| 1. |
- Vaitkevicius, Karolis, et al.
(författare)
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The metalloprotease PrtV from Vibrio cholerae
- 2008
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 275:12, s. 3167-3177
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Tidskriftsartikel (refereegranskat)abstract
- The Vibrio metalloprotease PrtV was purified from the culture supernatant of a Vibrio cholerae derivative that is deficient in several other secreted peptidases, including the otherwise abundant hemagglutinin/protease HapA. The PrtV is synthesized as a 102 kDa protein, but undergoes several N- and C-terminal processing steps during V. cholerae envelope translocation and prolonged incubation. Purified V. cholerae PrtV protease forms of 81 or 73 kDa were stabilized by calcium ions. Removal of calcium resulted in further rapid autoproteolysis. The two major products of autoproteolysis of the PrtV protease were approximately 37 and 18 kDa and could not be separated under non-denaturing conditions, indicating they are interacting domains. In an assay using cultured cells of the human intestinal cell line HCT8, the PrtV protein showed a cytotoxic effect leading to cell death. Using human blood plasma as a source of potential substrates of mammalian origin for the PrtV protease, we found that the extracellular matrix components fibronectin and fibrinogen were degraded by the enzyme. Additional tests with individual protein substrates revealed that plasminogen was also a possible target for the PrtV protease.
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| 2. |
- Bäreclev, Caroline, et al.
(författare)
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DExD-box RNA-helicases in Listeria monocytogenes are important for growth, ribosomal maturation, rRNA processing and virulence factor expression
- 2014
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Ingår i: RNA Biology. - : Informa UK Limited. - 1547-6286 .- 1555-8584. ; 11:11, s. 1458-1467
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Tidskriftsartikel (refereegranskat)abstract
- RNA-helicases are proteins required for the unwinding of occluding secondary RNA structures, especially at low temperatures. In this work, we have deleted all 4 DExD-box RNA helicases in various combinations in the Gram-positive pathogen Listeria monocytogenes. Our results show that 3 out of 4 RNA-helicases were important for growth at low temperatures, whereas the effect was less prominent at 37 degrees C. Over-expression of one RNA-helicase, Lmo1450, was able to overcome the reduced growth of the quadruple mutant strain at temperatures above 26 degrees C, but not at lower temperatures. The maturation of ribosomes was affected in different degrees in the various strains at 20 degrees C, whereas the effect was marginal at 37 degrees C. This was accompanied by an increased level of immature 23S rRNA precursors in some of the RNA-helicase mutants at low temperatures. Although the expression of the PrfA regulated virulence factors ActA and LLO decreased in the quadruple mutant strain, this strain showed a slightly increased infection ability. Interestingly, even though the level of the virulence factor LLO was decreased in the quadruple mutant strain as compared with the wild-type strain, the hly-transcript (encoding LLO) was increased. Hence, our results could suggest a role for the RNA-helicases during translation. In this work, we show that DExD-box RNA-helicases are involved in bacterial virulence gene-expression and infection of eukaryotic cells.
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| 3. |
- Crowe-McAuliffe, Caillan, et al.
(författare)
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Structural basis of ABCF-mediated resistance to pleuromutilin, lincosamide, and streptogramin A antibiotics in Gram-positive pathogens
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Target protection proteins confer resistance to the host organism by directly binding to the antibiotic target. One class of such proteins are the antibiotic resistance (ARE) ATP-binding cassette (ABC) proteins of the F-subtype (ARE-ABCFs), which are widely distributed throughout Gram-positive bacteria and bind the ribosome to alleviate translational inhibition from antibiotics that target the large ribosomal subunit. Here, we present single-particle cryo-EM structures of ARE-ABCF-ribosome complexes from three Gram-positive pathogens: Enterococcus faecalis LsaA, Staphylococcus haemolyticus VgaALC and Listeria monocytogenes VgaL. Supported by extensive mutagenesis analysis, these structures enable a general model for antibiotic resistance mediated by these ARE-ABCFs to be proposed. In this model, ABCF binding to the antibiotic-stalled ribosome mediates antibiotic release via mechanistically diverse long-range conformational relays that converge on a few conserved ribosomal RNA nucleotides located at the peptidyltransferase center. These insights are important for the future development of antibiotics that overcome such target protection resistance mechanisms.
