scholarly journals The Campylobacter jejuni Response Regulator, CbrR, Modulates Sodium Deoxycholate Resistance and Chicken Colonization

2005 ◽  
Vol 187 (11) ◽  
pp. 3662-3670 ◽  
Author(s):  
Brian H. Raphael ◽  
Sonia Pereira ◽  
Gary A. Flom ◽  
Qijing Zhang ◽  
Julian M. Ketley ◽  
...  
Keyword(s):  
Campylobacter Jejuni ◽  
Histidine Kinase ◽  
Bile Salts ◽  
Type Strain ◽  
Target Genes ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Sodium Deoxycholate ◽  
Wild Type ◽  
Bile Resistance

ABSTRACT Two-component regulatory systems play a major role in the physiological response of bacteria to environmental stimuli. Such systems are composed of a sensor histidine kinase and a response regulator whose ultimate function is to affect the expression of target genes. Response regulator mutants of Campylobacter jejuni strain F38011 were screened for sensitivity to sodium deoxycholate. A mutation in Cj0643, which encodes a response regulator with no obvious cognate histidine kinase, resulted in an absence of growth on plates containing a subinhibitory concentration of sodium deoxcholate (1%, wt/vol). In broth cultures containing 0.05% (wt/vol) sodium deoxycholate, growth of the mutant was significantly inhibited compared to growth of the C. jejuni F38011 wild-type strain. Complementation of the C. jejuni cbrR mutant in trans restored growth in both broth and plate cultures supplemented with sodium deoxycholate. Based on the phenotype displayed by its mutation, we designated the gene corresponding to Cj0643 as cbrR (Campylobacter bile resistance regulator). While the MICs of a variety of bile salts and other detergents for the C. jejuni cbrR mutant were lower, no difference was noted in its sensitivity to antibiotics or osmolarity. Finally, chicken colonization studies demonstrated that the C. jejuni cbrR mutant had a reduced ability to colonize compared to the wild-type strain. These data support previous findings that bile resistance contributes to colonization of chickens and establish that the response regulator, CbrR, modulates resistance to bile salts in C. jejuni.

scholarly journals FixJ family regulator AcfR of Azorhizobium caulinodans is involved in symbiosis with the host plant

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Wei Liu ◽  
Xue Bai ◽  
Yan Li ◽  
Haikun Zhang ◽  
Xiaoke Hu
Keyword(s):  
Signal Transduction ◽  
Host Plant ◽  
Type Strain ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Azorhizobium Caulinodans ◽  
Wild Type ◽  
Response Regulators ◽  
Free Living ◽  
Two Component

Abstract Background A wide variety of bacterial adaptative responses to environmental conditions are mediated by signal transduction pathways. Two-component signal transduction systems are one of the predominant means used by bacteria to sense the signals of the host plant and adjust their interaction behaviour. A total of seven open reading frames have been identified as putative two-component response regulators in the gram-negative nitrogen-fixing bacteria Azorhizobium caulinodans ORS571. However, the biological functions of these response regulators in the symbiotic interactions between A. caulinodans ORS571 and the host plant Sesbania rostrata have not been elucidated to date. Results In this study, we identified and investigated a two-component response regulator, AcfR, with a phosphorylatable N-terminal REC (receiver) domain and a C-terminal HTH (helix-turn-helix) LuxR DNA-binding domain in A. caulinodans ORS571. Phylogenetic analysis showed that AcfR possessed close evolutionary relationships with NarL/FixJ family regulators. In addition, six histidine kinases containing HATPase_c and HisKA domains were predicted to interact with AcfR. Furthermore, the biological function of AcfR in free-living and symbiotic conditions was elucidated by comparing the wild-type strain and the ΔacfR mutant strain. In the free-living state, the cell motility behaviour and exopolysaccharide production of the ΔacfR mutant were significantly reduced compared to those of the wild-type strain. In the symbiotic state, the ΔacfR mutant showed a competitive nodule defect on the stems and roots of the host plant, suggesting that AcfR can provide A. caulinodans with an effective competitive ability for symbiotic nodulation. Conclusions Our results showed that AcfR, as a response regulator, regulates numerous phenotypes of A. caulinodans under the free-living conditions and in symbiosis with the host plant. The results of this study help to elucidate the involvement of a REC + HTH_LuxR two-component response regulator in the Rhizobium-host plant interaction.

