Behavior of Free Amino Acids in Soil

Abstract

The behavior of a mixture of amino acids in a soil environment was studied. Extractions were made with 80% ethanol. The extract was concentrated and then was analyzed for amino acids by gradient elution chromatography. After 1 hour of soil contact in the cold, at least some of each amino acid could be recovered, but the extraction was not efficient. Replicate soil flasks to which amino acids had been added were incubated at 28° C. under conditions that allowed for both CO 2 and amino acid analysis of the same flask. After 24 hours, substantial degradation had occurred but at least trace amounts of each of the added amino acids except threonine could still be detected. Beta alanine appeared on the 24-hour chromatogram although it was not among the amino acids added initially. Results of both chromatographic analysis and CO 2 collection suggested that nearly all of the added amino acids were degraded by the end of 96 hours. Separate studies using microbiological assay failed to confirm the persistence of threonine in soil as reported in the literature. The possibility that the beta alanine found in the soil environment was formed from aspartic acid decarboxylation was explored, but large additions of aspartic acid to soil did not result in substantial increases in beta alanine. R ECENTLY Putnam and Schmidt (5) reported on the occurrence of small bvit detectable quantities of free amino acids in soil. Soil amended with glucose and inorganic nitrogen yielded more amino acids and a greater variety of amino acids than control soil. The amount and nature of the free amino fraction obtained was considered to be a function not only of the interactions between microbial synthesis and degradation, but also the extent to which amino acids adsorbed to the soil could be extracted. The chromatographic techniques used in the work cited were applied in the present study to follow simultaneously the behavior of numerous amino acids in a soil environment. EXPERIMENTAL PROCEDURESTen-milligram quantities of each of 12 amino acids were placed in solution and added to 100 g. of Waukegan loam (pH 6.4) obtained from the University Farm. The following amino acids were included: aspartic acid, glutamic acid, threonine, proline, alanine, valine, methionine, isoleucine, leucine, phenylalanine, glycine, and serine. After 1 hour incubation at 4° C., the soil was extracted with 80% ethanol, the extract was concentrated, and 1 ml. of the concentrate was analyzed for amino acids by gradient elution chromatography on Dowex 50-X4 resin. The procedures for extraction, concentration, and analysis were as described previously (5).The persistence of amino acids exposed to normal microbiological activity in soil was investigated with a second mix-'Paper No. 4207 of the Scientific Journal Series, Minnesota Agr. Exp. Sta., University of Minnesota, St. Paul. Received Aug. 17, 1959. Approved Sept. 17, 1959 2 Associate Professor, jointly, Department of Soils and Department of Bacteriology and Immunology; Research Assistant, Department of Bacteriolog...

The biology of mycorrhiza in the Ericaceae XI. The distribution of nitrogen in soil of a typical upland Callunetum with special reference to the ‘free’ amino acids

“…Ammonium-nitrogen in the hydrolysate was determined by distillation of an aliquot of the hydrolysate of each soil segment using a BUCHI 322 distillation unit. Schmidt, Putnam & Paul (1960) showed that those agents, water and ethanol, which are routinely employed for extraction of amino acids from biological materials are inappropriate for use witb soil. In a detailed con-iparative analysis of amino acid extraction Paul & Scbmidt (1960) sbowed tbat dilute solutions eitber of ammonium acetate (0-5 M) or barium hydroxide (O'l N) gave mucb superior recoveries of added amino acids.…”

Significance of organic nitrogen acquisition for dominant plant species in an alpine meadow on the Tibet plateau, China

“…In this regard, however, there still exists an obvious shortcoming that the amino acids were injected into the soil only once and in the form of aqueous solutions of one amino acid (Nä sholm et al 2000;Nordin et al 2001;Taylor et al 2004;Weigelt et al 2005) or a mixture of several amino acids (Chapin et al 1993;Persson and Nä sholm 2003) while in soils free amino acids are continuously produced by microbial decomposition as a mixture of amino acids and therefore continuously contribute to plant organic N acquisition. Single injections of amino acids into soils in short-term studies are problematic because of fast decomposition and immobilization of free amino acids in soils (Schmidt et al 1960;Kassim et al 1981;Jones 1999;Jones and Kielland 2002).…”

Growth-Modifying & Antimetabolite Effects of Amino Acids on Chrysanthemum

“…The quantities of amino acids found were quite variable. Amino acids added to soil were quite rapidly transformed, and usually undetectable in extracts made after 72 to 96 hours of incubation (11,16). D-Amino acids and L-alloisoleucine appeared more resistant to change than other amino acids studied (16).…”

“…The question of the significance of free amino acids in soil or other cultural media has received attention in recent years in the fields of plant physiology (1,3,7,13,14,15,16,17), soil microbiology (4,5,11,16) and soil chemistry (9,10,12). Although it originally appeared that free amino acids were not to be found in soils, later reports (2, 10) indicated they could be extracted with aqueous and alcoholic solutions and determinations made with chromatographic methods.…”

“…The coenzyme in R. meliloti (11) has been isolated and identified as the 5,6-dimethylbenzimidazole derivative (vitamiin B1.2 coenzyme). Further investigations have provided evidence that the B12 coenzyme content of R. ineliloti cells is positively correlated with the cobalt concentration of the culture medium (12).…”