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| 4. |
- Good, James A. D., 1985-, et al.
(författare)
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Attenuating Listeria monocytogenes virulence by targeting the regulatory protein PrfA
- 2016
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Ingår i: Cell chemical biology. - : Elsevier BV. - 2451-9448 .- 2451-9456. ; 23:3, s. 404-414
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Tidskriftsartikel (refereegranskat)abstract
- The transcriptional activator PrfA, a member of the Crp/Fnr family, controls the expression of some key virulence factors necessary for infection by the human bacterial pathogen Listeria monocytogenes. Phenotypic screening identified ring-fused 2-pyridone molecules that at low micromolar concentrations attenuate L. monocytogenes infectivity by reducing the expression of virulence genes, without compromising bacterial growth. These inhibitors bind the transcriptional regulator PrfA and decrease its affinity for the consensus DNA binding site. Structural characterization of this interaction revealed that one of the ring-fused 2-pyridones, compound 1, binds within a hydrophobic pocket, located between the C- and N-terminal domains of PrfA, and interacts with residues important for PrfA activation. This indicates that these inhibitors maintain the DNA-binding helix-turn-helix motif of PrfA in a disordered state, thereby preventing a PrfA:DNA interaction. Ring-fused 2-pyridones represent a new class of chemical probes for studying virulence in L. monocytogenes.
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| 5. |
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| 6. |
- Ignatov, Dmitriy, et al.
(författare)
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An mRNA-mRNA Interaction Couples Expression of a Virulence Factor and Its Chaperone in Listeria monocytogenes
- 2020
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Ingår i: Cell Reports. - : cell press. - 2211-1247. ; 30:12, s. 4027-
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial pathogens often employ RNA regulatory elements located in the 5' untranslated regions (UTRs) to control gene expression. Using a comparative structural analysis, we examine the structure of 5' UTRs at a global scale in the pathogenic bacterium Listeria monocytogenes under different conditions. In addition to discovering an RNA thermoswitch and detecting simultaneous interaction of ribosomes and small RNAs with mRNA, we identify structural changes in the 5' UTR of an mRNA encoding the post-translocation chaperone PrsA2 during infection conditions. We demonstrate that the 5' UTR of the prsA2 mRNA base pairs with the 3' UTR of the full-length hly mRNA encoding listeriolysin O, thus preventing RNase J1-mediated degradation of the prsA2 transcript. Mutants lacking the hly-prsA2 interaction exhibit reduced virulence properties. This work highlights an additional level of RNA regulation, where the mRNA encoding a chaperone is stabilized by the mRNA encoding its substrate.
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| 7. |
- Ignatov, Dmitriy, et al.
(författare)
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Generation of Sequencing Libraries for Structural Analysis of Bacterial 5′ UTRs
- 2020
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Ingår i: STAR Protocols. - : Elsevier BV. - 2666-1667. ; 1:2
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Tidskriftsartikel (refereegranskat)abstract
- The structure of 5′ untranslated regions (5′ UTRs) of bacterial mRNAs often determines the fate of the transcripts. Using a dimethyl sulfate mutational profiling with sequencing (DMS-MaPseq) approach, we developed a protocol to generate sequence libraries to determine the base-pairing status of adenines and cytosines in the 5′ UTRs of bacterial mRNAs. Our method increases the sequencing depth of the 5′ UTRs and allows detection of changes in their structures by sequencing libraries of moderate sizes. For complete details on the use and execution of this protocol, please refer to Ignatov et al. (2020).
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| 8. |
- Koller, Timm O, et al.
