Abstract
BackgroundAvian pathogenic Escherichia coli (APEC) causes avian colibacillosis, which results in economic and welfare costs in the poultry industry worldwide. The pathogenesis of avian pathogenic E. coli strains is not well defined. Here, the function of an outer membrane protein encoded by the ireA gene of avian pathogenic E. coli strain DE205B was investigated.ResultsThe ireA gene was distributed in 32.9 % (46/140) of tested E. coli strains, with high percentages in the phylogenetic ECOR groups B2 (58.8 %, 10/17) and D (55.9 %, 19/34). The gene expression level of ireA of APEC strain DE205B in high Fe M9 media was 1.8 times higher (P < 0.05) than that in low Fe M9 media. An ireA deletion mutant and complementary strain were constructed. Compared with the wild-type strain DE205B, the expression of most ferric uptake genes in the ireA deletion mutant were significantly upregulated (P < 0.05). The adhesion ability of the ireA deletion mutant to DF-1 cells was significantly decreased. The survival rate of ireA deletion mutant was reduced 21.17 % (P < 0.01), 25.42 (P < 0.05) and 70.0 % (P < 0.01) under alkali, high osmolarity, and low temperature (4 °C) conditions, respectively, compared with the wild-type strain.ConclusionsThe results suggested that the protein encoded by the iron-regulated gene ireA has roles in adhesion and stress resistance in avian pathogenic E. coli.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0800-y) contains supplementary material, which is available to authorized users.
Highlights
Avian pathogenic Escherichia coli (APEC) causes avian colibacillosis, which results in economic and welfare costs in the poultry industry worldwide
Prevalence of the ireA gene among E. coli Strains As shown in Table 1, ireA was present in 32.9 % (46/140) of E. coli strains, with 19.0 % (12/63) in phylogenetic E. coli reference (ECOR) group A, 19.2 % (5/26) in B1, 58.8 % (10/17) in B2 and 55.9 % (19/34) in group D (Additional file 1: Table S1)
Western blotting was performed with anti-His serum, showing expected fusion protein bands for ireA (39 kDa) from strains DE205B
Summary
Avian pathogenic Escherichia coli (APEC) causes avian colibacillosis, which results in economic and welfare costs in the poultry industry worldwide. The pathogenesis of avian pathogenic E. coli strains is not well defined. The function of an outer membrane protein encoded by the ireA gene of avian pathogenic E. coli strain DE205B was investigated. Avian pathogenic Escherichia coli (APEC), a subgroup of extra-intestinal pathogenic E. coli (ExPEC) causes avian colibacillosis and imposes economic losses on the poultry industry worldwide [1]. Many virulence genes have been studied to identify virulence factors in APEC, including those involved in adhesion, iron-regulation, toxin/cytotoxin production and serum resistance [2]. Iron is an essential element involved in important biological processes [3]. Biological activities in cells, such as peroxide reduction, nucleotide biosynthesis and electron transport, are facilitated by iron ions [4]. Extra-intestinal sites have low iron contents; ExPEC strains struggle to take up iron from
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