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1
Sanowar, Sarah, Alexandre Martel, and Hervé Le Moual. "Mutational Analysis of the Residue at Position 48 in the Salmonella enterica Serovar Typhimurium PhoQ Sensor Kinase." Journal of Bacteriology 185, no. 6 (March 15, 2003): 1935–41. http://dx.doi.org/10.1128/jb.185.6.1935-1941.2003.
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ABSTRACT The PhoP/PhoQ two-component regulatory system of Salmonella enterica serovar Typhimurium plays an essential role in controlling virulence by mediating the adaptation to Mg2+ depletion. The pho-24 allele of phoQ harbors a single amino acid substitution (T48I) in the periplasmic domain of the PhoQ histidine kinase sensor. This mutation has been shown to increase net phosphorylation of the PhoP response regulator. We analyzed the effect on signaling by PhoP/PhoQ of various amino acid substitutions at this position (PhoQ-T48X [X = A, S, V, I, or L]). Mutations T48V, T48I, and T48L were found to affect signaling by PhoP/PhoQ both in vivo and in vitro. Mutations PhoQ-T48V and PhoQ-T48I increased both the expression of the mgtA::lacZ transcriptional fusion and the net phosphorylation of PhoP, conferring to cells a PhoP constitutively active phenotype. In contrast, mutation PhoQ-T48L barely responded to changes in the concentration of external Mg2+, in vivo and in vitro, conferring to cells a PhoP constitutively inactive phenotype. By analyzing in vitro the individual catalytic activities of the PhoQ-T48X sensors, we found that the PhoP constitutively active phenotype observed for the PhoQ-T48V and PhoQ-T48I proteins is solely due to decreased phosphatase activity. In contrast, the PhoP constitutively inactive phenotype observed for the PhoQ-T48L mutant resulted from both decreased autokinase activity and increased phosphatase activity. Our data are consistent with a model in which the residue at position 48 of PhoQ contributes to a conformational switch between kinase- and phosphatase-dominant states.
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Lejona, Sergio, María Eugenia Castelli, María Laura Cabeza, Linda J. Kenney, Eleonora García Véscovi, and Fernando C. Soncini. "PhoP Can Activate Its Target Genes in a PhoQ-Independent Manner." Journal of Bacteriology 186, no. 8 (April 15, 2004): 2476–80. http://dx.doi.org/10.1128/jb.186.8.2476-2480.2004.
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ABSTRACT The PhoP/PhoQ two-component system controls the extracellular magnesium depletion response in Salmonella enterica. Previous studies have shown that PhoP is unable to up-regulate its target genes in the absence of PhoQ function. In this work, we demonstrate that PhoP overexpression can substitute for PhoQ- and phosphorylation-dependent activation. Either a high concentration of PhoP or activation via phosphorylation stimulates PhoP self-association.
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Guina, Tina, Eugene C. Yi, Houle Wang, Murray Hackett, and Samuel I. Miller. "A PhoP-Regulated Outer Membrane Protease of Salmonella enterica Serovar Typhimurium Promotes Resistance to Alpha-Helical Antimicrobial Peptides." Journal of Bacteriology 182, no. 14 (July 15, 2000): 4077–86. http://dx.doi.org/10.1128/jb.182.14.4077-4086.2000.
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ABSTRACT The outer membrane protein contents of Salmonella enterica serovar Typhimurium strains with PhoP/PhoQ regulon mutations were compared by two-dimensional gel electrophoresis. At least 26 species of outer membrane proteins (OMPs) were identified as being regulated by PhoP/PhoQ activation. One PhoP/PhoQ-activated OMP was identified by semiautomated tandem mass spectrometry coupled with electronic database searching as PgtE, a member of theEscherichia coli OmpT and Yersinia pestis Pla family of outer membrane proteases. Salmonella PgtE expression promoted resistance to alpha-helical cationic antimicrobial peptides (α-CAMPs). Strains expressing PgtE cleaved C18G, an 18-residue α-CAMP present in culture medium, indicating that protease activity is likely to be the mechanism of OmpT-mediated resistance to α-CAMPs. PhoP/PhoQ did not regulate the transcription or export of PgtE, indicating that another PhoP/PhoQ-dependent mechanism is required for PgtE outer membrane localization. PgtE is a posttranscriptionally regulated component of the PhoP/PhoQ regulon that contributes toSalmonella resistance to innate immunity.
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Lesley, Joseph A., and Carey D. Waldburger. "Repression of Escherichia coli PhoP-PhoQ Signaling by Acetate Reveals a Regulatory Role for Acetyl Coenzyme A." Journal of Bacteriology 185, no. 8 (April 15, 2003): 2563–70. http://dx.doi.org/10.1128/jb.185.8.2563-2570.2003.
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ABSTRACT The PhoP-PhoQ two-component system regulates the transcription of numerous genes in response to changes in extracellular divalent cation concentration and pH. Here we demonstrate that the Escherichia coli PhoP-PhoQ two-component system also responds to acetate. Signaling by the E. coli PhoP-PhoQ system was repressed during growth in acetate (≥25 mM) in a PhoQ-dependent manner. The periplasmic sensor domain of PhoQ was not required for acetate to repress signaling. Acetate-mediated repression of the PhoP-PhoQ system was not related to changes in the intracellular concentration of acetate metabolites such as acetyl-phosphate or acetyladenylate. Genetic analysis of acetate metabolism pathways suggested that a perturbation of acetyl coenzyme A turnover was the cause of decreased PhoP-PhoQ signaling during growth in acetate. Consistent with this hypothesis, intracellular acetyl coenzyme A levels rose during growth in the presence of exogenous acetate. Acetyl coenzyme A inhibited the autokinase activity of PhoQ in vitro, suggesting that the in vivo repressing effect may be due to a direct inhibition mechanism.
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van Velkinburgh, Jennifer C., and John S. Gunn. "PhoP-PhoQ-Regulated Loci Are Required for Enhanced Bile Resistance in Salmonella spp." Infection and Immunity 67, no. 4 (April 1, 1999): 1614–22. http://dx.doi.org/10.1128/iai.67.4.1614-1622.1999.
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ABSTRACT As enteric pathogens, Salmonella spp. are resistant to the actions of bile. Salmonella typhimurium andSalmonella typhi strains were examined to better define the bile resistance phenotype. The MICs of bile for wild-typeS. typhimurium and S. typhi were 18 and 12%, respectively, and pretreatment of log-phase S. typhimurium with 15% bile dramatically increased bile resistance. Mutant strains of S. typhimurium andS. typhi lacking the virulence regulator PhoP-PhoQ were killed at significantly lower bile concentrations than wild-type strains, while strains with constitutively active PhoP were able to survive prolonged incubation with bile at concentrations of >60%. PhoP-PhoQ was shown to mediate resistance specifically to the bile components deoxycholate and conjugated forms of chenodeoxycholate, and the protective effect was not generalized to other membrane-active agents. Growth of both S. typhimurium and S. typhi in bile and in deoxycholate resulted in the induction or repression of a number of proteins, many of which appeared identical to PhoP-PhoQ-activated or -repressed products. The PhoP-PhoQ regulon was not induced by bile, nor did any of the 21 PhoP-activated or -repressed genes tested play a role in bile resistance. However, of the PhoP-activated or -repressed genes tested, two (prgC andprgH) were transcriptionally repressed by bile in the medium independent of PhoP-PhoQ. These data suggest that salmonellae can sense and respond to bile to increase resistance and that this response likely includes proteins that are members of the PhoP regulon. These bile- and PhoP-PhoQ-regulated products may play an important role in the survival of Salmonella spp. in the intestine or gallbladder.
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Liu, Wen, Xiang Li, Hong Qi, Yuning Wu, Jing Qu, Zhiyong Yin, Xuejuan Gao, Aidong Han, and Jianwei Shuai. "Biphasic regulation of transcriptional surge generated by the gene feedback loop in a two-component system." Bioinformatics 37, no. 17 (March 2, 2021): 2682–90. http://dx.doi.org/10.1093/bioinformatics/btab138.
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Abstract Motivation Transcriptional surges generated by two-component systems (TCSs) have been observed experimentally in various bacteria. Suppression of the transcriptional surge may reduce the activity, virulence and drug resistance of bacteria. In order to investigate the general mechanisms, we use a PhoP/PhoQ TCS as a model system to derive a comprehensive mathematical modeling that governs the surge. PhoP is a response regulator, which serves as a transcription factor under a phosphorylation-dependent modulation by PhoQ, a histidine kinase. Results Our model reveals two major signaling pathways to modulate the phosphorylated PhoP (P-PhoP) level, one of which promotes the generation of P-PhoP, while the other depresses the level of P-PhoP. The competition between the P-PhoP-promoting and the P-PhoP-depressing pathways determines the generation of the P-PhoP surge. Furthermore, besides PhoQ, PhoP is also a bifunctional modulator that contributes to the dynamic control of P-PhoP state, leading to a biphasic regulation of the surge by the gene feedback loop. In summary, the mechanisms derived from the PhoP/PhoQ system for the transcriptional surges provide a better understanding on such a sophisticated signal transduction system and aid to develop new antimicrobial strategies targeting TCSs. Availability and implementation https://github.com/jianweishuai/TCS. Supplementary information Supplementary data are available at Bioinformatics online.
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Eguchi, Yoko, Tadashi Okada, Shu Minagawa, Taku Oshima, Hirotada Mori, Kaneyoshi Yamamoto, Akira Ishihama, and Ryutaro Utsumi. "Signal Transduction Cascade between EvgA/EvgS and PhoP/PhoQ Two-Component Systems of Escherichia coli." Journal of Bacteriology 186, no. 10 (May 15, 2004): 3006–14. http://dx.doi.org/10.1128/jb.186.10.3006-3014.2004.
