A (p)ppGpp-null mutant of Haemophilus ducreyi is partially attenuated in humans due to multiple conflicting phenotypes

Concerta Holley, Dharanesh Gangaiah, Wei Li, Kate R. Fortney, Diane Janowicz, Sheila Ellinger, Beth Zwickl, Barry Katz, Stanley Spinola

Research output: Contribution to journalArticle

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Abstract

(p)ppGpp responds to nutrient limitation through a global change in gene regulation patterns to increase survival. The stringent response has been implicated in the virulence of several pathogenic bacterial species. Haemophilus ducreyi, the causative agent of chancroid, has homologs of both relA and spoT, which primarily synthesize and hydrolyze (p)ppGpp in Escherichia coli. We constructed relA and relA spoT deletion mutants to assess the contribution of (p)ppGpp to H. ducreyi pathogenesis. Both the relA single mutant and the relA spoT double mutant failed to synthesize (p)ppGpp, suggesting that relA is the primary synthetase of (p)ppGpp in H. ducreyi. Compared to the parent strain, the double mutant was partially attenuated for pustule formation in human volunteers. The double mutant had several phenotypes that favored attenuation, including increased sensitivity to oxidative stress. The increased sensitivity to oxidative stress could be complemented in trans. However, the double mutant also exhibited phenotypes that favored virulence. When grown to the mid-log phase, the double mutant was significantly more resistant than its parent to being taken up by human macrophages and exhibited increased transcription of lspB, which is involved in resistance to phagocytosis. Additionally, compared to the parent, the double mutant also exhibited prolonged survival in the stationary phase. In E. coli, overexpression of DksA compensates for the loss of (p)ppGpp; the H. ducreyi double mutant expressed higher transcript levels of dksA than the parent strain. These data suggest that the partial attenuation of the double mutant is likely the net result of multiple conflicting phenotypes.

Original languageEnglish
Pages (from-to)3492-3502
Number of pages11
JournalInfection and Immunity
Volume82
Issue number8
DOIs
StatePublished - 2014

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Haemophilus ducreyi
Phenotype
Virulence
Oxidative Stress
Chancroid
Escherichia coli
Survival
Phagocytosis
Volunteers
Macrophages
Food
Genes

ASJC Scopus subject areas

  • Immunology
  • Microbiology
  • Parasitology
  • Infectious Diseases

Cite this

A (p)ppGpp-null mutant of Haemophilus ducreyi is partially attenuated in humans due to multiple conflicting phenotypes. / Holley, Concerta; Gangaiah, Dharanesh; Li, Wei; Fortney, Kate R.; Janowicz, Diane; Ellinger, Sheila; Zwickl, Beth; Katz, Barry; Spinola, Stanley.

In: Infection and Immunity, Vol. 82, No. 8, 2014, p. 3492-3502.

Research output: Contribution to journalArticle

Holley, Concerta ; Gangaiah, Dharanesh ; Li, Wei ; Fortney, Kate R. ; Janowicz, Diane ; Ellinger, Sheila ; Zwickl, Beth ; Katz, Barry ; Spinola, Stanley. / A (p)ppGpp-null mutant of Haemophilus ducreyi is partially attenuated in humans due to multiple conflicting phenotypes. In: Infection and Immunity. 2014 ; Vol. 82, No. 8. pp. 3492-3502.
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AU - Li, Wei

AU - Fortney, Kate R.

AU - Janowicz, Diane

AU - Ellinger, Sheila

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AU - Katz, Barry

AU - Spinola, Stanley

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