scholarly journals Quorum Sensing Regulates Exopolysaccharide Production, Motility, and Virulence in Pseudomonas syringae

2005 ◽  
Vol 18 (7) ◽  
pp. 682-693 ◽  
Author(s):  
Beatriz Quiñones ◽  
Glenn Dulla ◽  
Steven E. Lindow
Keyword(s):  
Quorum Sensing ◽  
Pseudomonas Syringae ◽  
Type Strain ◽  
Double Mutant ◽  
Wild Type Strain ◽  
Homoserine Lactone ◽  
Brown Spot ◽  
Wild Type ◽  
In Planta ◽  
Alginate Production

The N-acyl homoserine lactone (AHL)-mediated quorumsensing system in the phytopathogen Pseudomonas syringae pv. syringae requires the AHL synthase AhlI and the regulator AhlR, and is additionally subject to regulation by AefR. The contribution of quorum sensing to the expression of a variety of traits expected to be involved in epiphytic fitness and virulence of P. syringae were examined. Both an aefR- mutant and an ahlR- double mutant, deficient in AHL production, were significantly impaired in alginate production and had an increased susceptibility to hydrogen peroxide compared with the wild-type strain. These mutants were hypermotile in culture, invaded leaves more rapidly, and caused an increased incidence of brown spot lesions on bean leaves after a 48-h moist incubation. Interestingly, an aefR- mutant was both the most motile and virulent. Like the wild-type strain, the AHL-deficient mutant strains incited water-soaked lesions on bean pods. However, lesions caused by an ahlI- ahlR- double mutant were larger, whereas those incited by an aefR- mutant were smaller. In contrast, tissue maceration of pods, which occurs at a later stage of infection, was completely abolished in the AHL-deficient mutants. Both the incidence of disease and in planta growth of P. syringae pv. tabaci were greatly reduced in transgenic tobacco plants that produced AHL compared with wild-type plants. These results demonstrate that quorum sensing in P. syringae regulates traits that contribute to epiphytic fitness as well as to distinct stages of disease development during plant infection.

scholarly journals Quorum-Sensing Systems in the Plant Growth-Promoting Bacterium Paraburkholderia phytofirmans PsJN Exhibit Cross-Regulation and Are Involved in Biofilm Formation

2017 ◽  
Vol 30 (7) ◽  
pp. 557-565 ◽  
Author(s):  
Ana Zúñiga ◽  
Raúl A. Donoso ◽  
Daniela Ruiz ◽  
Gonzalo A. Ruz ◽  
Bernardo González
Keyword(s):  
Quorum Sensing ◽  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Homoserine Lactone ◽  
Wild Type ◽  
Transcript Levels ◽  
Sensing Systems ◽  
Plant Growth Promoting ◽  
Growth Promoting

Quorum-sensing systems play important roles in host colonization and host establishment of Burkholderiales species. Beneficial Paraburkholderia species share a conserved quorum-sensing (QS) system, designated BraI/R, that controls different phenotypes. In this context, the plant growth-promoting bacterium Paraburkholderia phytofirmans PsJN possesses two different homoserine lactone QS systems BpI.1/R.1 and BpI.2/R.2 (BraI/R-like QS system). The BpI.1/R.1 QS system was previously reported to be important to colonize and produce beneficial effects in Arabidopsis thaliana plants. Here, we analyzed the temporal variations of the QS gene transcript levels in the wild-type strain colonizing plant roots. The gene expression patterns showed relevant differences in both QS systems compared with the wild-type strain in the unplanted control treatment. The gene expression data were used to reconstruct a regulatory network model of QS systems in P. phytofirmans PsJN, using a Boolean network model. Also, we examined the phenotypic traits and transcript levels of genes involved in QS systems, using P. phytofirmans mutants in homoserine lactone synthases genes. We observed that the BpI.1/R.1 QS system regulates biofilm formation production in strain PsJN and this phenotype was associated with the lower expression of a specific extracytoplasmic function sigma factor ecf26.1 gene (implicated in biofilm formation) in the bpI.1 mutant strain.

scholarly journals The Role of Ethylene Production in Virulence of Pseudomonas syringae pvs. glycinea and phaseolicola

