Identification of Genes in the σ<sup>22</sup> Regulon of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> Required for Cell Envelope Homeostasis in Either the Planktonic or the Sessile Mode of Growth

ABSTRACT The Pseudomonas aeruginosa extracytoplasmic functioning (ECF) sigma factor σ22 is encoded by algT/algU and is inhibited by anti-sigma factor MucA. σ22 was originally discovered for its essential role in the expression of the exopolysaccharide alginate by mucoid strains associated with chron...

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Autores principales:	Lynn F. Wood, Dennis E. Ohman
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2012
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/a756b0bb5ae74765a7e29c4ce3aa690c
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spelling	oai:doaj.org-article:a756b0bb5ae74765a7e29c4ce3aa690c2021-11-15T15:39:01ZIdentification of Genes in the σ<sup>22</sup> Regulon of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> Required for Cell Envelope Homeostasis in Either the Planktonic or the Sessile Mode of Growth10.1128/mBio.00094-122150-7511https://doaj.org/article/a756b0bb5ae74765a7e29c4ce3aa690c2012-07-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00094-12https://doaj.org/toc/2150-7511ABSTRACT The Pseudomonas aeruginosa extracytoplasmic functioning (ECF) sigma factor σ22 is encoded by algT/algU and is inhibited by anti-sigma factor MucA. σ22 was originally discovered for its essential role in the expression of the exopolysaccharide alginate by mucoid strains associated with chronic pulmonary infection. However, σ22 is now known to also have a large regulon associated with the response to cell wall stress. Our recent transcriptome analysis identified 293 open reading frames (ORFs) in the σ22 stress stimulon that include genes for outer envelope biogenesis and remodeling, although most of the genes have undefined functions. To better understand the σ22-dependent stress response, mutants affected in 27 genes of the σ22 stimulon were examined and expression was studied with lacZ fusions. Mutants constructed in the 27 genes showed no major change in response to cell wall-acting antibiotics or growth at elevated temperatures nor in alginate production. The mutants were examined for their effects on the expression of the σ22-dependent promoter of the alginate biosynthetic operon (PalgD) as a measure of σ22 derepression from MucA. By testing PalgD expression under both planktonic and sessile growth conditions, 11 genes were found to play a role in the stress response that activates σ22. Some mutations caused an increase or a decrease in the response to cell wall stress. Interestingly, mutations in 7 of the 11 genes caused constitutive PalgD expression under nonstressed conditions and thus showed that these genes are involved in maintaining envelope homeostasis. Mutations in PA0062 and PA1324 showed constitutive PalgD expression during both the planktonic and the sessile modes of growth. However, the PA5178 mutation caused constitutive PalgD expression only during planktonic growth. In contrast, mutations in PA2717, PA0567, PA3040, and PA0920 caused constitutive PalgD expression only in the sessile/biofilm mode of growth. This provides evidence that the σ22 stimulon for cell envelope homeostasis overlaps with biofilm control mechanisms. IMPORTANCE During chronic lung infections, such as in cystic fibrosis patients, Pseudomonas aeruginosa produces the exopolysaccharide alginate and forms biofilms that shield the organisms from the immune response and increase resistance to antibiotics. Activation of alginate genes is under the control of an extracytoplasmic stress response system that releases an alternative sigma factor (σ22) in response to cell wall stress and then activates expression of a large regulon. In this study, a mutant analysis of 27 members of the regulon showed that 11 play a role in envelope homeostasis and affect the stress response system itself. Interestingly, some genes demonstrate effects only in either the planktonic (free-swimming) or the sessile (biofilm) mode of growth, which leads to persistence and antibiotic tolerance. The studies presented here provide an important initial step in dissecting the mechanisms that regulate a critical signal transduction pathway that impacts P. aeruginosa pathogenesis.Lynn F. WoodDennis E. OhmanAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 3, Iss 3 (2012)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Lynn F. Wood Dennis E. Ohman Identification of Genes in the σ<sup>22</sup> Regulon of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> Required for Cell Envelope Homeostasis in Either the Planktonic or the Sessile Mode of Growth
