Morphogenesis of the bacterial division septum: a new class of septation-defective mutants.

A new class of mutants of Salmonella typhimurium (lkyD mutants) are described. The mutants are defective in morphogenesis of the division septum, and are characterized by a failure of the outer membrane to invaginate despite normal ingrowth of the cytoplasmic membrane and murein layers of the growing septum. The cell envelopes of the mutants show a significant decrease in the bound form of murein-lipoprotein and a corresponding increase in the free form of the lipoprotein. This suggests that the morphogenic defect may result from a defect in formation of covalent bonds between the free lipoprotein of the outer membrane and the murein of the nascent septum.