Mutants of Bacillus subtilis temperature sensitive in the outgrowth phase of spore germination

Thirteen thermosensitive mutants of Bacillus subtilis defective in the outgrowth phase of spore germination were isolated. The spores of the mutants grow into vegetative cells at 35 C but not at 47 C, whereas the vegetative cells grow equally well at both temperatures. At 47 C all the mutant spores are able to initiate germination, but the process stops at an early phase of outgrowth in one strain and in a late phase in the other 12 strains. The spore of the latter gives rise to a swollen cell unable to divide. In all mutants, the normal phenotype is restored when the spores are grown in the presence of 20% sucrose or 2% NaCl. The synthesis of deoxyribonucleic acid and proteins does not seem to be altered in the mutants giving swollen cells. The mutants were grouped into three distinct genetic classes by transformation.