PT - JOURNAL ARTICLE AU - Gábor M. Harami AU - Zoltán J. Kovács AU - Rita Pancsa AU - János Pálinkás AU - Veronika Baráth AU - Krisztián Tárnok AU - András Málnási-Csizmadia AU - Mihály Kovács TI - Phase separation by ssDNA binding protein controlled <em>via</em> protein-protein and protein-DNA interactions AID - 10.1101/797431 DP - 2019 Jan 01 TA - bioRxiv PG - 797431 4099 - http://biorxiv.org/content/early/2019/10/08/797431.short 4100 - http://biorxiv.org/content/early/2019/10/08/797431.full AB - Bacterial single stranded (ss) DNA-binding proteins (SSB) are essential for the replication and maintenance of the genome. SSBs share a conserved ssDNA-binding domain, a less conserved intrinsically disordered linker (IDL) and a highly conserved C-terminal peptide (CTP) motif that mediates a wide array of protein-protein interactions with DNA-metabolizing proteins. Here we show that the E. coli SSB protein forms liquid-liquid phase separated condensates in cellular-like conditions through multifaceted interactions involving all structural regions of the protein. SSB, ssDNA and SSB-interacting molecules are highly concentrated within the condensates, whereas phase separation is overall regulated by the stoichiometry of SSB and ssDNA. Together with recent results on subcellular SSB localization patterns, our results point to a conserved mechanism by which bacterial cells store a pool of SSB and SSB-interacting proteins. Dynamic phase separation enables rapid mobilization of this protein pool to protect exposed ssDNA and repair genomic loci affected by DNA damage.