title: Tetracycline tolerance mediated by gene amplification in Bacillus subtilis.
abstract: Bacillus subtilis can acquire a higher tolerance to tetracycline by increasing the gene dosage of its resistance gene tetB. In this study, we estimated the multiplication effect of tetB on tetracycline tolerance. Cells harbouring multiple copies of tetB were found to comprise approximately 30 % of the total tetracycline-resistant cell population when selected on medium containing 10 µg tetracycline ml(-1). Disruption of recA resulted in a significant decrease in the frequency of tetB amplification. Although four direct repeats exist around tetB, the majority of tetB amplicons were found to be flanked by non-homologous sequences, indicating that the initial duplication of tetB can occur largely through RecA-independent recombination. The correlation between the tetB copy number and the MIC values for tetracycline indicated that more than three copies of tetB were required for tolerance to 10 µg tetracycline ml(-1). Thus, the RecA-dependent expansion step appears to be necessary for developing significant tetracycline tolerance mediated by tetB amplification.
authors.affiliation: Nanotechnology and Biotechnology Unit, Kasetsart Agricultural and Agro-Industrial Production Improvement Institute (KAPI), Kasetsart University, Bangkok, Thailand.|Microbial Function Laboratory, National Food Research Institute, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan.
authors.forename: Wannasiri
authors.initials: W
authors.lastname: Wannarat
authors.affiliation: Microbial Function Laboratory, National Food Research Institute, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan.
authors.forename: Shiori
authors.initials: S
authors.lastname: Motoyama
authors.affiliation: Rikkyo University, Department of Life Science, College of Science, Toshima-ku, Tokyo, Japan.
authors.forename: Kenta
authors.initials: K
authors.lastname: Masuda
authors.affiliation: Rikkyo University, Department of Life Science, College of Science, Toshima-ku, Tokyo, Japan.
authors.forename: Fujio
authors.initials: F
authors.lastname: Kawamura
authors.affiliation: Microbial Function Laboratory, National Food Research Institute, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Inaoka
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D005784:Gene Amplification / Q000187:drug effects*; D018628:Gene Dosage / Q000187:drug effects; D013752:Tetracycline / Q000494:pharmacology*; D013753:Tetracycline Resistance
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D013752:Tetracycline