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ABSTRACT Transcriptional analysis of a constitutively active mutant of the EvgA/EvgS two-component system of Escherichia coli resulted in enhanced expression of 13 PhoP/PhoQ-regulated genes, crcA, hemL, mgtA, ompT, phoP, phoQ, proP, rstA, rstB, slyB, ybjG, yrbL, and mgrB. This regulatory network between the two systems also occurred as a result of overproduction of the EvgA regulator; however, enhanced transcription of the phoPQ genes did not further activate expression of the PhoP/PhoQ-regulated genes. These results demonstrated signal transduction from the EvgA/EvgS system to the PhoP/PhoQ system in E. coli and also identified the genes that required the two systems for enhanced expression. This is one example of the intricate signal transduction networks that are posited to exist in E. coli.
8
Sanowar, Sarah, and Hervé Le Moual. "Functional reconstitution of the Salmonella typhimurium PhoQ histidine kinase sensor in proteoliposomes." Biochemical Journal 390, no. 3 (September 5, 2005): 769–76. http://dx.doi.org/10.1042/bj20050060.
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Two-component signal-transduction systems are widespread in bacteria. They are usually composed of a transmembrane histidine kinase sensor and a cytoplasmic response regulator. The PhoP/PhoQ two-component system of Salmonella typhimurium contributes to virulence by co-ordinating the adaptation to low concentrations of environmental Mg2+. Limiting concentrations of extracellular Mg2+ activate the PhoP/PhoQ phosphorylation cascade modulating the transcription of PhoP-regulated genes. In contrast, high concentrations of extracellular Mg2+ stimulate the dephosphorylation of the response regulator PhoP by the PhoQ kinase sensor. In the present study, we report the purification and functional reconstitution of PhoQHis, a PhoQ variant with a C-terminal His tag, into Escherichia coli liposomes. The functionality of PhoQHis was essentially similar to that of PhoQ as shown in vivo and in vitro. Purified PhoQHis was inserted into liposomes in a unidirectional orientation, with the sensory domain facing the lumen and the catalytic domain facing the extraluminal environment. Reconstituted PhoQHis exhibited all the catalytic activities that have been described for histidine kinase sensors. Reconstituted PhoQHis was capable of autokinase activity when incubated in the presence of Mg2+-ATP. The phosphoryl group could be transferred from reconstituted PhoQHis to PhoP. Reconstituted PhoQHis catalysed the dephosphorylation of phospho-PhoP and this activity was stimulated by the addition of extraluminal ADP.
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Tu, Jian, Boyan Huang, Yu Zhang, Yuxi Zhang, Ting Xue, Shaocan Li, and Kezong Qi. "Modulation of virulence genes by the two-component system PhoP-PhoQ in avian pathogenic Escherichia coli." Polish Journal of Veterinary Sciences 19, no. 1 (March 1, 2016): 31–40. http://dx.doi.org/10.1515/pjvs-2016-0005.
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Abstract Avian pathogenic Escherichia coli (APEC) infections are a very important problem in the poultry industry. PhoP-PhoQ is a two-component system that regulates virulence genes in APEC. In this study, we constructed strains that lacked the PhoP or PhoQ genes to assess regulation of APEC pathogenicity by the PhoP-PhoQ two-component system. The PhoP mutant strain AE18, PhoQ mutant strain AE19, and PhoP/PhoQ mutant strain AE20 were constructed by the Red homologous recombination method. Swim plates were used to evaluate the motility of the APEC strains, viable bacteria counting was used to assess adhesion and invasion of chick embryo fibroblasts, and Real-Time PCR was used to measure mRNA expression of virulence genes. We first confirmed that AE18, AE19, and AE20 were successfully constructed from the wild-type AE17 strain. AE18, AE19, and AE20 showed significant decreases in motility of 70.97%, 83.87%, and 37.1%, respectively, in comparison with AE17. Moreover, in comparison with AE17, AE18, AE19, and AE20 showed significant decreases of 63.11%, 65.42%, and 30.26%, respectively, in CEF cell adhesion, and significant decreases of 59.83%, 57.82%, and 37.90%, respectively, in CEF cell invasion. In comparison with AE17, transcript levels of sodA, polA, and iss were significantly decreased in AE18, while transcript levels of fimC and iss were significantly decreased in AE19. Our results demonstrate that deletion of PhoP or PhoQ inhibits invasion and adhesion of APEC to CEF cells and significantly reduces APEC virulence by regulating transcription of virulence genes.
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Yuan, Jing, Fan Jin, Timo Glatter, and Victor Sourjik. "Osmosensing by the bacterial PhoQ/PhoP two-component system." Proceedings of the National Academy of Sciences 114, no. 50 (November 28, 2017): E10792—E10798. http://dx.doi.org/10.1073/pnas.1717272114.
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The PhoQ/PhoP two-component system plays an essential role in the response of enterobacteria to the environment of their mammalian hosts. It is known to sense several stimuli that are potentially associated with the host, including extracellular magnesium limitation, low pH, and the presence of cationic antimicrobial peptides. Here, we show that the PhoQ/PhoP two-component systems ofEscherichia coliandSalmonellacan also perceive an osmotic upshift, another key stimulus to which bacteria become exposed within the host. In contrast to most previously established stimuli of PhoQ, the detection of osmotic upshift does not require its periplasmic sensor domain. Instead, we show that the activity of PhoQ is affected by the length of the transmembrane (TM) helix as well as by membrane lateral pressure. We therefore propose that osmosensing relies on a conformational change within the TM domain of PhoQ induced by a perturbation in cell membrane thickness and lateral pressure under hyperosmotic conditions. Furthermore, the response mediated by the PhoQ/PhoP two-component system was found to improve bacterial growth recovery under hyperosmotic stress, partly through stabilization of the sigma factor RpoS. Our findings directly link the PhoQ/PhoP two-component system to bacterial osmosensing, suggesting that this system can mediate a concerted response to most of the established host-related cues.
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Choi, Eunna, Eduardo A. Groisman, and Dongwoo Shin. "Activated by Different Signals, the PhoP/PhoQ Two-Component System Differentially Regulates Metal Uptake." Journal of Bacteriology 191, no. 23 (October 2, 2009): 7174–81. http://dx.doi.org/10.1128/jb.00958-09.
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ABSTRACT The PhoP/PhoQ two-component system controls several physiological and virulence functions in Salmonella enterica. This system is activated by low Mg2+, acidic pH, and antimicrobial peptides, but the biological consequences resulting from sensing multiple signals are presently unclear. Here, we report that the PhoP/PhoQ system regulates different Salmonella genes depending on whether the inducing signal is acidic pH or low Mg2+. When Salmonella experiences acidic pH, the PhoP/PhoQ system promotes Fe2+ uptake in a process that requires the response regulator RstA, activating transcription of the Fe2+ transporter gene feoB. In contrast, the PhoP-induced RstA protein did not promote feoB expression at neutral pH with low Mg2+. The PhoP/PhoQ system promotes the expression of the Mg2+ transporter mgtA gene only when activated in bacteria starved for Mg2+. This is because mgtA transcription promoted at high Mg2+ concentrations by the acidic-pH-activated PhoP protein failed to reach the mgtA coding region due to the mgtA leader region functioning as a Mg2+ sensor. Our results show that a single two-component regulatory system can regulate distinct sets of genes in response to different input signals.
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Choi, Jeongjoon, and Eduardo A. Groisman. "Horizontally acquired regulatory gene activates ancestral regulatory system to promote Salmonella virulence." Nucleic Acids Research 48, no. 19 (October 12, 2020): 10832–47. http://dx.doi.org/10.1093/nar/gkaa813.
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Abstract Horizontally acquired genes are typically regulated by ancestral regulators. This regulation enables expression of horizontally acquired genes to be coordinated with that of preexisting genes. Here, we report a singular example of the opposite regulation: a horizontally acquired gene that controls an ancestral regulator, thereby promoting bacterial virulence. We establish that the horizontally acquired regulatory gene ssrB is necessary to activate the ancestral regulatory system PhoP/PhoQ of Salmonella enterica serovar Typhimurium (S. Typhimurium) in mildly acidic pH, which S. Typhimurium experiences inside macrophages. SsrB promotes phoP transcription by binding upstream of the phoP promoter. SsrB also increases ugtL transcription by binding to the ugtL promoter region, where it overcomes gene silencing by the heat-stable nucleoid structuring protein H-NS, enhancing virulence. The largely non-pathogenic species S. bongori failed to activate PhoP/PhoQ in mildly acidic pH because it lacks both the ssrB gene and the SsrB binding site in the target promoter. Low Mg2+ activated PhoP/PhoQ in both S. bongori and ssrB-lacking S. Typhimurium, indicating that the SsrB requirement for PhoP/PhoQ activation is signal-dependent. By controlling the ancestral genome, horizontally acquired genes are responsible for more crucial abilities, including virulence, than currently thought.
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Llama-Palacios, Arancha, Emilia López-Solanilla, and Pablo Rodríguez-Palenzuela. "Role of the PhoP-PhoQ System in the Virulence of Erwinia chrysanthemi Strain 3937: Involvement in Sensitivity to Plant Antimicrobial Peptides, Survival at Acid pH, and Regulation of Pectolytic Enzymes." Journal of Bacteriology 187, no. 6 (March 15, 2005): 2157–62. http://dx.doi.org/10.1128/jb.187.6.2157-2162.2005.
