Nitrogen fixation has been detected by the acetylene reduction method in the sediments of the Waccasassa estuary, a shallow embayment on the Florida Gulf Coast. Fixation rates in the range 1.6-15.0 ng C2H4/g sediment-hr were found within the top 2-5cm stratum of sediments. Expressed in terms of equivalent nitrogen fixed, the range was 0.64-6.0 ng N/g-hr.Much lower rates (0.03-0.40 ng GHa/g-hr) were found at greater depths in the sediment, and no fixation was observed in the flocculent unconsolidated l-2 cm at the sediment surface.All evidence indicates that the reduction of acetylene to ethylene is a biological phenomenon, directly related to the activity of nitrogen-fixing organisms in the sediments. Nitrogen-free media produced growths of Gram-positive spore-forming rods from sediments under an Nz atmosphere.A pure culture similar to Clostridium sp. was isolated on nitrogen-free media from Waccasassa sediments and was shown capable of nitrogen fixation by the acetylene reduction method.
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...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.