Sporulation in Bacillus subtilis. Characterization of Oligosporogenous Mutants and Comparison of Their Phenotypes with Those of Asporogenous Mutants

Abstract

SUMMARY An investigation was undertaken to determine to what extent the properties of oligosporogenous (Osp) mutants allow them to be considered as a separate class of sporulation mutant, distinct from asporogenous (Sp-) mutants. Of thirty Osp mutants examined, seventeen at least had a phenotype which had previously been identified with a Sp- mutant. The majority of cells in an Osp culture either reached a particular stage in the sporulation process and then stopped, or in some cases went on to produce aberrant forms. Some of these aberrant forms have their counterparts in Sp- mutants described by other authors, but some present new features. The morphological and biochemical sequences were linked so that if the majority of cells were blocked at a certain stage, then the biochemical sequence stopped accordingly. The general similarity in behaviour between the two types of mutant is consistent with the assumption that at least some of the Osp mutants have leaky mutations in genes where mutation can also give rise to Sp- phenotypes. Evidence is presented to suggest that the ability of a cell of an Osp mutant to over- come its block, and so go on to form a spore, is a chance event when that stage in the process is reached. A mutant has been obtained in which the spores are octanol- resistant yet contain no measurable dipicolinate. In several other mutants the spores contained well-developed coat layers, but the cortex was poorly formed or com- pletely missing.