title: All Three TonB Systems Are Required for Vibrio vulnificus CMCP6 Tissue Invasiveness by Controlling Flagellum Expression.
abstract: TonB systems actively transport iron-bound substrates across the outer membranes of Gram-negative bacteria. Vibrio vulnificus CMCP6, which causes fatal septicemia and necrotizing wound infections, possesses three active TonB systems. It is not known why V. vulnificus CMCP6 has maintained three TonB systems throughout its evolution. The TonB1 and TonB2 systems are relatively well characterized, while the pathophysiological function of the TonB3 system is still elusive. A reverse transcription-PCR (RT-PCR) study showed that the tonB1 and tonB2 genes are preferentially induced in vivo, whereas tonB3 is persistently transcribed, albeit at low expression levels, under both in vitro and in vivo conditions. The goal of the present study was to elucidate the raison d'être of these three TonB systems. In contrast to previous studies, we constructed in-frame single-, double-, and triple-deletion mutants of the entire structural genes in TonB loci, and the changes in various virulence-related phenotypes were evaluated. Surprisingly, only the tonB123 mutant exhibited a significant delay in killing eukaryotic cells, which was complemented in trans with any TonB operon. Very interestingly, we discovered that flagellum biogenesis was defective in the tonB123 mutant. The loss of flagellation contributed to severe defects in motility and adhesion of the mutant. Because of the difficulty of making contact with host cells, the mutant manifested defective RtxA1 toxin production, which resulted in impaired invasiveness, delayed cytotoxicity, and decreased lethality for mice. Taken together, these results indicate that a series of virulence defects in all three TonB systems of V. vulnificus CMCP6 coordinately complement each other for iron assimilation and full virulence expression by ensuring flagellar biogenesis.
authors.affiliation: Clinical Vaccine R&D Center, Chonnam National University, Gwangju, Republic of Korea Department of Molecular Medicine, Graduate School, Chonnam National University, Gwangju, Republic of Korea.
authors.forename: Tra-My
authors.initials: TM
authors.lastname: Duong-Nu
authors.affiliation: Clinical Vaccine R&D Center, Chonnam National University, Gwangju, Republic of Korea Department of Microbiology, Chonnam National University Medical School, Gwangju, Republic of Korea.
authors.forename: Kwangjoon
authors.initials: K
authors.lastname: Jeong
authors.affiliation: Clinical Vaccine R&D Center, Chonnam National University, Gwangju, Republic of Korea Department of Pharmacology and Dental Therapeutics, School of Dentistry, Chonnam National University, Gwangju, Republic of Korea.
authors.forename: Seol Hee
authors.initials: SH
authors.lastname: Hong
authors.affiliation: Department of Nuclear Medicine, Chonnam National University Medical School, Gwangju, Republic of Korea.
authors.forename: Hong-Vu
authors.initials: HV
authors.lastname: Nguyen
authors.affiliation: Clinical Vaccine R&D Center, Chonnam National University, Gwangju, Republic of Korea.
authors.forename: Van-Hoan
authors.initials: VH
authors.lastname: Ngo
authors.affiliation: Department of Nuclear Medicine, Chonnam National University Medical School, Gwangju, Republic of Korea.
authors.forename: Jung-Joon
authors.initials: JJ
authors.lastname: Min
authors.affiliation: Clinical Vaccine R&D Center, Chonnam National University, Gwangju, Republic of Korea Department of Pharmacology and Dental Therapeutics, School of Dentistry, Chonnam National University, Gwangju, Republic of Korea selee@chonnam.ac.kr jhrhee@chonnam.ac.kr.
authors.forename: Shee Eun
authors.initials: SE
authors.lastname: Lee
authors.affiliation: Clinical Vaccine R&D Center, Chonnam National University, Gwangju, Republic of Korea Department of Microbiology, Chonnam National University Medical School, Gwangju, Republic of Korea selee@chonnam.ac.kr jhrhee@chonnam.ac.kr.
authors.forename: Joon Haeng
authors.initials: JH
authors.lastname: Rhee
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D001427:Bacterial Toxins / Q000096:biosynthesis; D001692:Biological Transport / Q000235:genetics; D045744:Cell Line, Tumor; D005260:Female; D005407:Flagella / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D007501:Iron / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D010529:Peritoneal Cavity / Q000382:microbiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014735:Vibrio Infections / Q000382:microbiology; D041261:Vibrio vulnificus / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D008565:Membrane Proteins; C057616:tonB protein, Bacteria; D007501:Iron