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ABSTRACT Erwinia chrysanthemi is a phytopathogenic bacterium that causes soft-rot diseases in a broad number of crops. The PhoP-PhoQ system is a key factor in pathogenicity of several bacteria and is involved in the bacterial resistance to different factors, including acid stress. Since E. chrysanthemi is confronted by acid pH during pathogenesis, we have studied the role of this system in the virulence of this bacterium. In this work, we have isolated and characterized the phoP and phoQ mutants of E. chrysanthemi strain 3937. It was found that: (i) they were not altered in their growth at acid pH; (ii) the phoQ mutant showed diminished ability to survive at acid pH; (iii) susceptibility to the antimicrobial peptide thionin was increased; (iv) the virulence of the phoQ mutant was diminished at low and high magnesium concentrations, whereas the virulence of the phoP was diminished only at low magnesium concentrations; (v) in planta Pel activity of both mutant strains was drastically reduced; and (vi) both mutants lagged behind the wild type in their capacity to change the apoplastic pH. These results suggest that the PhoP-PhoQ system plays a role in the virulence of this bacterium in plant tissues, although it does not contribute to bacterial growth at acid pH.
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Yan, Qing, Wei Gao, Xiao-Gang Wu, and Li-Qun Zhang. "Regulation of the PcoI/PcoR quorum-sensing system in Pseudomonas fluorescens 2P24 by the PhoP/PhoQ two-component system." Microbiology 155, no. 1 (January 1, 2009): 124–33. http://dx.doi.org/10.1099/mic.0.020750-0.
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A quorum-sensing locus, pcoI/pcoR, which is involved in the regulation of root colonization and plant disease-suppressive ability, was previously identified in Pseudomonas fluorescens 2P24. In this study, we performed random mutagenesis using mini-Tn5 in order to screen the upstream transcriptional regulators of pcoI, a biosynthase gene responsible for the synthesis of N-acylhomoserine lactone signal molecules. Two mutants, PM400 and PM410, with elevated pcoI gene promoter activity, were identified from ∼10 000 insertion clones. The amino acid sequences of the interrupted genes in these two mutants were highly similar to PhoQ, a sensor protein of the two-component regulatory system PhoP/PhoQ, which responds to environmental Mg2+ starvation and regulates virulence in Salmonella typhimurium and antimicrobial peptide resistance in Pseudomonas aeruginosa. The promoter activity of pcoI was also induced under low-Mg2+ conditions in the 2P24 strain of P. fluorescens. Deletion mutagenesis and complementation experiments demonstrated that the transcription of pcoI was negatively regulated by the sensor PhoQ but positively regulated by the response regulator PhoP. Genetic evidence also indicated that transcription of the outer-membrane protein gene oprH was induced by Mg2+ starvation through regulation of the wild-type PhoP/PhoQ system. Additionally, PhoQ was involved in biofilm formation by 2P24 under low-Mg2+ conditions through a PhoP-independent pathway.
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Podgornaia, Anna I., and Michael T. Laub. "Pervasive degeneracy and epistasis in a protein-protein interface." Science 347, no. 6222 (February 5, 2015): 673–77. http://dx.doi.org/10.1126/science.1257360.
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Mapping protein sequence space is a difficult problem that necessitates the analysis of 20N combinations for sequences of length N. We systematically mapped the sequence space of four key residues in the Escherichia coli protein kinase PhoQ that drive recognition of its substrate PhoP. We generated a library containing all 160,000 variants of PhoQ at these positions and used a two-step selection coupled to next-generation sequencing to identify 1659 functional variants. Our results reveal extensive degeneracy in the PhoQ-PhoP interface and epistasis, with the effect of individual substitutions often highly dependent on context. Together, epistasis and the genetic code create a pattern of connectivity of functional variants in sequence space that likely constrains PhoQ evolution. Consequently, the diversity of PhoQ orthologs is substantially lower than that of functional PhoQ variants.
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Carabajal, María Ayelén, Gastón Viarengo, Lucía Yim, Adriana Martínez-Sanguiné, Javier F. Mariscotti, José A. Chabalgoity, Rodolfo M. Rasia, and Eleonora García Véscovi. "PhoQ is an unsaturated fatty acid receptor that fine-tunes Salmonella pathogenic traits." Science Signaling 13, no. 628 (April 21, 2020): eaaz3334. http://dx.doi.org/10.1126/scisignal.aaz3334.
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The Salmonella enterica PhoP/PhoQ two-component signaling system coordinates the spatiotemporal expression of key virulence factors that confer pathogenic traits. Through biochemical and structural analyses, we found that the sensor histidine kinase PhoQ acted as a receptor for long-chain unsaturated fatty acids (LCUFAs), which induced a conformational change in the periplasmic domain of the PhoQ protein. This resulted in the repression of PhoQ autokinase activity, leading to inhibition of the expression of PhoP/PhoQ-dependent genes. Recognition of the LCUFA linoleic acid (LA) by PhoQ was not stereospecific because positional and geometrical isomers of LA equally inhibited PhoQ autophosphorylation, which was conserved in multiple S. enterica serovars. Because orally acquired Salmonella encounters conjugated LA (CLA), a product of the metabolic conversion of LA by microbiota, in the human intestine, we tested how short-term oral administration of CLA affected gut colonization and systemic dissemination in a mouse model of Salmonella-induced colitis. Compared to untreated mice, CLA-treated mice showed increased gut colonization by wild-type Salmonella, as well as increased dissemination to the spleen. In contrast, the inability of the phoP strain to disseminate systemically remained unchanged by CLA treatment. Together, our results reveal that, by inhibiting PhoQ, environmental LCUFAs fine-tune the fate of Salmonella during infection. These findings may aid in the design of new anti-Salmonella therapies.
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Bourret, Travis J., Miryoung Song, and Andrés Vázquez-Torres. "Codependent and Independent Effects of Nitric Oxide-Mediated Suppression of PhoPQ and Salmonella Pathogenicity Island 2 on Intracellular Salmonella enterica Serovar Typhimurium Survival." Infection and Immunity 77, no. 11 (September 8, 2009): 5107–15. http://dx.doi.org/10.1128/iai.00759-09.
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ABSTRACT Here we show that the Salmonella enterica serovar Typhimurium PhoQ sensor kinase lessens the cytotoxicity of reactive nitrogen species (RNS) generated by inducible nitric oxide synthase (iNOS) in the innate response of mononuclear phagocytic cells. This observation is consistent with the expression patterns of PhoP-activated genes during moderate nitrosative stress in the innate host response. In contrast, RNS synthesized during high-NO fluxes of gamma interferon (IFN-γ)-activated macrophages repress PhoP-activated lpxO, pagP, and phoP gene transcription. Because PhoP-regulated Salmonella pathogenicity island 2 (SPI2) genes are also repressed by high-order RNS (39), we investigated whether the NO-mediated inhibition of PhoPQ underlies the repression of SPI2. Our studies indicate that a third of the expression of the SPI2 spiC gene recorded in nonactivated macrophages depends on PhoQ. Transcription of spiC is repressed in IFN-γ-primed macrophages in an iNOS-dependent manner, irrespective of the phoQ status of the bacteria. Transcription of spiC is restored in IFN-γ-treated, iNOS-deficient macrophages to levels sustained by a phoQ mutant in nonactivated phagocytes, suggesting that most NO-dependent repression of spiC is due to the inhibition of PhoPQ-independent targets. Comparison of the intracellular fitness of spiC, phoQ, and spiC phoQ mutants revealed that PhoPQ and SPI2 have codependent and independent effects on S. Typhimurium survival during innate nitrosative stress. However, the intracellular survival of most S. Typhimurium bacteria is conferred by the PhoPQ two-component regulator, and the SPI2 type III secretion system is repressed by high-order RNS of IFN-γ-activated macrophages.
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Tierrez, Alberto, and Francisco García-del Portillo. "The Salmonella Membrane Protein IgaA Modulates the Activity of the RcsC-YojN-RcsB and PhoP-PhoQ Regulons." Journal of Bacteriology 186, no. 22 (November 15, 2004): 7481–89. http://dx.doi.org/10.1128/jb.186.22.7481-7489.2004.
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ABSTRACT The Salmonella enterica serovar Typhimurium membrane protein IgaA and the PhoP-PhoQ two-component system are used by this pathogen to attenuate the intracellular growth rate within fibroblasts. IgaA has also recently been shown to contribute to virulence by exerting tight repression of the RcsC-YojN-RcsB phosphorelay in host tissues. Here we show that loss of repression of the RcsC-YojN-RcsB system, linked to an R188H mutation in the IgaA protein (igaA1 allele), is accompanied by altered expression of PhoP-PhoQ-activated (pag) genes. The changes in gene expression were different depending on the specific pag gene analyzed. Thus, transcription of ugd, which is required for lipopolysaccharide modification and colanic acid capsule synthesis, was enhanced in the igaA1 mutant. RcsB and its coregulator RcsA promoted this alteration in a PhoP-PmrA-independent manner. Unlike ugd, activation of the RcsC-YojN-RcsB phosphorelay negatively affected the expression of all other pag genes tested. In this case, RcsB alone was responsible for this effect. We also found that PhoP, but not PmrA, negatively modulates the expression of gmm, a gene required for colanic acid synthesis that is regulated positively by RcsC-YojN-RcsB. Finally, it was observed that the fine regulation of pag genes exerted by RcsB requires the RpoS protein and that an active RcsB, but not RcsA, diminishes expression of the phoP gene. These data support the hypothesis that in Salmonella there is an intimate regulatory circuit between the PhoP-PhoQ and RcsC-YojN-RcsB phosphorelays, which is revealed only when the RcsC-YojN-RcsB signaling route is derepressed. Consistent with the phenotypes observed in fibroblast cells, IgaA is predicted to favor expression of the entire PhoP-PhoQ regulon based on its repression of the RcsC-YojN-RcsB phosphorelay.
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Minagawa, Shu, Hiroshi Ogasawara, Akinori Kato, Kaneyoshi Yamamoto, Yoko Eguchi, Taku Oshima, Hirotada Mori, Akira Ishihama, and Ryutaro Utsumi. "Identification and Molecular Characterization of the Mg2+ Stimulon of Escherichia coli." Journal of Bacteriology 185, no. 13 (July 1, 2003): 3696–702. http://dx.doi.org/10.1128/jb.185.13.3696-3702.2003.
