Adenosine deaminase and ribosidase in spores of Bacillus cereus.

Inosine is a more effective germination stimulant than adenosine for spores of Bacillus cereus and B. anthracis (Powell & Hunter, 1955). A crude method of assessment, based on the paper-ionophoresis technique of Wade & Morgan (1954), indicated that extracts from disintegrated resting spores of B. cereus converted adenosine into inosine. This suggested the possibility that inosine might be, in fact, the germination stimulant, and that germination of a given spore suspension in adenosine might depend, to some extent, on its adenosine-deaminase activity. We have now studied quantitatively the deamination of adenosine by resting and germinated spores of B. cereus, and also its further breakdown to the purine and free ribose. The possible relationships between these reactions and spore germination in B. cereus are discussed. Part of this work has already been briefly reported (Powell, 1955). 40 mm sodium potassium phosphate buffer pH 7-3. Resting and germinated spores were disintegrated in suspensions containing 2 x 1010 spores/ml., using the Mickle (1948) tissue disintegrator with Ballotini beads size 12. The suspensions were ice-cooled at 10 min. intervals during disintegration, which usually took 1 hr. Homogenates were separated by centrifuging for 30 min. at 6000 g to give extract and 'debris' preparations. For some experiments (see below) the deaminase was precipitated from extracts with 30% (v/v) ethanol at 0°. It redissolved readily in water and buffer solutions. A spore-coat preparation was obtained by disintegrating a resting-spore suspension for approximately 20 min., i.e. until the appearance of stained films indicated that disruption had occurred, but the suspension still consisted mainly of recognizable spore-coat fragments. Smaller particles of doubtful origin were removed by repeatedly suspending in