Abstract
Hfq is an RNA-binding protein that is common to diverse bacterial lineages and has, amongst many, a key role in RNA metabolism. We reveal that Hfq is required by Escherichia coli to adapt to nitrogen (N) starvation. By using single molecule tracking photoactivated localisation microscopy imaging of individual Hfq molecules in live E. coli cells, we have uncovered an unusual behaviour of Hfq: We demonstrate that Hfq forms a distinct and reversible focus-like structure specifically in long-term N starved E. coli cells. We show that foci formation by Hfq is a constituent process of the adaptive response to N starvation and provide evidence which implies that the Hfq foci, analogous to processing (P) bodies of stressed eukaryotic cells, contribute to the management of cellular resources to allow E. coli cells to optimally adapt to long-term N starvation stress.