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The σ-factor FliA, ppGpp and DksA coordinate transcriptional control of the aer2 gene of Pseudomonas putida
Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
2010 (English)In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 12, no 6, 1439-1451 p.Article in journal (Refereed) Published
Abstract [en]

Here the σ-factor requirement for transcription of three similar, but differentially regulated, aer genes of Pseudomonas putida KT2440 is investigated. Previous work has shown that the three Aer proteins, like chemoreceptors, colocalize to a single pole in a CheA-dependent manner. Lack of Aer2 - the most abundant of these three proteins - mediates defects in metabolism-dependent taxis and aerotaxis, while lack of Aer1 or Aer3 has no apparent phenotype. We show, using wild-type and mutant P. putida derivatives combined with P. putida reconstituted FliA- (σ28) and σ70-dependent in vitro transcription assays, that transcription of aer2 is coupled to motility through the flagella σ-factor FliA, while σ70 is responsible for transcription of aer1 and aer3. By comparing activities of the wild-type and mutant forms of the aer2 promoter, we present evidence (i) that transcription from FliA-dependent Paer2 is enhanced by changes towards the Escherichia coli consensus for FliA promoters rather than towards that of P. putida, (ii) that the nature of the AT-rich upstream region is important for both output and σ70 discrimination of this promoter, and (iii) that Paer2 output is directly stimulated by the bacterial alarmone ppGpp and its cofactor DksA.

Place, publisher, year, edition, pages
John Wiley & Sons, 2010. Vol. 12, no 6, 1439-1451 p.
National Category
URN: urn:nbn:se:umu:diva-33333DOI: 10.1111/j.1462-2920.2009.02139.xISI: 000278394400007PubMedID: 20089044OAI: diva2:311555

E-pub ahead of print

Available from: 2010-04-21 Created: 2010-04-21 Last updated: 2013-02-20Bibliographically approved
In thesis
1. Metabolism-dependent taxis and control of motility in Pseudomonas putida
Open this publication in new window or tab >>Metabolism-dependent taxis and control of motility in Pseudomonas putida
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bacteria living in soil and aquatic habitats rapidly adapt to changes in physico-chemical parameters that influence their energy status and thus their ability to proliferate and survive. One immediate survival strategy is to relocate to more metabolically optimal environments. To aid their movement through gradients (a process called taxis), many bacteria use whip like flagella organelles. Soil-dwelling Pseudomonas putida possesses a polar bundle of flagella that propel the bacterium forward in directed swimming motility. P. putida strains are generally fast growing, have a broad metabolic capacity, and are resistant to many harmful substances – qualities that make them interesting for an array of industrial and biotechnological application. This thesis identifies some of the factors that are involved in controlling the flagella driven motility of P. putida.

In the first part of the thesis, I present evidence that P. putida displays energy-taxis towards metabolisable substrates and that the surface located Aer2 receptor (named after its similarities to the Escherichia coli Aer receptor) is responsible for detecting the changes in energy-status and oxygen-gradients that underlie this response. Aer2 is expressed simultaneously with the flagella needed for taxis responses and its expression is ensured during nutrient scares conditions through the global transcriptional regulators ppGpp and DksA.

In addition to Aer2, P. putida possesses two more Aer-like receptors (Aer1 and Aer3) that are differentially expressed. Like Aer2, Aer1 and Aer3 co-localize to one cell pole. Although the signals to which Aer1 and Aer3 respond are unknown, analysis of Aer1 uncovered a role in motility control for a protein encoded within the same operon. This protein, called PP2258, instigated the work described in the second part of my thesis on the involvement of the second messenger c-di-GMP in regulation of P. putida motility. Genetic dissection of the catalytic activities of PP2258 revealed that it has the unusual capacity to both synthesize and degrade c-di-GMP. Coupling of the c-di-GMP signal originating from PP2258 to motility control was traced to the c-di-GMP binding properties of the protein PP4397. In the last part of the thesis, I present possible mechanisms for how these different components might interact to create a signal transduction cascade – from the surface located Aer1 receptor to PP2258 and the c-di-GMP responsive PP4397, and from there to the flagella motors – to ultimately determine flagella performance and the motility status of P. putida.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2013. 48 p.
Motility, c-di-GMP, metabolism-dependent taxis, receptors, transcription, Pseudomonas putida
National Category
Research subject
Molecular Biology
urn:nbn:se:umu:diva-66138 (URN)978-91-7459-563-5 (ISBN)
Public defence
2013-03-21, Norrlands universitetssjukhus, Byggnad 6L, Major Groove, Umeå universitet, Umeå, 09:00 (English)
Available from: 2013-02-28 Created: 2013-02-15 Last updated: 2013-02-20Bibliographically approved

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Österberg, SofiaSkärfstad, EleonoreShingler, Victoria
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Department of Molecular Biology (Faculty of Science and Technology)Umeå Centre for Microbial Research (UCMR)
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