(författare)
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Structural basis for HflXr-mediated antibiotic resistance in Listeria monocytogenes
- 2022
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 1362-4962 .- 0305-1048. ; 50:19, s. 11285-11300
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Tidskriftsartikel (refereegranskat)abstract
- HflX is a ubiquitous bacterial GTPase that splits and recycles stressed ribosomes. In addition to HflX, Listeria monocytogenes contains a second HflX homolog, HflXr. Unlike HflX, HflXr confers resistance to macrolide and lincosamide antibiotics by an experimentally unexplored mechanism. Here, we have determined cryo-EM structures of L. monocytogenes HflXr-50S and HflX-50S complexes as well as L. monocytogenes 70S ribosomes in the presence and absence of the lincosamide lincomycin. While the overall geometry of HflXr on the 50S subunit is similar to that of HflX, a loop within the N-terminal domain of HflXr, which is two amino acids longer than in HflX, reaches deeper into the peptidyltransferase center. Moreover, unlike HflX, the binding of HflXr induces conformational changes within adjacent rRNA nucleotides that would be incompatible with drug binding. These findings suggest that HflXr confers resistance using an allosteric ribosome protection mechanism, rather than by simply splitting and recycling antibiotic-stalled ribosomes.
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| 9. |
- Lindmark, Barbro, 1963-, et al.
(författare)
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Outer membrane vesicle-mediated release of cytolethal distending toxin (CDT) from Campylobacter jejuni
- 2009
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Ingår i: BMC Microbiology. - : Springer Science and Business Media LLC. - 1471-2180. ; 16:9, s. 220-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Cytolethal distending toxin (CDT) is one of the well-characterized virulence factors of Campylobacter jejuni, but it is unknown how CDT becomes surface-exposed or is released from the bacterium to the surrounding environment.RESULTS: Our data suggest that CDT is secreted to the bacterial culture supernatant via outer membrane vesicles (OMVs) released from the bacteria. All three subunits (the CdtA, CdtB, and CdtC proteins) were detected by immunogold labeling and electron microscopy of OMVs. Subcellular fractionation of the bacteria indicated that, apart from the majority of CDT detected in the cytoplasmic compartment, appreciable amounts (20-50%) of the cellular pool of CDT proteins were present in the periplasmic compartment. In the bacterial culture supernatant, we found that a majority of the extracellular CDT was tightly associated with the OMVs. Isolated OMVs could exert the cell distending effects typical of CDT on a human intestinal cell line, indicating that CDT is present there in a biologically active form.CONCLUSION: Our results strongly suggest that the release of outer membrane vesicles is functioning as a route of C. jejuni to deliver all the subunits of CDT toxin (CdtA, CdtB, and CdtC) to the surrounding environment, including infected host tissue.
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| 10. |
- Loh, Edmund, 1981-, et al.
(författare)
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A trans-acting riboswitch controls expression of the virulence regulator PrfA in Listeria monocytogenes
- 2009
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Ingår i: Cell. - : Elsevier BV. - 0092-8674 .- 1097-4172. ; 139:4, s. 770-779
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Tidskriftsartikel (refereegranskat)abstract
- Riboswitches are RNA elements acting in cis, controlling expression of their downstream genes through a metabolite-induced alteration of their secondary structure. Here, we demonstrate that two S-adenosylmethionine (SAM) riboswitches, SreA and SreB, can also function in trans and act as noncoding RNAs in Listeria monocytogenes. SreA and SreB control expression of the virulence regulator PrfA by binding to the 5´-untranslated region of its mRNA. Absence of the SAM riboswitches SreA and SreB increases the level of PrfA and virulence gene expression in L. monocytogenes. Thus, the impact of the SAM riboswitches on PrfA expression highlights a link between bacterial virulence and nutrient availability. Together, our results uncover an unexpected role for riboswitches and a distinct class of regulatory noncoding RNAs in bacteria.
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| 11. |
- Loh, Edmund, et al.
