The repB gene required for production of extracellular enzymes and fluorescent siderophores in Pseudomonas viridiflava is an analog of the gacA gene of Pseudomonas syringae

1996 ◽  
Vol 42 (2) ◽  
pp. 177-182 ◽  
Author(s):  
C.-H. Liao ◽  
D. E. McCallus ◽  
J. M. Wells ◽  
S.-S. Tzean ◽  
G.-Y. Kang
Keyword(s):  
Pseudomonas Syringae ◽  
Extracellular Enzymes ◽  
Response Regulator ◽  
Regulatory System ◽  
Pectate Lyase ◽  
Soft Rot ◽  
Reading Frame ◽  
Repa Gene ◽  
Gene Regulatory System ◽  
Pseudomonas Viridiflava

Two genes, designated repA and repB, are involved in the regulation of the synthesis of extracellular pectate lyase, protease, and alginate in Pseudomonas viridiflava. The repA gene has been shown to encode a protein highly homologous to several bacterial sensors in the two-component regulator family including the LemA of Pseudomonas syringae. In this study, the repB locus, initially identified in a 6.3-kb EcoRI genomic fragment of P. viridiflava, was further characterized. Results obtained from restriction mapping, deletion subclonings, and mini-Mu-LacZ fusions indicated that the repB gene was contained within a 0.8-kb HindIII–PstI region. Sequence analysis of this repB region revealed the presence of an open reading frame, which was predicted to encode a protein similar or identical to the gacA response regulator found in P. syringae and Pseudomonas fluorescens. The repB gene of P. viridiflava also regulated the production of fluorescent siderophores, in addition to the aforementioned extracellular enzymes and alginate. The repB or gacA homologs were detected in the genomes of nine other strains of P. viridiflava, P. fluorescens, and P. syringae included in the study. The data presented here and earlier indicate that the repA/repB gene regulatory system of P. viridiflava is analogous to the lemA/gacA system of P. syringae and P. fluorescens.Key words: response regulator, signal transduction, soft-rot bacteria, enzyme production.

scholarly journals RNA chaperones Hfq and ProQ play a key role in the virulence of the plant pathogenic bacterium Dickeya dadantii

2021 ◽  
Author(s):  
Simon Leonard ◽  
Camille Villard ◽  
William Nasser ◽  
Sylvie Reverchon ◽  
Florence Hommais
Keyword(s):  
Extracellular Enzymes ◽  
Pectate Lyase ◽  
Soft Rot ◽  
Pathogenic Bacterium ◽  
Growth Defect ◽  
Dickeya Dadantii ◽  
Genes Encoding ◽  
Lyase Activity ◽  
Rna Chaperones ◽  
Post Transcriptional Regulation

Dickeya dadantii is an important pathogenic bacterium that infects a number of crops including potato and chicory. While extensive works have been carried out on the control of the transcription of its genes encoding the main virulence functions, little information is available on the post-transcriptional regulation of these functions. We investigated the involvement of the RNA chaperones Hfq and ProQ in the production of the main D. dadantii virulence functions. Phenotypic assays on the hfq and proQ mutants showed that inactivation of hfq resulted in a growth defect, a modified capacity for biofilm formation and strongly reduced motility, and in the production of degradative extracellular enzymes (proteases, cellulase and pectate lyases). Accordingly, the hfq mutant failed to cause soft rot on chicory leaves. The proQ mutant had reduced resistance to osmotic stress, reduced extracellular pectate lyase activity compared to the wild-type strain, and reduced virulence on chicory leaves. Most of the phenotypes of the hfq and proQ mutants were related to the low amounts of mRNA of the corresponding virulence factors. Complementation of the double mutant hfq-proQ by each individual protein and cross-complementation of each chaperone suggested that they might exert their effects via partially overlapping but different sets of targets. Overall, it clearly appeared that the two Hfq and ProQ RNA chaperones are important regulators of pathogenicity in D. dadantii. This underscores that virulence genes are regulated post transcriptionally by non-coding RNAs.

scholarly journals Transcriptional Organization of the czcHeavy-Metal Homeostasis Determinant from Alcaligenes eutrophus

