scholarly journals Virulence Genetics of an Erwinia amylovora Putative Polysaccharide Transporter Family Member

2020 ◽  
Vol 202 (22) ◽  
Author(s):  
Sara M. Klee ◽  
Judith P. Sinn ◽  
Elena Christian ◽  
Aleah C. Holmes ◽  
Kaixi Zhao ◽  
...  
Keyword(s):  
Virulence Factors ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Control Measures ◽  
Detectable Effect ◽  
Wild Type ◽  
Content Type ◽  
Transporter Family ◽  
Blight Disease ◽  
Suppressor Screen

ABSTRACT The Gram-negative enterobacterium Erwinia amylovora causes fire blight disease in apple and pear trees. Lipopolysaccharides and the exopolysaccharide amylovoran are essential E. amylovora virulence factors. We found that mutations in rfbX disrupted amylovoran production and virulence in apple fruits and tree shoots and that the deletion of yibD suppressed the rfbX mutant phenotype. The level of expression of yibD was about 10-fold higher in the ΔrfbX mutant than the wild type. A forward genetic suppressor screen in the ΔrfbX mutant uncovered multiple mutations in yibD and supported the conclusion that the virulence defect of rfbX mutants is due to reduced amylovoran production. The yibD and rfbX genes are expressed as a two-gene operon, yibD rfbX. The rfbX gene encodes a previously uncharacterized putative polysaccharide subunit transporter, while yibD encodes a predicted glycosyltransferase. Mutation of rfbX did not have a detectable effect on lipopolysaccharide patterns; however, the overexpression of yibD in both the wild-type and ΔyibD ΔrfbX genetic backgrounds disrupted both amylovoran and lipopolysaccharide production. Additionally, the overexpression of yibD in the ΔyibD ΔrfbX mutant inhibited bacterial growth in amylovoran-inducing medium. This growth inhibition phenotype was used in a forward genetic suppressor screen and reverse-genetics tests to identify several genes involved in lipopolysaccharide production, which, when mutated, restored the ability of the ΔyibD ΔrfbX mutant overexpressing yibD to grow in amylovoran-inducing medium. Remarkably, all the lipopolysaccharide gene mutants tested were defective in lipopolysaccharide and amylovoran production. These results reveal a genetic connection between amylovoran and lipopolysaccharide production in E. amylovora. IMPORTANCE This study discovered previously unknown genetic connections between exopolysaccharide and lipopolysaccharide production in the fire blight pathogen Erwinia amylovora. This represents a step forward in our understanding of the biology underlying the production of these two macromolecules. Fire blight is an economically important disease that impacts the production of apples and pears worldwide. Few fire blight control measures are available, and growers rely heavily on antibiotic applications at bloom time. Both exopolysaccharide and lipopolysaccharide are E. amylovora virulence factors. Our results indicate that the overexpression of the yibD gene in E. amylovora disrupts both lipopolysaccharide production and exopolysaccharide production. This effect could potentially be used as the basis for the development of an antivirulence treatment for the prevention of fire blight disease.

scholarly journals The Type IX Secretion System Is Required for Virulence of the Fish Pathogen Flavobacterium psychrophilum

2020 ◽  
Vol 86 (16) ◽  
Author(s):  
Paul Barbier ◽  
Tatiana Rochat ◽  
Haitham H. Mohammed ◽  
Gregory D. Wiens ◽  
Jean-François Bernardet ◽  
...  
Keyword(s):  
Virulence Factors ◽  
Gene Deletion ◽  
Cold Water ◽  
Secretion System ◽  
Gliding Motility ◽  
Control Measures ◽  
Fish Pathogen ◽  
Wild Type ◽  
Content Type ◽  
Bacterial Cold Water Disease

