title: A TonB-dependent outer membrane receptor of Pseudomonas fluorescens: virulence and vaccine potential.
abstract: Pseudomonas fluorescens is a Gram-negative bacterium and a common aquaculture pathogen. In this study, we identified from a pathogenic P. fluorescens strain a TonB-dependent outer membrane receptor, TdrA, as a secreted protein and examined its function and vaccine potential. TdrA is composed of 746 residues and possesses conserved structural domains of TonB-dependent outer membrane receptors. Quantitative real-time reverse transcriptase-PCR analysis showed that expression of tdrA was upregulated under conditions of iron starvation and during infection of host cells. Consistently, iron depletion induced increased production of TdrA protein in the outer membrane. Compared to the wild type, a tdrA-knock out mutant (1) was unable to grow in the absence of iron, (2) exhibited drastically attenuated overall bacterial virulence, and (3) was impaired in the ability to establish lethal infection in host tissues. Purified recombinant TdrA (rTdrA), when used as a subunit vaccine to immunize flounder, was able to induce strong protective immunity, including production of serum-specific antibodies that resulted in effective protection against lethal-dose P. fluorescens challenge. Together, these results indicate that TdrA is an outer membrane receptor and a protective immunogen that is likely to be involved in iron acquisition and, as a result, required for optimal bacterial virulence.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, People's Republic of China.
authors.forename: Yong-hua
authors.initials: YH
authors.lastname: Hu
authors.forename: Wei
authors.initials: W
authors.lastname: Dang
authors.forename: Li
authors.initials: L
authors.lastname: Sun
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D001428:Bacterial Vaccines / Q000276:immunology*; D005393:Fish Diseases / Q000276:immunology; D005432:Flounder / Q000276:immunology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D055786:Gene Knockout Techniques; D007501:Iron / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011552:Pseudomonas Infections / Q000276:immunology / Q000662:veterinary*; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D008565:Membrane Proteins; C057616:tonB protein, Bacteria; D007501:Iron