1999 ◽  
Vol 181 (8) ◽  
pp. 2385-2393 ◽  
Author(s):  
Cornelia Große ◽  
Gregor Grass ◽  
Andreas Anton ◽  
Sylvia Franke ◽  
Alexander Navarrete Santos ◽  
...  
Keyword(s):  
Response Regulator ◽  
Regulatory System ◽  
Alcaligenes Eutrophus ◽  
Northern Blotting ◽  
Open Reading Frames ◽  
Mrna Synthesis ◽  
Reading Frame ◽  
Reverse Transcription Pcr ◽  
Reporter Strains ◽  
Reading Frames

ABSTRACT The Czc system of Alcaligenes eutrophus mediates resistance to cobalt, zinc, and cadmium through ion efflux catalyzed by the CzcCB2A cation-proton antiporter. DNA sequencing of the region upstream of the czcNICBADRS determinant located on megaplasmid pMOL30 revealed the 5′ end of czcN and a gene for a MgtC-like protein which is transcribed in the orientation opposite that of czc. Additional open reading frames upstream of czc had no homologs in the current databases. Using oligonucleotide-probed Northern blotting experiments, a 500-nucleotide czcN message and a 400-nucleotideczcI message were found, and the presence of 6,200-nucleotide czcCBA message (D. Van der Lelie et al., Mol. Microbiol. 23:493–503, 1997) was confirmed. Induction ofczcN, czcI, czcCBA, andczcDRS followed a similar pattern: transcription was induced best by 300 μM zinc, less by 300 μM cobalt, and only slightly by 300 μM cadmium. Reverse transcription-PCR gave evidence for additional continuous transcription from czcN toczcC and from czcD to czcS, but not between czcA and czcD nor betweenczcS and a 131-amino-acid open reading frame followingczcS. The CzcR putative response regulator was purified and shown to bind in the 5′ region of czcN. A reporter strain carrying a czcNIC-lacZ-czcBADRS determinant on plasmid pMOL30 was constructed, as were ΔczcR and ΔczcS mutants of this strain and of AE128(pMOL30) wild type. Experiments on (i) growth of these strains in liquid culture containing 5 mM Zn2+, (ii) induction of the β-galactosidase in the reporter strains by zinc, cobalt, and cadmium, and (iii) cDNA analysis of czcCBA mRNA synthesis under inducing and noninducing conditions showed that the CzcRS two-component regulatory system is involved in Czc regulation.

scholarly journals A Pectate Lyase Homolog, xagP, in Xanthomonas axonopodis pv. glycines Is Associated with Hypersensitive Response Induction on Tobacco

2006 ◽  
Vol 96 (11) ◽  
pp. 1230-1236 ◽  
Author(s):  
S. Kaewnum ◽  
S. Prathuangwong ◽  
T. J. Burr
Keyword(s):  
Hypersensitive Response ◽  
Pectate Lyase ◽  
Soft Rot ◽  
Wild Type ◽  
Reading Frame ◽  
Xanthomonas Axonopodis ◽  
Transposon Insertion ◽  
Pectolytic Activity ◽  
Highly Correlated ◽  
Type Strains

Xanthomonas axonopodis pv. glycines is the causal agent of bacterial pustule disease of soybeans. A transposon insertional mutant (KU-P-M670) of X. axonopodis pv. glycines derived from wild-type strain KU-P-34017 lost the ability to induce the hypersensitive response (HR) on tobacco and pepper but retained its HR induction capacity on cucumber, sesame, and tomato. The mutation also resulted in loss of ability to cause a potato soft rot and express pectolytic activity at pH 6.5. An approximate 1.4-kb DNA fragment carrying the transposon insertion contained a single open reading frame that showed high homology with PSTRU-3, a pectate lyase gene in X. axonopodis pv. malvacearum. Complemented KU-P-M670 regained HR induction on tobacco and also pectolytic activity. Treatment of plants with inhibitors of eukaryotic metabolism blocked HR induction by wild-type strains and by complemented KU-P-M670. The presence of the pectate lyase homolog, which we designated xagP, in 26 X. axonopodis pv. glycines strains was highly correlated with their ability to induce an HR on tobacco. To our knowledge, this is the first study indicating a role for a functional pectate lyase in induction of a plant HR.

scholarly journals RNA Chaperones Hfq and ProQ Play a Key Role in the Virulence of the Plant Pathogenic Bacterium Dickeya dadantii

