E. Martusewitsch et al., High spontaneous mutation rate in the hyperthermophilic archaeon Sulfolobus solfataricus is mediated by transposable elements, J BACT, 182(9), 2000, pp. 2574-2581
We have isolated uracil-auxotrophic mutants of the hyperthermophilic archae
on Sulfolobus solfataricus in order to explore the genomic stability and mu
tational frequencies of this organism and to identify complementable recipi
ents for a selectable genetic transformation system, Positive selection of
spontaneous mutants resistant to 5-fluoroorotate yielded uracil auxotrophs
with frequencies of between 10(-4) and 10(-5) per sensitive, viable cell. F
our different, nonhomologous insertion sequences (ISs) were identified at d
ifferent positions within the chromosomal pyrEF locus of these mutants. The
y ranged in size from 1,058 to 1,439 bp and possessed properties typical of
known transposable elements, i,e,, terminal inverted repeats, flanking dup
licated target sequences, and putative transposase genes encoding motifs th
at are indicative of the IS4-IS5 IS element families. Between 12 and 25 cop
ies of each IS element were found in chromosomal DNAs by Southern analyses.
While characteristic fingerprint patterns created by IS element-specific p
robes were observed with genomic DNA of different S. solfataricus strains,
no homologous sequences were identified in DNA of other well-characterized
strains of the order Sulfolobales.