GENOME ANALYSIS OF DIFFERENT HALOFERAX-MEDITERRANEI STRAINS USING PULSED-FIELD GEL-ELECTROPHORESIS

Pulsed-field gel electrophoresis (PFGE) has been used to analyze the different genomic elements of the halophilic archaeon Haloferax mediterranei strains characterized by numerical taxonomy (M2a/b, M4, M6, M10 and M14) and to compare them with those of the type collection microorganism, ATCC 33500 (strain R-4), whose characterization had been previously reported. Both PFGE and DNA/DNA hybridization experiments have shown that M14 does not belong to this species. The rest of the strains contained the same four replicons described for Hf. mediterranei ATCC 33500 (chromosome, pHM500, pHM300 and pHM100) except for M10, which contained an additional replicon of approximately 66 Kb (pHM50). The size and topology of all the elements have been established, their BamHI and PacI restriction patterns characterized, and as a result, a high level of polymorphism observed. Chromosomal physical maps of M2a, M2b, M4, and M10 were constructed using PacI. Comparative genomic analysis allowed us to establish three subgroups for these strains. The potential applicability of PFGE techniques for archaeal taxonomy and the understanding of the evolution of genomic lineages is discussed.