The cell plate in bacterial cytokinesis.

The first phase of bacterial cytokinesis was described by Knaysi (1951) as involving an inward growth of the cytoplasmic membrane to form a septum across the cell. Transverse plasma rnembranes or boundaries were previously reported by Migula (1894) in Bacillus oxalaticus, by Guillermond (1908) in Bacillus mycoides, by Knaysi (1930) in B. mycoides and Bacillus mesentericus, and by Robinow (1942, 1944) in Escherichia coli. Robinow (1945) and Knaysi (1951) concluded that cross wall material is formed at the position of the transverse membrane by centripetal growth of the lateral wall; however, the authors diffeIred considerably in details of the process. Bisset (1948) emphasized the differences in the mode of cell division between morphologically smooth and rough forms of bacteria and suggested that cross walls do not "grow" but rather are produced by secretion at the surface or interface of cell membranes. The nature and origin of the "transverse membrane" often reported as initiating cytokinesis in the bacilli are still subject to controversy (Chapman and Hillier, 1953). Chance (1953a, b) demonstrated through the use of the crystal violet nuclear stain that a cell plate of nuclear origin forms just piior to cytokinesis in 12 species of cocci and 5 species of bacilli. The cell plate was obseirved to form within the dividing nucleus and to develop in a manner similar in many respects to cell plate formation during cytokinesis of higher plant cells. The cell plate was shown to be neither a cytoplasmic membrane nor of cell wall material, since the crystal violet nuclear stain does not stain cell wall material, cytoplasm, oIr cytoplasmic membranes. The stain was shown to be specific for a protein component of the bacterial nucleus