Chemical and bacterial changes in a forest soil percolated with some amino acids and leaf litter extract

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Abstract
Chemical and bacterial changes in the forest soil percolated with glycine and glutamate solution and leaf litter extract were studied. When the forest soil was percolated with 25 mM glycine or glutamate, it took about 20 days for the number of bacteria to reach the maximum in number and the amino acids to be completely ellhausted, the rate being much slower than that in the cultivated soil. Supplementation of 0.01% yeast extract to the percolate much rnhanced the growth of bacteria and degradation of glycine. In this percolation the metabolic pattern of glycine was comparable to that in the cultivated soil except for the absence of an appreciable amount of nitrate formation. Growth of bacteria in the forest soil was also rapid when percolated with leaf litter extract and only 3 days were sufficient for reaching the maximum number. Neither ammonia nor nitrate was detected throughout the percolation period and only change observed in the solution was a slight rise in pH. Characteristics of bacteria enriched in the forest soil percolated will) glycine with and without yeast extract, and leaf litter extract were studied, No one group was dominant in the soil before percolation. Bacteria enriched by glycine were almost occupied with Gram-negative nonmotile rods with rather complex nutritional requirement regarded as Achromobacter, which were characteristically unable to utilize glycine as a sole nitrogen source. When the soil was percolated with glycine supplemented with yeast extract, enriched bacteria were composed of many kinds. The soil percolated with leaf litter extract was occupied with bacteria with simple nutritional requirement, which were regarded as Pseudamonas.