Limits...
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.

Show MeSH

Related in: MedlinePlus

Dissemination studies of mice challenged intranasally with Y. pestis.Mice were challenged with CO92 (113,000 CFU) or ΔtatA mutant (76,000 CFU). At set time points, mice were euthanized, and the lungs and spleens were harvested. The A) lungs and B) spleens were homogenized and plated to determine bacterial recovery. For each time point, five mice were assayed, except for day 3 for wild-type challenged mice. Only four mice were tested as the remaining challenged mice had succumbed to infection. The lines (solid = CO92 and hashed = ΔtatA) are connecting at the geometrical means at the data points of CFU recovery from the respective organs are represent the overall trend during the course of infection.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4125294&req=5

pone-0104524-g009: Dissemination studies of mice challenged intranasally with Y. pestis.Mice were challenged with CO92 (113,000 CFU) or ΔtatA mutant (76,000 CFU). At set time points, mice were euthanized, and the lungs and spleens were harvested. The A) lungs and B) spleens were homogenized and plated to determine bacterial recovery. For each time point, five mice were assayed, except for day 3 for wild-type challenged mice. Only four mice were tested as the remaining challenged mice had succumbed to infection. The lines (solid = CO92 and hashed = ΔtatA) are connecting at the geometrical means at the data points of CFU recovery from the respective organs are represent the overall trend during the course of infection.

Mentions: Since there was little difference in the intranasal LD50 calculated between strains but a significant increase in TTD for mutant challenged mice, the dissemination of wild-type and mutant bacteria following intranasal challenge was compared. Groups of mice were separately challenged with approximately equal doses of either CO92 (113,000 CFU) or the ΔtatA mutant (76,000 CFU). For mice challenged with wild-type CO92, CFU recovery from the lungs showed some progression by day 1 and then increased rapidly for days 3 and 4 for all mice tested (Fig. 9A). By day 3, only four mice were alive for testing, while the remaining animals had succumbed to infection. For recovery of CFU from the spleen, wild-type bacteria were detected for one mouse by day 1; however, spleens for all mice had increased bacterial burden loads by days 2 and 3 (Fig. 9B).


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)

Dissemination studies of mice challenged intranasally with Y. pestis.Mice were challenged with CO92 (113,000 CFU) or ΔtatA mutant (76,000 CFU). At set time points, mice were euthanized, and the lungs and spleens were harvested. The A) lungs and B) spleens were homogenized and plated to determine bacterial recovery. For each time point, five mice were assayed, except for day 3 for wild-type challenged mice. Only four mice were tested as the remaining challenged mice had succumbed to infection. The lines (solid = CO92 and hashed = ΔtatA) are connecting at the geometrical means at the data points of CFU recovery from the respective organs are represent the overall trend during the course of infection.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0104524-g009: Dissemination studies of mice challenged intranasally with Y. pestis.Mice were challenged with CO92 (113,000 CFU) or ΔtatA mutant (76,000 CFU). At set time points, mice were euthanized, and the lungs and spleens were harvested. The A) lungs and B) spleens were homogenized and plated to determine bacterial recovery. For each time point, five mice were assayed, except for day 3 for wild-type challenged mice. Only four mice were tested as the remaining challenged mice had succumbed to infection. The lines (solid = CO92 and hashed = ΔtatA) are connecting at the geometrical means at the data points of CFU recovery from the respective organs are represent the overall trend during the course of infection.
Mentions: Since there was little difference in the intranasal LD50 calculated between strains but a significant increase in TTD for mutant challenged mice, the dissemination of wild-type and mutant bacteria following intranasal challenge was compared. Groups of mice were separately challenged with approximately equal doses of either CO92 (113,000 CFU) or the ΔtatA mutant (76,000 CFU). For mice challenged with wild-type CO92, CFU recovery from the lungs showed some progression by day 1 and then increased rapidly for days 3 and 4 for all mice tested (Fig. 9A). By day 3, only four mice were alive for testing, while the remaining animals had succumbed to infection. For recovery of CFU from the spleen, wild-type bacteria were detected for one mouse by day 1; however, spleens for all mice had increased bacterial burden loads by days 2 and 3 (Fig. 9B).

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