Effects of microbial population and culture phosphate composition on the activity of pyrophosphatases from soil microorganisms

The quantity of intracellular pyrophosphatases produced in mixed cultures was not related to pyrophosphate or orthophosphate concentration in the culture medium, but high pyrophosphate concentration initially depressed microbial growth, delayed the first signs of pyrophosphate hydrolysis and gave rise to a lower initial rate of pyrophosphate hydrolysis in the culture. Not all cultures produced intracellular pyrophosphatases, but when they were present, the same functional kinds of enzymes appeared to be present when compared on the basis of activation by five cations. All cultures inoculated with fresh soil were able to hydrolyse pyrophosphate in the culture medium, but not all cultures inoculated with stored soil displayed culture pyrophosphatase activity. There was evidence that intracellular pyrophosphatases were responsible for culture pyrophosphatase activity. It was found that cultures showing low intracellular and culture pyrophosphatase activity were dominated by Gram +ve rods. When intracellular and culture phosphatase activities were high, Gram -ve rods and Gram -ve cocci dominated the culture populations. As cultures dominated by Gram +ve rods were obtained only from stored soil inoculum, it is considered that during soil storage, Gram +ve rods became dominant in the soil because of the ability of some members of this group to form resistant endospores