ssDNA-binding protein that contributes to the ionizing radiation resistance of D.radiodurans. Plays a role in DNA repair and genome reconstitution in a RecA-independent process. Required for recovery from severe genomic fragmentation as a result of exposure to severe levels of ionizing radiation. Binds ssDNA but not dsDNA. Stimulates annealing of complementary ssDNA. Does not complement an ssb disruption. Homopentamer arranged in a ring-structure; DNA binds between subunits and along the top of the ring. The pentamers self-associate to coat ssDNA in higher-ordered structures; oligomerization facilitates the assembly of extended nucleoprotein complexes. Self-assembly does not however require ssDNA-binding. Interacts with SSB. Induced to high levels following extreme ionizing radiation exposure. Also highly induced in response to desiccation stress. Contains a novel ssDNA-binding fold, which is structurally and topologically distinct from the OB-fold universally found in standard SSB proteins. The disordered C-terminus of DdrB may mediate interactions with other proteins important for DNA damage recovery (By similarity). Tagged N-terminally with 6 His residues. Cells lacking this gene show a normal growth rate, do not exhibit a decrease in the efficiency of natural transformation, but display a reduced capacity to survive ionizing radiation when exposed at doses superior to 2.5 kGy. DNA repair following irradiations is slower. Cannot be complemented by ssb. A double recA-ddrB disruption shows no signs of DNA repair 24 hours after irradiation. Extended N-terminus.