Conservation of chromosomal arrangement among three strains of the genetically unstable archaeon Halobacterium salinarium.
Phenotypic variants of Halobacterium salinarium NRC-1 arise at a frequency of 10(-2). These result from transpositions of halobacterial insertion sequences and rearrangements mediated by halobacterial insertion sequences. We have tested the hypothesis that such mutations are confined to only a portion of the genome by comparing the chromosomal restriction map of H. salinarium NRC-1 and that of the derivative S9, which was made in 1969. The two chromosomes were mapped by using two-dimensional pulsed-field gel electrophoresis and the restriction enzymes AflII, AseI, and DraI. A comparison of the two deduced maps showed a domain of about 210 kbp to be subject to many rearrangements, including an inversion in S9 relative to NRC-1. However, the rest of the chromosome was conserved among NRC-1, S9, and an independent Halobacterium isolate, GRB, previously mapped by St. Jean et al. (A. St. Jean, B. A. Trieselmann, and R. L. Charlebois, Nucleic Acids Res. 22:1476-1483, 1994). This concurs with data from eubacteria suggesting strong selective forces maintaining gene order even in the face of rearrangement events occurring at a high frequency.
Hackett
N R
NR
Department of Microbiology, Cornell University Medical College, New York, New York 10021.
Bobovnikova
Y
Y
Heyrovska
N
N
D015139:Blotting, Southern; D002876:Chromosomes, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D015321:Gene Rearrangement; D014644:Genetic Variation; D016680:Genome, Bacterial; D006217:Halobacterium / Q000145:classification / Q000235:genetics*; D016254:Mutagenesis, Insertional; D015183:Restriction Mapping