Basal Levels of (p)ppGpp in <named-content content-type="genus-species">Enterococcus faecalis</named-content>: the Magic beyond the Stringent Response

ABSTRACT The stringent response (SR), mediated by the alarmone (p)ppGpp, is a conserved bacterial adaptation system controlling broad metabolic alterations necessary for survival under adverse conditions. In Enterococcus faecalis, production of (p)ppGpp is controlled by the bifunctional protein RSH...

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Autores principales:	Anthony O. Gaca, Jessica K. Kajfasz, James H. Miller, Kuanqing Liu, Jue D. Wang, Jacqueline Abranches, José A. Lemos
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2013
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/1da50432dd994ef4b83f531c5a323739
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spelling	oai:doaj.org-article:1da50432dd994ef4b83f531c5a3237392021-11-15T15:42:47ZBasal Levels of (p)ppGpp in <named-content content-type="genus-species">Enterococcus faecalis</named-content>: the Magic beyond the Stringent Response10.1128/mBio.00646-132150-7511https://doaj.org/article/1da50432dd994ef4b83f531c5a3237392013-11-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00646-13https://doaj.org/toc/2150-7511ABSTRACT The stringent response (SR), mediated by the alarmone (p)ppGpp, is a conserved bacterial adaptation system controlling broad metabolic alterations necessary for survival under adverse conditions. In Enterococcus faecalis, production of (p)ppGpp is controlled by the bifunctional protein RSH (for “Rel SpoT homologue”; also known as RelA) and by the monofunctional synthetase RelQ. Previous characterization of E. faecalis strains lacking rsh, relQ, or both revealed that RSH is responsible for activation of the SR and that alterations in (p)ppGpp production negatively impact bacterial stress survival and virulence. Despite its well-characterized role as the effector of the SR, the significance of (p)ppGpp during balanced growth remains poorly understood. Microarrays of E. faecalis strains producing different basal amounts of (p)ppGpp identified several genes and pathways regulated by modest changes in (p)ppGpp. Notably, expression of numerous genes involved in energy generation were induced in the ∆rsh ∆relQ [(p)ppGpp0] strain, suggesting that a lack of basal (p)ppGpp places the cell in a “transcriptionally relaxed” state. Alterations in the fermentation profile and increased production of H2O2 in the (p)ppGpp0 strain substantiate the observed transcriptional changes. We confirm that, similar to what is seen in Bacillus subtilis, (p)ppGpp directly inhibits the activity of enzymes involved in GTP biosynthesis, and complete loss of (p)ppGpp leads to dysregulation of GTP homeostasis. Finally, we show that the association of (p)ppGpp with antibiotic survival does not relate to the SR but rather relates to basal (p)ppGpp pools. Collectively, this study highlights the critical but still underappreciated role of basal (p)ppGpp pools under balanced growth conditions. IMPORTANCE Drug-resistant bacterial infections continue to pose a significant public health threat by limiting therapeutic options available to care providers. The stringent response (SR), mediated by the accumulation of two modified guanine nucleotides collectively known as (p)ppGpp, is a highly conserved stress response that broadly remodels bacterial physiology to a survival state. Given the strong correlation of the SR with the ability of bacteria to survive antibiotic treatment and the direct association of (p)ppGpp production with bacterial infectivity, understanding how bacteria produce and utilize (p)ppGpp may reveal potential targets for the development of new antimicrobial therapies. Using the multidrug-resistant pathogen Enterococcus faecalis as a model, we show that small alterations to (p)ppGpp levels, well below concentrations needed to trigger the SR, severely affected bacterial metabolism and antibiotic survival. Our findings highlight the often-underappreciated contribution of basal (p)ppGpp levels to metabolic balance and stress tolerance in bacteria.Anthony O. GacaJessica K. KajfaszJames H. MillerKuanqing LiuJue D. WangJacqueline AbranchesJosé A. LemosAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 4, Iss 5 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Anthony O. Gaca Jessica K. Kajfasz James H. Miller Kuanqing Liu Jue D. Wang Jacqueline Abranches José A. Lemos Basal Levels of (p)ppGpp in <named-content content-type="genus-species">Enterococcus faecalis</named-content>: the Magic beyond the Stringent Response