2001 ◽  
Vol 91 (5) ◽  
pp. 511-518 ◽  
Author(s):  
Helge Weingart ◽  
Henriette Ullrich ◽  
Klaus Geider ◽  
Beate Völksch
Keyword(s):  
Pseudomonas Syringae ◽  
Ethylene Production ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
In Planta ◽  
Population Sizes ◽  
Soybean Plants ◽  
Type Strains

The importance of ethylene production for virulence of Pseudomonas syringae pvs. glycinea and phaseolicola was assayed by comparing bacterial multiplication and symptom development in bean and soybean plants inoculated with ethylene-negative (efe) mutants and wild-type strains. The efe mutants of Pseudomonas syringae pv. glycinea were significantly reduced in their ability to grow in planta. However, the degree of reduction was strain-dependent. Population sizes of efe mutant 16/83-E1 that did not produce the phototoxin coronatine were 10- and 15-fold lower than those of the wild-type strain on soybean and on bean, and 16/83-E1 produced very weak symptoms compared with the wild-type strain. The coronatine-producing efe mutant 7a/90-E1 reached fourfold and twofold lower population sizes compared with the wild-type strain on soybean and bean, respectively, and caused disease symptoms typical of the wild-type strain. Experiments with ethylene-insensitive soybeans confirmed these results. The virulence of the wild-type strains was reduced to the same extent in ethylene-insensitive soybean plants as the virulence of the efe mutants in ethylene-susceptible soybeans. In contrast, the virulence of Pseudomonas syringae pv. phaseolicola was not affected by disruption of the efe gene.

scholarly journals PA0305 of Pseudomonas aeruginosa is a quorum quenching acylhomoserine lactone acylase belonging to the Ntn hydrolase superfamily

Microbiology ◽  
2011 ◽  
Vol 157 (7) ◽  
pp. 2042-2055 ◽  
Author(s):  
Mariana Wahjudi ◽  
Evelina Papaioannou ◽  
Oktavia Hendrawati ◽  
Aart H. G. van Assen ◽  
Ronald van Merkerk ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Pseudomonas Syringae ◽  
Type Strain ◽  
Wild Type Strain ◽  
Functional Characterization ◽  
Homoserine Lactone ◽  
Insertion Mutant ◽  
Wild Type ◽  
Signal Molecule ◽  
Acylhomoserine Lactone

The Pseudomonas aeruginosa PAO1 genome has at least two genes, pvdQ and quiP, encoding acylhomoserine lactone (AHL) acylases. Two additional genes, pa1893 and pa0305, have been predicted to encode penicillin acylase proteins, but have not been characterized. Initial studies on a pa0305 transposon insertion mutant suggested that the gene is not related to the AHL growth phenotype of P. aeruginosa. The close similarity (67 %) of pa0305 to HacB, an AHL acylase of Pseudomonas syringae, prompted us to investigate whether the PA0305 protein might also function as an AHL acylase. The pa0305 gene has been cloned and the protein (PA0305) has been overproduced, purified and subjected to functional characterization. Analysis of the purified protein showed that, like β-lactam acylases, PA0305 undergoes post-translational processing resulting in α- and β-subunits, with the catalytic serine as the first amino acid of the β-subunit, strongly suggesting that PA0305 is a member of the N-terminal nucleophile hydrolase superfamily. Using a biosensor assay, PA0305his was shown to degrade AHLs with acyl side chains ranging in length from 6 to 14 carbons. Kinetics studies using N-octanoyl-l-homoserine lactone (C8-HSL) and N-(3-oxo-dodecanoyl)-l-homoserine lactone (3-oxo-C12-HSL) as substrates showed that the enzyme has a robust activity towards these two AHLs, with apparent K cat/K m values of 0.14×104 M−1 s−1 towards C8-HSL and 7.8×104 M−1 s−1 towards 3-oxo-C12-HSL. Overexpression of the pa0305 gene in P. aeruginosa showed significant reductions in both accumulation of 3-oxo-C12-HSL and expression of virulence factors. A mutant P. aeruginosa strain with a deleted pa0305 gene showed a slightly increased capacity to kill Caenorhabditis elegans compared with the P. aeruginosa PAO1 wild-type strain and the PAO1 strain carrying a plasmid overexpressing pa0305. The harmful effects of the Δpa0305 strain on the animals were most visible at 5 days post-exposure and the mortality rate of the animals fed on the Δpa0305 strain was faster than for the animals fed on either the wild-type strain or the strain overexpressing pa0305. In conclusion, the pa0305 gene encodes an efficient acylase with activity towards long-chain homoserine lactones, including 3-oxo-C12-HSL, the natural quorum sensing signal molecule in P. aeruginosa, and we propose to name this acylase HacB.

