[Seminar] Building a cell wall from scratch: de novo morphogenesis in l-forms of Escherichia coli

ITQB Seminar

Title: Building a cell wall from scratch: de novo morphogenesis in l-forms of Escherichia coli

Speaker: Gabriel Billings

Affiliation: Stanford University

Host: Mariana G. Pinho, Bacterial Cell Biology Lab

Abstract:
In virtually all bacteria, the cell wall is crucial for mechanical integrity and for determining cell shape. Escherichia coli's rod-like shape is maintained via the spatiotemporal patterning of cell-wall synthesis by the actin homologue MreB. Despite its important role, the cell wall is conditionally dispensible; many bacteria can, after
inhibition of cell wall synthesis, proliferate as cell-wall deficient 'L-forms.' In my talk, I will present evidence that L-forms of E. coli robustly revert to a rod-like shape within several generations after inhibition cessation. During this process, the chemical composition of the cell wall remains essentially unchanged, as indicated by liquid chromatography. Throughout reversion, MreB localizes to inwardly curved regions of the cell, and fluorescent cell wall labelling reveals that MreB targets synthesis to those regions. When exposed to the MreB inhibitor A22, reverting cells regrow a cell wall but fail to recover a rod-like shape. Our results suggest that MreB provides the geometric measure that allows E. coli to actively establish and regulate its morphology.