2021 ◽  
Vol 12 ◽  
Author(s):  
Simon Leonard ◽  
Camille Villard ◽  
William Nasser ◽  
Sylvie Reverchon ◽  
Florence Hommais
Keyword(s):  
Extracellular Enzymes ◽  
Pectate Lyase ◽  
Soft Rot ◽  
Pathogenic Bacterium ◽  
Growth Defect ◽  
Dickeya Dadantii ◽  
Genes Encoding ◽  
Lyase Activity ◽  
Rna Chaperones ◽  
Post Transcriptional Regulation

Dickeya dadantii is an important pathogenic bacterium that infects a number of crops including potato and chicory. While extensive works have been carried out on the control of the transcription of its genes encoding the main virulence functions, little information is available on the post-transcriptional regulation of these functions. We investigated the involvement of the RNA chaperones Hfq and ProQ in the production of the main D. dadantii virulence functions. Phenotypic assays on the hfq and proQ mutants showed that inactivation of hfq resulted in a growth defect, a modified capacity for biofilm formation and strongly reduced motility, and in the production of degradative extracellular enzymes (proteases, cellulase, and pectate lyases). Accordingly, the hfq mutant failed to cause soft rot on chicory leaves. The proQ mutant had reduced resistance to osmotic stress, reduced extracellular pectate lyase activity compared to the wild-type strain, and reduced virulence on chicory leaves. Most of the phenotypes of the hfq and proQ mutants were related to the low amounts of mRNA of the corresponding virulence factors. Complementation of the double mutant hfq-proQ by each individual protein and cross-complementation of each chaperone suggested that they might exert their effects via partially overlapping but different sets of targets. Overall, it clearly appeared that the two Hfq and ProQ RNA chaperones are important regulators of pathogenicity in D. dadantii. This underscores that virulence genes are regulated post-transcriptionally by non-coding RNAs.

scholarly journals Effects of the Two-Component System Comprising GacA and GacS of Erwinia carotovora subsp. carotovora on the Production of Global Regulatory rsmB RNA, Extracellular Enzymes, and HarpinEcc

2001 ◽  
Vol 14 (4) ◽  
pp. 516-526 ◽  
Author(s):  
Yaya Cui ◽  
Asita Chatterjee ◽  
Arun K. Chatterjee
Keyword(s):  
Pseudomonas Syringae ◽  
Extracellular Enzymes ◽  
Rna Binding ◽  
Blot Hybridization ◽  
Pectate Lyase ◽  
Erwinia Carotovora ◽  
Southern Blot Hybridization ◽  
Two Component System ◽  
Component System ◽  
Two Component

Posttranscriptional regulation mediated by the regulator of secondary metabolites (RSM) RsmA-rsmB pair is the most important factor in the expression of genes for extracellular enzymes and HarpinEcc in Erwinia carotovora subsp. carotovora. RsmA is a small RNA-binding protein, which acts by lowering the half-life of a mRNA species. rsmB specifies an untranslated regulatory RNA and neutralizes the RsmA effect. It has been speculated that GacA-GacS, members of a two-component system, may affect gene expression via RsmA. Because expA, a gacA homolog, and expS (or rpfA), a gacS homolog, have been identified in E. carotovora subsp. carotovora, we examined the effects of these gacA and gacS homologs on the expression of rsmA, rsmB, and an assortment of exoprotein genes. The gacA gene of E. carotovora subsp. carotovora strain 71 stimulated transcription of genes for several extracellular enzymes (pel-1, a pectate lyase gene; peh-1, a polygalacturonase gene; and celV, a cellulase gene), hrpNEcc (an E. carotovora subsp. carotovora gene specifying the elicitor of hypersensitive reaction), and rsmB in GacA+ and GacS+ E. carotovora subsp. carotovora strains. Similarly, the E. carotovora subsp. carotovora gacA gene stimulated csrB (rsmB) transcription in Escherichia coli. A GacS¯ mutant of E. carotovora subsp. carotovora strain AH2 and a GacA¯ mutant of E. carotovora subsp. carotovora strain Ecc71 compared with their parent strains produced very low levels of rsmB, pel-1, peh-1, celV, and hrpNEcc transcripts but produced similar levels of rsmA RNA and RsmA protein as well as transcripts of hyper-production of extracellular enzymes (Hex) hexA, kdgR (repressor of genes for uronate and pectate catabolism), rsmC, and rpoS (gene for Sigma-S, an alternate Sigma factor). The levels of rsmB, pel-1, peh-1, celV, and hrpNEcc transcripts as well as production of pectate lyase, polygalacturonase, cellulase, protease, and HarpinEcc proteins were stimulated in GacS¯ and GacA¯ mutants by GacS+ or GacA+ plasmids, respectively. The GacA effect on exoenzyme genes and hrpNEcc was abrogated in E. carotovora subsp. carotovora mutants deficient in RsmA and RsmC or RsmA, RsmC, and rsmB RNA. The expression of lacZ transcriptional fusions of rsmB of Erwinia amylovora and Erwinia herbicola pv. gypsophilae was markedly reduced in a GacA¯ and a GacS¯ mutant of Pseudomonas syringae pv. syringae. Southern blot hybridization revealed the presence of gacA and gacS homologs in all tested strains of soft-rotting Erwinia spp. and several nonsoft-rotting Erwinia species such as E. amylovora, E. rhapontici, E. herbicola, E. stewartii, and E. herbicola pv. gypsophilae. These findings establish that the GacA-GacS system controls transcription of rsmB of E. carotovora subsp. carotovora, E. amylovora, and E. herbicola pv. gypsophilae and support the hypothesis that the effects of this two-component system on extracellular protein production in E. carotovora subsp. carotovora is mediated, at least in part, via the levels of rsmB transcripts.

