Interrelationship between extracellular enzyme activity,ATP content,total counts of bacteria and CO2 evolution

Summary In an incubation experiment, soil was amended to induce changes in microbial growth and enzyme production. The soluble fraction of newly produced protease (extracellular enzyme) was separated from the soil by a sterilized millipore filter. The activity of total and soluble protease, ATP content, number of acridine orange-stained bacteria, and CO₂ evolution in soils were measured during the incubation. Increases in soluble and total protease activities in soils amended with agar and glucose coincided with increases in ATP content, total counts of bacteria, growth of fungi, and CO₂ evolution. In amended soils, the activity of soluble extracellular protease was about 30% of the total protease activity. Soluble extracellular protease activity was highly correlated with total protease activity (r=0.78, P<0.01), ATP content (r=0.74, P<0.01), and total counts of bacteria (r=0.94, P<0.01) during the first 6 days of incubation. Hence measurement of microbial biomass appeared to be an index for the level of extracellular enzymes in soil.