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ABSTRACT Transcription profile microarray analysis in Escherichia coli was performed to identify the member genes of the Mg2+ stimulon that respond to the availability of external Mg2+ in a PhoP/PhoQ two-component system-dependent manner. The mRNA levels of W3110 in the presence of 30 mM MgCl2, WP3022 (phoP defective), and WQ3007 (phoQ defective) were compared with those of W3110 in the absence of MgCl2. The expression ratios of a total of 232 genes were <0.75 in all three strains (the supplemental data are shown at http://www.nara.kindai.ac.jp/nogei/seiken/array.html ), suggesting that the PhoP/PhoQ system is involved directly or indirectly in the transcription of these genes. Of those, 26 contained the PhoP box-like sequences with the direct repeats of (T/G)GTTTA within 500 bp upstream of the initiation codon. Furthermore, S1 nuclease assays of 26 promoters were performed to verify six new Mg2+ stimulon genes, hemL, nagA, rstAB, slyB, vboR, and yrbL, in addition to the phoPQ, mgrB, and mgtA genes reported previously. In gel shift and DNase I footprinting assays, all of these genes were found to be regulated directly by PhoP. Thus, we concluded that the phoPQ, mgrB, mgtA, hemL, nagA, rstAB, slyB, vboR, and yrbL genes make up the Mg2+ stimulon in E. coli.
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Xu, Qingqing, Teng Xu, Yuan Zhuang, Xiaofen Liu, Ying Li, and Yijian Chen. "In Vivo Development of Polymyxin B Resistance in Klebsiella pneumoniae owing to a 42 bp Deletion in the Sequence of phoQ." BioMed Research International 2020 (April 22, 2020): 1–6. http://dx.doi.org/10.1155/2020/5868479.
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Polymyxins resistance has emerged worldwide and is threatening the treatment efficacy of multidrug resistant Klebsiella pneumoniae in humans and animals. In this research, we employed whole-genome sequencing (WGS) to investigate the polymyxin B resistance mechanism in selected polymyxin B-susceptible and polymyxin B-resistant K. pneumoniae, isolated from one patient of Huashan Hospital affiliated to Fudan University. The WGS results showed that the two K. pneumoniae all belong to ST11. The average nucleotide identity between the two K. pneumoniae was nearly 100%. No sense mutations of polymyxins resistance associated genes (pmrA, pmrB, phoP, mgrB) were observed in polymyxin B-resistant K. pneumonia (PRKP) compared to the polymyxin B-susceptible isolate. A 42 bp deletion was found in the sequence of phoQ in PRKP. The deletion of amino acid occurred on the periplasmic domain of PhoQ protein. We speculate that this is the domain that MgrB protein interact with the PhoQ protein and negatively regulate the PhoP/PhoQ system. qRT-PCR analysis revealed an overexpression of the pmrA (6.8-fold), pmrB (151.9-fold), pmrC (14.5-fold), pmrK (287.9-fold), phoP (14.5-fold), and phoQ (16.8-fold) genes in the polymyxin B-resistant isolate compared to the expression of the polymyxin B-susceptible K. pneumoniae isolate, suggesting that the phoQ deletion maybe responsible for the increased expression levels of those genes. In conclusion, this study identified a 42 bp deletion in the sequence of phoQ as being responsible for the overexpression of pmrCAB and pmrHFIJKLM operons, leading to resistance to polymyxin B.
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Miller, S. I. "PhoP/PhoQ: macrophage-specific modulators ofSalmonellavirulence?" Molecular Microbiology 5, no. 9 (September 1991): 2073–78. http://dx.doi.org/10.1111/j.1365-2958.1991.tb02135.x.
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Gooderham, W. James, Shaan L. Gellatly, François Sanschagrin, Joseph B. McPhee, Manjeet Bains, Celine Cosseau, Roger C. Levesque, and Robert E. W. Hancock. "The sensor kinase PhoQ mediates virulence in Pseudomonas aeruginosa." Microbiology 155, no. 3 (March 1, 2009): 699–711. http://dx.doi.org/10.1099/mic.0.024554-0.
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Pseudomonas aeruginosa is a ubiquitous environmental Gram-negative bacterium that is also a major opportunistic human pathogen in nosocomial infections and cystic fibrosis chronic lung infections. PhoP-PhoQ is a two-component regulatory system that has been identified as essential for virulence and cationic antimicrobial peptide resistance in several other Gram-negative bacteria. This study demonstrated that mutation of phoQ caused reduced twitching motility, biofilm formation and rapid attachment to surfaces, 2.2-fold reduced cytotoxicity to human lung epithelial cells, substantially reduced lettuce leaf virulence, and a major, 10 000-fold reduction in competitiveness in chronic rat lung infections. Microarray analysis revealed that PhoQ controlled the expression of many genes consistent with these phenotypes and with its known role in polymyxin B resistance. It was also demonstrated that PhoQ controls the expression of many genes outside the known PhoP regulon.
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Núñez-Hernández, Cristina, Alberto Tierrez, Álvaro D. Ortega, M. Graciela Pucciarelli, Marta Godoy, Blanca Eisman, Josep Casadesús, and Francisco García-del Portillo. "Genome Expression Analysis of Nonproliferating Intracellular Salmonella enterica Serovar Typhimurium Unravels an Acid pH-Dependent PhoP-PhoQ Response Essential for Dormancy." Infection and Immunity 81, no. 1 (October 22, 2012): 154–65. http://dx.doi.org/10.1128/iai.01080-12.
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Genome-wide expression analyses have provided clues on howSalmonellaproliferates inside cultured macrophages and epithelial cells. However,in vivostudies show thatSalmonelladoes not replicate massively within host cells, leaving the underlying mechanisms of such growth control largely undefined.In vitroinfection models based on fibroblasts or dendritic cells reveal limited proliferation of the pathogen, but it is presently unknown whether these phenomena reflect events occurringin vivo. Fibroblasts are distinctive, since they represent a nonphagocytic cell type in whichS. entericaserovar Typhimurium actively attenuates intracellular growth. Here, we show in the mouse model thatS. Typhimurium restrains intracellular growth within nonphagocytic cells positioned in the intestinal lamina propria. This response requires a functional PhoP-PhoQ system and is reproduced in primary fibroblasts isolated from the mouse intestine. The fibroblast infection model was exploited to generate transcriptome data, which revealed that ∼2% (98 genes) of theS. Typhimurium genome is differentially expressed in nongrowing intracellular bacteria. Changes include metabolic reprogramming to microaerophilic conditions, induction of virulence plasmid genes, upregulation of the pathogenicity islands SPI-1 and SPI-2, and shutdown of flagella production and chemotaxis. Comparison of relative protein levels of several PhoP-PhoQ-regulated functions (PagN, PagP, and VirK) in nongrowing intracellular bacteria and extracellular bacteria exposed to diverse PhoP-PhoQ-inducing signals denoted a regulation responding to acidic pH. These data demonstrate thatS. Typhimurium restrains intracellular growthin vivoand support a model in which dormant intracellular bacteria could sense vacuolar acidification to stimulate the PhoP-PhoQ system for preventing intracellular overgrowth.
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Gunn, John S., Robert K. Ernst, Andrea J. McCoy, and Samuel I. Miller. "Constitutive Mutations of the Salmonella entericaSerovar Typhimurium Transcriptional Virulence RegulatorphoP." Infection and Immunity 68, no. 6 (June 1, 2000): 3758–62. http://dx.doi.org/10.1128/iai.68.6.3758-3762.2000.
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ABSTRACT The PhoP-PhoQ two-component system is necessary for the virulence of Salmonella spp. and is responsible for regulating several modifications of the lipopolysaccharide (LPS). Mutagenesis of the transcriptional regulator phoP resulted in the identification of a mutant able to activate transcription of regulated genes ∼100-fold in the absence of PhoQ. Sequence analysis showed two single-base alterations resulting in amino acid changes at positions 93 (S93N) and 203 (Q203R). These mutations were individually created, and although each resulted in a constitutive phenotype, the double mutant displayed a synergistic effect both in the induction of PhoP-activated gene expression and in resistance to antimicrobial peptides. The constitutive phoP gene was placed under the control of an arabinose-inducible promoter to examine the kinetics of PhoP-activated gene induction and the resultant modifications of LPS. Gene induction and 2-hydroxymyristate modification of the lipid A were shown to occur within minutes of the addition of arabinose and to peak at 4 h. As the first constitutive mutant of phoP identified, this allele will be invaluable to future genetic and biochemical studies of this and likely other regulatory systems.
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Regelmann, Adam G., Joseph A. Lesley, Christina Mott, Lissette Stokes, and Carey D. Waldburger. "Mutational Analysis of the Escherichia coli PhoQ Sensor Kinase: Differences with the Salmonella enterica Serovar Typhimurium PhoQ Protein and in the Mechanism of Mg2+ and Ca2+ Sensing." Journal of Bacteriology 184, no. 19 (October 1, 2002): 5468–78. http://dx.doi.org/10.1128/jb.184.19.5468-5478.2002.