scholarly journals Group III Histidine Kinase Is a Positive Regulator of Hog1-Type Mitogen-Activated Protein Kinase in Filamentous Fungi

2005 ◽  
Vol 4 (11) ◽  
pp. 1820-1828 ◽  
Author(s):  
Akira Yoshimi ◽  
Kaihei Kojima ◽  
Yoshitaka Takano ◽  
Chihiro Tanaka
Keyword(s):  
Osmotic Stress ◽  
Filamentous Fungi ◽  
Histidine Kinase ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
Group Iii ◽  
Positive Regulator ◽  
Mitogen Activated Protein ◽  
In The Wild

ABSTRACT We previously reported that the group III histidine kinase Dic1p in the maize pathogen Cochliobolus heterostrophus is involved in resistance to dicarboximide and phenylpyrrole fungicides and in osmotic adaptation. In addition, exposure to the phenylpyrrole fungicide fludioxonil led to improper activation of Hog1-type mitogen-activated protein kinases (MAPKs) in some phytopathogenic fungi, including C. heterostrophus. Here we report, for the first time, the relationship between the group III histidine kinase and Hog1-related MAPK: group III histidine kinase is a positive regulator of Hog1-related MAPK in filamentous fungi. The phosphorylation pattern of C. heterostrophus BmHog1p (Hog1-type MAPK) was analyzed in wild-type and dic1-deficient strains by Western blotting. In the wild-type strain, phosphorylated BmHog1p was detected after exposure to both iprodione and fludioxonil at a concentration of 1 μg/ml. In the dic1-deficient strains, phosphorylated BmHog1p was not detected after exposure to 10 μg/ml of the fungicides. In response to osmotic stress (0.4 M KCl), a trace of phosphorylated BmHog1p was found in the dic1-deficient strains, whereas the band representing active BmHog1p was clearly detected in the wild-type strain. Similar results were obtained for Neurospora crassa Os-2p MAPK phosphorylation in the mutant of the group III histidine kinase gene os-1. These results indicate that group III histidine kinase positively regulates the activation of Hog1-type MAPKs in filamentous fungi. Notably, the Hog1-type MAPKs were activated at high fungicide (100 μg/ml) and osmotic stress (0.8 M KCl) levels in the histidine kinase mutants of both fungi, suggesting that another signaling pathway activates Hog1-type MAPKs in these conditions.

scholarly journals Mutations in Four Regulatory Genes Have Interrelated Effects on Heterocyst Maturation in Anabaena sp. Strain PCC 7120

2006 ◽  
Vol 188 (21) ◽  
pp. 7387-7395 ◽  
Author(s):  
Sigal Lechno-Yossef ◽  
Qing Fan ◽  
Shigeki Ehira ◽  
Naoki Sato ◽  
C. Peter Wolk
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Regulatory System ◽  
Transcript Abundance ◽  
Regulatory Genes ◽  
Wild Type ◽  
Serine Threonine Kinase ◽  
In The Wild ◽  
Pcc 7120

ABSTRACT Regulatory genes hepK, hepN, henR, and hepS are required for heterocyst maturation in Anabaena sp. strain PCC 7120. They presumptively encode two histidine kinases, a response regulator, and a serine/threonine kinase, respectively. To identify relationships between those genes, we compared global patterns of gene expression, at 14 h after nitrogen step-down, in corresponding mutants and in the wild-type strain. Heterocyst envelopes of mutants affected in any of those genes lack a homogeneous, polysaccharide layer. Those of a henR mutant also lack a glycolipid layer. patA, which encodes a positive effector of heterocyst differentiation, was up-regulated in all mutants except the hepK mutant, suggesting that patA expression may be inhibited by products related to heterocyst development. hepS and hepK were up-regulated if mutated and so appear to be negatively autoregulated. HepS and HenR regulated a common set of genes and so appear to belong to one regulatory system. Some nontranscriptional mechanism may account for the observation that henR mutants lack, and hepS mutants possess, a glycolipid layer, even though both mutations down-regulated genes involved in formation of the glycolipid layer. HepK and HepN also affected transcription of a common set of genes and therefore appear to share a regulatory pathway. However, the transcript abundance of other genes differed very significantly from expression in the wild-type strain in either the hepK or hepN mutant while differing very little from wild-type expression in the other of those two mutants. Therefore, hepK and hepN appear to participate also in separate pathways.

