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LadS is a calcium-responsive kinase that induces acute-to-chronic virulence switch in Pseudomonas aeruginosa

Abstract

Virulence of pathogenic bacteria is a tightly controlled process to facilitate invasion and survival in host tissues. Although pathways controlling virulence have been defined in detail, signals modulating these processes are poorly understood. The opportunistic pathogen Pseudomonas aeruginosa causes acute and chronic infections in humans. Disease progression is typically associated with a loss of acute virulence and the emergence of biofilms and chronic behaviour. The acute-to-chronic switch is governed by the global Gac/Rsm pathway. Using a newly developed acute–chronic dual reporter system we show that calcium stimulates the Gac/Rsm pathway via the Gac-associated hybrid histidine kinase LadS. We show that calcium binds to the periplasmic DISMED2 sensor domain of LadS to activate its kinase activity. Activation of the Gac/Rsm pathway by calcium leads to a switch to the chronic program and confers drug tolerance by reducing P. aeruginosa growth rate. Clinical isolates from cystic fibrosis airways retain their calcium response during chronic infections. Our data imply that calcium sensing evolved as an adaptation to the opportunistic lifestyle of P. aeruginosa and that calcium serves as a host signal to balance acute-to-chronic behaviour during infections. Establishing calcium signalling in host–pathogen interaction adds to growing evidence indicating key roles for calcium in bacterial signalling.

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Figure 1: Calcium stimulates the Gac/Rsm cascade.
Figure 2: LadS is required for calcium-mediated stimulation of the Gac/Rsm cascade.
Figure 3: LadS senses calcium through the periplasmic DISMED2 domain.
Figure 4: The calcium-induced LadS regulon overlaps with known Gac/RsmA targets.
Figure 5: Activation of the Gac/Rsm cascade leads to reduced growth and increased drug tolerance.
Figure 6: Calcium sensing is retained in clinical isolates from chronically infected CF patients.

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Acknowledgements

The authors thank P. Manfredi for help with sequence analysis, B. Laventie for help with manuscript editing, J. Malone for bacterial strains and I. Attrée for the mini-CTX-PilV-GFP plasmid. This work was supported by a Werner Siemens PhD Fellowship to U.N.B. and by Swiss National Science Foundation grant 310030B_147090 to U.J.

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U.N.B. and U.J. designed the study, performed the analyses and wrote the paper. U.N.B. and T.J. collected and processed data.

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Correspondence to Urs Jenal.

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Supplementary Figures 1–11, Supplementary Table 1, legends for Supplementary Videos 1 and 2, Supplementary References (PDF 14697 kb)

Supplementary Video 1

Shift from high calcium to low calcium conditions (AVI 7688 kb)

Supplementary Video 2

Shift from low calcium to high calcium conditions (AVI 6779 kb)

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Broder, U., Jaeger, T. & Jenal, U. LadS is a calcium-responsive kinase that induces acute-to-chronic virulence switch in Pseudomonas aeruginosa. Nat Microbiol 2, 16184 (2017). https://doi.org/10.1038/nmicrobiol.2016.184

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