RNA sequencing results of wild-type TmaR (WT) and cells deleted for the tmaR gene (TmaR-KO)

TmaR is a newly discovered protein that clusters at the E. coli cell poles and controls localization and activity of the major sugar regulator EI in a tyrosine phosphorylation-dependent manner. Here we show that TmaR assembles by phase separation (PS) via heterotypic interactions with RNA in vivo and in vitro. An unbiased automated mutant screen combined with directed mutagenesis and genetic manipulations uncovered the importance of a predicted nucleic-acid- 38 binding domain, a disordered region and charged patches, one containg the phosphorylated 39 tyrosine, for TmaR condensation. We demonstrate that by protecting flagella-related transcripts, TmaR controls flagella production and, thus cell motility and biofilm formation. These results connect PS in bacteria to survival and provide an explanation for the linkage between metabolism and motility. Intriguingly, a point mutation or increase in its cellular concentration induce irreversible liquid-to-solid transition of TmaR, similar to disease-causing proteins in human, which affects bacterial cell morphology and division.