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ABSTRACT The PhoP-PhoQ two-component system plays a role in Mg2+ homeostasis and/or the virulence properties of a number of bacterial species. A Salmonella enterica serovar Typhimurium PhoQ sensor kinase mutant, in which the threonine at residue 48 in the periplasmic sensor domain is changed to an isoleucine, was shown previously to result in elevated expression of PhoP-activated genes and to affect mouse virulence, epithelial cell invasion, and sensitivity to macrophage killing. We characterized a complete set of proteins having amino acid substitutions at position 48 in the closely related Escherichia coli PhoQ protein. Numerous mutant proteins having amino acid substitutions with side chains of various sizes and characters displayed signaling phenotypes similar to that of the wild-type protein, indicating that interactions mediated by the wild-type threonine side chain are not required for normal protein function. Changes to amino acids with aromatic side chains had little impact on signaling in response to extracellular Mg2+ but resulted in reduced sensitivity to extracellular Ca2+, suggesting that the mechanisms of signal transduction in response to these two divalent cations are different. Surprisingly, the Ile48 protein displayed a defective phenotype rather than the hyperactive phenotype seen with the S. enterica serovar Typhimurium protein. We also describe a mutant PhoQ protein lacking the extracellular sensor domain with a defect in the ability to activate PhoP. The defect does not appear to be due to reduced autokinase activity but rather appears to be due to an effect on the stability of the aspartyl-phosphate bond of phospho-PhoP.
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Beuzón, Carmen R., Kate E. Unsworth, and David W. Holden. "In Vivo Genetic Analysis Indicates That PhoP-PhoQ and the Salmonella Pathogenicity Island 2 Type III Secretion System Contribute Independently to Salmonella enterica Serovar Typhimurium Virulence." Infection and Immunity 69, no. 12 (December 1, 2001): 7254–61. http://dx.doi.org/10.1128/iai.69.12.7254-7261.2001.
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ABSTRACT Many virulence factors are required for Salmonella enterica serovar Typhimurium to replicate intracellularly and proliferate systemically within mice. In this work, we have carried out genetic analyses in vivo to determine the functional relationship between two major virulence factors necessary for systemic infection byS. enterica serovar Typhimurium: theSalmonella pathogenicity island 2 (SPI-2) type III secretion system (TTSS) and the PhoP-PhoQ two-component regulatory system. Although previous work suggested that PhoP-PhoQ regulates SPI-2 TTSS gene expression in vitro, in vivo competitive analysis of mutant strains indicates that these systems contribute independently toS. typhimurium virulence. Our results also suggest that mutation of phoP may compensate partially for defects in the SPI-2 TTSS by deregulating SPI-1 TTSS expression. These results provide an explanation for previous reports showing an apparent functional overlap between these two systems in vitro.
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Fukuto, Hana S., Gloria I. Viboud, and Viveka Vadyvaloo. "The Diverse Roles of the Global Transcriptional Regulator PhoP in the Lifecycle of Yersinia pestis." Pathogens 9, no. 12 (December 11, 2020): 1039. http://dx.doi.org/10.3390/pathogens9121039.
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Yersinia pestis, the causative agent of plague, has a complex infectious cycle that alternates between mammalian hosts (rodents and humans) and insect vectors (fleas). Consequently, it must adapt to a wide range of host environments to achieve successful propagation. Y. pestis PhoP is a response regulator of the PhoP/PhoQ two-component signal transduction system that plays a critical role in the pathogen’s adaptation to hostile conditions. PhoP is activated in response to various host-associated stress signals detected by the sensor kinase PhoQ and mediates changes in global gene expression profiles that lead to cellular responses. Y. pestis PhoP is required for resistance to antimicrobial peptides, as well as growth under low Mg2+ and other stress conditions, and controls a number of metabolic pathways, including an alternate carbon catabolism. Loss of phoP function in Y. pestis causes severe defects in survival inside mammalian macrophages and neutrophils in vitro, and a mild attenuation in murine plague models in vivo, suggesting its role in pathogenesis. A Y. pestisphoP mutant also exhibits reduced ability to form biofilm and to block fleas in vivo, indicating that the gene is also important for establishing a transmissible infection in this vector. Additionally, phoP promotes the survival of Y. pestis inside the soil-dwelling amoeba Acanthamoeba castellanii, a potential reservoir while the pathogen is quiescent. In this review, we summarize our current knowledge on the mechanisms of PhoP-mediated gene regulation in Y. pestis and examine the significance of the roles played by the PhoP regulon at each stage of the Y. pestis life cycle.
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Yang, Baopeng, Chang Liu, Xiaolei Pan, Weixin Fu, Zheng Fan, Yongxin Jin, Fang Bai, Zhihui Cheng, and Weihui Wu. "Identification of Novel phoP-phoQ Regulated Genes that Contribute to Polymyxin B Tolerance in Pseudomonas aeruginosa." Microorganisms 9, no. 2 (February 9, 2021): 344. http://dx.doi.org/10.3390/microorganisms9020344.
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Polymyxin B and E (colistin) are the last resorts to treat multidrug-resistant Gram-negative pathogens. Pseudomonas aeruginosa is intrinsically resistant to a variety of antibiotics. The PhoP-PhoQ two-component regulatory system contributes to the resistance to polymyxins by regulating an arnBCADTEF-pmrE operon that encodes lipopolysaccharide modification enzymes. To identify additional PhoP-regulated genes that contribute to the tolerance to polymyxin B, we performed a chromatin immunoprecipitation sequencing (ChIP-Seq) assay and found novel PhoP binding sites on the chromosome. We further verified that PhoP directly controls the expression of PA14_46900, PA14_50740 and PA14_52340, and the operons of PA14_11970-PA14_11960 and PA14_52350-PA14_52370. Our results demonstrated that mutation of PA14_46900 increased the bacterial binding and susceptibility to polymyxin B. Meanwhile, mutation of PA14_11960 (papP), PA14_11970 (mpl), PA14_50740 (slyB), PA14_52350 (ppgS), and PA14_52370 (ppgH) reduced the bacterial survival rates and increased ethidium bromide influx under polymyxin B or Sodium dodecyl sulfate (SDS) treatment, indicating roles of these genes in maintaining membrane integrity in response to the stresses. By 1-N-phenylnaphthylamine (NPN) and propidium iodide (PI) staining assay, we found that papP and slyB are involved in maintaining outer membrane integrity, and mpl and ppgS-ppgH are involved in maintaining inner membrane integrity. Overall, our results reveal novel PhoP-PhoQ regulated genes that contribute to polymyxin B tolerance.
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McPhee, Joseph B., Manjeet Bains, Geoff Winsor, Shawn Lewenza, Agnieszka Kwasnicka, Michelle D. Brazas, Fiona S. L. Brinkman, and R. E. W. Hancock. "Contribution of the PhoP-PhoQ and PmrA-PmrB Two-Component Regulatory Systems to Mg2+-Induced Gene Regulation in Pseudomonas aeruginosa." Journal of Bacteriology 188, no. 11 (June 1, 2006): 3995–4006. http://dx.doi.org/10.1128/jb.00053-06.
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ABSTRACT When grown in divalent cation-limited medium, Pseudomonas aeruginosa becomes resistant to cationic antimicrobial peptides and polymyxin B. This resistance is regulated by the PhoP-PhoQ and PmrA-PmrB two-component regulatory systems. To further characterize Mg2+ regulation in P. aeruginosa, microarray transcriptional profiling was conducted to compare wild-type P. aeruginosa grown under Mg2+-limited and Mg2+-replete conditions to isogenic phoP and pmrA mutants grown under Mg2+-limited conditions. Under Mg2+-limited conditions (0.02 mM Mg2+), approximately 3% of the P. aeruginosa genes were differentially expressed compared to the expression in bacteria grown under Mg2+-replete conditions (2 mM Mg2+). Only a modest subset of the Mg2+-regulated genes were regulated through either PhoP or PmrA. To determine which genes were directly regulated, a bioinformatic search for conserved binding motifs was combined with confirmatory reverse transcriptase PCR and gel shift promoter binding assays, and the results indicated that very few genes were directly regulated by these response regulators. It was found that in addition to the previously known oprH-phoP-phoQ operon and the pmrHFIJKLM-ugd operon, the PA0921 and PA1343 genes, encoding small basic proteins, were regulated by Mg2+ in a PhoP-dependent manner. The number of known PmrA-regulated genes was expanded to include the PA1559-PA1560, PA4782-PA4781, and feoAB operons, in addition to the previously known PA4773-PA4775-pmrAB and pmrHFIJKLM-ugd operons.
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Montagne, Martin, Alexandre Martel, and Hervé Le Moual. "Characterization of the Catalytic Activities of the PhoQ Histidine Protein Kinase of Salmonella entericaSerovar Typhimurium." Journal of Bacteriology 183, no. 5 (March 1, 2001): 1787–91. http://dx.doi.org/10.1128/jb.183.5.1787-1791.2001.
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ABSTRACT Studies of Escherichia coli membranes that were highly enriched in the Salmonella enterica serovar Typhimurium PhoQ protein showed that the presence of ATP and divalent cations such as Mg2+, Mn2+, Ca2+, or Ba2+ resulted in PhoQ autophosphorylation. However, when Mg2+ or Mn2+was present at concentrations higher than 0.1 mM, the kinetics of PhoQ autophosphorylation were strongly biphasic, with a rapid autophosphorylation phase followed by a slower dephosphorylation phase. A fusion protein lacking the sensory and transmembrane domains retained the autokinase activity but could not be dephosphosphorylated when Mg2+ or Mn2+ was present at high concentrations. The instability of purified [32P]phospho-PhoP in the presence of PhoQ-containing membranes indicated that PhoQ also possesses a phosphatase activity. The PhoQ phosphatase activity was stimulated by increasing the Mg2+ concentration. These data are consistent with a model in which Mg2+ binding to the sensory domain of PhoQ coordinately regulates autokinase and phosphatase activities.
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Bachhawat, Priti, and Ann M. Stock. "Crystal Structures of the Receiver Domain of the Response Regulator PhoP from Escherichia coli in the Absence and Presence of the Phosphoryl Analog Beryllofluoride." Journal of Bacteriology 189, no. 16 (June 1, 2007): 5987–95. http://dx.doi.org/10.1128/jb.00049-07.
