Transformation of Riboflavin and Pantothenic Acid during Decomposition of Plant Materials

V ITAMINS of the B-complex are of particular interest to the microbiologist since they are required for microbial development. Some organisms are able to synthesize all of the necessary vitamins, whereas others require an external source of at least some of them. Higher plants likewise require these vitamins, but from available information there is little reason to believe that they depend upon vitamins contained in soil to satisfy their requirements. Since excised roots can absorb vitamins from cultural media (28), however, it is reasonable to expect that plants can and probably do. take up such material from the soil. Whether or not absorption is appreciable under farming conditions and can be regulated to affect the quality of the plant material still remains to be established. In this connection the observation of Nath (19), Hunt (12), Clark (i, 2, 3) and others (10, 1-5, 20) are of interest. Since little is known of the vitamin content of soils or the factors affecting the formation, persistence, or destruction of vitamins in the soil, it would be premature to conclude that absorption by plants is negligible or that an external source of vitamins is without effect on plant development. Thiamin and . biotin were found in soil by Lilly and Leonian (16), and Lochhead and Chase (17) obtained evidence that various growth factors, including some as yet unidentified, are present in soil. It can surely be supposed that all of the vitamins of the B-complex occur in soil, since they are present in plant materials which become admixed with the soil, and since these vitamins are also contained in the cells of the microbial inhabitants of the soil. Information concerning the amounts of vitamins and factors affecting their persistence is of more interest than evidence of their mere presence in soil. West and Lochhead and associates (24, 25, 26, 27, 17) made the interesting observation that many of the bacteria in soils require preformed vitamins. The fastidious bacteria were prevalent about plant roots and in soil that received additions of plant residues. The accessory growth substances required by thesfe bacteria could have been derived directly from the plant materials as well as from associated microorganisms which produced the growth substances during decomposition of the plant residues. It is also of interest that the bacteria requiring accessory growth substances were more abundant in fertile soil than in poor soil. These results may be taken as evidence that some vitamins are more abundant in the rhizosphere than elsewhere in the soil. The present study deals with the influence of microorganisms on the vitamin content of certain plant residues and of cow manure during periods of decomposition in composts. Information concerning the transformation of vitamins during microbial attack of plant materials not only may be expected to contribute to a better appreciation of soil processes that affect plant development but may also give some indication of the influence of microorganisms on the vitamin content of the animal feeding materials that undergo more or less alteration by microorganisms.