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Plasmid-determined cytotoxicity in Yersinia pestis and Yersinia pseudotuberculosis
Abstract:
Yersinia pestis KIM5 was found to be cytotoxic for the IC21 and P388D1 mouse macrophage cell lines, as well as for resident peritoneal macrophages from C57BL/6 mice. Affected cells phagocytosed KIM5 inefficiently, became spherical, detached readily from culture dishes, and retained 51Cr poorly. The cytotoxic effect was dependent on the presence of the 75-kilobase plasmid pCD1. Because this plasmid also encodes the low calcium response (LCR), three Mu d1 insertion mutants previously shown to be LCR- and of reduced virulence in mice were examined for cytotoxicity; all were found to be atoxic. The insertions in these mutants lie within three distinct LCR loci (lcrB, C, and D). Like LCR, cytotoxicity was expressed only at 37 degrees C. Unlike LCR, it was not influenced by Ca2+ concentration, indicating that the V and W antigens are probably not involved. Yersinia pseudotuberculosis was found to have a similar plasmid-dependent cytotoxicity. Thus, biological activity observed as cytotoxicity in vitro may well be a common feature contributing to virulence of the yersiniae.
Insights
Yersinia pestis KIM5 exhibits cytotoxicity against mouse macrophages, a trait dependent on the pCD1 plasmid. This plasmid-mediated cytotoxicity is linked to the low calcium response (LCR) and contributes to bacterial virulence.
Area of Science:
- Microbiology
- Cell Biology
- Pathogen Virulence
Background:
- Yersinia pestis is a significant human pathogen responsible for plague.
- Understanding the mechanisms of Yersinia virulence is crucial for developing effective treatments.
- Macrophage dysfunction is a key aspect of Yersinia pathogenesis.
Purpose of the Study:
- To investigate the cytotoxic effects of Yersinia pestis KIM5 on mouse macrophage cell lines.
- To determine the role of the pCD1 plasmid and its associated low calcium response (LCR) in Yersinia-induced cytotoxicity.
- To explore the contribution of in vitro cytotoxicity to the overall virulence of Yersinia species.
Main Methods:
- Exposure of macrophage cell lines (IC21, P388D1) and primary macrophages (C57BL/6) to Yersinia pestis KIM5.
- Assessment of cell viability, morphology, adherence, and phagocytosis.
- Analysis of cytotoxicity in Yersinia pestis mutants with insertions in LCR loci (lcrB, lcrC, lcrD).
- Comparison of cytotoxicity under varying temperature and calcium concentrations.
- Examination of Yersinia pseudotuberculosis for similar cytotoxic properties.
Main Results:
- Yersinia pestis KIM5 demonstrated significant cytotoxicity towards mouse macrophages, leading to cell rounding, detachment, and impaired phagocytosis.
- The cytotoxic effect was strictly dependent on the presence of the 75-kilobase pCD1 plasmid.
- Yersinia pestis mutants lacking functional LCR loci (lcrB, lcrC, lcrD) were found to be non-cytotoxic.
- Cytotoxicity was expressed at 37°C but not influenced by calcium concentration, suggesting V and W antigens are not involved.
- Yersinia pseudotuberculosis also exhibited similar plasmid-dependent cytotoxicity.
Conclusions:
- The pCD1 plasmid of Yersinia pestis mediates a cytotoxic effect on macrophages, contributing to virulence.
- The low calcium response (LCR) pathway is essential for Yersinia-induced cytotoxicity.
- In vitro cytotoxicity represents a significant virulence factor common among Yersinia species.