  Membraneless droplets formed through liquid-liquid phase separation (LLPS)
play a crucial role in mRNA storage, enabling organisms to swiftly respond to
environmental changes. However, the mechanisms underlying mRNA integration and
protection within droplets remain unclear. Here, we unravel the role of
bacterial aggresomes as stress granules (SGs) in safeguarding mRNA during
stress. We discovered that upon stress onset, mobile mRNA molecules selectively
incorporate into individual proteinaceous SGs based on length-dependent
enthalpic gain over entropic loss. As stress prolongs, SGs undergo compaction
facilitated by stronger non-specific RNA-protein interactions, thereby
promoting recruitment of shorter RNA chains. Remarkably, mRNA ribonucleases are
repelled from bacterial SGs, due to the influence of protein surface charge.
This exclusion mechanism ensures the integrity and preservation of mRNA within
SGs during stress conditions, explaining how mRNA can be stored and protected
from degradation. Following stress removal, SGs facilitate mRNA translation,
thereby enhancing cell fitness in changing environments. These droplets
maintain mRNA physiological activity during storage, making them an intriguing
new candidate for mRNA therapeutics manufacturing.
