Autonomous division of the outer membranes in Gram-negative bacteria

Gram-negative bacteria divide by separating two cell wall layers: peptidoglycan (PG) and the outer membrane (OM). In certain model organisms, the OMs are tethered to PG, ensuring it closely follows PG when cells constrict at division sites. In contrast, the OMs of Myxococcus xanthus exhibit slight invagination at the onset of cell division but do not follow the constriction of PG, instead separating significantly later, only after complete PG fission. However, reinforcing the OM-PG connection by overexpressing tethering proteins, either the endogenous Pal or the exogenous Lpp, synchronizes the constriction of both layers. Our findings suggest that OMs can divide by simple mechanical force. The variability in OM division mechanisms among Gram-negative bacteria reflects differences in both the mode of PG division and the strength of PG-OM interactions.