(författare)
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An unstructured 5'-coding region of the prfA mRNA is required for efficient translation
- 2012
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Ingår i: Nucleic Acids Research. - Oxford, England : Oxford University Press. - 0305-1048 .- 1362-4962. ; 40:4, s. 1818-1827
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Tidskriftsartikel (refereegranskat)abstract
- Expression of virulence factors in the human bacterial pathogen Listeria monocytogenes is almost exclusively regulated by the transcriptional activator PrfA. The translation of prfA is controlled by a thermosensor located in the 5'-untranslated RNA (UTR), and is high at 37 degrees C and low at temperatures < 30 degrees C. In order to develop a thermoregulated translational expression system, the 5'-UTR and different lengths of the prfA-coding sequences were placed in front of lacZ. When expressed in Escherichia coli, the beta-galactosidase expression was directly correlated to the length of the prfA-coding mRNA lying in front of lacZ. A similar effect was detected with gfp as a reporter gene in both L. monocytogenes and E. coli, emphasizing the requirement of the prfA-coding RNA for maximal expression. In vitro transcription/translation and mutational analysis suggests a role for the first 20 codons of the native prfA-mRNA for maximal expression. By toe-print and RNA-probing analysis, a flexible hairpin-loop located immediately downstream of the start-codon was shown to be important for ribosomal binding. The present work determines the importance of an unstructured part of the 5'-coding region of the prfA-mRNA for efficient translation.
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| 12. |
- Netterling, Sakura, et al.
(författare)
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A listeria monocytogenes RNA-helicase essential for growth and ribosomal maturation at low temperatures, uses its C-terminus for appropriate interaction with the ribosome
- 2012
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 194:16, s. 4377-4385
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Tidskriftsartikel (refereegranskat)abstract
- Listeria monocytogenes, a Gram-positive food-borne human pathogen, is able to grow at temperatures close to 0°C and is thus of great concern for the food-industry. In this work, we have investigated the physiological role of one DExD-box RNA-helicase in Listeria monocytogenes. The RNA-helicase Lmo1722 was required for optimal growth at low temperatures, whereas it was dispensable at 37°C. A Δlmo1722 strain was less motile due to a down-regulation of the major subunit of the flagellum, FlaA, caused by decreased flaA expression. By ribosomal fractionation experiments, it was observed that Lmo1722 was mainly associated with the 50S subunit of the ribosome. Absence of Lmo1722 decreased the fraction of 50S ribosomal subunits and mature 70S ribosomes and affected the processing of the 23S precursor rRNA. The ribosomal profile could be restored to wild-type levels in a Δlmo1722 strain expressing Lmo1722. Interestingly, the C-terminal part of Lmo1722 was redundant for low temperature growth, motility, 23S rRNA processing and appropriate ribosomal maturation. However, Lmo1722 lacking the C-terminus showed a reduced affinity for the 50S and 70S fractions, suggesting that the C-terminus is important for proper guidance of Lmo1722 to the 50S subunit. Taken together, our results show that the Listeria RNA helicase Lmo1722 is essential for growth at low temperatures, motility, ribosomal RNA processing and is important for ribosomal maturation being associated mainly with the 50S subunit of the ribosome.
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| 13. |
- Netterling, Sakura, et al.
(författare)
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RNA helicase important for Listeria monocytogenes hemolytic activity and virulence factor expression
- 2016
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Ingår i: Infection and Immunity. - : American Society for Microbiology. - 0019-9567 .- 1098-5522. ; 84:1, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- RNA helicases have been shown to be important for the function of RNA molecules at several levels, although their putative involvement in microbial pathogenesis has remained elusive. We have previously shown that Listeria monocytogenes DExD-box RNA helicases are important for bacterial growth, motility, ribosomal maturation, and rRNA processing. We assessed the importance of the RNA helicase Lmo0866 (here named CshA) for expression of virulence traits. We observed a reduction in hemolytic activity in a strain lacking CshA compared to the wild type. This phenomenon was less evident in strains lacking other RNA helicases. The reduced hemolysis was accompanied by lower expression of major listerial virulence factors in the ΔcshA strain, mainly listeriolysin O, but also to some degree the actin polymerizing factor ActA. Reduced expression of these virulence factors in the strain lacking CshA did not, however, correlate with a decreased level of the virulence regulator PrfA. When combining the ΔcshA knockout with a mutation creating a constitutively active PrfA protein (PrfA*), the effect of the ΔcshA knockout on LLO expression was negated. These data suggest a role for the RNA helicase CshA in posttranslational activation of PrfA. Surprisingly, although the expression of several virulence factors was reduced, the ΔcshA strain did not demonstrate any reduced ability to infect nonphagocytic cells compared to the wild-type strain.
