Bacteria possess a sophisticated arsenal of defense mechanisms that allow them to survive in adverse conditions. Adaptation to acid stress and hypoxia is crucial for the enterobacterial transmission in the gastrointestinal tract of their human host. Using three-dimensional superresolution fluorescence microscopy and electron cryo-microscopy, the researchers of the MICA group, in collaboration with the PIXEL team and the M4D platform at the IBS, have shown that in response to acid stress, the enzyme lysine decarboxylase (LdcI) forms supramolecular assemblies in vivo in E. coli and polymerizes into filaments. They determined the atomic structure of those filaments in vitro and proposed a mechanistic model for LdcI function and offer tools for further in vivo investigations. This work has also made it possible to develop tools applicable to all types of cells, to study molecular assemblies by combining the two types of microscopy while preserving their structural integrity and their interactions with cellular partners.
Supramolecular assembly of the Escherichia coli LdcI upon acid stress. Jessop M, Liesche C, Felix J, Desfosses A, Baulard M, Adam V, Fraudeau A, Huard K, Effantin G, Kleman JP, Bacia-Verloop M, Bourgeois D, Gutsche I. Proc Natl Acad Sci U S A. 2021 Jan 12 ;118(2):e2014383118.