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ABSTRACT The response regulator PhoP is part of the PhoQ/PhoP two-component system involved in responses to depletion of extracellular Mg2+. Here, we report the crystal structures of the receiver domain of Escherichia coli PhoP determined in the absence and presence of the phosphoryl analog beryllofluoride. In the presence of beryllofluoride, the active receiver domain forms a twofold symmetric dimer similar to that seen in structures of other regulatory domains from the OmpR/PhoB family, providing further evidence that members of this family utilize a common mode of dimerization in the active state. In the absence of activating agents, the PhoP receiver domain crystallizes with a similar structure, consistent with the previous observation that high concentrations can promote an active state of PhoP independent of phosphorylation.
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Groisman, Eduardo A. "The Pleiotropic Two-Component Regulatory System PhoP-PhoQ." Journal of Bacteriology 183, no. 6 (March 15, 2001): 1835–42. http://dx.doi.org/10.1128/jb.183.6.1835-1842.2001.
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Huang, Liang, Yu Feng, and Zhiyong Zong. "Heterogeneous resistance to colistin in Enterobacter cloacae complex due to a new small transmembrane protein." Journal of Antimicrobial Chemotherapy 74, no. 9 (June 6, 2019): 2551–58. http://dx.doi.org/10.1093/jac/dkz236.
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Abstract Background Enterobacter strains can display heterogeneous resistance (heteroresistance) to colistin but the mechanisms remain largely unknown. We investigated potential mechanisms of colistin heteroresistance in an Enterobacter clinical strain, WCHECl-1060, and found a new mechanism. Methods Strain WCHECl-1060 was subjected to WGS to identify known colistin resistance mechanisms. Tn5 insertional mutagenesis, gene knockout and complementation and shotgun cloning were employed to investigate unknown colistin heteroresistance mechanisms. RNA sequencing was performed to link the newly identified mechanism with known ones. Results We showed that the phoP gene [encoding part of the PhoP-PhoQ two-component system (TCS)], the dedA(Ecl) gene (encoding an inner membrane protein of the DedA family) and the tolC gene (encoding part of the AcrAB-TolC efflux pump) are required for colistin heteroresistance. We identified a new gene, ecr, encoding a 72 amino acid transmembrane protein, which was able to mediate colistin heteroresistance. We then performed RNA sequencing and transcriptome analysis and found that in the presence of ecr the expression of phoP and the arnBCADTEF operon, which synthesizes and transfers l-Ara4N to lipid A, was increased significantly. Conclusions The small protein encoded by ecr represents a new colistin heteroresistance mechanism and is likely to mediate colistin heteroresistance via the PhoP-PhoQ TCS to act on the arnBCADTEF operon.
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Merighi, Massimo, Craig D. Ellermeier, James M. Slauch, and John S. Gunn. "Resolvase-In Vivo Expression Technology Analysis of the Salmonella enterica Serovar Typhimurium PhoP and PmrA Regulons in BALB/c Mice." Journal of Bacteriology 187, no. 21 (November 1, 2005): 7407–16. http://dx.doi.org/10.1128/jb.187.21.7407-7416.2005.
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ABSTRACT Salmonella enterica modulates resistance to antimicrobial peptides in part via covalent modifications of the lipopolysaccharide (LPS). The two-component systems PhoP/PhoQ and PmrA/PmrB are activated during infection and regulate several genes involved in LPS modifications by responding to signals such as pH, iron, magnesium, and antimicrobial peptides. A recombination-based in vivo expression technology approach was adopted to analyze the spatial-temporal patterns of in vivo expression of genes of the PhoP and PmrA regulons and to identify the in vivo signals modulating their transcription. In vitro, we showed PhoP- and/or PmrA-dependent induction of pmrH (LPS aminoarabinose modification operon) by acidic pH, low levels of magnesium, or high levels of Fe(III). Upregulation in cultured J774A.1 macrophages was shown for pmrH, pagP (LPS palmitate addition), and ssaB (pathogenicity island II secretion) but not for prgH (pathogenicity island I secretion). Increased levels of pmrH, phoP, and prgH transcription but not ssaB were observed in bacteria isolated from the lumen of the distal ileum. Bacteria isolated from spleens of orally inoculated mice showed no further induction of prgH but had the highest expression of pmrH, pagP, and ssaB. In vivo induction of pmrH was fully dependent on pmrA and phoP, and buffering stomach acidity, iron chelation, or low-iron diets did not affect the expression of pmrH in the intestinal lumen. The observation of pmrH and pagP expression in the intestine refutes the paradigm of PhoP/PhoQ and PmrA/PmrB in vivo expression as solely intracellularly induced and supports previous data demonstrating peroral virulence attenuation of pmrH mutants.
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Rublenko, N. "Molecular genetics of salmonela survival and resistance." Naukovij vìsnik veterinarnoï medicini, no. 2 (144) (December 24, 2018): 6–12. http://dx.doi.org/10.33245/2310-4902-2018-144-2-6-12.
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Salmonella is one of the most common cause of the food borne illness. Salmonella belongs to Enterobacteriacae family and consists of 2 species, which diverge on 6 subspecies.These subspecies consists of 2700 serovars. There are typhoid serovars among them - S. Typhi, Paratyphi A, B, C - which cause typhoid fever in human. The rest of the serovars are non-typhoidal and leads to gastroenteritis both in animal and human. Salmonella enters to a mammal organism as a result of consumption of contaminated food products: meat, eggs, milk and products containing them. The entry of the infection for salmonellosis is the small intestine mucosa. Salmonella attaches to cell walls by fimbria and pili. Salmonella has several systems that are activated in response to adverse conditions such as: high osmolarity, acid or heat shock and nutrient deficiencies. They are based on the principle of a two-component system in which there is a sensor that receives cytoplasmic signals, and a regulator. Regulator (usually DNA-binding protein) initiates the transcription of the virulence genes (Chakraborty, 2015). The sensor is histidine kinase, which phosphorylates the regulatory protein, thereby activating it.During the infectious cycle of salmonella in mammalian organism the formation of specific vacuole SCV takes place (Salmonella-containing vacuole-containing vacuole containing salmonella) in the cytoplasm of the eukaryotic cell (Steele-Mortimer, 2008). SCV is a modified phagosome, which is formed as a result of cytoskeleton rearrangements. The target are usually phagocytic cells : neutrophils, macrophages and epithelial cells of the small intestine mucosa - M-cells (Akhmetova, 2012). Given the specific mechanism of infection, salmonella is considered a facultative intracellular pathogen. Bacterium invades the eukaryotic cell by rearrangement of its cytoskeleton with effector proteins and continue to persistence in a form of SCV. It is well-known nowadays that tolerance to high osmotic pressure is achieved through the EnvZ / OmpR system, which also regulates the expression of the ssrAB operon that is localized on the Salmonella pathogenicity island SPI-2 and triggers the expression of the effector proteins. The ssrAB operon is also regulated by the two-component acid shock response system PhoP / PhoQ (Worley, 2000). The functioning of the PhoP / PhoQ system directly depends on the sigma factor RpoS, which accumulates under low concentrations of magnesium cations (Tu, 2006). According to the researches of transduction between the EnvZ / OmpR components, it is clear that salmonella receives signals from the cytoplasmic environment, and sensory molecules are located on the inner membrane (Kenney, 2019; Wang et al., 2012). The ability to survive under acid shock is provided by the PhoP / PhoQ system, which also operates on the principle of signal transduction. PhoQ is a Histidine Kinase Signal Sensor. Signals are acidic pH, divalent cations and positively charged antimicrobial peptides. An important function of the two-component PhoP / PhoQ system is the control of spi ssa gene expression in a macrophage environment (Bijlsma, 2005). These genes are the main component of the type III secretion systems and are transcribed only when salmonella enters eukaryotic cell. (Bijlsma, 2005). The main regulator of signal transduction systems PhoP/PhoQ and EnvZ/OmpR is sigma-factor RpoS - subunit of bacterial RNA-polymerase - which operates in stationary phase at low pH, high omolarity, heat shock or nutrient deficiency. RpoS protein accumulates in adverse conditions during stationary phase (Mg2+ deficiency, low pH, high osmolarity). Need in magnesium cations is dependent on their ability to act as cofactors in many enzymatic activities. The accumulation begins at exponential (logarithmic) phase of bacterial reproduction. This is the phase of active cell division. Two factors MgtA and MgtB are responsible for Mg2+ transport. Another molecule with the same function is CorA - bivalent cation channel, though its transcriptions doesn’t depent on magnesium concentration in cell. In a case of magnesium deficiency at the stationary phase, RpoS accumulates vigorously an initiates replication of PhoP/PhoQ. PhoP/PhoQ regulates tolerance to inorganic acids. Also, PhoP/PhoQ controls adaptation to magnesium cations deficiency and macrophage activity. Results of many studies on genes coding this system and their mutations led to conclusion the mutation or inactivation of one factor causes decrease in virulence and makes bacterial susceptible to acid environment. To date, the stages of the infectious process for salmonellosis have been studied and described in detail in the literature. Particular attention is paid to signal transduction systems that are common among enterobacteria and help to avoid adverse conditions. Their functioning and regulation are investigated. It is known that salmonella receives signals for the activation of sensors from the cytoplasm, but the nature of these signals is not yet fully understood. Adaptation of the bacteria to adverse conditions and the response to phagocytosis is initiated by the transcription of pathogenic genes and the suppression of the transcription of the operon, which neutralize the conditions in the cytoplasm of salmonella cells. Thus, adapting to the conditions of target cells, salmonella continues to multiply in the body. Key words: salmonella, pH, osmolarity, virulencegenes, operon, signal transduction.
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Park, Sun-Yang, Mauricio H. Pontes, and Eduardo A. Groisman. "Flagella-independent surface motility inSalmonella entericaserovar Typhimurium." Proceedings of the National Academy of Sciences 112, no. 6 (January 26, 2015): 1850–55. http://dx.doi.org/10.1073/pnas.1422938112.
