FimC binds the promoter region of agn43 to modulate autoaggregation

Zhihao Wang¹Xiangpeng Niu²Ningyuan Zhong¹Lanfang Kong¹Saqib Nawaz¹Haiyang Zhang¹Wei Jiang¹Yuanyuan Liu³Jian Tu²Xiangan Han^1*

• ¹Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, Shanghai Municipality, China
• ²Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
• ³Qingdao Orisess Biotechnology Co.,Ltd, Qingdao, China

Background: Avian pathogenic Escherichia coli (APEC) infection causes high mortality in chicks and leads to significant economic losses in the poultry industry. During the initial infection, APEC colonizes host cells using type 1 fimbriae and subsequently forms biofilms, resulting in persistent and chronic infections. FimC is a chaperone protein associated with type 1 fimbriae and plays a crucial role in the assembly of fimbriae. However, its regulatory role in agn43-mediated autoaggregation remains unclear.Methods: By constructing fimC gene mutant strains, autoaggregation, motility, biofilm formation, and the adhesion and invasion ability to HD-11 cell were examined. The transcriptome and electrophoretic mobility shift assay (EMSA) were used to screen and verify the regulation of FimC on downstream genes.Results: It demonstrated that lacking fimC but not fimbriae significantly increasing the autoaggregation (P < 0.001), meanwhile promoted the transcription of agn43 (P < 0.01).Transcriptomic analysis showed that deleting fimC caused significant changes in gene transcription levels in a variety of pathways, such as flagellar synthesis, biofilm formation, quorum sensing and c-di-GMP metabolism. Further investigation revealed that FimC directly interacts with the promoter region of agn43 and inhibits the transcription of the agn43. In adiition, both fimC and agn43 have regulatory effects on biofilm, motility, adhesion and invasion.This study demonstrated that FimC acts as an atypical DNA-binding protein to regulate the transcription of agn43. It also highlights the importance of fimC in biofilm formation and adhesion ability of APEC, which provides new insights into the functions of fimbriae chaperone proteins fimC.