Reprogrammed peptidoglycan elongation reveals plasticity in bacterial growth modes

Most bacteria are enclosed by a peptidoglycan (PG) cell wall that must be expanded for growth. In rod-shaped species, PG elongation is spatially organized in a species-specific manner, occurring either at the cell poles or along the lateral wall. MreB filaments organize the Rod machinery and are typically required for dispersed, nonpolar PG elongation but are dispensable for polar growth. Whether elongation modes are inherently fixed or can be reprogrammed remains unclear. Escherichia coli and Myxococcus xanthus both elongate PG in a dispersed, nonpolar fashion. Here, we show that heterologous expression of M. xanthus MreB in E. coli relocalizes native MreB to the cell poles, thereby redirecting the Rod machinery and PG elongation to polar sites. Moreover, direct targeting of the Rod synthase PBP2 to the poles is sufficient to drive polar PG elongation in E. coli while preserving rod shape. This reprogrammed growth mode bypasses the requirement for MreB filaments, highlighting a plasticity of the Rod system that suggests polar elongation may have emerged through the evolutionary loss of MreB.