scholarly journals Genetic Evidence that Loss of Virulence Associated with gacS or gacA Mutations in Pseudomonas syringae B728a Does Not Result from Effects on Alginate Production

2001 ◽  
Vol 67 (3) ◽  
pp. 1400-1403 ◽  
Author(s):  
David K. Willis ◽  
Jeremy J. Holmstadt ◽  
Thomas G. Kinscherf
Keyword(s):  
Pseudomonas Syringae ◽  
Type Strain ◽  
Wild Type Strain ◽  
Regulatory Genes ◽  
Genetic Evidence ◽  
Wild Type ◽  
Alginate Production ◽  
Bean Plants ◽  
Pathogenic Interaction

ABSTRACT Mutations in the global regulatory genes gacS andgacA render Pseudomonas syringae pv. syringae strain B728a completely nonpathogenic in foliar infiltration assays on bean plants. It had been previously demonstrated that gacgenes regulate alginate production in Pseudomonas species, while other published work indicated that alginate is involved in the pathogenic interaction of P. syringae on bean plants. Together, these results suggested that the effects of gacSand gacA mutations on virulence in B728a might stem directly from a role in regulating alginate. In this report, we confirm a role for gac genes in both algD expression and alginate production in B728a. However, B728a mutants completely devoid of detectable alginate were as virulent as the wild-type strain in our assay. Thus, factors other than, or in addition to, a deficiency of alginate must be involved in the lack of pathogenicity observed withgacS and gacA mutants.

scholarly journals Virulence of Pseudomonas syringae pv. tomato DC3000 Is Influenced by the Catabolite Repression Control Protein Crc

2017 ◽  
Vol 30 (4) ◽  
pp. 283-294 ◽  
Author(s):  
Suma Chakravarthy ◽  
Bronwyn G. Butcher ◽  
Yingyu Liu ◽  
Katherine D’Amico ◽  
Matthew Coster ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Catabolite Repression ◽  
Type Strain ◽  
Wild Type Strain ◽  
Rna Binding ◽  
Plant Diseases ◽  
Wild Type ◽  
In Planta ◽  
Growth And Survival ◽  
Control Protein

Pseudomonas syringae infects diverse plant species and is widely used as a model system in the study of effector function and the molecular basis of plant diseases. Although the relationship between bacterial metabolism, nutrient acquisition, and virulence has attracted increasing attention in bacterial pathology, it is largely unexplored in P. syringae. The Crc (catabolite repression control) protein is a putative RNA-binding protein that regulates carbon metabolism as well as a number of other factors in the pseudomonads. Here, we show that deletion of crc increased bacterial swarming motility and biofilm formation. The crc mutant showed reduced growth and symptoms in Arabidopsis and tomato when compared with the wild-type strain. We have evidence that the crc mutant shows delayed hypersensitive response (HR) when infiltrated into Nicotiana benthamiana and tobacco. Interestingly, the crc mutant was more susceptible to hydrogen peroxide, suggesting that, in planta, the mutant may be sensitive to reactive oxygen species generated during pathogen-associated molecular pattern–triggered immunity (PTI). Indeed, HR was further delayed when PTI-induced tissues were challenged with the crc mutant. The crc mutant did not elicit an altered PTI response in plants compared with the wild-type strain. We conclude that Crc plays an important role in growth and survival during infection.

scholarly journals Use of an Intergenic Region in Pseudomonas syringae pv. Syringae B728a for Site-Directed Genomic Marking of Bacterial Strains for Field Experiments

2001 ◽  
Vol 67 (8) ◽  
pp. 3735-3738 ◽  
Author(s):  
Susan S. Hirano ◽  
David K. Willis ◽  
Murray K. Clayton ◽  
Christen D. Upper
Keyword(s):  
Pseudomonas Syringae ◽  
Intergenic Region ◽  
Type Strain ◽  
Field Experiments ◽  
Wild Type Strain ◽  
Brown Spot ◽  
Wild Type ◽  
Bacterial Strains ◽  
Snap Bean ◽  
Bean Plants

