The role of YbdO in regulating acid resistance and biofilm formation in avian pathogenic Escherichia coli

Avian pathogenic Escherichia coli (APEC) causes severe systemic infectious diseases known as colibacillosis in avian species, resulting in significant economic losses to the poultry industry worldwide, and threatening food security and human health. Previous studies showed that acid resistance is an indispensable mechanism that allows E. coli to survive in the gastrointestinal tract. Biofilm formation results in persistent and recurrent infections in the host, and is the main reason why treatment of colibacillosis with antimicrobial agents is difficult. In this study, we confirmed YbdO as a transcriptional regulator that increases biofilm formation by upregulating the transcription of the biofilm-associated genes bcsE, csgD, pgaA, wcaD, fimH, and flhD and acid resistance by activating the expression of acid stress chaperone HdeA and acid stress response protein YqgB in APEC CE1. Additionally, electrophoretic mobility shift assay (EMSA) indicated that YbdO directly activated the expression of CsgD, HdeA and YqgB by directly binding to the promoters of csgD, hdeA and yqgB, respectively. These findings demonstrate the regulatory mechanism of YbdO on acid resistance and biofilm formation and enhance our understanding of how APEC improves its adaptability to environmental stresses, thereby increasing the pathogenicity of APEC. Therefore, this study might provide a paradigm for the regulation of biofilm formation and acid resistance that can be used to study other bacterial pathogens. YbdO increases biofilm formation and acid resistance.YbdO upregulates the transcription levels of the biofilm-associated genes bcsE, csgD, pgaA, wcaD, fimH, and flhD.YbdO activates the expression of acid stress-associated genes hdeA and yqgB.YbdO contributes to improving the adaptability of APEC to environmental stresses. YbdO increases biofilm formation and acid resistance. YbdO upregulates the transcription levels of the biofilm-associated genes bcsE, csgD, pgaA, wcaD, fimH, and flhD. YbdO activates the expression of acid stress-associated genes hdeA and yqgB. YbdO contributes to improving the adaptability of APEC to environmental stresses.