152. Genomics and Engineering of a Radioresistant Bacterium 

Kenneth W. Minton, Kira S. Makarova, Michael J. Daly, Eugene V. Koonin, Hassan Brim, L. Aravind, and Ajay Sharma 
Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799 kminton@usuhs.mil 

The eubacterium Deinococcus radiodurans is the most DNA damage-resistant organism discovered to date. It is therefore of intrinsic interest to study its DNA repair mechanisms, and towards this end the full genomic sequence of this organism has recently been obtained by TIGR. We have fully annotated this sequence with special attention to properties that might render this organism radioresistant. Features noted to date include a novel enzyme, combining potential repair domains from three independent repair proteins. This gene is currently being knocked out of the deinococcal genome and properties of the null mutant will be reported. Similarly, desiccation-resistance proteins similar to those seen in plants have also been discovered in the Deinococcus radiodurans genome. This is of particular significance, as there is a known positive correlation between deinococcal desiccation-resistance and radioresistance. The properties of knock out mutants will be reported. 

Finally, an expansion of several protein families, including phosphatases, proteases, acyl transferases, the mutT family of pyrophosphatases, and thioredoxins have been noted. Deinococcus radiodurans' genome is extraordinarily rich in repeated sequences, suggesting a mechanism of repair that will be presented. In addition, it is the first bacterium to be sequenced that has multiple chromosomes (three). Engineering of this versatile organism for organopollutant degradation in radioactive mixed waste environments and engineering of heavy metal resistance in this organism will be described. Finally, current attempts to acquire large amounts and crystallize Deinococcus' extraordinary and highly toxic RecA protein will be described.