Abstract
Rhodothermus marinus is a halophilic extreme thermophile, with potential as a model organism for studies of the structural basis of antibiotic resistance. In order to facilitate genetic studies of this organism, we have surveyed the antibiotic sensitivity spectrum of R. marinus and identified spontaneous antibiotic-resistant mutants. R. marinus is naturally insensitive to aminoglycosides, aminocylitols and tuberactinomycins that target the 30S ribosomal subunit, but is sensitive to all 50S ribosomal subunit-targeting antibiotics examined, including macrolides, lincosamides, streptogramin B, chloramphenicol, and thiostrepton. It is also sensitive to kirromycin and fusidic acid, which target protein synthesis factors. It is sensitive to rifampicin (RNA polymerase inhibitor) and to the fluoroquinolones ofloxacin and ciprofloxacin (DNA gyrase inhibitors), but insensitive to nalidixic acid. Drug-resistant mutants were identified using rifampicin, thiostrepton, erythromycin, spiramycin, tylosin, lincomycin, and chloramphenicol. The majority of these were found to have mutations that are similar or identical to those previously found in other species, while several novel mutations were identified. This study provides potential selectable markers for genetic manipulations and demonstrates the feasibility of using R. marinus as a model system for studies of ribosome and RNA polymerase structure, function, and evolution.
Highlights
We established the range of antibiotics inhibitory to
We examined antibiotics targeting the ribosome and associated factors, as well as drugs targeting RNA polymerase or DNA
We identified a number of R. marinus mutants selected for resistance to several macmacrolides, including erythromycin, spiramycin, and tylosin, and sequenced both rplD
Summary
Ribosomes from thermophiles have historically been attractive targets for structural studies due to their greater conformational homogeneity Such investigations can potentially reveal the basis for adaptation to extreme environments, especially when coupled to genetic approaches. While the most thoroughly examined thermophilic organism is the bacterium Thermus thermophilus, studies of other, phylogenetically distant thermophiles could potentially facilitate a comparative approach. This is especially relevant to the extent that species-specific idiosyncrasies, such as differences in DNA repair patterns or codon usage bias, can influence the spectrum of mutants arising. Such idiosyncrasies provide a compelling motivation to explore novel model systems
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