The Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content>

ABSTRACT The bacterial stringent stress response, mediated by the signaling molecule guanosine tetraphosphate, ppGpp, has recently gained attention as being important during normal cellular growth and as a potential new therapeutic target, which warrants detailed mechanistic understanding. Here, we...

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Autores principales:	Daniel Pletzer, Travis M. Blimkie, Heidi Wolfmeier, Yicong Li, Arjun Baghela, Amy H. Y. Lee, Reza Falsafi, Robert E. W. Hancock
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	ppGpp relA spoT aprA global transcriptional regulator global regulatory networks Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/94197f6636d04bce954a708fe7e6bc0a
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spelling	oai:doaj.org-article:94197f6636d04bce954a708fe7e6bc0a2021-12-02T19:47:38ZThe Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content>10.1128/mSystems.00495-202379-5077https://doaj.org/article/94197f6636d04bce954a708fe7e6bc0a2020-08-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSystems.00495-20https://doaj.org/toc/2379-5077ABSTRACT The bacterial stringent stress response, mediated by the signaling molecule guanosine tetraphosphate, ppGpp, has recently gained attention as being important during normal cellular growth and as a potential new therapeutic target, which warrants detailed mechanistic understanding. Here, we used intracellular protein tracking in Pseudomonas aeruginosa PAO1, which indicated that RelA was bound to the ribosome, while SpoT localized at the cell poles. Transcriptome sequencing (RNA-Seq) was used to investigate the transcriptome of a ppGpp-deficient strain under nonstressful, nutrient-rich broth conditions where the mutant grew at the same rate as the parent strain. In the exponential growth phase, the lack of ppGpp led to >1,600 transcriptional changes (fold change cutoff of ±1.5), providing further novel insights into the normal physiological role of ppGpp. The stringent response was linked to gene expression of various proteases and secretion systems, including aprA, PA0277, impA, and clpP2. The previously observed reduction in cytotoxicity toward red blood cells in a stringent response mutant appeared to be due to aprA. Investigation of an aprA mutant in a murine skin infection model showed increased survival rates of mice infected with the aprA mutant, consistent with previous observations that stringent response mutants have reduced virulence. In addition, the overexpression of relA, but not induction of ppGpp with serine hydroxamate, dysregulated global transcriptional regulators as well as >30% of the regulatory networks controlled by AlgR, OxyR, LasR, and AmrZ. Together, these data expand our knowledge about ppGpp and its regulatory network and role in environmental adaptation. It also confirms its important role throughout the normal growth cycle of bacteria. IMPORTANCE Microorganisms need to adapt rapidly to survive harsh environmental changes. Here, we showed the broad influence of the highly studied bacterial stringent stress response under nonstressful conditions that indicate its general physiological importance and might reflect the readiness of bacteria to respond to and activate acute stress responses. Using RNA-Seq to investigate the transcriptional network of Pseudomonas aeruginosa cells revealed that >30% of all genes changed expression in a stringent response mutant under optimal growth conditions. This included genes regulated by global transcriptional regulators and novel downstream effectors. Our results help to understand the importance of this stress regulator in bacterial lifestyle under relatively unstressed conditions. As such, it draws attention to the consequences of targeting this ubiquitous bacterial signaling molecule.Daniel PletzerTravis M. BlimkieHeidi WolfmeierYicong LiArjun BaghelaAmy H. Y. LeeReza FalsafiRobert E. W. HancockAmerican Society for MicrobiologyarticleppGpprelAspoTaprAglobal transcriptional regulatorglobal regulatory networksMicrobiologyQR1-502ENmSystems, Vol 5, Iss 4 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	ppGpp relA spoT aprA global transcriptional regulator global regulatory networks Microbiology QR1-502
spellingShingle	ppGpp relA spoT aprA global transcriptional regulator global regulatory networks Microbiology QR1-502 Daniel Pletzer Travis M. Blimkie Heidi Wolfmeier Yicong Li Arjun Baghela Amy H. Y. Lee Reza Falsafi Robert E. W. Hancock The Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content>
description	ABSTRACT The bacterial stringent stress response, mediated by the signaling molecule guanosine tetraphosphate, ppGpp, has recently gained attention as being important during normal cellular growth and as a potential new therapeutic target, which warrants detailed mechanistic understanding. Here, we used intracellular protein tracking in Pseudomonas aeruginosa PAO1, which indicated that RelA was bound to the ribosome, while SpoT localized at the cell poles. Transcriptome sequencing (RNA-Seq) was used to investigate the transcriptome of a ppGpp-deficient strain under nonstressful, nutrient-rich broth conditions where the mutant grew at the same rate as the parent strain. In the exponential growth phase, the lack of ppGpp led to >1,600 transcriptional changes (fold change cutoff of ±1.5), providing further novel insights into the normal physiological role of ppGpp. The stringent response was linked to gene expression of various proteases and secretion systems, including aprA, PA0277, impA, and clpP2. The previously observed reduction in cytotoxicity toward red blood cells in a stringent response mutant appeared to be due to aprA. Investigation of an aprA mutant in a murine skin infection model showed increased survival rates of mice infected with the aprA mutant, consistent with previous observations that stringent response mutants have reduced virulence. In addition, the overexpression of relA, but not induction of ppGpp with serine hydroxamate, dysregulated global transcriptional regulators as well as >30% of the regulatory networks controlled by AlgR, OxyR, LasR, and AmrZ. Together, these data expand our knowledge about ppGpp and its regulatory network and role in environmental adaptation. It also confirms its important role throughout the normal growth cycle of bacteria. IMPORTANCE Microorganisms need to adapt rapidly to survive harsh environmental changes. Here, we showed the broad influence of the highly studied bacterial stringent stress response under nonstressful conditions that indicate its general physiological importance and might reflect the readiness of bacteria to respond to and activate acute stress responses. Using RNA-Seq to investigate the transcriptional network of Pseudomonas aeruginosa cells revealed that >30% of all genes changed expression in a stringent response mutant under optimal growth conditions. This included genes regulated by global transcriptional regulators and novel downstream effectors. Our results help to understand the importance of this stress regulator in bacterial lifestyle under relatively unstressed conditions. As such, it draws attention to the consequences of targeting this ubiquitous bacterial signaling molecule.
format	article
author	Daniel Pletzer Travis M. Blimkie Heidi Wolfmeier Yicong Li Arjun Baghela Amy H. Y. Lee Reza Falsafi Robert E. W. Hancock
author_facet	Daniel Pletzer Travis M. Blimkie Heidi Wolfmeier Yicong Li Arjun Baghela Amy H. Y. Lee Reza Falsafi Robert E. W. Hancock
author_sort	Daniel Pletzer
title	The Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content>
title_short	The Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content>
title_full	The Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content>
title_fullStr	The Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content>
title_full_unstemmed	The Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content>
title_sort	stringent stress response controls proteases and global regulators under optimal growth conditions in <named-content content-type="genus-species">pseudomonas aeruginosa</named-content>
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/94197f6636d04bce954a708fe7e6bc0a
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The Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content>

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