Reprinted from ANatyricat BiocHemistry, Volume 17, Number 1, October 1966 Copyright © 1966 by Academic Press Inc. Printed in U.S.A. Demonstration of the Stereospecific Action of Microorganisms in Soil by Gas Liquid Chromatography Many microorganisms and enzymes are endowed with the ability to preferentially metabolize, incorporate, or chemically alter one antipode of a racemic substrate while leaving the other antipode intact. This in- trinsic property can form the basis of experiments aimed at the detection of biological agents in planetary soils. A high-sensitivity gas-liquid chro- matographie technique (1) has been employed to monitor the stereospe- cific consumption of several racemic amino acid substrates in a prototype terrestrial experiment. In a typical assay, soil (10 gm), the racemic amino acid substrate (10 mg), and distilled water (10 ml) were shaken at room temperature. From time to time aliquots (approx. 1 ml) were removed and diluted with water (10 ml). The soil was centrifuged down and the supernatant solution lyophilized. After esterification with thionylchloride-methanol (0.4 ml in 5 ml) (2) and evaporating, the residue was coupled with NV- trifluoroacetyl-L-proly! chloride (0.2 mM) in methylene chloride (2 ml) (1) in the presence of triethylamine (0.06 ml). After washing (H,O) and drying (Na.SO,), a part of the solution (~2 yl) was injected into the gas chromatograph. By computing the peak areas of the two diastereoiso- mers, a fast sensitive recording of unused p/L amino acid concentration could be obtained (Table 1, Fig. 1). Our results show that the t-antipodes of the substrates are prefer- entially attacked, but that different amino acids are used at different rates. The observation that the stereospecific action is lost after heat sterilization of the soils confirms that a biological process is involved. SHORT COMMUNICATIONS 180 ‘COGT ‘taquIddaq, Ul PAOJUBIG 1B payaT]OO [los UapAVY) p “AY FZ LOJ OGET 18 Surjvay Aq pazipiszays a10M sadures [10g » “S0'9 Jo Wd B pwy [los ayy, ‘urdd Qge’g sem UOqred o1UBdIO ayy puw wdd ggpF{T sea sisAyRUG UadOI]IU D1URSIO OIL, “SAUTY YSVN Aq pazuayoereyo pus “eM; [ED ‘PT, WEQOWL 1B P9ye]]09 [Log g “(F1Z) plow orueynys-1 puv (Z'9Z) Plow orureynys-a ‘(ZFT) aurpord-1 ‘(QrET) euTpoad-a ‘(e°OT) plow o1