XRE-Type Regulator BioX Acts as a Negative Transcriptional Factor of Biotin Metabolism in Riemerella anatipestifer

Abstract

Biotin is essential for the growth and pathogenicity of microorganisms. Damage to biotin biosynthesis results in impaired bacterial growth and decreased virulence in vivo. However, the mechanisms of biotin biosynthesis in Riemerella anatipestifer remain unclear. In this study, two R. anatipestifer genes associated with biotin biosynthesis were identified. AS87_RS05840 encoded a BirA protein lacking the N-terminal winged helix-turn-helix DNA binding domain, identifying it as a Group I biotin protein ligase, and AS87_RS09325 encoded a BioX protein, which was in the helix-turn-helix xenobiotic response element family of transcription factors. Electrophoretic mobility shift assays demonstrated that BioX bound to the promoter region of bioF. In addition, the R. anatipestifer genes bioF (7-keto-8-aminopelargonic acid synthase), bioD (dethiobiotin synthase), and bioA (7,8-diaminopelargonic acid synthase) were in an operon and were regulated by BioX. Quantitative reverse-transcription PCR showed that transcription of the bioFDA operon increased in the mutant Yb2ΔbioX in the presence of excessive biotin, compared with that in the wild-type strain Yb2, suggesting that BioX acted as a repressor of biotin biosynthesis. Streptavidin blot analysis showed that BirA caused biotinylation of BioX, indicating that biotinylated BioX was involved in metabolic pathways. Moreover, as determined by the median lethal dose, the virulence of Yb2ΔbioX was attenuated a 500-fold compared with that of Yb2. To summarize, the genes bioA and bioX were identified in R. anatipestifer, and BioX was found to act as a repressor of the bioFDA operon involved in the biotin biosynthesis pathway and identified as a bacterial virulence factor. IMPORTANCE Riemerella anatipestifer is a causative agent of diseases in ducks, geese, turkeys, and various other domestic and wild birds. Our study reveals that biotin synthesis of R. anatipestifer is regulated by the BioX through binding to the promoter region of bioF gene to inhibit transcription of bioFDA operon. Moreover, bioX is required for R. anatipestifer pathogenicity, suggesting BioX is a potential target for treatment of the pathogen. R. anatipestifer BioX is thus identified as a novel negative regulator involved in biotin metabolism and associated with bacterial virulence in this study.

Epidemiological investigation and drug resistance characteristics of Riemerella anatipestifer strains from large-scale duck farms in Shandong Province, China from March 2020 to March 2022

“…Riemerella anatipestifer ( R. anatipestifer ) is a common pathogen of waterfowl, mainly infecting ducks and geese, but also turkeys and wild birds ( Hu et al, 2012 ). Poor sanitation and nutrition, sudden changes in environment or climate usually make poultry susceptible to R. anatipestifer infection, there has a high morbidity and mortality in ducks between 2 and 8 wk of age ( Ren et al, 2021 ). Septicemia and infectious serositis are common in sick animals, showing drooping head and neck, loss of appetite, respiratory distress, diarrhea, lethargy, and neurological symptoms ( Kardos et al, 2007 ).…”

Transcriptional activation of ompA in Neisseria gonorrhoeae mediated by the XRE family member protein NceR

“…XRE transcriptional regulators are a large family of proteins possessing HTH DNA-binding motifs ( 23 ) and are the second most commonly occurring regulator family in bacteria ( 31 ). Members of this family regulate genes involved in virulence, stress response, and metabolism, often galvanized by environmental cues ( 17 , 18 , 32 - 35 ). A previously studied XRE family member in Ng, the NHTF ( Neisseria hypothetical transcription factor) protein, represses the expression of its downstream genes including a conserved nitrogen-response protein ( 32 ).…”

Identification of Critical Immune Regulators and Potential Interactions of IL-26 in Riemerella anatipestifer-Infected Ducks by Transcriptome Analysis and Profiling

“…It mainly infects ducklings and contributes to strain-dependent mortality and morbidity rates of up to 90% and 100%, respectively, in infected ducks or stunted growth in convalescent birds [4][5][6]. RA infection can be acute or chronic, with acute infection being more common in ducks younger than 8 weeks of age [7]. Infection is often referred to as new duck disease, riemerellosis, infectious serositis, or duck septicemia, and clinical characteristics include diarrhea, lethargy, ocular and nasal discharge, respiratory symptoms (i.e., dyspnea, mild coughing and sneezing), and nervous symptoms (i.e., tremors of the head and neck or head and legs and ataxia) in addition to pathologic lesions such as fibrinous pericarditis, perihepatitis, airsacculitis, and meningitis [7][8][9][10].…”