scholarly journals Molecular Analysis of the Locus Responsible for Production of Plantaricin S, a Two-Peptide Bacteriocin Produced byLactobacillus plantarum LPCO10

1998 ◽  
Vol 64 (5) ◽  
pp. 1871-1877 ◽  
Author(s):  
Sarah K. Stephens ◽  
Bel�n Floriano ◽  
Declan P. Cathcart ◽  
Susan A. Bayley ◽  
Valerie F. Witt ◽  
...  
Keyword(s):  
Northern Blot Analysis ◽  
Response Regulator ◽  
Regulatory System ◽  
Chromosomal Dna ◽  
Reading Frame ◽  
Strong Homology ◽  
Regulator Genes ◽  
The Moment ◽  
Potential Orfs

ABSTRACT A 4.5-kb region of chromosomal DNA carrying the locus responsible for the production of plantaricin S, a two-peptide bacteriocin produced by Lactobacillus plantarum LPCO10 (R. Jim�nez-Dı́az, J. L. Ruiz-Barba, D. P. Cathcart, H. Holo, I. F. Nes, K. H. Sletten, and P. J. Warner, Appl. Environ. Microbiol. 61:4459–4463, 1995), has been cloned, and the nucleotide sequence has been elucidated. Two genes, designatedplsA and plsB and encoding peptides α and β, respectively, of plantaricin S, plus an open reading frame (ORF), ORF2, were found to be organized in an operon. Northern blot analysis showed that these genes are cotranscribed, giving a ca. 0.7-kb mRNA, whose transcription start point was determined by primer extension. Nucleotide sequences of plsA and plsB revealed that both genes are translated as bacteriocin precursors which include N-terminal leader sequences of the double-glycine type. The role of ORF2 is unknown at the moment, although it might be expected to encode an immunity protein of the type described for other bacteriocin operons. In addition, several other potential ORFs have been found, including some which may be responsible for the regulation of bacteriocin production. Two of them, ORF8 and ORF14, show strong homology with histidine protein kinase and response regulator genes, respectively, which have been found to be involved in the regulation of the production of other bacteriocins from lactic acid bacteria. A third ORF, ORF5, shows homology with gene agrB fromStaphylococcus aureus, which is involved in the mechanism of regulation of the virulence phenotype in this species. Thus, anagr-like regulatory system for the production of plantaricin S is postulated.

scholarly journals Two-Component Transcriptional Regulation of N -Acyl-Homoserine Lactone Production inPseudomonas aureofaciens

1999 ◽  
Vol 65 (6) ◽  
pp. 2294-2299 ◽  
Author(s):  
S. T. Chancey ◽  
D. W. Wood ◽  
L. S. Pierson
Keyword(s):  
Pseudomonas Syringae ◽  
Genomic Library ◽  
Response Regulator ◽  
Regulatory System ◽  
Homoserine Lactone ◽  
Nucleotide Sequence Analysis ◽  
Acyl Homoserine Lactone ◽  
System L ◽  
Two Component ◽  
Phenazine Production

