Three sporulation mutants have been isolated which produce spores with an atypical resistance phenotype, i,e. they are sensitive to organic solvents and heat but resistant to lysozyme. All three mutants produced serine protease, alkaline phosphatase and glucose dehydrogenase which are biochemical marker events for stages I, I1 and 111. Two of the three mutants produced dipicolinic acid, a late marker, but the third was defective in its production. Heat-resistance was not restored to any of the mutants by the provision of exogenous dipicolinate. Gel electrophoresis showed that the mutant spores had similar patterns of spore coat proteins to the wild-type and electron microscopy revealed no significant structural differences. The three mutations responsible for the phenotypes of the mutant spores lie in the phe-argA region of the Bacillus subtilis chromosome. Recombination index values indicate that the mutations are in three separate genes. They define at least two new sporulation loci, designated spoVH and spo VJ. , 1980; Jenkinson et al., 1980, 1981). It should, therefore, be possible to isolate mutants in which a 'late' property is normal while an 'earlier' one is defective. We have now been able to show that mutants with this previously unexpected phenotype do exist and in this paper the isolation and characterization of three organic solvent-sensitive, heat-sensitive but lysozyme-resistant mutants are described. The mutations carried by these three mutants identify two new sporulation loci.
METHODS
Chemicals.Unless otherwise stated chemicals were obtained from Sigma. Organisms. Bacillus subtilis Marburg 168 trpC2 which requires either indole or tryptophan and which sporulates normally is referred to as the wild-type. Details of sporulation defective (Spo-) mutants derived from 168 and Spo+ auxotrophic strains used for genetic analysis are shown in Table 1