RfaL is required for Yersinia pestis type III secretion and virulence

Andrew S. Houppert, Lesley Bohman, Peter M. Merritt, Christopher B. Cole, Adam J. Caulfield, Wyndham W. Lathem, Melanie M. Marketon*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Yersinia pestis, the causative agent of plague, uses a type III secretion system (T3SS) to inject cytotoxic Yop proteins directly into the cytosol of mammalian host cells. The T3SS can also be activated in vitro at 37°C in the absence of calcium. The chromosomal gene rfaL (waaL) was recently identified as a virulence factor required for proper function of the T3SS. RfaL functions as a ligase that adds the terminal N-acetylglucosamine to the lipooligosaccharide core of Y. pestis. We previously showed that deletion of rfaL prevents secretion of Yops in vitro. Here we show that the divalent cations calcium, strontium, and magnesium can partially or fully rescue Yop secretion in vitro, indicating that the secretion phenotype of the rfaL mutant may be due to structural changes in the outer membrane and the corresponding feedback inhibition on the T3SS. In support of this, we found that the defect can be overcome by deleting the regulatory gene lcrQ. Consistent with a defective T3SS, the rfaL mutant is less virulent than the wild type. We show here that the virulence defect of the mutant correlates with a decrease in both T3SS gene expression and ability to inject innate immune cells, combined with an increased sensitivity to cationic antimicrobial peptides.

Original languageEnglish (US)
Pages (from-to)1186-1197
Number of pages12
JournalInfection and immunity
Issue number4
StatePublished - Apr 2013

ASJC Scopus subject areas

  • Infectious Diseases
  • Parasitology
  • Microbiology
  • Immunology


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