Genetic mechanism regulating bacterial cell shape and metabolism.

The bacterium Escherichia coli is rod-shaped, and a unit cell keeps regular dimensions of about 1.5 microm long and 0.5 microm wide. The rod-shaped cell is composed of two parts: a cylinder in the center and caps at both ends. The length of the cylinder corresponds to the length of the rod cell. A recent paper reported the genetic regulation of the cell length by rodZ. RodZ is a membrane protein with bitopic topology that assembles underneath the cell membrane to form helical filaments along the lateral axis of the cell with the bacterial actin MreB. RodZ filaments probably interact with enzymes that contribute to peptidoglycan synthesis. Cells lacking rodZ shorten only along the lateral axis of the cell so that the cells become round-shaped instead of rod-shaped. Such spheroidal cells consist only of caps due to the loss of almost all of the cylinder. In addition, carbon metabolism is remarkably disturbed by the deficiency of RodZ. This suggests that the transport of nutrients at the surface of the cylinder is reduced in rodZ mutant cells. Thus, cell morphology is also critical for proper metabolism for cell proliferation.