scholarly journals The Atypical Response Regulator AtvR Is a New Player in Pseudomonas aeruginosa Response to Hypoxia and Virulence

2017 ◽  
Vol 85 (8) ◽  
Author(s):  
Gilberto Hideo Kaihami ◽  
Leandro Carvalho Dantas Breda ◽  
José Roberto Fogaça de Almeida ◽  
Thays de Oliveira Pereira ◽  
Gianlucca Gonçalves Nicastro ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Type Strain ◽  
Wild Type Strain ◽  
Environmental Changes ◽  
Response Regulator ◽  
Classical Pathway ◽  
Wild Type ◽  
Macrophage Infection ◽  
Content Type ◽  
Successful Infection

ABSTRACT Two-component systems are widespread in bacteria, allowing adaptation to environmental changes. The classical pathway is composed of a histidine kinase that phosphorylates an aspartate residue in the cognate response regulator (RR). RRs lacking the phosphorylatable aspartate also occur, but their function and contribution during host-pathogen interactions are poorly characterized. AtvR (PA14_26570) is the only atypical response regulator with a DNA-binding domain in the opportunistic pathogen Pseudomonas aeruginosa. Macrophage infection with the atvR mutant strain resulted in higher levels of tumor necrosis factor alpha secretion as well as increased bacterial clearance compared to those for macrophages infected with the wild-type strain. In an acute pneumonia model, mice infected with the atvR mutant presented increased amounts of proinflammatory cytokines, increased neutrophil recruitment to the lungs, reductions in bacterial burdens, and higher survival rates in comparison with the findings for mice infected with the wild-type strain. Further, several genes involved in hypoxia/anoxia adaptation were upregulated upon atvR overexpression, as seen by high-throughput transcriptome sequencing (RNA-Seq) analysis. In addition, atvR was more expressed in hypoxia in the presence of nitrate and required for full expression of nitrate reductase genes, promoting bacterial growth under this condition. Thus, AtvR would be crucial for successful infection, aiding P. aeruginosa survival under conditions of low oxygen tension in the host. Taken together, our data demonstrate that the atypical response regulator AtvR is part of the repertoire of transcriptional regulators involved in the lifestyle switch from aerobic to anaerobic conditions. This finding increases the complexity of regulation of one of the central metabolic pathways that contributes to Pseudomonas ubiquity and versatility.

scholarly journals Campylobacter jejuni FlpA Binds Fibronectin and Is Required for Maximal Host Cell Adherence

2009 ◽  
Vol 192 (1) ◽  
pp. 68-76 ◽  
Author(s):  
Michael E. Konkel ◽  
Charles L. Larson ◽  
Rebecca C. Flanagan
Keyword(s):  
Amino Acids ◽  
Epithelial Cells ◽  
Campylobacter Jejuni ◽  
Type Strain ◽  
Wild Type Strain ◽  
Major Constituent ◽  
Enzyme Linked Immunosorbent Assay ◽  
Type I ◽  
Wild Type ◽  
Type Iii

