Demonstration of cell division by septation in a variety of gram-negative rods.

Through use of an initial fixative employing a combination of crotonaldehyde and glutaraldehyde, septa were preserved in thin sections of dividing cells of strains of Pseudomonas aeruginosa, Salmonella typhimurium, Shigella sonnei, and Escherichia coli when grown at 30 C in a dilute basal medium. The same procedures, however, revealed only a constrictive division process in Proteus vulgaris and Erwinia sp. This adds to the evidence that septation, although difficult to demonstrate, is the process of cell division in the enteric gram-negative rods and the pseudomonads and that constriction is a fixation artifact in these organisms.