Change search
ReferencesLink to record
Permanent link

Direct link
Cycles of light and dark co-ordinate reversible colony differentiation in Listeria monocytogenes
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
2013 (English)In: Molecular Microbiology, ISSN 0950-382X, E-ISSN 1365-2958, Vol. 87, no 4, 909-924 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2013. Vol. 87, no 4, 909-924 p.
National Category
Microbiology in the medical area
URN: urn:nbn:se:umu:diva-67399DOI: 10.1111/mmi.12140ISI: 000314925700015OAI: diva2:615217
Available from: 2013-04-09 Created: 2013-03-18 Last updated: 2016-01-13Bibliographically approved
In thesis
1. Regulatory pathways and virulence inhibition in Listeria monocytogenes
Open this publication in new window or tab >>Regulatory pathways and virulence inhibition in Listeria monocytogenes
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Listeria monocytogenes is a rod-shaped Gram positive bacterium. It generally exist ubiquitously in nature, where it lives as a saprophyte. Occasionally it however enters the food chain, from where it can be ingested by humans and cause gastro-intestinal distress. In immunocompetent individuals L. monocytogenes is generally cleared within a couple of weeks, but in immunocompromised patients it can progress to listeriosis, a potentially life-threatening infection in the central nervous system. If the infected individual is pregnant, the bacteria can cross the placental barrier and infect the fetus, possibly leading to spontaneous abortion.

The infectivity of L. monocytogenes requires a certain set of genes, and the majority of them is dependent on the transcriptional regulator PrfA. The expression and activity of PrfA is controlled at several levels, and has traditionally been viewed to be active at 37 °C (virulence conditions) where it bind as a homodimer to a “PrfA-box” and induces the expression of the downstream gene.

One of these genes is ActA, which enables intracellular movement by recruiting an actin polymerizing protein complex. When studying the effects of a blue light receptor we surprisingly found an effect of ActA at non-virulent conditions, where it is required for the bacteria to properly react to light exposure.

To further study the PrfA regulon we tested deletion mutants of several PrfA-regulated virulence genes in chicken embryo infection studies. Based on these studies we could conclude that the chicken embryo model is a viable complement to traditional murine models, especially when investigating non-traditional internalin pathogenicity pathways. We have also studied the effects of small molecule virulence inhibitors that, by acting on PrfA, can inhibit L. monocytogenes infectivity in cell cultures with concentrations in the low micro-molar range.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2016. 37 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1772
Listeria monocytogenes, PrfA, ActA, infection
National Category
Cell and Molecular Biology
Research subject
Molecular Biology
urn:nbn:se:umu:diva-114085 (URN)978-91-7601-397-7 (ISBN)
Public defence
2016-02-04, KB3B1, KBC-huset, Umeå, 09:00 (English)
Available from: 2016-01-14 Created: 2016-01-12 Last updated: 2016-01-26Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Tiensuu, TeresaAndersson, ChristopherRyden, PatrikJohansson, Jörgen
By organisation
Department of Molecular Biology (Faculty of Medicine)Department of Mathematics and Mathematical Statistics
In the same journal
Molecular Microbiology
Microbiology in the medical area

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 192 hits
ReferencesLink to record
Permanent link

Direct link