ArcA Controls Metabolism, Chemotaxis, and Motility Contributing to the Pathogenicity of Avian Pathogenic Escherichia coli

Abstract

f Avian pathogenic Escherichia coli (APEC) strains cause one of the three most significant infectious diseases in the poultry industry and are also potential food-borne pathogens threating human health. In this study, we showed that ArcA (aerobic respiratory control), a global regulator important for E. coli's adaptation from anaerobic to aerobic conditions and control of that bacterium's enzymatic defenses against reactive oxygen species (ROS), is involved in the virulence of APEC. Deletion of arcA significantly attenuates the virulence of APEC in the duck model. Transcriptome sequencing (RNA-Seq) analyses comparing the APEC wild type and the arcA mutant indicate that ArcA regulates the expression of 129 genes, including genes involved in citrate transport and metabolism, flagellum synthesis, and chemotaxis. Further investigations revealed that citCEFXG contributed to APEC's microaerobic growth at the lag and log phases when cultured in duck serum and that ArcA played a dual role in the control of citrate metabolism and transportation. In addition, deletion of flagellar genes motA and motB and chemotaxis gene cheA significantly attenuated the virulence of APEC, and ArcA was shown to directly regulate the expression of motA, motB, and cheA. The combined results indicate that ArcA controls metabolism, chemotaxis, and motility contributing to the pathogenicity of APEC. Commensal and pathogenic Escherichia coli strains can grow under both aerobic and anaerobic conditions. The enzymes required for catabolism under aerobic versus anaerobic conditions are substantially different, and E. coli has the ability to switch among anaerobic, anaerobic respiratory, and fermentative pathways (1). The expression of genes involved in cellular functions such as nutrient uptake and/or excretion systems, biosynthetic pathways, and macromolecular synthesis are also adjusted in response to oxygen availability (2). The Arc two-component signal transduction system, comprised of the kinase sensor ArcB and its cognate response regulator ArcA, is one of the mechanisms that enable E. coli adaptation to changing oxygen availability (3). Once an environmental signal is received, ArcB undergoes autophosphorylation and catalyzes the transphosphorylation of ArcA, which then promotes or represses expression of Arc-regulated genes. Rather than directly detecting environmental O 2 , ArcB probably senses the redox state of the cell through detection of a reduced electron transport component (4). Under aerobic conditions (5), oxidized forms of quinone electron carriers in the membrane inhibit the autophosphorylation of ArcB, while under anaerobic and microaerobic conditions, ArcB undergoes autophosphorylation. The net activity of ArcB as a kinase for ArcA is expected to progressively increase during the transition from aerobic to anaerobic growth.The ArcA regulon of E. coli K-12 strains has been extensively studied under both aerobic and anaerobic conditions (6, 7). A previous study indicated that about 1,139 genes in the E. coli K-12 genome are regu...

Extraintestinal pathogenic Escherichia coli increase extracytoplasmic polysaccharide biosynthesis for serum resistance in response to bloodstream signals

“…The role of these genes in ExPEC virulence was also determined using a duck infection (septicemia) model (Ma et al ., ; Jiang et al ., ). With an inoculation dose of 2 × 10 5 CFU per duck, groups infected with fur , fnr , rcsDB , kpsFEDU and wcaABCDE deletion mutants exhibited significantly lower mortality and longer survival time as compared to the wild‐type group (Fig.…”

“…The RNA sequencing data were mapped to the genome sequences of APEC O1 (Accession: CP000468) or ExPEC XM (Accession: CP025328), using Bowtie (Langmead et al, 2009). The comparative transcriptomics analyses to estimate the fold change between the LB and serum growth under low oxygen conditions were performed as previously described (Jiang et al, 2015). Using the P values for each comparison, the approach of Nettleton et al (Curl et al, 2015) was used to convert the P values to q values.…”

“…ExPEC confront challenging environment conditions upon initiating extraintestinal infections, including low oxygen tension and low free iron (Jones et al, 2011;Huja et al, 2014;Jiang et al, 2015) in the bloodstream; in addition, they must overcome various host defenses. These defenses include the effects of phagocytes, the complement system (Taylor et al, 1983), lysozymes (Callewaert and Michiels, 2010) and antimicrobial peptides (Jacobson et al, 1992).…”

Proteomic Delineation of the ArcA Regulon in Salmonella Typhimurium During Anaerobiosis

“…Bacteria were routinely grown on LB plates with 1.5% agar and 30 g/mL streptomycin at 37°C. A single colony was inoculated into 3 mL of MOPS (morpholinepropanesulfonic acid)-buffered (100 mM, pH 7.4) LB broth supplemented with 20 mM D-xylose (LB-MOPS-X, to avoid potential indirect effects of pH and catabolite repression [14]) [10,15] and grown overnight at 37°C with shaking. The overnight culture was then diluted 1:20 into 5 mL of LB-MOPS-X broth in a centrifugal tube (5 mL).…”

“…The regulatory role of the Arc TCS has been extensively studied in E. coli by using various techniques, especially high-throughput transcriptomic profiling [5][6][7][9][10][11][12][13]. In S. Typhimurium, however, few studies have been carried out to define its ArcA regulon.…”