Cloning and Expression of Pigeon-Derived Escherichia coli Type 1 Pilus Clusters and Analysis of Amino Acid Sequence Characteristics of Functional Proteins.

Abstract

Type 1 pili, as an important virulence factor of E. coli, has certain homology between APEC and UPEC, but the homology degree is not clear enough. This study aims to compare the homology between them. The recombinant bacteria were constructed by homologous recombination. The pili were observed by TEM, and the hemagglutination characteristics were determined by MHSA. The complete gene sequence was determined by sequencing, and the amino acid sequences of the functional proteins of type 1 pili of APEC and UPEC were compared. TEM showed that they could express pili, which were slender, straight, and dense. Stable-pUC-fimBH has MHSA but stable-pUC-fimBG does not. The amino acid sequence similarity of FimB of NJ05 and UPEC was 98.8%, FimE was 99.4%, and the similarity between them was 51.5%. Compared with UPEC's type 1 pili FimC and FimD sequences, the similarity was 99.52% and 87.8%, respectively. The amino acid sequence of FimA of NJ05 was 89-96%, similar to UPEC, and the N-terminal and C-terminal amino acid sequences were exactly the same. The gene sequence and amino acid sequence similarity of FimH between them were both above 99%. The similarity of the pilus binding domain of FimH was 52.8%, but only 27.6% in the receptor binding domain. A few of the same amino acid residues were found in the corresponding regions of FimA, FimF, FimG, and FimH. The type 1 pili of APEC and UPEC come from the same origin, which is helpful to further reveal the pathogenic mechanism of E. coli infection in the poultry respiratory tract.