ABSTRACT Production of phenazine antibiotics by the biological control bacterium Pseudomonas aureofaciens 30-84 is regulated in part by the PhzI/PhzR N-acyl-homoserine lactone (AHL) response system (L. S. Pierson III, V. D. Keppenne, and D. W. Wood, J. Bacteriol. 176:3966–3974, 1994; D. W. Wood and L. S. Pierson III, Gene 168:49–53, 1996). Two mutants, 30-84W and 30-84.A2, were isolated and were found to be deficient in the production of phenazine, protease, hydrogen cyanide (HCN), and the AHL signal N-hexanoyl-homoserine lactone. These mutants were not complemented by phzI, phzR, or the phenazine biosynthetic genes (phzFABCD) (L. S. Pierson III, T. Gaffney, S. Lam, and F. Gong, FEMS Microbiol. Lett. 134:299–307, 1995). A 2.2-kb region of the 30-84 chromosome which fully restored production of all of these compounds in strain 30-84W was identified. Nucleotide sequence analysis of this region revealed a single open reading frame encoding a predicted 213-amino-acid protein which is very similar to the global response regulator GacA. Strain 30-84.A2 was not complemented by gacA or any cosmid from a genomic library of strain 30-84 but was complemented bygacS (formerly lemA) homologs fromPseudomonas fluorescens Pf-5 (N. Corbel and J. E. Loper, J. Bacteriol. 177:6230–6236, 1995) and Pseudomonas syringae pv. syringae B728a (E. M. Hrabek and D. K. Willis, J. Bacteriol. 174:3011–3020, 1992). Transcription ofphzR was not altered in either mutant; however,phzI transcription was eliminated in strains 30-84W and 30-84.A2. These results indicated that the GacS/GacA two-component signal transduction system of P. aureofaciens 30-84 controls the production of AHL required for phenazine production by mediating the transcription of phzI. Addition of exogenous AHL did not complement either mutant for phenazine production, indicating that the GacS/GacA global regulatory system controls phenazine production at multiple levels. Our results reveal for the first time a mechanism by which a two-component regulatory system and an AHL-mediated regulatory system interact.

scholarly journals Connection Between Chromosomal Location and Function of CtrA Phosphorelay Genes in Alphaproteobacteria

2021 ◽  
Vol 12 ◽  
Author(s):  
Jürgen Tomasch ◽  
Sonja Koppenhöfer ◽  
Andrew S. Lang
Keyword(s):  
Regulatory Networks ◽  
Caulobacter Crescentus ◽  
Response Regulator ◽  
Regulatory System ◽  
Physiological Processes ◽  
Gene Regulatory System ◽  
Bacterial Chromosomes ◽  
Differential Positioning ◽  
Gene Regulatory ◽  
And Function

Most bacterial chromosomes are circular, with replication starting at one origin (ori) and proceeding on both replichores toward the terminus (ter). Several studies have shown that the location of genes relative to ori and ter can have profound effects on regulatory networks and physiological processes. The CtrA phosphorelay is a gene regulatory system conserved in most alphaproteobacteria. It was first discovered in Caulobacter crescentus where it controls replication and division into a stalked and a motile cell in coordination with other factors. The locations of the ctrA gene and targets of this response regulator on the chromosome affect their expression through replication-induced DNA hemi-methylation and specific positioning along a CtrA activity gradient in the dividing cell, respectively. Here we asked to what extent the location of CtrA regulatory network genes might be conserved in the alphaproteobacteria. We determined the locations of the CtrA phosphorelay and associated genes in closed genomes with unambiguously identifiable ori from members of five alphaproteobacterial orders. The location of the phosphorelay genes was the least conserved in the Rhodospirillales followed by the Sphingomonadales. In the Rhizobiales a trend toward certain chromosomal positions could be observed. Compared to the other orders, the CtrA phosphorelay genes were conserved closer to ori in the Caulobacterales. In contrast, the genes were highly conserved closer to ter in the Rhodobacterales. Our data suggest selection pressure results in differential positioning of CtrA phosphorelay and associated genes in alphaproteobacteria, particularly in the orders Rhodobacterales, Caulobacterales and Rhizobiales that is worth deeper investigation.

