An in vitro polypeptide synthesizing system from methanogenic bacteria: Sensitivity to antibiotics

An in vitro polypeptide synthesis system was set up for three methanogenic bacteria, Methanococcus vannielii, Methanobacterium formicicum and Methanosarcina barkeri, and the effect of classical 70S and 80S protein synthesis inhibitors studied. The following results were obtained: (i) The activity of ribosomes from all three methanogens was unaffected by a number of 70S inhibitors such as tetracycline, chloramphenicol, streptomycin, tiamulin and, probably, erythromycin as well; (ii) However, the ribosomes were sensitive to thiostrepton, virginiamycin and, to varying degrees, to those aminoglycosides containing a 2-deoxystreptamine moiety. Among the aminoglycosides examined, streptomycin induced no translational misreading. The compounds containing 2-deoxystreptamine stimulated misreading, albeit only at high concentrations (neomycin being an exception); (iii) Ribosomes from all three organisms were insensitive to the 80S inhibitors cycloheximide and ricin, but those from Methanobacterium formicicum were highly sensitive to anisomycin and moderately sensitive to verrucarin. The results support those of in vivo studies and provide conclusive evidence that archaebacterial ribosomes despite being 70S ribosomes lack binding sites for many classical eubacterial ribosome inhibitors. At the same time they possess sites for others, as well as for some inhibitors of 80S ribosomes.