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| 14. |
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| 15. |
- Ou, Gangwei, et al.
(författare)
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Vibrio cholerae cytolysin causes an inflammatory response in human intestinal epithelial cells that is modulated by the PrtV protease
- 2009
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Ingår i: PLOS ONE. - San Francisco : Public Library of Science. - 1932-6203. ; 4:11
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Tidskriftsartikel (refereegranskat)abstract
- We suggest that VCC is capable of causing an inflammatory response characterized by increased permeability and production of IL-8 and TNF-alpha in tight monolayers. Pure VCC at a concentration of 160 ng/ml caused an inflammatory response that reached the magnitude of that caused by Vibrio-secreted factors, while higher concentrations caused epithelial cell death. The inflammatory response was totally abolished by treatment with PrtV. The findings suggest that low doses of VCC initiate a local immune defense reaction while high doses lead to intestinal epithelial lesions. Furthermore, VCC is indeed a substrate for PrtV and PrtV seems to execute an environment-dependent modulation of the activity of VCC that may be the cause of V. cholerae reactogenicity.
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| 16. |
- Toledo-Arana, Alejandro, et al.
(författare)
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The Listeria transcriptional landscape from saprophytism to virulence
- 2009
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 459:7249, s. 950-956
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Tidskriftsartikel (refereegranskat)abstract
- The bacterium Listeria monocytogenes is ubiquitous in the environment and can lead to severe food-borne infections. It has recently emerged as a multifaceted model in pathogenesis. However, how this bacterium switches from a saprophyte to a pathogen is largely unknown. Here, using tiling arrays and RNAs from wild-type and mutant bacteria grown in vitro, ex vivo and in vivo, we have analysed the transcription of its entire genome. We provide the complete Listeria operon map and have uncovered far more diverse types of RNAs than expected: in addition to 50 small RNAs (<500 nucleotides), at least two of which are involved in virulence in mice, we have identified antisense RNAs covering several open-reading frames and long overlapping 5' and 3' untranslated regions. We discovered that riboswitches can act as terminators for upstream genes. When Listeria reaches the host intestinal lumen, an extensive transcriptional reshaping occurs with a SigB-mediated activation of virulence genes. In contrast, in the blood, PrfA controls transcription of virulence genes. Remarkably, several non-coding RNAs absent in the non-pathogenic species Listeria innocua exhibit the same expression patterns as the virulence genes. Together, our data unravel successive and coordinated global transcriptional changes during infection and point to previously unknown regulatory mechanisms in bacteria.
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| 17. |
- Tükenmez, Hasan, 1987-, et al.
