Morphology and growth pattern of a rod‐negative env B mutant of Escherichia coli K12

An env B mutant (strain D23) of Escherichia coli K12 showing a distorted cell form was studied. The cells in a logarithmically growing D23 population are extremely heterogeneous with respect to size and shape. Different types of cells were studied in the electron microscope and the growth pattern was followed under the phase contrast microscope. The following observations were made: 1. All cells increase their mass by longitudinal growth. Inhibition of cell division results in filament or snake formation; the diameter of such cells is dependent on that of the original cell. 2. To a certain degree the size and shape of daughter cells is phenotypically determined by the parental cell. 3. Division of rod-shaped cells of D23 is symmetric, whereas ovoid or coccoid cells show an asymmetric constriction. 4. After division of irregularly shaped cells, elongation of the daughter cells does not necessarily proceed perpendicular to the preceding division plane. The dependence of cell shape on growth direction and division pattern is emphasized.