description	ABSTRACT The stringent response (SR), mediated by the alarmone (p)ppGpp, is a conserved bacterial adaptation system controlling broad metabolic alterations necessary for survival under adverse conditions. In Enterococcus faecalis, production of (p)ppGpp is controlled by the bifunctional protein RSH (for “Rel SpoT homologue”; also known as RelA) and by the monofunctional synthetase RelQ. Previous characterization of E. faecalis strains lacking rsh, relQ, or both revealed that RSH is responsible for activation of the SR and that alterations in (p)ppGpp production negatively impact bacterial stress survival and virulence. Despite its well-characterized role as the effector of the SR, the significance of (p)ppGpp during balanced growth remains poorly understood. Microarrays of E. faecalis strains producing different basal amounts of (p)ppGpp identified several genes and pathways regulated by modest changes in (p)ppGpp. Notably, expression of numerous genes involved in energy generation were induced in the ∆rsh ∆relQ [(p)ppGpp0] strain, suggesting that a lack of basal (p)ppGpp places the cell in a “transcriptionally relaxed” state. Alterations in the fermentation profile and increased production of H2O2 in the (p)ppGpp0 strain substantiate the observed transcriptional changes. We confirm that, similar to what is seen in Bacillus subtilis, (p)ppGpp directly inhibits the activity of enzymes involved in GTP biosynthesis, and complete loss of (p)ppGpp leads to dysregulation of GTP homeostasis. Finally, we show that the association of (p)ppGpp with antibiotic survival does not relate to the SR but rather relates to basal (p)ppGpp pools. Collectively, this study highlights the critical but still underappreciated role of basal (p)ppGpp pools under balanced growth conditions. IMPORTANCE Drug-resistant bacterial infections continue to pose a significant public health threat by limiting therapeutic options available to care providers. The stringent response (SR), mediated by the accumulation of two modified guanine nucleotides collectively known as (p)ppGpp, is a highly conserved stress response that broadly remodels bacterial physiology to a survival state. Given the strong correlation of the SR with the ability of bacteria to survive antibiotic treatment and the direct association of (p)ppGpp production with bacterial infectivity, understanding how bacteria produce and utilize (p)ppGpp may reveal potential targets for the development of new antimicrobial therapies. Using the multidrug-resistant pathogen Enterococcus faecalis as a model, we show that small alterations to (p)ppGpp levels, well below concentrations needed to trigger the SR, severely affected bacterial metabolism and antibiotic survival. Our findings highlight the often-underappreciated contribution of basal (p)ppGpp levels to metabolic balance and stress tolerance in bacteria.
format	article
author	Anthony O. Gaca Jessica K. Kajfasz James H. Miller Kuanqing Liu Jue D. Wang Jacqueline Abranches José A. Lemos
author_facet	Anthony O. Gaca Jessica K. Kajfasz James H. Miller Kuanqing Liu Jue D. Wang Jacqueline Abranches José A. Lemos
author_sort	Anthony O. Gaca
title	Basal Levels of (p)ppGpp in <named-content content-type="genus-species">Enterococcus faecalis</named-content>: the Magic beyond the Stringent Response
title_short	Basal Levels of (p)ppGpp in <named-content content-type="genus-species">Enterococcus faecalis</named-content>: the Magic beyond the Stringent Response
title_full	Basal Levels of (p)ppGpp in <named-content content-type="genus-species">Enterococcus faecalis</named-content>: the Magic beyond the Stringent Response
title_fullStr	Basal Levels of (p)ppGpp in <named-content content-type="genus-species">Enterococcus faecalis</named-content>: the Magic beyond the Stringent Response
title_full_unstemmed	Basal Levels of (p)ppGpp in <named-content content-type="genus-species">Enterococcus faecalis</named-content>: the Magic beyond the Stringent Response
title_sort	basal levels of (p)ppgpp in <named-content content-type="genus-species">enterococcus faecalis</named-content>: the magic beyond the stringent response
publisher	American Society for Microbiology
publishDate	2013
url	https://doaj.org/article/1da50432dd994ef4b83f531c5a323739
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Basal Levels of (p)ppGpp in <named-content content-type="genus-species">Enterococcus faecalis</named-content>: the Magic beyond the Stringent Response

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