A Yersinia pestis tat Mutant Is Attenuated in Bubonic and Small-Aerosol Pneumonic Challenge Models of Infection but Not As Attenuated by Intranasal Challenge

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.

Disruption of the NlpD lipoprotein of the plague pathogen Yersinia pestis affects iron acquisition and the activity of the twin-arginine translocation system

“…Furthermore, the tatA mutated bacteria could not be detected in the draining lymph node or the spleen of mice 48 hours after s.c. inoculation with high doses (10 7 cfu/mouse), similar to the observations reported with respect to the nlpD mutated bacteria [20]. The results obtained with the s.c. administration of the TatA mutant are consistent with those of Bozue and colleagues [61], who showed that a Y . pestis CO92 tatA mutant was severely attenuated upon subcutaneous infection of Swiss Webster mice.…”

“…Tat substrates function in energy metabolism, cellular division, motility and adaptation to environmental stress [52,58]. The system has been shown to be important for virulence in many bacterial pathogens including Yersinia species [25,52,59,60,61].…”

“…Indeed, it has been shown that the TatA protein is important for Y . pestis virulence in mouse models of plague [61]. Thus, we further addressed the attenuation of virulence and other phenotypic characteristics associated with the deletion of Tat proteins, in mutant strains exhibiting disruption of Tat genes in comparison to the phenotype exhibited by the nlpD mutated strain.…”

“…Importantly, similar to the situation of the Y . pestis nlpD mutant, the loss of virulence of Yersinia Tat mutated strains could not be explained by the dysfunction of the T3SS [60,61].…”

Formaldehyde and Glutaraldehyde Inactivation of Bacterial Tier 1 Select Agents in Tissues

“…B. pseudomallei 1026b ( 26 ), F. tularensis Schu S4 ( 27 ), and Y. pestis CO92 ( 28 ) were grown until mid-log phase. Bacterial doses and the infection routes used were based on previous studies (Table 4) ( 26 , 29 – 31 ).…”