ABSTRACT Campylobacter jejuni is one of the most frequent bacterial causes of food-borne gastrointestinal disease in developed countries. Previous work indicates that the binding of C. jejuni to human intestinal cells is crucial for host colonization and disease. Fibronectin (Fn), a major constituent of the extracellular matrix, is a ∼250-kDa glycoprotein present at regions of cell-to-cell contact in the intestinal epithelium. Fn is composed of three types of repeating units: type I (∼45 amino acids), type II (∼60 amino acids), and type III (∼90 amino acids). The deduced amino acid sequence of C. jejuni flpA (Cj1279c) contains at least three Fn type III domains. Based on the presence of the Fn type III domains, we hypothesized that FlpA contributes to the binding of C. jejuni to human INT 407 epithelial cells and Fn. We assessed the contribution of FlpA in C. jejuni binding to host cells by in vitro adherence assays with a C. jejuni wild-type strain and a C. jejuni flpA mutant and binding of purified FlpA protein to Fn by enzyme-linked immunosorbent assay (ELISA). Adherence assays revealed the binding of the C. jejuni flpA mutant to INT 407 epithelial cells was significantly reduced compared with that for a wild-type strain. In addition, rabbit polyclonal serum generated against FlpA blocked C. jejuni adherence to INT 407 cells in a concentration-dependent manner. Binding of FlpA to Fn was found to be dose dependent and saturable by ELISA, demonstrating the specificity of the interaction. Based on these data, we conclude that FlpA mediates C. jejuni attachment to host epithelial cells via Fn binding.

scholarly journals A Mutation in the 3-Phosphoglycerate Kinase Gene Allows Anaerobic Growth of Bacillus subtilis in the Absence of ResE Kinase

1999 ◽  
Vol 181 (22) ◽  
pp. 7087-7097 ◽  
Author(s):  
Michiko M. Nakano ◽  
Yi Zhu ◽  
Koki Haga ◽  
Hirofumi Yoshikawa ◽  
Abraham L. Sonenshein ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Anaerobic Respiration ◽  
Phosphoglycerate Kinase ◽  
Anaerobic Growth ◽  
Wild Type ◽  
Kinase Gene ◽  
Glycolytic Intermediate

ABSTRACT The Bacillus subtilis ResD-ResE two-component signal transduction system is essential for aerobic and anaerobic respiration. A spontaneous suppressor mutant that expresses ResD-controlled genes and grows anaerobically in the absence of the ResE histidine kinase was isolated. In addition, aerobic expression of ResD-controlled genes in the suppressed strain was constitutive and occurred at a much higher level than that observed in the wild-type strain. The suppressing mutation, which mapped to pgk, the gene encoding 3-phosphoglycerate kinase, failed to suppress a resDmutation, suggesting that the suppressing mutation creates a pathway for phosphorylation of the response regulator, ResD, which is independent of the cognate sensor kinase, ResE. The pgk-1mutant exhibited very low but measurable 3-phosphoglycerate kinase activity compared to the wild-type strain. The results suggest that accumulation of a glycolytic intermediate, probably 1,3-diphosphoglycerate, is responsible for the observed effect of thepgk-1 mutation on anaerobiosis of resE mutant cells.

scholarly journals Serratia marcescensarn, a PhoP-Regulated Locus Necessary for Polymyxin B Resistance

2014 ◽  
Vol 58 (9) ◽  
pp. 5181-5190 ◽  
Author(s):  
Quei Yen Lin ◽  
Yi-Lin Tsai ◽  
Ming-Che Liu ◽  
Wei-Cheng Lin ◽  
Po-Ren Hsueh ◽  
...  
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Challenge Test ◽  
Polymyxin B ◽  
Resistant Bacteria ◽  
Wild Type ◽  
Mobility Shift ◽  
Content Type ◽  
In The Wild

ABSTRACTPolymyxins, which are increasingly being used to treat infections caused by multidrug-resistant bacteria, perform poorly againstSerratia marcescens. To investigate the underlying mechanisms, Tn5mutagenesis was performed and two mutants exhibiting increased polymyxin B (PB) susceptibility were isolated. The mutants were found to have Tn5inserted into thearnBandarnCgenes. In other bacteria,arnBandarnCbelong to the seven-genearnoperon, which is involved in lipopolysaccharide (LPS) modification. LPSs ofarnmutants had greater PB-binding abilities than that of wild-type LPS. Further, we identified PhoP, a bacterial two-component response regulator, as a regulator of PB susceptibility inS. marcescens. By the reporter assay, we found PB- and low-Mg2+-induced expression ofphoPandarnin the wild-type strain but not in thephoPmutant. Complementation of thephoPmutant with the full-lengthphoPgene restored the PB MIC and induction by PB and low Mg2+levels, as in the wild type. An electrophoretic mobility shift assay (EMSA) further demonstrated that PhoP bound directly to thearnpromoter. The PB challenge test confirmed that pretreatment with PB and low Mg2+levels protectedS. marcescensfrom a PB challenge in the wild-type strain but not in thephoPmutant. Real-time reverse transcriptase-PCR also indicated that PB serves as a signal to regulate expression ofugd, a gene required for LPS modification, inS. marcescensthrough a PhoP-dependent pathway. Finally, we found that PB-resistant clinical isolates displayed greater expression ofarnAupon exposure to PB than did susceptible isolates. This is the first report to describe the role ofS. marcescensarnin PB resistance and its modulation by PB and Mg2+through the PhoP protein.

