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Published February 25, 2020 | Supplemental Material + Published
Journal Article Open

Heat-shock proteases promote survival of Pseudomonas aeruginosa during growth arrest

Abstract

When nutrients in their environment are exhausted, bacterial cells become arrested for growth. During these periods, a primary challenge is maintaining cellular integrity with a reduced capacity for renewal or repair. Here, we show that the heat-shock protease FtsH is generally required for growth arrest survival of Pseudomonas aeruginosa, and that this requirement is independent of a role in regulating lipopolysaccharide synthesis, as has been suggested for Escherichia coli. We find that ftsH interacts with diverse genes during growth and overlaps functionally with the other heat-shock protease-encoding genes hslVU, lon, and clpXP to promote survival during growth arrest. Systematic deletion of the heat-shock protease-encoding genes reveals that the proteases function hierarchically during growth arrest, with FtsH and ClpXP having primary, nonredundant roles, and HslVU and Lon deploying a secondary response to aging stress. This hierarchy is partially conserved during growth at high temperature and alkaline pH, suggesting that heat, pH, and growth arrest effectively impose a similar type of proteostatic stress at the cellular level. In support of this inference, heat and growth arrest act synergistically to kill cells, and protein aggregation appears to occur more rapidly in protease mutants during growth arrest and correlates with the onset of cell death. Our findings suggest that protein aggregation is a major driver of aging and cell death during growth arrest, and that coordinated activity of the heat-shock response is required to ensure ongoing protein quality control in the absence of growth.

Additional Information

© 2020 The Author(s). Published under the PNAS license. Edited by Caroline S. Harwood, University of Washington, Seattle, WA, and approved January 8, 2020 (received for review July 14, 2019) PNAS first published February 6, 2020. We thank members of the D.K.N. laboratory for thoughtful discussions and critical feedback on the manuscript, and Lisa Racki (The Scripps Research Institute) for the gift of pLREX97. This manuscript derives from a chapter in D.W.B.'s doctoral thesis from the California Institute of Technology. This work was supported by the Millard and Muriel Jacobs Genetics and Genomics Laboratory at the California Institute of Technology and by the NIH (1R01AI127850-01A1 and 1R21AI146987-01). Author contributions: D.W.B., D.A.-A., M.A.S., J.A.C., and D.K.N. designed research; D.W.B., D.A.-A., M.A.S., and J.A.C. performed research; D.W.B., D.A.-A., M.A.S., J.A.C., and D.K.N. analyzed data; and D.W.B. and D.K.N. wrote the paper. The authors declare no competing interest. This article is a PNAS Direct Submission. This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1912082117/-/DCSupplemental.

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Published - 4358.full.pdf

Supplemental Material - pnas.1912082117.sapp.pdf

Supplemental Material - pnas.1912082117.sd01.xlsx

Supplemental Material - pnas.1912082117.sd02.xlsx

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Additional details

Created:
August 19, 2023
Modified:
December 22, 2023