoelectric points of the proteins were shown to be in the 

 vicinity of pH 5.0 and 5.5, respectively. When Robbins stained 

 the mycelial mat of R. nigricans with an acid dye, it retained the 

 dye on the acid side of the isoelectric point, but the mycelium 

 was unstained on the basic side. This result was determined by 

 washing mycelia stained with eosin, for example, with solutions 

 of pH 3.5, 3.9, 4.5, 5.7, 5.8 and 6.9. These solutions were made 

 with appropriate mixtures of 0.1 M phosphoric acid and of 0.1 M 

 sodium hydroxide. After thorough washing with a buffer solu- 

 tion of pH 3.5 or 3.9, the mycelia were bright red; with a solution 

 of pH 4.5, intermediate red; with a solution of pH 5.7 or 5.8, 

 pink; with a solution of pH 6.9, hyaline. 



Variation of pH range with media. Failure of various work- 

 ers to agree on the pH range that will support growth in a ^iven 

 fungus may be attributed to differences in culture media. These 

 differences involve kind and proportion of nutrients, buffering, 

 and initial reaction. The influence of the composite of these 

 factors is illustrated bv the work of Wolpert (1924). He em- 

 ployed a modified Richards' solution, on the one hand, and a 

 2.5% peptone-mineral nutrient, on the other, with the results 

 shown in Table 13. 



TABLE 13 



Comparison of pH Range of Certain Basidiomycetes on Two Different 



Media 



pH Range That Inhibits Growth 



Organisms Richards' solution Peptone solution 



Lenzites saepiaria 3 . 4 and 7.3 2.8 and 7 . 5 



Daedalea confragosa 3 . 5 and 7.2 2.8 and 7 . 6 



Polystictus versicolor 2 . 5 and 7.6 2.5 and 7 . 5 



Armillaria mellea 2.9 and 7.4 2.0 and 7.8 



Pholiota adiposa 2 . 8 and 7.0 2.8 and 7 . 8 



Pleurotus ostreatus 3-. and 7.5 3.0 and 8 . 5 



Schizophyllum commune 3.4 and 7.0 2.8 and 8.5 



During growth each species increased the acidity in Richards' 

 solution, Lenzites saepiaria being the most active acid-producer. 

 All of them except L. saepiaria and Pleiirotns ostreatus decreased 

 the acidity in peptone solution when the initial reaction was less 

 than pH 6.0 and increased it when the initial reaction was greater 

 than pH 6.0. 



