Sizing chromosomes and megaplasmids in haloarchaea.

PFGE was used for the genomic analysis of different species and strains belonging to four out of the six recognized haloarchaeal (halobacterial) genera. All of them were found to carry one chromosome from 1.8-3 Mb, and usually several, but at least one, large plasmids of approximately 90-680 kb, which were detected in supercoiled and linear forms. From the data gathered, chromosomal size appears to be conserved at genus level, whereas plasmid composition and size seems to be subjected to certain variability.