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Flagella are multiprotein complexes necessary for swimming and swarming motility. InSalmonella entericaserovar Typhimurium, flagella-mediated motility is repressed by the PhoP/PhoQ regulatory system. We now report thatSalmonellacan move on 0.3% agarose media in a flagella-independent manner when experiencing the PhoP/PhoQ-inducing signal low Mg2+. This motility requires the PhoP-activatedmgtA,mgtC, andpagMgenes, which specify a Mg2+transporter, an inhibitor ofSalmonella’s own F1FoATPase, and a small protein of unknown function, respectively. The MgtA and MgtC proteins are necessary forpagMexpression becausepagMmRNA levels were lower inmgtAandmgtCmutants than in wild-typeSalmonella, and also becausepagMexpression from a heterologous promoter rescued motility inmgtAandmgtCmutants. PagM promotes group motility by a surface protein(s), as apagM-expressing strain conferred motility upon apagMnull mutant, and proteinase K treatment eliminated motility. ThepagMgene is rarely found outside subspecies I ofS. entericaand often present in nonfunctional allelic forms in organisms lacking the identified motility. Deletion of thepagMgene reduced bacterial replication on 0.3% agarose low Mg2+media but not in low Mg2+liquid media. Our findings define a form of motility that allowsSalmonellato scavenge nutrients and to escape toxic compounds in low Mg2+semisolid environments.
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Aguirre, Andrés, María Laura Cabeza, Silvana V. Spinelli, Michael McClelland, Eleonora García Véscovi, and Fernando C. Soncini. "PhoP-Induced Genes within Salmonella Pathogenicity Island 1." Journal of Bacteriology 188, no. 19 (October 1, 2006): 6889–98. http://dx.doi.org/10.1128/jb.00804-06.
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ABSTRACT The invasive pathogen Salmonella enterica has evolved a sophisticated device that allows it to enter nonphagocytic host cells. This process requires the expression of Salmonella pathogenicity island 1 (SPI-1), which encodes a specialized type III protein secretion system (TTSS). This TTSS delivers a set of effectors that produce a marked rearrangement of the host cytoskeleton, generating a profuse membrane ruffling at the site of interaction, driving bacterial entry. It has been shown that the PhoP/PhoQ two-component system represses the expression of the SPI-1 machinery by down-regulating the transcription of its master regulator, HilA. In this work, we reveal the presence of a PhoP-activated operon within SPI-1. This operon is composed of the orgB and orgC genes, which encode a protein that interacts with the InvC ATPase and a putative effector protein of the TTSS, respectively. Under PhoP-inducing conditions, expression of this operon is directly activated by the phosphorylated form of the response regulator, which recognizes a PhoP box located at the −35 region relative to the transcription start site. Additionally, under invasion-inducing conditions, orgBC expression is driven both by the prgH promoter, induced by the SPI-1 master regulator HilA, and by the directly controlled PhoP/PhoQ promoter. Together, these results indicate that in contrast to the rest of the genes encompassed in the SPI-1 locus, orgBC is expressed during and after Salmonella entry into its host cell, and they suggest a role for the products of this operon after host cell internalization.
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Cano, David A., Marina Martı́nez-Moya, M. Graciela Pucciarelli, Eduardo A. Groisman, Josep Casadesús, and Francisco Garcı́a-Del Portillo. "Salmonella enterica Serovar Typhimurium Response Involved in Attenuation of Pathogen Intracellular Proliferation." Infection and Immunity 69, no. 10 (October 1, 2001): 6463–74. http://dx.doi.org/10.1128/iai.69.10.6463-6474.2001.
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ABSTRACT Salmonella enterica serovar Typhimurium proliferates within cultured epithelial and macrophage cells. Intracellular bacterial proliferation is, however, restricted within normal fibroblast cells. To characterize this phenomenon in detail, we investigated the possibility that the pathogen itself might contribute to attenuating the intracellular growth rate. S.enterica serovar Typhimurium mutants were selected in normal rat kidney fibroblasts displaying an increased intracellular proliferation rate. These mutants harbored loss-of-function mutations in the virulence-related regulatory genes phoQ,rpoS, slyA, and spvR. Lack of a functional PhoP-PhoQ system caused the most dramatic change in the intracellular growth rate. phoP- andphoQ-null mutants exhibited an intracellular growth rate 20- to 30-fold higher than that of the wild-type strain. This result showed that the PhoP-PhoQ system exerts a master regulatory function for preventing bacterial overgrowth within fibroblasts. In addition, an overgrowing clone was isolated harboring a mutation in a previously unknown serovar Typhimurium open reading frame, namedigaA for intracellular growth attenuator. Mutations in other serovar Typhimurium virulence genes, such as ompR,dam, crp, cya,mviA, spiR (ssrA), spiA, and rpoE, did not result in pathogen intracellular overgrowth. Nonetheless, lack of either SpiA or the alternate sigma factor RpoE led to a substantial decrease in intracellular bacterial viability. These results prove for the first time that specific serovar Typhimurium virulence regulators are involved in a response designed to attenuate the intracellular growth rate within a nonphagocytic host cell. This growth-attenuating response is accompanied by functions that ensure the viability of intracellular bacteria.
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Lejona, Sergio, Andrés Aguirre, María Laura Cabeza, Eleonora García Véscovi, and Fernando C. Soncini. "Molecular Characterization of the Mg2+-Responsive PhoP-PhoQ Regulon in Salmonella enterica." Journal of Bacteriology 185, no. 21 (November 1, 2003): 6287–94. http://dx.doi.org/10.1128/jb.185.21.6287-6294.2003.
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ABSTRACT The PhoP/PhoQ two-component system controls the extracellular magnesium deprivation response in Salmonella enterica. In addition, several virulence-associated genes that are mainly required for intramacrophage survival during the infection process are under the control of its transcriptional regulation. Despite shared Mg2+ modulation of the expression of the PhoP-activated genes, no consensus sequence common to all of them could be detected in their promoter regions. We have investigated the transcriptional regulation and the interaction of the response regulator PhoP with the promoter regions of the PhoP-activated loci phoPQ, mgtA, slyB, pmrD, pcgL, phoN, pagC, and mgtCB. A direct repeat of the heptanucleotide sequence (G/T)GTTTA(A/T) was identified as the conserved motif recognized by PhoP to directly control the gene expression of the first five loci, among which the first four are ancestral to enterobacteria. On the other hand, no direct interaction of the response regulator with the promoter of phoN, pagC, or mgtCB was apparent by either in vitro or in vivo assays. These loci are Salmonella specific and were probably acquired by horizontal DNA transfer. Besides, sequence analysis of pag promoters revealed the presence of a conserved PhoP box in 6 out of the 12 genes analyzed. Our results strongly suggest that the expression of a set of Mg2+-controlled genes is driven by PhoP via unknown intermediate regulatory mechanisms that could also involve ancillary factors.
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Lee, Sang-Won, Kyu-Sik Jeong, Sang-Wook Han, Seung-Eun Lee, Bong-Kwan Phee, Tae-Ryong Hahn, and Pamela Ronald. "The Xanthomonas oryzae pv. oryzae PhoPQ Two-Component System Is Required for AvrXA21 Activity, hrpG Expression, and Virulence." Journal of Bacteriology 190, no. 6 (January 18, 2008): 2183–97. http://dx.doi.org/10.1128/jb.01406-07.
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ABSTRACT The rice pathogen recognition receptor, XA21, confers resistance to Xanthomonas oryzae pv. oryzae strains producing the type one system-secreted molecule, AvrXA21. X. oryzae pv. oryzae requires a regulatory two-component system (TCS) called RaxRH to regulate expression of eight rax (required for AvrXA21 activity) genes and to sense population cell density. To identify other key components in this critical regulatory circuit, we assayed proteins expressed in a raxR gene knockout strain. This survey led to the identification of the phoP gene encoding a response regulator that is up-regulated in the raxR knockout strain. Next we generated a phoP knockout strain and found it to be impaired in X. oryzae pv. oryzae virulence and no longer able to activate the response regulator HrpG (hypersensitive reaction and pathogenicity G) in response to low levels of Ca2+. The impaired virulence of the phoP knockout strain can be partially complemented by constitutive expression of hrpG, indicating that PhoP controls a key aspect of X. oryzae pv. oryzae virulence through regulation of hrpG. A gene encoding the cognate putative histidine protein kinase, phoQ, was also isolated. Growth curve analysis revealed that AvrXA21 activity is impaired in a phoQ knockout strain as reflected by enhanced growth of this strain in rice lines carrying XA21. These results suggest that the X. oryzae pv. oryzae PhoPQ TCS functions in virulence and in the production of AvrXA21 in partnership with RaxRH.
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Kasahara, M., A. Nakata, and H. Shinagawa. "Molecular analysis of the Escherichia coli phoP-phoQ operon." Journal of Bacteriology 174, no. 2 (1992): 492–98. http://dx.doi.org/10.1128/jb.174.2.492-498.1992.
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Bearson, Bradley L., Lee Wilson, and John W. Foster. "A Low pH-Inducible, PhoPQ-Dependent Acid Tolerance Response Protects Salmonella typhimurium against Inorganic Acid Stress." Journal of Bacteriology 180, no. 9 (May 1, 1998): 2409–17. http://dx.doi.org/10.1128/jb.180.9.2409-2417.1998.
