Identification of d-Alanine as the Auto-Inhibitor of Germination of Bacillus globigii Spores

Summary: Thick suspensions of spores of Bacillus globigii did not germinate completely in nutrient media because the first spores to germinate released a substance which inhibited germination of the remainder. The inhibitory substance was identified as d-alanine by chromatography, high voltage electrophoresis, and its destruction by d-amino acid oxidase. When 14C-l-alanine was used to induce germination of B. globigii spores, the resulting inhibitory d-alanine was 14C-labelled with the same specific activity as the 14C-l-alanine used. Auto-inhibition of B. globigii spore germination is therefore due to racemization of exogenous l-alanine, which forms sufficient d-alanine to arrest the germination process in thick suspensions of spores.