Identification of gene loci controlling pectate lyase production and soft-rot pathogenicity in Pseudomonas marginalis

1997 ◽  
Vol 43 (5) ◽  
pp. 425-431 ◽  
Author(s):  
Ching-Hsing Liao ◽  
Daniel E. McCallus ◽  
William F. Fett ◽  
Yue-gyu Kang
Keyword(s):  
Plant Tissue ◽  
Fruits And Vegetables ◽  
Pectate Lyase ◽  
Soft Rot ◽  
Colony Morphology ◽  
Gram Negative Bacteria ◽  
Wild Type ◽  
Gram Negative ◽  
Pseudomonas Viridiflava ◽  
Two Component

Pseudomonas marginalis is an important postharvest pathogen capable of causing soft rot in a wide variety of harvested fruits and vegetables. Following transposon mutagenesis, we isolated two groups of P. marginalis CY091 mutants deficient in production of pectate lyase (Pel) and soft-rot pathogenicity in plants. The first group, designated Pel−, was caused by the insertion of Tn5 into a pel structural gene, and the second group, designated LemA−, was caused by the insertion of Tn5 into a regulatory locus corresponding to the lemA gene previously identified in other Gram-negative bacteria. The LemA− mutants also exhibited alteration in colony morphology and showed deficiency in production of protease (Prt). A cosmid clone pCIC carrying the P. marginalis lemA gene was isolated and characterized. pCIC was capable of restoring Pel production and soft-rot pathogenicity in LemA− mutants of P. marginalis and Pseudomonas viridiflava, indicating that the function of lemA gene in these two pseudomonads was similar and interchangeable. Using MudI-mediated mutagenesis, we isolated a third group of P. marginalis mutants deficient in production of Pel, Prt, and soft-rot pathogenicity. Mutants in this group (designated GacA−1) contained an insertion of MudI in a locus corresponding to the gacA gene of P. viridiflava. Like LemA− mutants, GacA− mutants also exhibited alteration in colony morphology and showed deficiency in production of Pel and Prt. However, GacA− mutants produced much lower levels of levan and fluorescent pyoverdine siderophore than the wild type and LemA− mutants. These results provide the first genetic evidence that P. marginalis produces a single alkaline Pel for maceration of plant tissue and demonstrate that production of Pel, Prt, levan, and pyoverdin by this bacterium is mediated by the two-component lemA/gacA gene system.Key words: two-component regulators, pectate lyase, protease, levan, pyoverdin.

scholarly journals Signal Transduction and Regulatory Mechanisms Involved in Control of the σS (RpoS) Subunit of RNA Polymerase

2002 ◽  
Vol 66 (3) ◽  
pp. 373-395 ◽  
Author(s):  
Regine Hengge-Aronis
Keyword(s):  
Rna Polymerase ◽  
Translational Control ◽  
Current Knowledge ◽  
Response Regulator ◽  
Regulatory System ◽  
Stress Conditions ◽  
Acidic Ph ◽  
High Osmolarity ◽  
Multiple Signal ◽  
Rpos Mrna

SUMMARY The σS (RpoS) subunit of RNA polymerase is the master regulator of the general stress response in Escherichia coli and related bacteria. While rapidly growing cells contain very little σS, exposure to many different stress conditions results in rapid and strong σS induction. Consequently, transcription of numerous σS-dependent genes is activated, many of which encode gene products with stress-protective functions. Multiple signal integration in the control of the cellular σS level is achieved by rpoS transcriptional and translational control as well as by regulated σS proteolysis, with various stress conditions differentially affecting these levels of σS control. Thus, a reduced growth rate results in increased rpoS transcription whereas high osmolarity, low temperature, acidic pH, and some late-log-phase signals stimulate the translation of already present rpoS mRNA. In addition, carbon starvation, high osmolarity, acidic pH, and high temperature result in stabilization of σS, which, under nonstress conditions, is degraded with a half-life of one to several minutes. Important cis-regulatory determinants as well as trans-acting regulatory factors involved at all levels of σS regulation have been identified. rpoS translation is controlled by several proteins (Hfq and HU) and small regulatory RNAs that probably affect the secondary structure of rpoS mRNA. For σS proteolysis, the response regulator RssB is essential. RssB is a specific direct σS recognition factor, whose affinity for σS is modulated by phosphorylation of its receiver domain. RssB delivers σS to the ClpXP protease, where σS is unfolded and completely degraded. This review summarizes our current knowledge about the molecular functions and interactions of these components and tries to establish a framework for further research on the mode of multiple signal input into this complex regulatory system.

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