AutA and AutR, Two Novel Global Transcriptional Regulators, Facilitate Avian Pathogenic Escherichia coli Infection

Abstract

Bacteria can change its lifestyle during inhabiting in host niches where they survive and replicate by rapidly altering gene expression pattern to accommodate the new environment. In this study, two novel regulators in avian pathogenic Escherichia coli (APEC) were identified and designated as AutA and AutR. RT-PCR and β-galactosidase assay results showed that AutA and AutR co-regulated the expression of adhesin UpaB in APEC strain DE205B. Electrophoretic mobility shift assay showed that AutA and AutR could directly bind the upaB promoter DNA. In vitro transcription assay indicated that AutA could activate the upaB transcription, while AutR inhibited the upaB transcription due to directly suppressing the activating effect of AutA on UpaB expression. Transcriptome analysis showed that AutA and AutR coherently affected the expression of hundreds of genes. Our study confirmed that AutA and AutR co-regulated the expression of DE205B K1 capsule and acid resistance systems in E. coli acid fitness island (AFI). Moreover, phenotypic heterogeneity in expression of K1 capsule and acid resistance systems in AFI during host–pathogen interaction was associated with the regulation of AutA and AutR. Collectively speaking, our studies presented that AutA and AutR are involved in APEC adaptive lifestyle change to facilitate its infection.

A Novel PhoP/PhoQ Regulation Pathway Modulates the Survival of Extraintestinal Pathogenic Escherichia coli in Macrophages

“…The highly virulent FY26 (O2:K1; ST95; ECOR B2; isolated from chicken), is a typical model used to study the ExPEC pathogenesis. The hlyF -, Mig-14p -, OmpTp -, and phoP- deficient FY26 mutants, and others deletion mutants were constructed by Red recombinase method previously described ( 15 ). The hlyF : lacZ-zeo fusion transcriptional reporter in FY26Δ lacI-Z was constructed using Red recombinase system according to the previous study by Vigil ( 11 ).…”

“…hlyF : lacZ-zeo fusion reporter was constructed in FY26Δ lacI-Z by Red recombinase system. To construct the complemented plasmids for stable expression of HlyF, Mig-14p, OmpTp, and PhoP, a medium-copy plasmid pSTV28 (pACYC184 origin, TaKaRa) was used as the carrier ( 15 ). The hlyF / Mig-14p operon, OmpTp , and phoP genes (containing the predicted promoters) were amplified and ligated into pSTV28, and the complemented plasmids were electroporated into the corresponding FY26 mutants, respectively.…”

“…The plasmids were transformed into E. coli BL21 (DE3). GST:HlyF, MBP:Mig-14p, OmpTp, and PhoP proteins were purified by a HisTrap high-performance column (GE Healthcare, Shanghai, China) ( 15 ).…”

“…When ExPEC colonizes in urinary tract, respiratory and central nervous systems (the brain and meninges), it must evade the host innate immune defense, including both cellular components (e.g., macrophages) and immune factors (e.g., complement proteins) ( 15 – 18 ). ExPEC replicates in lung epithelial cells and then escapes from phagocytes clearance to enter the bloodstream.…”

Autotransporter Adhesins in Escherichia coli Pathogenesis

“…UpaB encoded by the upaB gene was first identified in the UPEC strain CFT073, and has since been found evenly distributed throughout pathogenic intestinal and extraintestinal E. coli strains along with commensal strains . In addition, to a widespread occurrence in human E. coli strains, upaB has also been found in avian pathogenic E. coli (APEC), where its transcription is under the control of the AutA activator and AutR repressor …”