Sporulation of a Cortexless Mutant of a Variant of Bacillus cereus

Abstract

A stage 4 sporulation mutant of a strain of Bacillus cereus var. alesti fails to synthesize a cortex although all other structural components appear normal. With terminal lysis the spore core as well as the sporangium is lysed. Both the uptake of 45 Ca and the synthesis of dipicolinic acid (DPA) are similar to these activities in the parent strain, but these components (DPA and Ca) are lost to the medium with the drastic lysis. The first stage of diaminopimelic acid incorporation, that into germ cell wall mucopeptide, is intact in the mutant; the second stage, that into cortical mucopeptide, is absent. These biochemical studies as well as phospholipid metabolism and freeze-etch analysis suggest the lesion lies in the outer forespore membrane.

Spore Refractility in Variants of Bacillus cereus Treated with Actinomycin D

“…Concurrently, the deoxyribonucleic acid (DNA) condenses into semi-crystalline masses at the periphery. In the mutant A(-)I, some refractility is seen at peak phase whitening (15). In this work, the degree of refractility was increased and maintained by the addition of actinomycin D, since synthesis of the lytic enzyme was prevented, thus halting terminal lysis.…”

“…Experiments with the cortexiess mutant A(-)l. The characteristics of sporulation in this mutant have been described previously (15). Briefly, sporulation as seen by phase microscopy appears to proceed normally to stage 5; however, full refractility is not observed, and a drastic lysis terminates the sporulation process, leaving lysed spore hulls as the final product.…”

“…A non-crystal-forming strain of Bacillus cereus var. alesti, A(-), described previously (5), and a mutant, A(-)I, derived from this (15), were used. Growth and sporulation conditions were those detailed by Young and Fitz-James (21).…”

“…Nigrosin smears (4) examined by brightfield microscopy were also used for the detection of refractility. Samples for electron microscopy were prepared essentially by the method of Kellenberger et al (9) with minor modifications detailed elsewhere (15). Freeze fracture etching of samples quick frozen in Freon 22 was done in a Balzers unit (AG, Furstentum Lichtenstein).…”

Recent Advances in the Understanding of Resistance and Dormancy in Bacterial Spores

“…For instance, peptidoglycan is laid down, in the cortex, between the two forespore membranes (Warth et al 1963), and peptidoglycan is normally laid down on the outer surface of the bacterial cell. Mutants are known which show defective synthesis of the outer cortex (Pearce & Fitz-James 1971;Imae & Strominger 1976a, c) which is probably synthesized by the mother cell. This outer region of the cortex differs chemically from the inner region or 'germ cell wall' (Tipper & Gauthier 1972) which is probably synthesized by the core.…”