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A Yersinia pestis tat mutant is attenuated in bubonic and small-aerosol pneumonic challenge models of infection but not as attenuated by intranasal challenge.

Bozue J, Cote CK, Chance T, Kugelman J, Kern SJ, Kijek TK, Jenkins A, Mou S, Moody K, Fritz D, Robinson CG, Bell T, Worsham P - PLoS ONE (2014)

Bottom Line: Deletion of the tatA gene resulted in several consequences for the mutant as compared to wild-type.In contrast, when mice were challenged intranasally with the mutant, very little difference in the LD50 was observed between wild-type and mutant strains.Collectively, these findings demonstrate an essential role for the Tat pathway in the virulence of Y. pestis in bubonic and small-aerosol pneumonic infection but less important role for intranasal challenge.

View Article: PubMed Central - PubMed

Affiliation: Bacteriology Division, The United States Army of Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, United States of America.

ABSTRACT
Bacterial proteins destined for the Tat pathway are folded before crossing the inner membrane and are typically identified by an N-terminal signal peptide containing a twin arginine motif. Translocation by the Tat pathway is dependent on the products of genes which encode proteins possessing the binding site of the signal peptide and mediating the actual translocation event. In the fully virulent CO92 strain of Yersinia pestis, the tatA gene was deleted. The mutant was assayed for loss of virulence through various in vitro and in vivo assays. Deletion of the tatA gene resulted in several consequences for the mutant as compared to wild-type. Cell morphology of the mutant bacteria was altered and demonstrated a more elongated form. In addition, while cultures of the mutant strain were able to produce a biofilm, we observed a loss of adhesion of the mutant biofilm structure compared to the biofilm produced by the wild-type strain. Immuno-electron microscopy revealed a partial disruption of the F1 antigen on the surface of the mutant. The virulence of the ΔtatA mutant was assessed in various murine models of plague. The mutant was severely attenuated in the bubonic model with full virulence restored by complementation with the native gene. After small-particle aerosol challenge in a pneumonic model of infection, the mutant was also shown to be attenuated. In contrast, when mice were challenged intranasally with the mutant, very little difference in the LD50 was observed between wild-type and mutant strains. However, an increased time-to-death and delay in bacterial dissemination was observed in mice infected with the ΔtatA mutant as compared to the parent strain. Collectively, these findings demonstrate an essential role for the Tat pathway in the virulence of Y. pestis in bubonic and small-aerosol pneumonic infection but less important role for intranasal challenge.

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Growth assays.Y. pestis wild type and ΔtatA mutant strains were grown in HI broth at 28°C (A and B), 37°C with CaCl2 (C and D), or 37°C with MOX (E and F). Growth was monitored by both optical density (A, C, and E) and CFU counts (B, D, and F). OD measurements are based upon quadruplicate samples and bars represent standard deviation. CFU measurements are based upon triplicate samples and bars represent standard deviation. These data represent at least two separate experiments.
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pone-0104524-g001: Growth assays.Y. pestis wild type and ΔtatA mutant strains were grown in HI broth at 28°C (A and B), 37°C with CaCl2 (C and D), or 37°C with MOX (E and F). Growth was monitored by both optical density (A, C, and E) and CFU counts (B, D, and F). OD measurements are based upon quadruplicate samples and bars represent standard deviation. CFU measurements are based upon triplicate samples and bars represent standard deviation. These data represent at least two separate experiments.

Mentions: Growth curves were performed comparing the wild-type and ΔtatA mutant in HI broth (28°C, 37°C with CaCl2, and 37°C with MOX) by both optical density (OD600) and CFU counts (Fig. 1). No differences in growth rates were observed between strains as observed by OD (Fig. 1). However, CFU counts at all-time points (even for the starting inoculum at Time 0), were consistently lower in the mutant strain compared to the wild-type strain despite having similar OD measurements. However, the increase in CFU counts of both parent and mutant strains over the time course was still similar.