(författare)
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A highly substituted ring-fused 2-pyridone compound targeting PrfA and the efflux regulator BrtA in listeria monocytogenes
- 2023
-
Ingår i: mBio. - : American Society for Microbiology. - 2161-2129 .- 2150-7511. ; 14:3
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Tidskriftsartikel (refereegranskat)abstract
- Listeria monocytogenes is a facultative Gram-positive bacterium that causes listeriosis, a severe foodborne disease. We previously discovered that ring-fused 2-pyridone compounds can decrease virulence factor expression in Listeria by binding and inactivating the PrfA virulence activator. In this study, we tested PS900, a highly substituted 2-pyridone that was recently discovered to be bactericidal to other Gram-positive pathogenic bacteria, such as Staphylococcus aureus and Enterococcus faecalis. We show that PS900 can interact with PrfA and reduce the expression of virulence factors. Unlike previous ring-fused 2-pyridones shown to inactivate PrfA, PS900 had an additional antibacterial activity and was found to potentiate sensitivity toward cholic acid. Two PS900-tolerant mutants able to grow in the presence of PS900 carried mutations in the brtA gene, encoding the BrtA repressor. In wild-type (WT) bacteria, cholic acid binds and inactivates BrtA, thereby alleviating the expression of the multidrug transporter MdrT. Interestingly, we found that PS900 also binds to BrtA and that this interaction causes BrtA to dissociate from its binding site in front of the mdrT gene. In addition, we observed that PS900 potentiated the effect of different osmolytes. We suggest that the increased potency of cholic acid and osmolytes to kill bacteria in the presence of PS900 is due to the ability of the latter to inhibit general efflux, through a yet-unknown mechanism. Our data indicate that thiazolino 2-pyridones constitute an attractive scaffold when designing new types of antibacterial agents.IMPORTANCE: Bacteria resistant to one or several antibiotics are a very large problem, threatening not only treatment of infections but also surgery and cancer treatments. Thus, new types of antibacterial drugs are desperately needed. In this work, we show that a new generation of substituted ring-fused 2-pyridones not only inhibit Listeria monocytogenes virulence gene expression, presumably by inactivating the PrfA virulence regulator, but also potentiate the bactericidal effects of cholic acid and different osmolytes. We identified a multidrug repressor as a second target of 2-pyridones. The repressor–2-pyridone interaction displaces the repressor from DNA, thus increasing the expression of a multidrug transporter. In addition, our data suggest that the new class of ring-fused 2-pyridones are efficient efflux inhibitors, possibly explaining why the simultaneous addition of 2-pyridones together with cholic acid or osmolytes is detrimental for the bacterium. This work proves conclusively that 2-pyridones constitute a promising scaffold to build on for future antibacterial drug design.
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| 18. |
- Vaitkevicius, Karolis, et al.
(författare)
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A Vibrio cholerae protease needed for killing of Caenorhabditis elegans has a role in protection from natural predator grazing
- 2006
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 103:24, s. 9280-9285
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Tidskriftsartikel (refereegranskat)abstract
- Vibrio cholerae is the causal bacterium of the diarrheal disease cholera, and its growth and survival are thought to be curtailed by bacteriovorous predators, e.g., ciliates and flagellates. We explored Caenorhabditis elegans as a test organism after finding that V. cholerae can cause lethal infection of this nematode. By reverse genetics we identified an extracellular protease, the previously uncharacterized PrtV protein, as being necessary for killing. The killing effect is associated with the colonization of bacteria within the Caenorhabditis elegans intestine. We also show that PrtV is essential for V. cholerae in the bacterial survival from grazing by the flagellate Cafeteria roenbergensis and the ciliate Tetrahymena pyriformis. The PrtV protein appears to have an indirect role in the interaction of V. cholerae with mammalian host cells as judged from tests with tight monolayers of human intestinal epithelial cells. Our results demonstrate a key role for PrtV in V. cholerae interaction with grazing predators, and we establish Caenorhabditis elegans as a convenient organism for identification of V. cholerae factors involved in host interactions and environmental persistence.
