The coupled transcription-translation system, formerly involving extracts of Streptomyces lividans, has been developed such that it functions with ribosomes (or their subunits) from at least 20 different Streptomyces species. This fractionated system has been used to investigate the antibiotic responses of ribosomes from various Streptomyces which synthesize inhibitors of protein synthesis. Of the 11 organisms included in this study, two strains possessed ribosomes that were specifically resistant to the autogenous antibiotic. These were Streptomyces pactum and Streptomyces karnatakensis, both of which produce pactamycin. Ribosomal subunit exchange analysis further demonstrated that resistance to pactamycin in those strains is due to some property of the 30S ribosomal subunits.