A temperature sensitive TCA cycle mutant of Bacillus subtilis: physiological effects on sporulation

A temperature sensitive sporulation mutant of Bacillus subtilis was isolated and and shown to be defective in aconitase activity at the restrictive temperature (37°C). Sporulation specific production of antibiotic and protease a.ppea.r to be unaffected. At 37°C in a minim medium sporulation is almost completely inhibited, while at 30°C, a temperature which allows a very low level of aconitese activity to be expressed, abnormal spores are formed which are non-refractile, lysozyme resistant, and unstable to storage. The addition of glutamate does not affect the behavior of this mutant at 37°C, but at 30°C it permits a production of n0rmal spores at &. frequency near that of the wild type. Temperature shift experiments suggest the possibility of two critical periods during sporulation requiring aconitase activity: one early in the process (T1-T2) prior to the formation of the prespore, and one later in the process (T3-T5) associated with spore maturation.