Biochemical genetics of bacterial sporulation

Summary The development of membrane structures during the early steps of spore formation was reexamined. These steps include the formation of a ringshaped membrane invagination in contact with a mesosome, the growth of which leads to a straight closed double-membrane diaphragm with a cell wall spike (ringshaped thickening) at its base. Later the diaphragm protrudes into the sporangial cytoplasm in the form of a half-blown balloon. The last step toward completion of the prespore consists of the detachment of the diaphragm from the cell wall spike and its growth (probably from a new growing region) into a completely closed spherical structure.Some of the sporulation mutants are blocked at one of these steps, others present abnormal structures. Bilateral development, the occurrence of multiple membrane invaginations and derepression of cell wall growth are at the origin of certain abnormal mutants. In other mutants the diaphragm is not detached from the cell wall spike, perhaps because of the lack of initiation of a new membrane growth site. This leads to abnormal hemisphere prespores. Satellite prespores have been also observed and attributed to derepressed growth of the cell wall spike.The author was on leave of absence from the Centre National de la Recherche Scientifique, Paris. Present adress: see end of paper.