orf20 in prophage phiv142-3 contributes to the adhesion and colonization ability of avian pathogenic Escherichia coli strain DE142 by affecting the formation of flagella and I fimbriae.

•KO of orf20 from APEC strain DE142 decreases its adhesion and colonization ability.•Genes related to the exportation of flagellar protein are down regulated in the KO mutant.•Formation of I fimbriae is decreased in the KO mutant.