Date of this Version
Journal of Bacteriology, Jan. 2001, p. 287–291 Vol. 183, No. 1
Few antibiotics targeting members of the archaeal domain are currently available for genetic studies. Since
bacterial antibiotics are frequently directed against competing and related organisms, archaea by analogy
might produce effective antiarchaeal antibiotics. Peptide antibiotic (halocin) preparations from euryarchaeal
halophilic strains S8a, GN101, and TuA4 were found to be toxic for members of the hyperthermophilic
crenarchaeal genus Sulfolobus. No toxicity was evident against representative bacteria or eukarya. Halocin S8
(strain S8a) and halocin R1 (strain GN101) preparations were cytostatic, while halocin A4 (strain TuA4)
preparations were cytocidal. Subsequent studies focused on the use of halocin A4 preparations and Sulfolobus
solfataricus. Strain TuA4 cell lysates were not toxic for S. solfataricus, and protease (but not nuclease) treatment
of the halocin A4 preparation inactivated toxicity, indicating that the A4 toxic factor must be a secreted protein.
Potassium chloride supplementation of the Sulfolobus assay medium potentiated toxicity, implicating use of a
salt-dependent mechanism. The utility of halocin A4 preparations for genetic manipulation of S. solfataricus
was assessed through the isolation of UV-induced resistant mutants. The mutants exhibited stable phenotypes
and were placed into distinct classes based on their levels of resistance.