[Change in the ultrastructure of Bacillus polymyxa cells in the process of sporogenesis].

The fine structure of consecutive modifications was studied in sporulating cells of Bacillus polymyxa 153 growing in a liquid aerated medium. The stages of sporogenesis were found to be similar, in principle, with those in other species of the Bacillus genus, but also had certain peculiarities. In contrast to other bacilli, the nucleoid axial thread was not formed in B. polymyxa cells at the first stage of sporulation. The structure of the of the prospore nucleoid forming the local central zone differed from that of the vegetative cell nucleoid at the second stage. The ultrastructural changes observed when the spore septa was formed indicated that its structure was identical with that of the septa of vegetative division, in contrast to which the cell wall material did not undergo lysis but was preserved at the following stages of sporogenesis. The formation of the spore envelope material could easily be discerned in the cytoplasm of the mother cell. The fine structure of mature spores is described in this paper for B. polymyxa. The outer rigid part of its spore envelope was shown, for the first time, to consist of three layers, the surface one having an ordered fibrillar structure.