A Yersinia pestis tat mutant is attenuated in bubonic and small-aerosol pneumonic challenge models of infection but not as attenuated by intranasal challenge.

Bozue J, Cote CK, Chance T, Kugelman J, Kern SJ, Kijek TK, Jenkins A, Mou S, Moody K, Fritz D, Robinson CG, Bell T, Worsham P - PLoS ONE (2014)

Growth assays.Y. pestis wild type and ΔtatA mutant strains were grown in HI broth at 28°C (A and B), 37°C with CaCl2 (C and D), or 37°C with MOX (E and F). Growth was monitored by both optical density (A, C, and E) and CFU counts (B, D, and F). OD measurements are based upon quadruplicate samples and bars represent standard deviation. CFU measurements are based upon triplicate samples and bars represent standard deviation. These data represent at least two separate experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4125294&req=5

pone-0104524-g001: Growth assays.Y. pestis wild type and ΔtatA mutant strains were grown in HI broth at 28°C (A and B), 37°C with CaCl2 (C and D), or 37°C with MOX (E and F). Growth was monitored by both optical density (A, C, and E) and CFU counts (B, D, and F). OD measurements are based upon quadruplicate samples and bars represent standard deviation. CFU measurements are based upon triplicate samples and bars represent standard deviation. These data represent at least two separate experiments.
Mentions: Growth curves were performed comparing the wild-type and ΔtatA mutant in HI broth (28°C, 37°C with CaCl2, and 37°C with MOX) by both optical density (OD600) and CFU counts (Fig. 1). No differences in growth rates were observed between strains as observed by OD (Fig. 1). However, CFU counts at all-time points (even for the starting inoculum at Time 0), were consistently lower in the mutant strain compared to the wild-type strain despite having similar OD measurements. However, the increase in CFU counts of both parent and mutant strains over the time course was still similar.

Bottom Line: Deletion of the tatA gene resulted in several consequences for the mutant as compared to wild-type.In contrast, when mice were challenged intranasally with the mutant, very little difference in the LD50 was observed between wild-type and mutant strains.Collectively, these findings demonstrate an essential role for the Tat pathway in the virulence of Y. pestis in bubonic and small-aerosol pneumonic infection but less important role for intranasal challenge.

View Article: PubMed Central - PubMed

Affiliation: Bacteriology Division, The United States Army of Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, United States of America.

ABSTRACT
Bacterial proteins destined for the Tat pathway are folded before crossing the inner membrane and are typically identified by an N-terminal signal peptide containing a twin arginine motif. Translocation by the Tat pathway is dependent on the products of genes which encode proteins possessing the binding site of the signal peptide and mediating the actual translocation event. In the fully virulent CO92 strain of Yersinia pestis, the tatA gene was deleted. The mutant was assayed for loss of virulence through various in vitro and in vivo assays. Deletion of the tatA gene resulted in several consequences for the mutant as compared to wild-type. Cell morphology of the mutant bacteria was altered and demonstrated a more elongated form. In addition, while cultures of the mutant strain were able to produce a biofilm, we observed a loss of adhesion of the mutant biofilm structure compared to the biofilm produced by the wild-type strain. Immuno-electron microscopy revealed a partial disruption of the F1 antigen on the surface of the mutant. The virulence of the ΔtatA mutant was assessed in various murine models of plague. The mutant was severely attenuated in the bubonic model with full virulence restored by complementation with the native gene. After small-particle aerosol challenge in a pneumonic model of infection, the mutant was also shown to be attenuated. In contrast, when mice were challenged intranasally with the mutant, very little difference in the LD50 was observed between wild-type and mutant strains. However, an increased time-to-death and delay in bacterial dissemination was observed in mice infected with the ΔtatA mutant as compared to the parent strain. Collectively, these findings demonstrate an essential role for the Tat pathway in the virulence of Y. pestis in bubonic and small-aerosol pneumonic infection but less important role for intranasal challenge.

Show MeSH
Related in: MedlinePlus