The WbIC/WhiB7 Transcription Factor Controls Intrinsic Resistance to Translation-Targeting Antibiotics by Altering Ribosome Composition

Bacteria that encounter antibiotics can efficiently change their physiology to develop resistance. This intrinsic antibiotic resistance is mediated by multiple pathways, including a regulatory system(s) that activates specific genes. In some Streptomyces and Mycobacterium spp., the WbIC/WhiB7 transcription factor is required for intrinsic resistance to translation-targeting antibiotics. Wide conservation of WbIC/WhiB7 within Actinobacteria indicates a critical role of WbIC/WhiB7 in developing resistance to such antibiotics. Here, we identified 312 WbIC target genes in Streptomyces coelicolor, a model antibiotic-producing bacterium, using a combined analysis of RNA sequencing and chromatin immunoprecipitation sequencing. Interestingly, WbIC controls many genes involved in translation, in addition to previously identified antibiotic resistance genes. Moreover, WbIC promotes translation rate during antibiotic stress by altering the ribosome-associated protein composition. Our genome-wide analyses highlight a previously unappreciated antibiotic resistance mechanism that modifies ribosome composition and maintains the translation rate in the presence of sub-MIC levels of antibiotics. IMPORTANCE The emergence of antibiotic-resistant bacteria is one of the top threats in human health. Therefore, we need to understand how bacteria acquire resistance to antibiotics and continue growth even in the presence of antibiotics. Streptomyces coelicolor, an antibiotic-producing soil bacterium, intrinsically develops resistance to translation-targeting antibiotics. Intrinsic resistance is controlled by the WbIC/WhiB7 transcription factor that is highly conserved within Actinobacteria, including Mycobacterium tuberculosis. Here, identification of the WbIC/WhiB7 regulon revealed that WbIC/WhiB7 controls ribosome maintenance genes and promotes translation in the presence of antibiotics by altering the composition of ribosome-associated proteins. Also, the WbIC-mediated ribosomal alteration is indeed required for resistance to translation-targeting antibiotics. This suggests that inactivation of the WbIC/WhiB7 regulon could be a potential target to treat antibiotic-resistant mycobacteria.