Metabolism of Bacillus thuringiensis in Relation to Spore and Crystal Formation

A general pattern of metabolism was determined for Bacillus thuringiensis grown in a glucose-yeast extract-salts medium. The pattern did not differ significantly from that of B. cereus grown in a similar medium. Acetic acid produced from glucose during exponential growth was further catabolized in the early sporulation phase of growth, at which time the specific activity of aconitate hydratase increased markedly. Fluoroacetate and α-picolinate prevented the removal of accumulated acid, and the resulting low pH inhibited spore and crystal synthesis. Neither crystal-related antigens nor insect toxicity was shown by cells whose crystal synthesis was inhibited in this way. α-Picolinate prevented the normal increase in specific activity of aconitate hydratase without inhibiting exponential growth. It also inhibited aconitate hydratase in vitro, but only if preincubated with the enzyme. α-Picolinate did not inhibit the increase in specific activity of aconitate hydratase or spore and crystal synthesis in a medium buffered near neutrality. Chloramphenicol and actinomycin D inhibited crystal enlargement and sporulation when added to cells in which small crystals had already begun to form. Typical messenger ribonucleic acid-dependent protein synthesis, rather than the type associated with peptide antibiotic synthesis, is thus indicated for the synthesis of crystal peptide subunits.