Characterization of a yjjQ mutant of avian pathogenic Escherichia coli (APEC)

Abstract

Infections with extraintestinal avian pathogenic Escherichia coli (APEC) cause significant economic losses in the poultry industry worldwide. In a previous study we applied signature-tagged transposon mutagenesis and identified 28 virulence-associated genes in APEC strain IMT5155 (O2 : H5 : K1). One of them, yjjQ, encodes a putative transcriptional regulator whose function and role in pathogenesis are still unknown. In the present study, this mutant has been characterized. The yjjQ-defective mutant of IMT5155 (M18E10) was out-competed by the wild-type strain in vivo, and infection of chickens with this yjjQ mutant led to strongly reduced bacterial loads in several organs. Expression studies showed that transcription of yjjQ was significantly upregulated in M9 minimal medium. Correspondingly, the yjjQ mutant showed significantly reduced growth in M9 medium. Although the mutation could not be complemented, a yjjQ deletion mutant showed phenotypes similar to the transposon-generated mutant M18E10, whereas deletion and overexpression of the downstream gene bglJ did not cause a growth defect in M9. To identify virulence genes regulated by YjjQ, one-and two-dimensional protein gel electrophoresis was performed. The proteomic analysis revealed that in the yjjQ mutant M18E10 the expression of several genes involved in iron uptake was downregulated and some other genes were upregulated. The regulation of genes involved in iron uptake was shown to occur at the transcription level using real-time RT-PCR. Taking the results together, this functional analysis strongly suggests that YjjQ is a regulator involved in virulence of APEC by affecting iron uptake.

A Metabolic Operon in Extraintestinal PathogenicEscherichia coliPromotes Fitness under Stressful Conditions and Invasion of Eukaryotic Cells

“…Whereas various virulence factors of ExPEC strains of avian origin were described, these factors, present in various combinations among strains, cannot completely explain the entire pathogenicity mechanism, which is complex and multifactorial (10,11,13,14,19,24,26,36,37,49,53). To improve our knowledge in that domain and identify new virulence factors, a subtractive hybridization between the genomes of the avian ExPEC strain MT512 (02:K1:H7) and of the avirulent avian strain EC79 (O2:K Ϫ :H Ϫ ) was performed in our laboratory.…”

Sequencing and Functional Annotation of Avian Pathogenic Escherichia coli Serogroup O78 Strains Reveal the Evolution of E. coli Lineages Pathogenic for Poultry via Distinct Mechanisms

“…Signature-tagged transposon mutagenesis (STM) assigned roles to 28 genes of an APEC ST95 O2:K1:H5 strain following intratracheal inoculation of chickens and recovery of mutants from the spleen (15), including genes associated with the production of proven APEC virulence factors, such as the capsule (16), lipopolysaccharide (16,17), SitABCD metal transporter (18), and YjjQ regulator (19). Analysis of the same APEC O2: K1:H5 mutant library in a low-dose model of chicken lung colonization identified a novel fimbrial locus, encoding ExPEC adhesin I (yqi), which influences virulence (20,21).…”

Transcriptome Analysis of Avian Pathogenic Escherichia coli O1 in Chicken Serum Reveals Adaptive Responses to Systemic Infection

“…One microgram of total RNA was reverse transcribed in triplicate using random hexamers and Moloney murine leukemia virus (MMLV) reverse transcriptase (Promega). Primer pairs used are listed in Table 1, and real-time PCR was performed as previously described (34). Melting-curve analyses were performed after each reaction to ensure amplification specificity.…”