A cold shock protein from a thermophile bacterium promotes the high-temperature growth of bacteria and fungi through binding to diverse RNA species

High temperatures deleteriously affect cells by damaging cellular structures and changing the behavior of diverse biomolecules, and extensive research about thermophilic microorganisms has elucidated some of the mechanisms that can overcome these effects and allow thriving in high-temperature ecological niches. We here used functional genomics methods to screen out a cold-shock protein (CspL) from a high-productivity lactate producing thermophile strain (Bacillus coagulans strain 2-6) grown at 37°C and 60°C. We subsequently made the highly striking finding that transgenic expression of CspL conferred massive increases in high temperature growth of other organisms including E. coli (2.4-fold biomass increase at 45°C) and the eukaryote S. cerevisiae (a 2.7-fold biomass increase at 34°C). Pursuing these findings, we used bio-layer interferometry assays to characterize the nucleotide-binding function of CspL in vitro, and used proteomics and RNA-Seq to characterize the global effects of CspL on mRNA transcript accumulation and used RIP-Seq to identify in vivo RNA targets of this nucleotide-binding protein (e.g. rpoE, and rmf, etc.). Finally, we confirmed that a nucleotide-binding-dead variant form of CspL does not have increased growth rates or biomass accumulation effects at high temperatures. Our study thus establishes that CspL can function as a global RNA chaperone.