ABSTRACT Flavobacterium psychrophilum causes bacterial cold-water disease in wild and aquaculture-reared fish and is a major problem for salmonid aquaculture. The mechanisms responsible for cold-water disease are not known. It was recently demonstrated that the related fish pathogen, Flavobacterium columnare, requires a functional type IX protein secretion system (T9SS) to cause disease. T9SSs secrete cell surface adhesins, gliding motility proteins, peptidases, and other enzymes, any of which may be virulence factors. The F. psychrophilum genome has genes predicted to encode components of a T9SS. Here, we used a SacB-mediated gene deletion technique recently adapted for use in the Bacteroidetes to delete a core F. psychrophilum T9SS gene, gldN. The ΔgldN mutant cells were deficient for secretion of many proteins in comparison to wild-type cells. Complementation of the mutant with wild-type gldN on a plasmid restored secretion. Compared to wild-type and complemented strains, the ΔgldN mutant was deficient in adhesion, gliding motility, and extracellular proteolytic and hemolytic activities. The ΔgldN mutant exhibited reduced virulence in rainbow trout and complementation restored virulence, suggesting that the T9SS plays an important role in the disease. IMPORTANCE Bacterial cold-water disease, caused by F. psychrophilum, is a major problem for salmonid aquaculture. Little is known regarding the virulence factors involved in this disease, and control measures are inadequate. A targeted gene deletion method was adapted to F. psychrophilum and used to demonstrate the importance of the T9SS in virulence. Proteins secreted by this system are likely virulence factors and targets for the development of control measures.

scholarly journals Discovery of Plant Phenolic Compounds That Act as Type III Secretion System Inhibitors or Inducers of the Fire Blight Pathogen, Erwinia amylovora

2013 ◽  
Vol 79 (18) ◽  
pp. 5424-5436 ◽  
Author(s):  
Devanshi Khokhani ◽  
Chengfang Zhang ◽  
Yan Li ◽  
Qi Wang ◽  
Quan Zeng ◽  
...  
Keyword(s):  
Phenolic Compounds ◽  
Virulence Factors ◽  
Type Iii Secretion ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Fluorescent Protein ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Content Type ◽  
Type Iii

ABSTRACTErwinia amylovoracauses a devastating disease called fire blight in rosaceous plants. The type III secretion system (T3SS) is one of the important virulence factors utilized byE. amylovorain order to successfully infect its hosts. By using a green fluorescent protein (GFP) reporter construct combined with a high-throughput flow cytometry assay, a library of phenolic compounds and their derivatives was studied for their ability to alter the expression of the T3SS. Based on the effectiveness of the compounds on the expression of the T3SS pilus, the T3SS inhibitors 4-methoxy-cinnamic acid (TMCA) and benzoic acid (BA) and one T3SS inducer,trans-2-(4-hydroxyphenyl)-ethenylsulfonate (EHPES), were chosen for further study. Both the T3SS inhibitors (TMCA and BA) and the T3SS inducer (EHPES) were found to alter the expression of T3SS through the HrpS-HrpL pathway. Additionally, TMCA altered T3SS expression through thersmBEa-RsmAEasystem. Finally, we found that TMCA and BA weakened the hypersensitive response (HR) in tobacco by suppressing the T3SS ofE. amylovora. In our study, we identified phenolic compounds that specifically targeted the T3SS. The T3SS inhibitor may offer an alternative approach to antimicrobial therapy by targeting virulence factors of bacterial pathogens.

scholarly journals The Leucine-Responsive Regulatory Protein Lrp Participates in Virulence Regulation Downstream of Small RNA ArcZ inErwinia amylovora

mBio ◽  
2019 ◽  
Vol 10 (3) ◽  
Author(s):  
Jeffrey K. Schachterle ◽  
George W. Sundin
Keyword(s):  
Small Rna ◽  
Transcriptional Activation ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Regulatory Protein ◽  
Regulatory Control ◽  
Transcriptional Level ◽  
Content Type ◽  
Virulence Regulation ◽  
Blight Disease

