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Identification of two novel in vivo-upregulated Francisella tularensis proteins involved in metal acquisition and virulence

Wu, Xiaojun
http://rave.ohiolink.edu/etdc/view?acc_num=mco1465662632

Abstract Details

2016, Doctor of Philosophy (PhD), University of Toledo, Biomedical Sciences (Infection, Immunity, and Transplantation).
Francisella tularensis is the causative agent of the lethal disease tularemia. Despite decades of research, little is understood about why F. tularensis is so virulent. Bacterial outer membrane proteins (OMPs) are involved in various virulence processes, including protein secretion, host cell attachment, and intracellular survival. Many pathogenic bacteria require metals for intracellular survival and OMPs often play important roles in metal binding and uptake. Previous studies identified three F. tularensis OMPs that play roles in iron acquisition. We have identified two new proteins, FTT0267 (named fmvA, for Francisella metal and virulence) and FTT0602c (fmvB), which are homologs of those iron acquisition genes and demonstrated that both are upregulated during mouse infections. Based on sequence homology and in vivo upregulation, we hypothesized that FmvA and FmvB are OMPs involved in metal acquisition and virulence. Despite sequence similarity to previously-characterized iron-acquisition genes, FmvA and FmvB do not appear to be involved iron uptake, as neither fmvA nor fmvB were upregulated in iron-limiting media and neither fmvA nor fmvB mutants exhibited growth defects in iron limitation. However, among other metals examined in this study, magnesium limitation significantly induced fmvB expression, fmvB mutant was found to express significantly higher levels of lipopolysaccharide (LPS) in magnesium-limiting medium, and increased numbers of surface protrusions were observed on fmvB mutant in magnesium-limiting medium, compared to wild-type F. tularensis grown in magnesium-limiting medium. RNA sequencing analysis of fmvB mutant revealed the potential mechanism for increased LPS expression, as LPS synthesis genes kdtA and wbtA were significantly upregulated in fmvB mutant, compared with wild-type F. tularensis. To provide further evidence for the potential role of FmvB in magnesium uptake, we demonstrated that FmvB was outer membrane-localized. Finally, both fmvA and fmvB mutants were found to be significantly attenuated in mice and cytokine analyses revealed that fmvB mutant-infected mice produced lower levels of pro-inflammatory cytokines, including GM-CSF, IL-3, and IL-10, compared with mice infected with wild-type F. tularensis. Taken together, these studies have characterized two previously-unstudied F. tularensis proteins, have shown that both play roles in F. tularensis virulence, and provide new insights into the importance of magnesium for intracellular pathogens.
Jason Huntley (Committee Chair)
Robert Blumenthal (Committee Member)
William Maltese (Committee Member)
Kevin Pan (Committee Member)
R.Mark Wooten (Committee Member)
172 p.
Biology; Biomedical Research; Health Sciences; Immunology; Microbiology
Francisella tularensis; outer membrane proteins; virulence; metal acquisition; hypothetical proteins

Recommended Citations

Citations

  • Wu, X. (2016). Identification of two novel in vivo-upregulated Francisella tularensis proteins involved in metal acquisition and virulence [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=mco1465662632

    APA Style (7th edition)

  • Wu, Xiaojun. Identification of two novel in vivo-upregulated Francisella tularensis proteins involved in metal acquisition and virulence. 2016. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=mco1465662632.

    MLA Style (8th edition)

  • Wu, Xiaojun. "Identification of two novel in vivo-upregulated Francisella tularensis proteins involved in metal acquisition and virulence." Doctoral dissertation, University of Toledo, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=mco1465662632

    Chicago Manual of Style (17th edition)

mco1465662632
479
© 2016, all rights reserved.
This open access ETD is published by University of Toledo Health Science Campus and OhioLINK.