A novel mechanism of bacteria to adapt to nutrient deprivation via the ribosome silencing factor RsfS (reference number: NMICROBIOL-19112987)

The factor RsfS is present in almost all bacteria and organelles. RsfS is important under conditions of nutrient downshifts leading to decreasing growth rates. A common feature of these conditions is a strong reduction of the translation capacity revealed by polysomal fraction decrease and a vast appearance of vacant 70S ribosomes, which might cause a devastating energy drain by stimulating the activity of GTPase proteins e.g. EF-G with idle ribosomes. Here we show that RsfS blocks association of free ribosomal subunits and induces dissociation exclusively of vacant ribosomes rather than of programmed ribosomes carrying tRNAs. As a consequence, RsfS reduces the abundance of the cellular translational apparatus, and the EF-G dependent burst of GTP cleavage in the presence of vacant 70S ribosomes as well as with 30S and 50S subunits is decreased. These observations hint to a regulatory role of RsfS by utilizing cellular resource in an economic way under conditions, where the amino acids are limited and energy has to be saved. Overall design: Ribo-seq of E. coli strain BW25113 and BW25113_?RsfS in M9 minimal medium.