The sensitivity of archaebacteria to antibiotics

Abstract

Most of the species of the two largest groups of archaebacteria - halobacteria (9 strains) and methanogens (10 strains) - were tested by the agar diffusion test for their sensitivity to 28 well-known antibiotics including typical inhibitors of membrane function and the synthesis of cell wall polymers, protein or RNA. Archaebacteria were found to be insensitive to many antibiotics acting against eubacteria and eucaryotes, e.g. those inhibiting the synthesis or cross-linkage of the peptide subunit of murein or the synthesis of RNA. They are, however, sensitive towards inhibitors of the lipid cycle of the biosynthesis of cell wall polymers, to the protein inhibitor chloramphenicol, and to the feed additives lasalocid and monensin, which interfere with the membrane function. It remains to be shown, whether this insensitivity to many of the antibiotics is due to the impermeability of the cytoplasmic membrane or to the inactivation of the antibiotic by the cell rather than to the lack of a particular target for the antibiotic. It is pointed out that the very characteristic sensitivity pattern of archaebacteria may serve as a guideline in the search for further biochemical and molecular differences between archaebacteria, eubacteria, and eucaryotes, and that it may also be helpful in designing selective media for the enrichment and isolation of new types of archaebacteria or in controlling mixed populations of eubacteria, archaebacteria, and eucaryotes, e.g. in the rumen and in biogas plants.