description	ABSTRACT The Pseudomonas aeruginosa extracytoplasmic functioning (ECF) sigma factor σ22 is encoded by algT/algU and is inhibited by anti-sigma factor MucA. σ22 was originally discovered for its essential role in the expression of the exopolysaccharide alginate by mucoid strains associated with chronic pulmonary infection. However, σ22 is now known to also have a large regulon associated with the response to cell wall stress. Our recent transcriptome analysis identified 293 open reading frames (ORFs) in the σ22 stress stimulon that include genes for outer envelope biogenesis and remodeling, although most of the genes have undefined functions. To better understand the σ22-dependent stress response, mutants affected in 27 genes of the σ22 stimulon were examined and expression was studied with lacZ fusions. Mutants constructed in the 27 genes showed no major change in response to cell wall-acting antibiotics or growth at elevated temperatures nor in alginate production. The mutants were examined for their effects on the expression of the σ22-dependent promoter of the alginate biosynthetic operon (PalgD) as a measure of σ22 derepression from MucA. By testing PalgD expression under both planktonic and sessile growth conditions, 11 genes were found to play a role in the stress response that activates σ22. Some mutations caused an increase or a decrease in the response to cell wall stress. Interestingly, mutations in 7 of the 11 genes caused constitutive PalgD expression under nonstressed conditions and thus showed that these genes are involved in maintaining envelope homeostasis. Mutations in PA0062 and PA1324 showed constitutive PalgD expression during both the planktonic and the sessile modes of growth. However, the PA5178 mutation caused constitutive PalgD expression only during planktonic growth. In contrast, mutations in PA2717, PA0567, PA3040, and PA0920 caused constitutive PalgD expression only in the sessile/biofilm mode of growth. This provides evidence that the σ22 stimulon for cell envelope homeostasis overlaps with biofilm control mechanisms. IMPORTANCE During chronic lung infections, such as in cystic fibrosis patients, Pseudomonas aeruginosa produces the exopolysaccharide alginate and forms biofilms that shield the organisms from the immune response and increase resistance to antibiotics. Activation of alginate genes is under the control of an extracytoplasmic stress response system that releases an alternative sigma factor (σ22) in response to cell wall stress and then activates expression of a large regulon. In this study, a mutant analysis of 27 members of the regulon showed that 11 play a role in envelope homeostasis and affect the stress response system itself. Interestingly, some genes demonstrate effects only in either the planktonic (free-swimming) or the sessile (biofilm) mode of growth, which leads to persistence and antibiotic tolerance. The studies presented here provide an important initial step in dissecting the mechanisms that regulate a critical signal transduction pathway that impacts P. aeruginosa pathogenesis.
format	article
author	Lynn F. Wood Dennis E. Ohman
author_facet	Lynn F. Wood Dennis E. Ohman
author_sort	Lynn F. Wood
title	Identification of Genes in the σ<sup>22</sup> Regulon of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> Required for Cell Envelope Homeostasis in Either the Planktonic or the Sessile Mode of Growth
title_short	Identification of Genes in the σ<sup>22</sup> Regulon of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> Required for Cell Envelope Homeostasis in Either the Planktonic or the Sessile Mode of Growth
title_full	Identification of Genes in the σ<sup>22</sup> Regulon of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> Required for Cell Envelope Homeostasis in Either the Planktonic or the Sessile Mode of Growth
title_fullStr	Identification of Genes in the σ<sup>22</sup> Regulon of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> Required for Cell Envelope Homeostasis in Either the Planktonic or the Sessile Mode of Growth
title_full_unstemmed	Identification of Genes in the σ<sup>22</sup> Regulon of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> Required for Cell Envelope Homeostasis in Either the Planktonic or the Sessile Mode of Growth
title_sort	identification of genes in the σ<sup>22</sup> regulon of <named-content content-type="genus-species">pseudomonas aeruginosa</named-content> required for cell envelope homeostasis in either the planktonic or the sessile mode of growth
publisher	American Society for Microbiology
publishDate	2012
url	https://doaj.org/article/a756b0bb5ae74765a7e29c4ce3aa690c
work_keys_str_mv	AT lynnfwood identificationofgenesinthessup22supregulonofnamedcontentcontenttypegenusspeciespseudomonasaeruginosanamedcontentrequiredforcellenvelopehomeostasisineithertheplanktonicorthesessilemodeofgrowth AT denniseohman identificationofgenesinthessup22supregulonofnamedcontentcontenttypegenusspeciespseudomonasaeruginosanamedcontentrequiredforcellenvelopehomeostasisineithertheplanktonicorthesessilemodeofgrowth
_version_	1718427842992144384

Identification of Genes in the σ<sup>22</sup> Regulon of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> Required for Cell Envelope Homeostasis in Either the Planktonic or the Sessile Mode of Growth

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