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ARS Home » Research » Publications at this Location » Publication #62905
Title: THE STRUCTURAL GENE ENCODING HUMAN ENTEROTOXIGENIC ESCHERICHIA COLI PCF020 IS HOMOLOGOUS TO THAT FOR PORCINE 987P

Author
item VIBOUD, GLORIA - GOTEBORG UNIV., SWEDEN
item JONSON, GUNHILD - GOTEBORG UNIV., SWEDEN
item Nystrom, Evelyn
item SVENNERHOLM, ANN-MARI - GOTEBORG UNIV., SWEDEN

Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Diarrhea is a common and costly disease in humans and domestic animals. Bacteria called Escherichia coli that produce toxins cause diarrhea in humans and in domestic animals. In order to cause disease, these bacteria use structures called fimbriae to bind to the surface of the small intestine, and different fimbriae are used by bacteria that cause disease in different species. This report describes identification of the gene that codes for a new type of fimbriae called PCFO20 that were identified on E. coli isolated from a child with diarrhea. The DNA sequence of PCFO20 was similar to the sequence of 987P fimbriae that are associated with E. coli that cause diarrhea in pigs. However, neither PCFO20 nor 987P reacted with DNA probes or specific antibodies for 987P or PCFO20, respectively. Also, PCFO20-positive bacteria did not bind to intestinal cells isolated from baby pigs, as do 987P-positive bacteria. Interestingly, 987P-positive bacteria could make PCFO20 fimbriae when they were given the PCFO20 gene. This showed that PCF020 and 987P share common assembly mechanisms. This information may help identify new ways to prevent diarrhea by E. coli in different species.

Technical Abstract: Putative colonization factor PCFO20 was recently identified in an ETEC strain of serogroup O20 isolated from a child with diarrhea in Argentina. The fotA gene encoding the structural subunit of PCFO20 fimbriae was cloned from ARG-2 strain in the expression phage vector lambda ZAP Express. One positive clone that carried a 3.3-kb fragment was identified on the basis of fimbrillin production using anti-PCFO20 serum. Nucleotide sequencing of a 1.3 kb Sau3 A-ClaI fragment of subclone pGV292 containing the region coding for PCFO20 fimbrillin revealed 2 open reading frames of which only one was complete. Western blot showed that the cloned protein migrated similarly to PCFO20 fimbrial subunit in SDS-PAGE, but no fimbriae were detected on the surface of bacteria containing pGV292 by immunoelectron microscopy or by inhibition ELISA, suggesting that additional genes are needed for assembly of fimbria. fotA encodes a 20,574 Da prefimbrillin protein, which contains a 21-amino acid signal sequence; the mature protein has a size of 18.1 kDa. PCFO20 was more homologous to porcine 987P than to any fimbriae produced by human ETEC. Despite lack of immunological relatedness between PCFO20 and 987P, the 2 proteins have an overall similarity of 82% and 90% homology at the N-terminus. PCFO20 and 987P have apparent affinity for different host cell receptors, as only 987P-producing bacteria bind to neonatal piglet enterocytes. When a 987P-positive strain was transformed with the pGV292 plasmid, fimbriated bacteria were seen by immunoelectron microscopy using anti-PCFO20 serum, suggesting that PCFO20 fimbrillin can be transported and assembled by the 987P biosynthesis machinery. We suggest that PCFO20 and 987P have evolved from a common ancestral gene.