scholarly journals Riboflavin Biosynthesis Is Associated with Assimilatory Ferric Reduction and Iron Acquisition by Campylobacter jejuni

2007 ◽  
Vol 73 (24) ◽  
pp. 7819-7825 ◽  
Author(s):  
Rachel A. Crossley ◽  
Duncan J. H. Gaskin ◽  
Kathryn Holmes ◽  
Francis Mulholland ◽  
Jerry M. Wells ◽  
...  
Keyword(s):  
Campylobacter Jejuni ◽  
Iron Uptake ◽  
Type Strain ◽  
Wild Type Strain ◽  
Iron Acquisition ◽  
Flavin Mononucleotide ◽  
Riboflavin Biosynthesis ◽  
Wild Type ◽  
Low Oxygen ◽  
Riboflavin Production

ABSTRACT One of the pathways involved in the acquisition of the essential metal iron by bacteria involves the reduction of insoluble Fe3+ to soluble Fe2+, followed by transport of Fe2+ to the cytoplasm. Flavins have been implicated as electron donors in this poorly understood process. Ferrous iron uptake is essential for intestinal colonization by the important pathogen Campylobacter jejuni and may be of particular importance under low-oxygen conditions. In this study, the links among riboflavin biosynthesis, ferric reduction, and iron acquisition in C. jejuni NCTC11168 have been investigated. A riboflavin auxotroph was generated by inactivation of the ribB riboflavin biosynthesis gene (Cj0572), and the resulting isogenic ribB mutant only grew in the presence of exogenous riboflavin or the riboflavin precursor diacetyl but not in the presence of the downstream products flavin adenine dinucleotide and flavin mononucleotide. Riboflavin uptake was unaffected in the ribB mutant under iron-limited conditions but was lower in both the wild-type strain and the ribB mutant under iron-replete conditions. Mutation of the fur gene, which encodes an iron uptake regulator of C. jejuni, resulted in an increase in riboflavin uptake which was independent of the iron content of the medium, suggesting a role for Fur in the regulation of the as-yet-unknown riboflavin transport system. Finally, ferric reduction activity was independent of iron availability in the growth medium but was lowered in the ribB mutant compared to the wild-type strain and, conversely, increased in the fur mutant. Taken together, the findings confirm close relationships among iron acquisition, riboflavin production, and riboflavin uptake in C. jejuni.

scholarly journals Mutation of waaC, Encoding Heptosyltransferase I in Campylobacter jejuni 81-176, Affects the Structure of both Lipooligosaccharide and Capsular Carbohydrate

2006 ◽  
Vol 188 (9) ◽  
pp. 3273-3279 ◽  
Author(s):  
Margaret I. Kanipes ◽  
Erzsebet Papp-Szabo ◽  
Patricia Guerry ◽  
Mario A. Monteiro
Keyword(s):  
Campylobacter Jejuni ◽  
Type Strain ◽  
Insertional Mutagenesis ◽  
Lipid A ◽  
Wild Type Strain ◽  
Capsular Polysaccharide ◽  
Resonance Spectroscopy ◽  
Gas Liquid Chromatography ◽  
Wild Type ◽  
Isolation And Characterization

