| 1. |
- Avican, Kemal, et al.
(författare)
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Reprogramming of Yersinia from Virulent to Persistent Mode Revealed by Complex In Vivo RNA-seq Analysis
- 2015
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Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- We recently found that Yersinia pseudotuberculosis can be used as a model of persistent bacterial infections. We performed in vivo RNA-seq of bacteria in small cecal tissue biopsies at early and persistent stages of infection to determine strategies associated with persistence. Comprehensive analysis of mixed RNA populations from infected tissues revealed that Y. pseudotuberculosis undergoes transcriptional reprogramming with drastic down-regulation of T3SS virulence genes during persistence when the pathogen resides within the cecum. At the persistent stage, the expression pattern in many respects resembles the pattern seen in vitro at 26oC, with for example, up-regulation of flagellar genes and invA. These findings are expected to have impact on future rationales to identify suitable bacterial targets for new antibiotics. Other genes that are up-regulated during persistence are genes involved in anaerobiosis, chemotaxis, and protection against oxidative and acidic stress, which indicates the influence of different environmental cues. We found that the Crp/CsrA/RovA regulatory cascades influence the pattern of bacterial gene expression during persistence. Furthermore, arcA, fnr, frdA, and wrbA play critical roles in persistence. Our findings suggest a model for the life cycle of this enteropathogen with reprogramming from a virulent to an adapted phenotype capable of persisting and spreading by fecal shedding.
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| 2. |
- Avican, Ummehan, et al.
(författare)
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Transcriptomic and phenotypic analysis reveals new functions for the Tat pathway in Yersinia pseudotuberculosis
- 2016
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Ingår i: Journal of Bacteriology. - Washington : American Society for Microbiology. - 0021-9193 .- 1098-5530. ; 198:20, s. 2876-2886
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Tidskriftsartikel (refereegranskat)abstract
- The Twin-arginine translocation (Tat) system mediates secretion of folded proteins that in bacteria, plants and archaea are identified via an N-terminal signal peptide. Tat systems are associated with virulence in many bacterial pathogens and our previous studies revealed that Tat deficient Yersinia pseudotuberculosis was severely attenuated for virulence. Aiming to identify Tat-dependent pathways and phenotypes of relevance for in vivo infection, we analysed the global transcriptome of parental and ∆tatC mutant strains of Y. pseudotuberculosis during exponential and stationary growth at 26oC and 37oC. The most significant changes in the transcriptome of the ∆tatC mutant were seen at 26oC during stationary phase growth and these included the altered expression of genes related to virulence, stress responses and metabolism. Subsequent phenotypic analysis based on these transcriptome changes revealed several novel Tat-dependent phenotypes including decreased YadA expression, impaired growth under iron-limiting and high copper conditions as well as acidic pH and SDS. Several functionally related Tat substrates were also verified to contribute to these phenotypes. Interestingly, the phenotypic defects observed in the Tat-deficient strain were generally more pronounced than in mutants lacking the Tat substrate predicted to contribute to that specific function. Altogether, this provides new insight into the impact of Tat deficiency on in vivo fitness and survival/replication of Y. pseudotuberculosis during infection.
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| 3. |
- Boehme, Katja, et al.
(författare)
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Concerted Actions of a Thermo-labile Regulator and a Unique Intergenic RNA Thermosensor Control Yersinia Virulence
- 2012
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Ingår i: PLOS PATHOGENS. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 8:2, s. e1002518-
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Tidskriftsartikel (refereegranskat)abstract
- Expression of all Yersinia pathogenicity factors encoded on the virulence plasmid, including the yop effector and the ysc type III secretion genes, is controlled by the transcriptional activator LcrF in response to temperature. Here, we show that a protein-and RNA-dependent hierarchy of thermosensors induce LcrF synthesis at body temperature. Thermally regulated transcription of lcrF is modest and mediated by the thermo-sensitive modulator YmoA, which represses transcription from a single promoter located far upstream of the yscW-lcrF operon at moderate temperatures. The transcriptional response is complemented by a second layer of temperature-control induced by a unique cis-acting RNA element located within the intergenic region of the yscW-lcrF transcript. Structure probing demonstrated that this region forms a secondary structure composed of two stemloops at 25 degrees C. The second hairpin sequesters the lcrF ribosomal binding site by a stretch of four uracils. Opening of this structure was favored at 37 degrees C and permitted ribosome binding at host body temperature. Our study further provides experimental evidence for the biological relevance of an RNA thermometer in an animal model. Following oral infections in mice, we found that two different Y. pseudotuberculosis patient isolates expressing a stabilized thermometer variant were strongly reduced in their ability to disseminate into the Peyer's patches, liver and spleen and have fully lost their lethality. Intriguingly, Yersinia strains with a destabilized version of the thermosensor were attenuated or exhibited a similar, but not a higher mortality. This illustrates that the RNA thermometer is the decisive control element providing just the appropriate amounts of LcrF protein for optimal infection efficiency.
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| 4. |
- Kusmierek, Maria, et al.
(författare)
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A bacterial secreted translocator hijacks riboregulators to control type III secretion in response to host cell contact
- 2019
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Ingår i: PLoS Pathogens. - : Public Library Science. - 1553-7366 .- 1553-7374. ; 15:6
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Tidskriftsartikel (refereegranskat)abstract
- Numerous Gram-negative pathogens use a Type III Secretion System (T3SS) to promote virulence by injecting effector proteins into targeted host cells, which subvert host cell processes. Expression of T3SS and the effectors is triggered upon host cell contact, but the underlying mechanism is poorly understood. Here, we report a novel strategy of Yersinia pseudotuberculosis in which this pathogen uses a secreted T3SS translocator protein (YopD) to control global RNA regulators. Secretion of the YopD translocator upon host cell contact increases the ratio of post-transcriptional regulator CsrA to its antagonistic small RNAs CsrB and CsrC and reduces the degradosome components PNPase and RNase E levels. This substantially elevates the amount of the common transcriptional activator (LcrF) of T3SS/Yop effector genes and triggers the synthesis of associated virulence-relevant traits. The observed hijacking of global riboregulators allows the pathogen to coordinate virulence factor expression and also readjusts its physiological response upon host cell contact. Author summary Many bacterial pathogens sense contact to host cells and respond by inducing expression of crucial virulence factors. This includes the type III secretion systems (T3SSs) and their substrates, which manipulate different host cell functions to promote colonization and survival of the pathogen within its host. In this study, we used enteropathogenic Yersinia pseudotuberculosis to elucidate the molecular mechanism of how cell contact is transmitted and translated to trigger this process. We found that multiple global riboregulators control the decay and/or translation of the major transcriptional activator of the T3SS. In the absence of cell contact, these important RNA regulators are coopted by one of the substrate proteins of the T3SS to repress expression of the secretion machinery. Translocation of the substrate protein upon cell contact relieves riboregulator-mediated repression. This leads to a strong induction of the master regulator of T3SS/effector gene expression promoting an increase of the virulence potential and provokes a fast adaptation of the pathogen's fitness, e.g. to compensate for the imposed energetic burden.
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