Aggresomes protect mRNA under stress in Escherichia coli

Membraneless droplets formed through liquid-liquid phase separation of ribonucleoprotein particles contribute to mRNA storage in eukaryotic cells. How such aggresomes contribute to mRNA dynamics under stress, and their functional role, is less understood in bacteria. Here we used multiple approaches including imaging, modelling and transcriptomics to show that prolonged stress leading to ATP depletion in Escherichia coli results in increased aggresome formation, their compaction, and enrichment of mRNA within aggresomes compared to the cytosol. Transcript length was longer in aggresomes compared to the cytosol. Mass spectrometry showed exclusion of mRNA ribonucleases from aggresomes, which was due to negative charge repulsion. Experiments with fluorescent reporters and disruption of aggresome formation showed that mRNA storage within aggresomes promoted translation and associated with reduced lag phases during growth after stress removal. Our findings suggest that mRNA storage within aggresomes confers an advantage for bacterial survival and recovery from stress. Overall design: We treated the cells with arsenite for 30 min, and extracted the aggresome RNA and cytol RNA respectively, and then analyzed the RNA SEQ.