466 PRINCIPLES OF SOIL MICROBIOLOGY 



Benzene ring compounds, including phenol, cresol and naphthalene 

 disappear rapidly in the soil, due largely to the action of various bac- 

 teria (Mycobacteria; large, sporangia-producing rods, and short, oval 

 pseudomonads). 122 However, Sen Gupta 123 found that the disappear- 

 ance of phenol in the soil is caused largely by the catalytic action of 

 manganese oxide. 



Decomposition of glucosides and monosaccharides. Glucosides are 

 widely distributed in the plant kingdom and are, therefore, introduced 

 into the soil by various bacteria and fungi. The first products of 

 hydrolysis are glucose and aromatic compounds, as shown in the case 

 of amygdalin: 



C20H27NOU + 2H 2 = 2C 6 H 12 6 + C 7 H 6 + HCN 

 Amygdalin Benzal- 



dehyde 



Salicin is decomposed into glucose and saligenin: 



C13 Hig O7 = C6 H12 Oe -f" C7H8O2 



The hydrolysis of indican (Ci 4 Hi 7 N0 6 ) with the formation of glu- 

 cose and indoxyl (C 8 H 6 NO), which changes in the air to indigo blue 

 (C16H10N2O2) belongs also to this type of reaction. 124 The glucose is 

 used by a great variety of microorganisms, benzaldehyde or the other 

 benzol ring compounds are decomposed sooner or later, as well as 

 hydrocyanic acid. 



Monosaccharides are decomposed by the great majority of hetero- 

 trophic microorganisms inhabiting the soil. The nature of the reac- 

 tion depends upon the organism concerned and environmental condi- 

 tions. Under certain conditions, the sugar is broken up to C0 2 and 

 H 2 0, liberating the maximum amount of energy; under other conditions, 

 acids, alcohols or both, with or without gases (H 2 , CH4, CO2) are 

 formed. The organic acids commonly formed by fungi are gluconic, 

 citric, oxalic and fumaric; by bacteria: butyric, lactic, acetic, propionic, 

 valerianic, formic, etc. Among the other products formed, largely by 

 bacteria, we find alcohols, including ethyl-, methyl- and butyl-, and 

 acetone. These substances are usually oxidized further or are re- 

 synthesized, with the result that complex products are formed again. 



122 Thornton, H. The destruction of aromatic antiseptics by soil bacteria. 

 Nature, 111: 347. 1923. 



123 Sen Gupta, N. N. Dephenolisation in soil. Jour. Agr. Sci., 11: 136-158 

 1921; 15: 497-515. 1925. 



144 Behrens, J. Glycosidspaltungen und Oxydasenwirkungen. Lafar'a 

 Handb. techn. Mykol., 1: 641-695. 1904. 