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| 19. |
- Vaitkevicius, Karolis, 1979-
(författare)
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Effects of Vibrio cholerae protease and pigment production on environmental survival and host interaction
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Only two out of more than 200 V. cholerae serogroups, classified on the basis of LPS structure, are associated with epidemic or pandemic cholera. These toxigenic serogroups carry phage-derived pathogenicity islands coding for the main virulence factors for establishment of cholera disease – cholera toxin (CTX) and toxin-coregulated pilus (TCP). The latter also serves as a bacterial surface receptor for the CTXΦ – the filamentous phage which carries the cholera toxin genes into otherwise harmless to human, environmental bacterium V. cholerae. In its natural aquatic habitat V. cholerae is subject to predator grazing, bacteriophage killing, temperature and pH changes, seasonality of plankton blooms and other environmental factors. Therefore understanding V. cholerae pathogenic and virulence potential requires the knowledge of its interaction not only with human host but also members of aquatic environment and environmental factors. V. cholerae is capable of killing the nematode Caenorhabditis elegans. Using a reverse genetics approach, we demonstrated that the quorum sensing regulated protease PrtV is essential for this killing. Other proteases did not seem to contribute to virulence in this model. The data from this study suggest that the PrtV could be important to V. cholerae in its natural niche for its resistance to the grazing predators. The PrtV protease belongs to an M6 family of metallopeptidases which is represented by an Immune Inhibitor A protease from the insect killing bacterium Bacillus thuringiensis. To characterize the protease in more detail, the PrtV was cloned, overexpressed in V. cholerae and purified from the culture supernatant. The enzyme was calcium stabilized and inhibited by metal ion chelators. In tests with in vitro cultured cells of the human intestinal cell line HCT8, the PrtV protein showed a cytotoxic effect leading to cell detachment and death. Using human blood plasma as a source of potential substrates, and by tests with purified candidate substrate proteins, we have identified fibrinogen (all α, β and γ chains), fibronectin and plasminogen to be degraded by the protease. Additionally, PrtV was found to alter the stability of V. cholerae cytolysin implicating its role in modulation of the reactogenicity of V. cholerae secreted factors. Pigmentation has been considered to be important in microbial pathogenesis because it has been associated with virulence in many microorganisms. Using transposon mutagenesis we identified the mutated locus of a pigment producing V. cholerae strain to encode a gene of a tyrosine catabolic pathway. The mutation in a putative homogentisate 1,2-dioxigenase gene lead to accumulation of homogentisic acid, its spontaneous oxidation and formation of a dark pigment. The pigment producing strain was altered in its ability to survive UV exposure and H2O2 stress, and was more efficient in colonizing the suckling mouse intestine compared to the wild type strain. Under the in vitro growth conditions the major virulence factor TcpA and CT expression was found to be somewhat enhanced too.
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| 20. |
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| 21. |
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| 22. |
- Valeru, Soni Priya, et al.
(författare)
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Role of melanin pigment in expression of Vibrio cholerae virulence factors.
- 2009
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Ingår i: Infection and immunity. - : American Society for Microbiology. - 1098-5522 .- 0019-9567. ; 77:3, s. 935-42
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Tidskriftsartikel (refereegranskat)abstract
- We identified the mutated gene locus in a pigment-overproducing Vibrio cholerae mutant of strain A1552. The deduced gene product is suggested to be an oxidoreductase based on partial homology to putative homogentisate 1,2-dioxygenase in Pseudomonas aeruginosa and Mesorhizobium loti, and we propose that the gene VC1345 in the V. cholerae genome be denoted hmgA in accordance with the nomenclature for other species. The hmgA::mini-Tn5 mutant showed a nonpigmented phenotype after complementation with a plasmid clone carrying the WT hmgA(+) locus. Microarray transcription analysis revealed that expression of hmgA and the neighboring genes encoding a postulated two-component sensor system was growth phase dependent. Results from quantitative reverse transcription-PCR analysis showed that hmgA operon expression was reduced in the rpoS mutant, but pigment production by the WT V. cholerae or the hmgA mutant was not detectably influenced by the stationary-phase regulator RpoS. The pigmented mutant showed increased UV resistance in comparison with the WT strain. Interestingly, the pigment-producing mutant expressed more toxin-coregulated pilus and cholera toxin than WT V. cholerae. Moreover, the hmgA mutant showed a fivefold increase in the ability to colonize the intestines of infant mice. A possible mechanism by which pigment production might cause induction of the ToxR regulon due to generation of hydrogen peroxide was supported by results from tests showing that externally supplied H(2)O(2) led to higher TcpA levels. Taken together, our findings suggest that melanin pigment formation may play a role in V. cholerae virulence factor expression.
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