EFFECT OF VARIOUS TREATMENTS ON CONTENTS OF ADENINE-NUCLEOTIDES AND RNA OF MEDITERRANEAN SOILS

Changes in adenine nucleotides (ATP, ADP and AMP) were investigated in soils subjected to various treatments and compared with bacterial and fungal counts. An organic and a clay soil stored for 3 yr at room tem perature showed low ATP concentrations (0.36 and 0.26 nmol g-1, respec tively) which markedly increased after moistening both soils; this ind icates that the prolonged storage did not eliminate the capacity of AT P synthesis by these soils; in the organic soil bacteria and fungi wer e unaffected by moistening while only bacterial counts were increased in the clay soil. By moistening soil with NaN3 solution the ATP increa se was annulled in the organic soil and only reduced in the clay soil. Air-drying a sandy clay-loam soil resulted in a 40% drop in ATP while microbial counts were unaffected; rewetting the air-dried soil to 50% of the water holding capacity (WHC) did not increase ATP. Decrease in the ATP content was more marked when moistened or rewetted soils rath er than fresh or air-dried soils were fumigated; the fumigation of soi ls moistened with the NaN3 solution generally decreased the ATP concen tration. Sodium azide generally decreased recoveries of ATP, ADP and A MP especially in the organic soil; the effect of the inhibitor on enzy matic conversion of AMP to ADP and of ADP to ATP was also investigated in the soil extracts. Adenylate energy charge (AEC) values of moist f ield samples were 0.65, 0.70 and 0.80 for clay, sandy-clay loam and or ganic soils, respectively. Air-drying moist soils caused a marked drop in ATP and RNA and an increase in ADP, AMP and total adenine nucleoti des. The AEC value of CHCl3 fumigated fresh moist soil were very low r anging from 0.06 to 0.1 thus indicating a large prevalance of dead cel ls even if the bacterial numbers by plate count were moderately affect ed.