TonB-Dependent Receptors Affect the Spontaneous Oxytetracycline Resistance Evolution in Aeromonas hydrophila

It is well known
that most microbial populations develop their
intrinsic antibiotics resistance at low concentrations in antibiotics
environments, but the factors influencing 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 was compared among them using iTRAQ-based quantitative
proteomics. Our following bioinformatic analysis showed that energy
metabolism-related proteins were downregulated, while several iron-related
proteins were upregulated 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 did not affect
the susceptibility to OXY, but showed different evolution rates in
the spontaneous OXY evolution compared with wild-type strain, especially
for AHA_0971 and AHA_4251. Therefore,
this study indicates 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.