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Whole genome transcriptomics reveals global effects including up-regulation of Francisella pathogenicity island gene expression during active stringent response in the highly virulent Francisella tularensis subsp. tularensis SCHU S4

Whole genome transcriptomics reveals global effects including up-regulation of Francisella pathogenicity island gene expression during active stringent response in the highly virulent Francisella tularensis subsp. tularensis SCHU S4
Whole genome transcriptomics reveals global effects including up-regulation of Francisella pathogenicity island gene expression during active stringent response in the highly virulent Francisella tularensis subsp. tularensis SCHU S4
During conditions of nutrient limitation bacteria undergo a series of global gene expression changes to survive conditions of amino acid and fatty acid starvation. Rapid reallocation of cellular resources is brought about by gene expression changes coordinated by the signalling nucleotides’ guanosine tetraphosphate or pentaphosphate, collectively termed (p)ppGpp and is known as the stringent response. The stringent response has been implicated in bacterial virulence, with elevated (p)ppGpp levels being associated with increased virulence gene expression. This has been observed in the highly pathogenic Francisella tularensis sub spp. tularensis SCHU S4, the causative agent of tularaemia. Here, we aimed to artificially induce the stringent response by culturing F. tularensis in the presence of the amino acid analogue L-serine hydroxamate. Serine
hydroxamate competitively inhibits tRNAser aminoacylation, causing an accumulation of uncharged tRNA. The uncharged tRNA enters the A site on the translating bacterial ribosome and causes ribosome stalling, in turn stimulating the production of (p)ppGpp and activation of the stringent response. Using the essential virulence gene iglC, which is encoded on the Francisella pathogenicity island (FPI) as a marker of active stringent response, we optimized the culture conditions required for the investigation of virulence gene expression under conditions of nutrient limitation. We subsequently used whole genome RNA-seq to show how F. tularensis alters gene expression on a global scale during active stringent response. Key findings included up-regulation of genes involved in virulence, stress responses and metabolism, and down-regulation of genes involved in metabolite transport and cell division. F. tularensis is a highly virulent intracellular pathogen capable of causing debilitating or fatal disease at extremely low infectious doses. However, virulence mechanisms are still poorly
understood. The stringent response is widely recognized as a diverse and complex bacterial stress response implicated in virulence. This work describes the global gene expression profile of F. tularensis SCHU S4 under active stringent response for the first time. Herein we provide evidence for an association of active stringent response with FPI virulence gene expression. Our results further the understanding of the molecular basis of virulence and regulation thereof in F. tularensis. These results also support research into genes involved in (p)ppGpp production and polyphosphate biosynthesis and their applicability as targets for novel antimicrobials.
francisella tularensis, pathogenicity islands, stringent response, transcriptional regulation, gene regulation
1350-0872
1664-1679
Murch, Amber L.
bc0eab88-a1d0-4d43-94a9-224b8c1ccd4c
Skipp, Paul J.
1ba7dcf6-9fe7-4b5c-a9d0-e32ed7f42aa5
Roach, Peter L.
ca94060c-4443-482b-af3e-979243488ba9
Oyston, Petra C.F.
0cadfaf6-a166-45cc-b64b-bb1182d6c26a
Murch, Amber L.
bc0eab88-a1d0-4d43-94a9-224b8c1ccd4c
Skipp, Paul J.
1ba7dcf6-9fe7-4b5c-a9d0-e32ed7f42aa5
Roach, Peter L.
ca94060c-4443-482b-af3e-979243488ba9
Oyston, Petra C.F.
0cadfaf6-a166-45cc-b64b-bb1182d6c26a

Murch, Amber L., Skipp, Paul J., Roach, Peter L. and Oyston, Petra C.F. (2017) Whole genome transcriptomics reveals global effects including up-regulation of Francisella pathogenicity island gene expression during active stringent response in the highly virulent Francisella tularensis subsp. tularensis SCHU S4. Microbiology, 163 (11), 1664-1679. (doi:10.1099/mic.0.000550).

Record type: Article

Abstract

During conditions of nutrient limitation bacteria undergo a series of global gene expression changes to survive conditions of amino acid and fatty acid starvation. Rapid reallocation of cellular resources is brought about by gene expression changes coordinated by the signalling nucleotides’ guanosine tetraphosphate or pentaphosphate, collectively termed (p)ppGpp and is known as the stringent response. The stringent response has been implicated in bacterial virulence, with elevated (p)ppGpp levels being associated with increased virulence gene expression. This has been observed in the highly pathogenic Francisella tularensis sub spp. tularensis SCHU S4, the causative agent of tularaemia. Here, we aimed to artificially induce the stringent response by culturing F. tularensis in the presence of the amino acid analogue L-serine hydroxamate. Serine
hydroxamate competitively inhibits tRNAser aminoacylation, causing an accumulation of uncharged tRNA. The uncharged tRNA enters the A site on the translating bacterial ribosome and causes ribosome stalling, in turn stimulating the production of (p)ppGpp and activation of the stringent response. Using the essential virulence gene iglC, which is encoded on the Francisella pathogenicity island (FPI) as a marker of active stringent response, we optimized the culture conditions required for the investigation of virulence gene expression under conditions of nutrient limitation. We subsequently used whole genome RNA-seq to show how F. tularensis alters gene expression on a global scale during active stringent response. Key findings included up-regulation of genes involved in virulence, stress responses and metabolism, and down-regulation of genes involved in metabolite transport and cell division. F. tularensis is a highly virulent intracellular pathogen capable of causing debilitating or fatal disease at extremely low infectious doses. However, virulence mechanisms are still poorly
understood. The stringent response is widely recognized as a diverse and complex bacterial stress response implicated in virulence. This work describes the global gene expression profile of F. tularensis SCHU S4 under active stringent response for the first time. Herein we provide evidence for an association of active stringent response with FPI virulence gene expression. Our results further the understanding of the molecular basis of virulence and regulation thereof in F. tularensis. These results also support research into genes involved in (p)ppGpp production and polyphosphate biosynthesis and their applicability as targets for novel antimicrobials.

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Accepted/In Press date: 1 October 2017
e-pub ahead of print date: 16 October 2017
Published date: 16 October 2017
Keywords: francisella tularensis, pathogenicity islands, stringent response, transcriptional regulation, gene regulation

Identifiers

Local EPrints ID: 416022
URI: http://eprints.soton.ac.uk/id/eprint/416022
ISSN: 1350-0872
PURE UUID: 68e3588a-b21d-4bff-a4c2-2f483afd5a86
ORCID for Paul J. Skipp: ORCID iD orcid.org/0000-0002-2995-2959
ORCID for Peter L. Roach: ORCID iD orcid.org/0000-0001-9880-2877

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Date deposited: 30 Nov 2017 17:30
Last modified: 22 Nov 2021 02:36

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Contributors

Author: Amber L. Murch
Author: Paul J. Skipp ORCID iD
Author: Peter L. Roach ORCID iD
Author: Petra C.F. Oyston

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