acteria \[[@B29],[@B30]\]. These structures are tightly packed, almost crystalline, and it is difficult to envision how an actively metabolizing cell could function under this circumstance; the DNA needs to remain accessible to proteins that catalyze essential housekeeping functions.

We also predict that the ionic composition of the cytosol of the deinococci examined favors the formation of the structures we observe. The *Deinococcaceae*exhibit unusually high intracellular levels of Mn^+2^\[[@B18]\] and it is possible that accumulating this metal creates an environment that facilitates DNA condensation within this species in vivo through direct or indirect mechanisms. In vitro, the condensation of DNA can be achieved by adding a condensing agent, such as a multivalent cation, to an aqueous solution of DNA. The strong electrostatic interaction of the DNA and these cations neutralizes the repulsion of phosphate groups in the DNA backbone, and it has been shown that approximately 90% of the DNA charge must be neutralized for condensation to occur \[[@B31]\]. Intracellular Mn^+2^may also indirectly facilitate nucleoid condensation by, for example, augmenting the function of deinococcal DNA-binding proteins. On the other hand, high Mn^+2^content may have no affect on nucleoid morphology since, as described above, *E. coli*can have a condensed nucleoid even though this species has a much lower level of intracellular Mn^+2^\[[@B18]\].

Years of experimental evidence irrefutably argue that DNA repair is essential for *D. radiodurans*recovery from high dose exposure to ionizing radiation, but this fact does not necessarily lead to the conclusion that efficient DNA repair is sufficient for extreme radioresistance. Although there has been a great deal of speculation concerning subtle differences in the properties of DNA repair proteins isolated from *D. radiodurans*, there has yet to be a convincing demonstration that this species\' DNA repair proteins are \"better\" relative to homologues found in more radiosensitive spec