TRANSFORMATION OF MINERALS IN THE SOIL 665 



In the metabolism of bacteria and especially of fungi, magnesium may- 

 form a more important mineral nutrient than calcium. The transfor- 

 mation of magnesium in the soil is very similar to that of calcium, al- 

 though Ames 56 found that magnesium compounds are less resistant 

 than calcium salts to the action of nitric and sulfuric acids formed in 

 the processes of nitrification and sulfur oxidation. 



Transformation of manganese in the soil. Beijerinck 57 described 

 several fungi and bacteria which are capable of oxidizing manganese 

 carbonate to oxides of manganese, using cellulose or other carbohy- 

 drates as sources of energy. It has been further shown 58 that, in alka- 

 line media, manganese salts are changed to manganese hydroxide, 

 which is then oxidized by atmospheric oxygen to MnCV Microor- 

 ganisms also oxidize manganese salts of organic acids to manganese 

 carbonate. Manganic compounds may also be reduced to manganous 

 compounds by biological processes. 



Mn0 2 + 2H 2 S = MnS + 2H 2 + S 

 M11SO4 + 2C + 2H 2 = 2H 2 C0 3 + MnS 

 MnS + H 2 C0 3 = H 2 S + MnC0 3 

 MnS + 2 2 = 2 MnS0 4 



This process was utilized for the determination of the number of 

 cellulose decomposing bacteria in the soil. Filter paper saturated with 

 MnS0 4 solution is placed in a KMn0 4 solution. The Mn0 2 formed 

 turns the paper black. The paper is then placed in petri dishes, steri- 

 lized and moistened with a solution of inorganic salts in tap water. 

 When this is inoculated with cellulose decomposing organisms, the oxy- 

 and fatty acids formed from the decomposing cellulose reduce the 

 manganese dioxide giving clear zones on the paper. 



When sulfur is oxidized in the soil, considerable quantities of man- 

 ganese may go into solution, especially in soils rich in this element. 

 The utilization of certain manganese compounds as sources of energy 

 by some of the iron bacteria has been pointed out elsewhere (p. 59). 

 Small quantities of manganese seem to act as a stimulant for various 

 organisms, 59 and especially for the nitrogen-fixing bacteria. 60 



56 Ames, 1921 (p. 658). 



57 Beijerinck, M. \Y. Oxydation des Mangancarbonats durch Bakterien und 

 Schimmelpilze. Folia Microb., 2: 123-135. 1913. 



68 Scihngen, N. L. Umwandlungen von Manganverbindungen unter dera 

 Einflusz mikrobiologischer Prozesse. Centrbl. Bakt. II, 40: 545-554. 1914. 



59 Pietruszczynski, Z. The influence of manganese on the nitrification of 

 ammonia. Rocz. Nauk Rolnicz., 9: 235-287. 1923. 



60 Olaru, 1920 (p. 534). 



