LAUSR

It is well known that most microbial populations develop their intrinsic antibiotics resistance at low concentrations of antibiotics environments, but the influence factors of spontaneous resistance are still largely unknown. In this study, Aeromonas hydrophila strains with different resistance levels to oxytetracycline (OXY) were induced by sublethal antibiotic selection pressure, and differential expression of proteins were compared among them using iTRAQ based quantitative proteomics. Our following bioinformatic analysis showed that energy metabolism related proteins were down-regulated, while several iron related proteins were up-regulated in high OXY-resistant strains. To further investigate the role of spontaneous OXY resistance evolution, four TonB-dependent receptor coded genes were deleted, and their OXY susceptibility capabilities and antibiotic evolutionary assays were performed, respectively. Our results showed that the deletion of these genes no affected the susceptibility to OXY, but showed different evolution rates in the spontaneous oxytetracycline evolution compared with wild-type strain, especially for AHA_0971 and AHA_4251. Therefore, this study indicated the important role of TonB-dependent receptor proteins during the bacterial antibiotics resistance evolution and may provide a new prophylactic strategy against the development of antibiotic resistance. Keywords: Antibiotics resistance evolution; Oxytetracycline; Aeromonas hydrophila; Proteomics.