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ABSTRACT The acid tolerance response enables Salmonella typhimurium to survive exposures to potentially lethal acidic environments. The acid stress imposed in a typical assay for acid tolerance (log-phase cells in minimal glucose medium) was shown to comprise both inorganic (i.e., low pH) and organic acid components. A gene previously determined to affect acid tolerance, atbR, was identified as pgi, the gene encoding phosphoglucoisomerase. Mutations in pgi were shown to increase acid tolerance by preventing the synthesis of organic acids. Protocols designed to separate the stresses of inorganic from organic acids revealed that the regulators ς38 (RpoS), Fur, and Ada have major effects on tolerance to organic acid stress but only minor effects on inorganic acid stress. In contrast, the two-component regulatory system PhoP (identified as acid shock protein ASP29) and PhoQ proved to be important for tolerance to organic acid stress but had little effect against organic acid stress. PhoP mutants also failed to induce four ASPs, confirming a role for this regulator in acid tolerance. Acid shock induction of PhoP appears to occur at the transcriptional level and requires the PhoPQ system. Furthermore, induction by acid occurs even in the presence of high concentrations of magnesium, the ion known to be sensed by PhoQ. These results suggest that PhoQ can sense both Mg2+ and pH. SincephoP mutants are avirulent, the low pH activation of this system has important implications concerning the pathogenesis ofS. typhimurium. The involvement of four regulators, two of which are implicated in virulence, underscores the complexity of the acid tolerance stress response and further suggests that features of acid tolerance and virulence are interwoven.
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Baud, David, Jalil Benyacoub, Véronique Revaz, Menno Kok, Françoise Ponci, Martine Bobst, Roy Curtiss, Pierre De Grandi, and Denise Nardelli-Haefliger. "Immunogenicity against Human Papillomavirus Type 16 Virus-Like Particles Is Strongly Enhanced by the PhoPc Phenotype in Salmonella enterica Serovar Typhimurium." Infection and Immunity 72, no. 2 (February 2004): 750–56. http://dx.doi.org/10.1128/iai.72.2.750-756.2004.
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ABSTRACT Recombinant Salmonella strains have been widely used to deliver heterologous antigens and induce immune responses in vaccinated animals and humans. It remains to be established, however, how these bacteria mount an immune response; this has prevented the rational design of vaccines. Here we report for the first time that a particular genetic program, PhoPc, is necessary for recombinant Salmonella strains to induce an antibody response to a heterologous antigen, the human papillomaviruses type 16 (HPV16) virus-like particle (VLP). The PhoPc phenotype results from a point mutation in phoQ, the gene encoding the sensor component of a two-component regulatory system (PhoP-PhoQ) that controls the expression of a number of virulence factors in Salmonellae. To demonstrate that immunogenicity of the viral antigen expressed by the bacterial vector was dependent on the PhoPc phenotype, we have expressed the phoQ mutant gene (phoQ24) in two differently attenuated Salmonella enterica serovar Typhimurium strains. Our data show extrachromosomal phoQ24 to be dominant over the chromosomal copy of the phoQ gene, conferring the PhoPc phenotype on the recipient strains. In addition, activation of PhoPQ-regulated genes by the plasmid-encoded PhoQ24 did not alter bacterial survival and conferred immunogenicity to the HPV16 VLP expressed in the two S. enterica serovar Typhimurium backgrounds, inducing the production of HPV-specific antibodies in mice. This strongly suggests that at least one of the PhoP-regulated genes is necessary for mounting an efficient antibody response to HPV16 VLP. This finding sets the stage for further development of a Salmonella-based vaccine against HPV infection and cervical cancer.
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Cannatelli, Antonio, Marco Maria D'Andrea, Tommaso Giani, Vincenzo Di Pilato, Fabio Arena, Simone Ambretti, Paolo Gaibani, and Gian Maria Rossolini. "In VivoEmergence of Colistin Resistance in Klebsiella pneumoniae Producing KPC-Type Carbapenemases Mediated by Insertional Inactivation of the PhoQ/PhoPmgrBRegulator." Antimicrobial Agents and Chemotherapy 57, no. 11 (August 26, 2013): 5521–26. http://dx.doi.org/10.1128/aac.01480-13.
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ABSTRACTColistin is one of the few agents that retain activity against extensively drug-resistant strains ofKlebsiella pneumoniaeproducing KPC-type carbapenemases (KPC-KP). However, resistance to colistin is increasingly reported among KPC-KP. Comparative genomic analysis of a pair of sequential KPC-KP isolates from the same patient including a colistin-susceptible isolate (KKBO-1) and a colistin-resistant isolate (KKBO-4) selected after colistin exposure revealed that insertional inactivation of themgrBgene, encoding a negative regulator of the PhoQ/PhoP signaling system, is a genetic mechanism for acquired colistin resistance. The role ofmgrBinactivation in acquired colistin resistance was confirmed by complementation experiments with wild-typemgrB, which restored colistin susceptibility in KKBO-4, and by construction of anmgrBdeletion mutant from KKBO-1, which exhibited a colistin-resistant phenotype. InsertionalmgrBinactivation was also detected in 60% of colistin-resistant mutants selected from KKBO-1in vitro, following plating on colistin-containing medium, confirming the role (although not unique) of this mechanism in the emergence of acquired colistin resistance. In colistin-resistant mutants carrying insertional inactivation or deletion of themgrBgene, upregulated transcription ofphoP,phoQ, andpmrK(which is part of thepmrHFIJKLMoperon) was detected. These findings confirmed the MgrB regulatory role inK. pneumoniaeand were in agreement with the known association between upregulation of the PhoQ/PhoP system and activation of thepmrHFIJKLMoperon, which eventually leads to resistance to polymyxins by modification of the lipopolysaccharide target.
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Perron-Savard, Philippe, Gregory De Crescenzo, and Hervé Le Moual. "Dimerization and DNA binding of the Salmonella enterica PhoP response regulator are phosphorylation independent." Microbiology 151, no. 12 (December 1, 2005): 3979–87. http://dx.doi.org/10.1099/mic.0.28236-0.
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In Salmonella enterica, PhoP is the response regulator of the PhoP/PhoQ two-component regulatory system that controls the expression of various virulence factors in response to external Mg2+. Previous studies have shown that phosphorylation of a PhoP variant with a C-terminal His tag (PhoPHis) enhances dimerization and binding to target DNA. Here, the effect of phosphorylation on the oligomerization and DNA binding properties of both wild-type PhoP (PhoP) and PhoPHis are compared. Gel filtration chromatography showed that PhoP exists as a mixture of monomer and dimer regardless of its phosphorylation state. In contrast, unphosphorylated PhoPHis was mostly monomeric, whereas PhoPHis∼P existed as a mixture of monomer and dimer. By monitoring the tryptophan fluorescence of the proteins and the fluorescence of the probe 1-anilinonaphthalene-8-sulfonic acid bound to them, it was found that PhoP and PhoPHis exhibited different spectral properties. The interaction between PhoP or PhoPHis and the PhoP box of the mgtA promoter was monitored by surface plasmon resonance. Binding of PhoP to the PhoP box was barely influenced by phosphorylation. In contrast, phosphorylation of PhoPHis clearly increased the interaction of PhoPHis with target DNA. Altogether, these data show that a His tag at the C-terminus of PhoP affects its biochemical properties, most likely by affecting its conformation and/or its oligomerization state. More importantly, these results show that wild-type PhoP dimerization and interaction with target DNA are independent of phosphorylation, which is in contrast to the previously proposed model.
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Kato, Akinori, Hiroyuki Tanabe, and Ryutaro Utsumi. "Molecular Characterization of the PhoP-PhoQ Two-Component System in Escherichia coli K-12: Identification of Extracellular Mg2+-Responsive Promoters." Journal of Bacteriology 181, no. 17 (September 1, 1999): 5516–20. http://dx.doi.org/10.1128/jb.181.17.5516-5520.1999.
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ABSTRACT We identified Mg2+-responsive promoters of thephoPQ, mgtA, and mgrB genes ofEscherichia coli K-12 by S1 nuclease analysis. Expression of these genes was induced by magnesium limitation and depended on PhoP and PhoQ. The transcription start sites were also determined, which allowed us to find a (T/G)GTTTA direct repeat in their corresponding promoter regions.
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Park, Sun-Yang, and Eduardo A. Groisman. "Signal-specific temporal response by theSalmonella PhoP/PhoQ regulatory system." Molecular Microbiology 91, no. 1 (November 20, 2013): 135–44. http://dx.doi.org/10.1111/mmi.12449.
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Tang, Tian, Anchun Cheng, Mingshu Wang, and Xin Li. "Reviews in Salmonella Typhimurium PhoP/PhoQ two-component regulatory system." Reviews in Medical Microbiology 24, no. 1 (January 2013): 18–21. http://dx.doi.org/10.1097/mrm.0b013e32835a9490.
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García Véscovi, E., F. C. Soncini, and E. A. Groisman. "The role of the PhoP/PhoQ regulon in Salmonella virulence." Research in Microbiology 145, no. 5-6 (January 1994): 473–80. http://dx.doi.org/10.1016/0923-2508(94)90096-5.
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Laidoudi, Younes, Edgarthe Priscilla Ngaiganam, Jean-Lou Marié, Isabelle Pagnier, Jean-Marc Rolain, Seydina Mouhamadou Diene, and Bernard Davoust. "Colistin Resistance Mechanism in Enterobacter hormaechei subsp. steigerwaltii Isolated from Wild Boar (Sus scrofa) in France." Pathogens 11, no. 9 (September 7, 2022): 1022. http://dx.doi.org/10.3390/pathogens11091022.
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Wild animals may act as efficient antimicrobial-resistance reservoirs and epidemiological links between humans, livestock, and natural environments. By using phenotypic and genotypic characterization, the present study highlighted the occurrence of an antimicrobial-resistant (i.e., amoxicillin, amoxicillin–clavulanic acid, cephalothin, and colistin) Enterobacter hormaechei subsp. steigerwaltii strain in wild boar (Sus scrofa) from France. The molecular analysis conducted showed non-synonymous mutations in the pmrA/pmrB and phoQ/phoP operons and the phoP/Q regulator mgrB gene, leading to colistin resistance. The present data highlight the need for continuous monitoring of multidrug-resistant bacteria in wild animals to limit the spread of these threatening pathogens.