442 SOIL SCIENCE 



part per million of nitrogen as nitrite is produced. However, the forma- 

 tion of this small amount is constant and is, therefore, of considerable 

 value as a diagnostic feature. 



Since many species produce nitrites in Dunham's solution, it is ob- 

 vious that erroneous conclusions might be drawn from the use of a 

 nitrate broth containing peptone. Peptone has therefore been left out of 

 the nitrate broth used in studying the nitrate reducing power of these or- 

 ganisms, and a small quantity of starch added to furnish the necessary 

 carbon. In this broth many of the species reduce nitrates to nitrites, but 

 only four forms reduce nitrates to ammonia. 



The Occurrence and Activity of Cellulose-Dissolving Bacteria in 

 Southern California Soils 



Examinations of 69 soils of southern California for cellulose-dissolv- 

 ing bacteria indicate that these soils contain numerous species of bacteria 

 which have the power of dissolving cellulose. All of the soils examined 

 were found to contain one or more active cellulose-destroying forms and 

 most of the species isolated were found in two or more soils from widely 

 separated districts. One of the most active forms (B. imminufus) was 

 isolated from ten of the sixty-nine soils examined. From the southern 

 California soils studied fifteen new species of cellulose-dissolving bacteria 

 have been isolated and described. In addition to the new species found, 

 seven species previously isolated from other soils have been identified. 

 The distribution of the cellulose-dissolving bacteria found in the southern 

 California soils is shown in Table I. 



It is well known that a very rapid destruction of cellulose occurs in 

 many citrus soils of southern Colifornia. The question naturally arises 

 whether the rapid destruction of cellulose in these soils is due to the 

 presence of unusually active cellulose-destroying organisms or to favor- 

 able conditions which make possible a very rapid multiplication of the 

 cellulose-dissolving organisms present. From the studies made, it is evi- 

 dent that the soils are abundantly supplied with active cellulose-destroy- 

 ing bacteria. Moreover, some of the most active forms appear to have a 

 very wide distribution in the soils of southern California. However, with 

 the possible exception of B. inmiinutus the cellulose-destroying bacteria 

 found in southern California soils, when placed under standard condi- 

 tions, appear to be no more active agents in the destruction of cellulose 

 than the organisms isolated from the humid regions of the United States. 

 In any explanation of the rapid destruction of cellulose in these soils we 

 must take into consideration the activity of filamentous fungi and possi- 

 bly the Actinomyces. The cellulose-destroying fungi are unquestionably 

 less numerous and less active in the semi-arid soils of southern California 

 than in the humid soils of the eastern part of the United States. The 

 same is apparently true of the cellulose-destroying species of Actino- 

 myces. 