ABSTRACT To construct differentially-marked derivatives of our model wild-type strain, Pseudomonas syringae pv. syringae B728a (a causal agent of bacterial brown spot disease in snap bean plants), for field experiments, we selected a site in the gacS-cysMintergenic region for site-directed insertion of antibiotic resistance marker cassettes. In each of three field experiments, population sizes of the site-directed chromosomally marked B728a derivatives in association with snap bean plants were not significantly different from that of the wild-type strain. Inserts of up to 7 kb of DNA in the intergenic region did not measurably affect fitness of B728a in the field. The site is useful for site-directed genomic insertions of single copies of genes of interest.

scholarly journals Quorum Sensing Is a Global Regulatory Mechanism in Enterohemorrhagic Escherichia coli O157:H7

2001 ◽  
Vol 183 (17) ◽  
pp. 5187-5197 ◽  
Author(s):  
Vanessa Sperandio ◽  
Alfredo G. Torres ◽  
Jorge A. Girón ◽  
James B. Kaper
Keyword(s):  
Escherichia Coli ◽  
Quorum Sensing ◽  
Type Strain ◽  
Wild Type Strain ◽  
Regulatory Mechanism ◽  
Sos Response ◽  
Enterohemorrhagic Escherichia Coli ◽  
Trna Genes ◽  
Wild Type ◽  
E Coli

ABSTRACT Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is responsible for outbreaks of bloody diarrhea and hemolytic-uremic syndrome in many countries. EHEC virulence mechanisms include the production of Shiga toxins (Stx) and formation of attaching and effacing (AE) lesions on intestinal epithelial cells. We recently reported that genes involved in the formation of the AE lesion were regulated by quorum sensing through autoinducer-2, which is synthesized by the product of the luxS gene. In this study we hybridized an E. coli gene array with cDNA synthesized from RNA that was extracted from EHEC strain 86-24 and its isogenicluxS mutant. We observed that 404 genes were regulated by luxS at least fivefold, which comprises approximately 10% of the array genes; 235 of these genes were up-regulated and 169 were down-regulated in the wild-type strain compared to in theluxS mutant. Down-regulated genes included several involved in cell division, as well as ribosomal and tRNA genes. Consistent with this pattern of gene expression, theluxS mutant grows faster than the wild-type strain (generation times of 37.5 and 60 min, respectively, in Dulbecco modified Eagle medium). Up-regulated genes included several involved in the expression and assembly of flagella, motility, and chemotaxis. Using operon::lacZ fusions to class I, II, and III flagellar genes, we were able to confirm this transcriptional regulation. We also observed fewer flagella by Western blotting and electron microscopy and decreased motility halos in semisolid agar in the luxS mutant. The average swimming speeds for the wild-type strain and the luxS mutant are 12.5 and 6.6 μm/s, respectively. We also observed an increase in the production of Stx due to quorum sensing. Genes encoding Stx, which are transcribed along with λ-like phage genes, are induced by an SOS response, and genes involved in the SOS response were also regulated by quorum sensing. These results indicate that quorum sensing is a global regulatory mechanism for basic physiological functions of E. coli as well as for virulence factors.

scholarly journals Bradyrhizobium elkanii rtxC Gene Is Required for Expression of Symbiotic Phenotypes in the Final Step of Rhizobitoxine Biosynthesis

2004 ◽  
Vol 70 (1) ◽  
pp. 535-541 ◽  
Author(s):  
Shin Okazaki ◽  
Masayuki Sugawara ◽  
Kiwamu Minamisawa
Keyword(s):  
Glycine Max ◽  
Type Strain ◽  
Wild Type Strain ◽  
Null Mutant ◽  
Wild Type ◽  
In Planta ◽  
Distinct Effect ◽  
Nodulation Competitiveness ◽  
Macroptilium Atropurpureum ◽  
Bradyrhizobium Elkanii

