Transformation of the archaebacterium Halobacterium volcanii with genomic DNA

<jats:p>We describe optimization of a transformation system for the halophilic archaebacterium Halobacterium volcanii. Transformation of spheroplasts in the presence of polyethylene glycol permits the uptake and expression of high-molecular-weight linear fragments of genomic DNA as well as plasmid or bacteriophage DNA. Transformations can be performed with either fresh or frozen cell preparations. Auxotrophic mutants were transformed to prototrophy with genomic DNA from wild-type cells with efficiencies of 5 x 10(4)/micrograms of DNA and frequencies of 8 x 10(-5) per regenerated spheroplast. The overall efficiency of transformation with genomic DNA implies that genetic recombination is an efficient process in H. volcanii.</jats:p>