| 1. |
- Song, Tianyan, et al.
(författare)
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A new Vibrio cholerae sRNA modulates colonization and affects release of outer membrane vesicles.
- 2008
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Ingår i: Molecular microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 70:1, s. 100-11
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Tidskriftsartikel (refereegranskat)abstract
- We discovered a new small non-coding RNA (sRNA) gene, vrrA of Vibrio cholerae O1 strain A1552. A vrrA mutant overproduces OmpA porin, and we demonstrate that the 140 nt VrrA RNA represses ompA translation by base-pairing with the 5' region of the mRNA. The RNA chaperone Hfq is not stringently required for VrrA action, but expression of the vrrA gene requires the membrane stress sigma factor, sigma(E), suggesting that VrrA acts on ompA in response to periplasmic protein folding stress. We also observed that OmpA levels inversely correlated with the number of outer membrane vesicles (OMVs), and that VrrA increased OMV production comparable to loss of OmpA. VrrA is the first sRNA known to control OMV formation. Moreover, a vrrA mutant showed a fivefold increased ability to colonize the intestines of infant mice as compared with the wild type. There was increased expression of the main colonization factor of V. cholerae, the toxin co-regulated pili, in the vrrA mutant as monitored by immunoblot detection of the TcpA protein. VrrA overproduction caused a distinct reduction in the TcpA protein level. Our findings suggest that VrrA contributes to bacterial fitness in certain stressful environments, and modulates infection of the host intestinal tract.
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| 2. |
- Mandin, Pierre, et al.
(författare)
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Feeling the heat at the millennium : thermosensors playing with fire
- 2020
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 113:3, s. 588-592
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Forskningsöversikt (refereegranskat)abstract
- An outstanding question regards the ability of organisms to sense their environments and respond in a suitable way. Pathogenic bacteria in particular exploit host-temperature sensing as a cue for triggering virulence gene expression. This micro-review does not attempt to fully cover the field of bacterial thermosensors and in detail describe each identified case. Instead, the review focus on the time-period at the end of the 1990's and beginning of the 2000's when several key discoveries were made, identifying protein, DNA and RNA as potential thermosensors controlling gene expression in several different bacterial pathogens in general and on the prfA thermosensor of Listeria monocytogenes in particular.
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| 3. |
- Tiensuu, Teresa, et al.
(författare)
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Cycles of light and dark co-ordinate reversible colony differentiation in Listeria monocytogenes
- 2013
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 87:4, s. 909-924
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Tidskriftsartikel (refereegranskat)abstract
- Recently, several light receptors have been identified in non-phototrophic bacteria, but their physiological roles still remain rather elusive. Here we show that colonies of the saprophytic bacterium Listeria monocytogenes undergo synchronized multicellular behaviour on agar plates, in response to oscillating light/dark conditions, giving rise to alternating ring formation (opaque and translucent rings). On agar plates, bacteria from opaque rings survive increased levels of reactive oxygen species (ROS), as well as repeated cycles of light and dark, better than bacteria from translucent rings. The ring formation is strictly dependent on a blue-light receptor, Lmo0799, acting through the stress-sigma factor, sigma B. A transposon screening identified 48 mutants unable to form rings at alternating light conditions, with several of them showing a decreased sigma B activity/level. However, some of the tested mutants displayed a varied sigma B activity depending on which of the two stress conditions tested (light or H2O2 exposure). Intriguingly, the transcriptional regulator PrfA and the virulence factor ActA were shown to be required for ring formation by a mechanism involving activation of sigma B. All in all, this suggests a distinct pathway for Lmo0799 that converge into a common signalling pathway for sigma B activation. Our results show that night and day cycles co-ordinate a reversible differentiation of a L.monocytogenes colony at room temperature, by a process synchronized by a blue-light receptor and sigma B.
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