ABSTRACT We disrupted the rtxC gene on the chromosome of Bradyrhizobium elkanii USDA94 by insertion of a nonpolar aph cartridge. The rtxC mutant, designated ΔrtxC, produced serinol and dihydrorhizobitoxine but no rhizobitoxine, both in culture and in planta. The introduction of cosmids harboring the rtxC gene into the ΔrtxC mutant complemented rhizobitoxine production, suggesting that rtxC is involved in the final step of rhizobitoxine biosynthesis in B. elkanii USDA94. Glycine max cv. Lee inoculated with ΔrtxC or with a null mutant, Δrtx::Ω1, showed no foliar chlorosis, whereas the wild-type strain USDA94 caused severe foliar chlorosis. The two mutants showed significantly less nodulation competitiveness than the wild-type strain on Macroptilium atropurpureum. These results indicate that dihydrorhizobitoxine, the immediate precursor of the oxidative form of rhizobitoxine, has no distinct effect on nodulation phenotype in these legumes. Thus, desaturation of dihydrorhizobitoxine by rtxC-encoded protein is essential for the bacterium to show rhizobitoxine phenotypes in planta. In addition, complementation analysis of rtxC by cosmids differing in rtxC transcription levels suggested that rhizobitoxine production correlates with the amount of rtxC transcript.

scholarly journals Expression of Erwinia chrysanthemi Pectinase Genes pelI, pelL, and pelZ During Infection of Potato Tubers

1999 ◽  
Vol 12 (10) ◽  
pp. 845-851 ◽  
Author(s):  
Sylwia Jafra ◽  
Izabela Figura ◽  
Nicole Hugouvieux-Cotte-Pattat ◽  
Ewa Lojkowska
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Pectate Lyase ◽  
Soft Rot ◽  
Erwinia Chrysanthemi ◽  
Potato Tubers ◽  
Wild Type ◽  
In Planta ◽  
Gene Encoding ◽  
Glucuronidase Activity

Erwinia chrysanthemi mutants, containing transcriptional fusions of one of the minor pectate lyase genes (pelI, pelL, pelZ) with the reporter gene encoding β-glucuronidase activity, were studied for their ability to cause disease symptoms and to synthesize pectinases after inoculation of potato tubers. The strains affected in pelI and pelL genes displayed reduced virulence on potato tubers, demonstrating the important role of these isoenzymes in soft rot disease. Inactivation of the pelZ gene slightly influences the ability to macerate. Analysis of the bacterial population showed rapid multiplication of bacteria during infection. Similar kinetics of growth were observed for all mutants and for the wild-type strain. Comparison of the mutants and the wild-type strain showed that the pelI, pelL, and pelZ mutants synthesized reduced levels of Pels. The expression of pelZ is fivefold higher in planta than in bacterial cultures. In contrast, both pelI and pelL are highly (10-fold factor) induced in planta, which is characteristic of the plant-inducible pectate lyases.

scholarly journals Inactivation of traP Has No Effect on the Agr Quorum-Sensing System or Virulence of Staphylococcus aureus

2007 ◽  
Vol 75 (9) ◽  
pp. 4519-4527 ◽  
Author(s):  
Lindsey N. Shaw ◽  
Ing-Marie Jonsson ◽  
Vineet K. Singh ◽  
Andrej Tarkowski ◽  
George C. Stewart
Keyword(s):  
Staphylococcus Aureus ◽  
Quorum Sensing ◽  
Type Strain ◽  
Wild Type Strain ◽  
Surface Proteins ◽  
Virulence Determinants ◽  
Wild Type ◽  
Expression Levels ◽  
Sensing System ◽  
Quorum Sensing System

ABSTRACT The success of Staphylococcus aureus as a pathogen can largely be attributed to the plethora of genetic regulators encoded within its genome that temporally regulate its arsenal of virulence determinants throughout its virulence lifestyle. Arguably the most important of these is the two-component, quorum-sensing system agr. Over the last decade, the controversial presence of a second quorum-sensing system (the TRAP system) has been proposed, and it has been mooted to function as the master regulator of virulence in S. aureus by modulating agr. Mutants defective in TRAP are reported to be devoid of agr expression, lacking in hemolytic activity, essentially deficient in the secretion of virulence determinants, and avirulent in infection models. A number of research groups have questioned the validity of the TRAP findings in recent years; however, a thorough and independent analysis of its role in S. aureus physiology and pathogenesis has not been forthcoming. Therefore, we have undertaken such an analysis of the TRAP locus of S. aureus. We found that a traP mutant was equally hemolytic as the wild-type strain. Furthermore, transcriptional profiling found no alterations in the traP mutant in expression levels of agr or in expression levels of multiple agr-regulated genes (hla, sspA, and spa). Analysis of secreted and surface proteins of the traP mutant revealed no deviation in comparison to the parent. Finally, analysis conducted using a murine model of S. aureus septic arthritis revealed that, in contrast to an agr mutant, the traP mutant was just as virulent as the wild-type strain.

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