ABSTRACT Campylobacter jejuni 81-176 lipooligosaccharide (LOS) is composed of two covalently linked domains: lipid A, a hydrophobic anchor, and a nonrepeating core oligosaccharide, consisting of an inner and outer core region. We report the isolation and characterization of the deepest rough C. jejuni 81-176 mutant by insertional mutagenesis into the waaC gene, encoding heptosyltransferase I that catalyzes the transfer of the first l-glycero-d-manno-heptose residue to 3-deoxy-d-manno-octulosonic residue (Kdo)-lipid A. Tricine gel electrophoresis, followed by silver staining, showed that site-specific mutation in the waaC gene resulted in the expression of a severely truncated LOS compared to wild-type strain 81-176. Gas-liquid chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy showed that the waaC LOS species lacked all sugars distal to Kdo-lipid A. Parallel structural studies of the capsular polysaccharides of the wild-type strain 81-176 and waaC mutant revealed loss of the 3-O-methyl group in the waaC mutant. Complementation of the C. jejuni mutant by insertion of the wild-type C. jejuni waaC gene into a chromosomal locus resulted in LOS and capsular structures identical to those expressed in the parent strain. We also report here the presence of O-methyl phosphoramidate in wild-type strain 81-176 capsular polysaccharide.

scholarly journals The role of two-component system response regulatorBceRin antimicrobial resistance, virulence, biofilm formation, and stress response of group B Streptococcus

2018 ◽  
Author(s):  
Ying Yang ◽  
Mingjing Luo ◽  
Haokui ◽  
Carmen Li ◽  
Alison W. S. Luk ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Group B Streptococcus ◽  
Invasive Disease ◽  
Wild Type ◽  
Non Invasive ◽  
Two Component ◽  
Group B

AbstractThe hypervirulent Group B Streptococcus (Streptococcus agalactiae, GBS) serogroup III clonal cluster 17 has been associated with neonatal GBS invasive disease and meningits. Serogroup III, ST283 has recently been implicated in invasive disease among non-pregnant adults in Asia. These strains cluster with strains from freshwater fishes from aquaculture and a foodborne outbreak of sepsis, especially with septic arthritis, had been linked to such consumption in Singapore in 2015. Through comparative genome analyses of invasive and non-invasive strains of ST283, we identified a truncated response regulator gene in the non-invasive strain. This two component response gene, previously named a DNA binding regulator, is conserved among GBS strains and is a homologue ofBacillus subtilis BceR, the response regulator of the BceRSAB system. Loss of function of theBceRresponse gene in the invasive GBS strain demonstrated bacitracin susceptibility inΔBceRmutant with MICs of 256-fold and four-fold reduction in bacitracin and human cathelicin LL-37 compared to wild type and complementation strains. Upregulation ofdltAof wild type strain vsΔBceRmutant was demonstrated (p<0.0001), and was previously shown inStaphylococcus aureusto resist and repel cationic peptides through excess positive charges with D-alanylation of teichoic acids on the cell wall. In addition,ΔBceRmutant was less susceptible under oxidative stress under H2O2stress when compared to wild type strain (p<0.001) and inhibited biofilm formation (p<0.05 andp< 0.0001 for crystal violet staining and cfu counts). TheΔBceRmutant also showed reduced mortality as compared to wild type strain (p<0.01) in a murine infection model. Taken together,BceRSis involved in bacitracin and antimicrobial peptide resistance, survival under oxidative stress, biofilm formation and play an important role in the virulence of GBS.Author SummaryTwo-component systems (TCSs) play an important role in virulence in bacteria, and are involved in detecting environmental changes. AlthoughS. agalactiaewas reported to contain more predicted TCSs thanStreptococcus pneumoniae,few have been studied in detail. In this work, comparative genomic analysis of GBS invasive (hyper-virulent) and non-invasive serotype III-4 strains were performed to determine any gene differences that may account for severity of disease in humans.BceR-likeTCS was selected and suspected to be involved in virulence, and thusBceRwas deleted in a hyper-virulent GBS serotype III-4 strain. We demonstrated that thisBceR-likeTCS is involved in GBS virulence and induced proinflammatory host immune responses. Our study of TCSBceRmay guide further research into the role of other TCSs in GBS pathogenicity, and further explore therapeutic targets for GBS disease.

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