ABSTRACTErwinia amylovoracauses the devastating fire blight disease of apple and pear trees. During systemic infection of host trees, pathogen cells must rapidly respond to changes in their environment as they move through different host tissues that present distinct challenges and sources of nutrition. Growing evidence indicates that small RNAs (sRNAs) play an important role in disease progression as posttranscriptional regulators. The sRNA ArcZ positively regulates the motility phenotype and transcription of flagellar genes inE. amylovoraEa1189 yet is a direct repressor of translation of the flagellar master regulator, FlhD. We utilized transposon mutagenesis to conduct a forward genetic screen and identified suppressor mutations that increase motility in the Ea1189ΔarcZmutant background. This enabled us to determine that the mechanism of transcriptional activation of theflhDCmRNA by ArcZ is mediated by the leucine-responsive regulatory protein, Lrp. We show that Lrp contributes to expression of virulence and several virulence-associated traits, including production of the exopolysaccharide amylovoran, levansucrase activity, and biofilm formation. We further show that Lrp is regulated posttranscriptionally by ArcZ through destabilization oflrpmRNA. Thus, ArcZ regulation of FlhDC directly and indirectly through Lrp forms an incoherent feed-forward loop that regulates levansucrase activity and motility as outputs. This work identifies Lrp as a novel participant in virulence regulation inE. amylovoraand places it in the context of a virulence-associated regulatory network.IMPORTANCEFire blight disease continues to plague the commercial production of apples and pears despite more than a century of research into disease epidemiology and disease control. The causative agent of fire blight,Erwinia amylovoracoordinates turning on or off specific virulence-associated traits at the appropriate time during disease development. The development of novel control strategies requires an in-depth understanding ofE. amylovoraregulatory mechanisms, including regulatory control of virulence-associated traits. This study investigates how the small RNA ArcZ regulates motility at the transcriptional level and identifies the transcription factor Lrp as a novel participant in the regulation of several virulence-associated traits. We report that ArcZ and Lrp together affect key virulence-associated traits through integration of transcriptional and posttranscriptional mechanisms. Further understanding of the topology of virulence regulatory networks can uncover weak points that can subsequently be exploited to controlE. amylovora.

scholarly journals Whole-Genome Sequence of Pseudomonas fluorescens EK007-RG4, a Promising Biocontrol Agent against a Broad Range of Bacteria, Including the Fire Blight Bacterium Erwinia amylovora

2017 ◽  
Vol 5 (13) ◽  
Author(s):  
Roghayeh Habibi ◽  
Saeed Tarighi ◽  
Javad Behravan ◽  
Parissa Taheri ◽  
Annelise Helene Kjøller ◽  
...  
Keyword(s):  
Pseudomonas Fluorescens ◽  
Genome Sequence ◽  
Pathogenic Bacteria ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Whole Genome Sequence ◽  
Whole Genome ◽  
Content Type ◽  
Pear Tree ◽  
Blight Disease

ABSTRACT Here, we report the first draft whole-genome sequence of Pseudomonas fluorescens strain EK007-RG4, which was isolated from the phylloplane of a pear tree. P. fluorescens EK007-RG4 displays strong antagonism against Erwinia amylovora, the causal agent for fire blight disease, in addition to several other pathogenic and non-pathogenic bacteria.

Isolation and characterization of Hena1 – a novel Erwinia amylovora bacteriophage

2020 ◽  
Vol 367 (9) ◽  
Author(s):  
Natalya V Besarab ◽  
Artur E Akhremchuk ◽  
Maryna A Zlatohurska ◽  
Liudmyla V Romaniuk ◽  
Leonid N Valentovich ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Fire Blight ◽  
Antimicrobial Agents ◽  
Erwinia Amylovora ◽  
Gc Content ◽  
Control Measures ◽  
Effective Control ◽  
Lytic Phage ◽  
Trna Genes ◽  
Isolation And Characterization

ABSTRACT Fire blight, caused by plant pathogenic bacterium Erwinia amylovora, is one of the most important diseases of Rosaceae plants. Due to the lack of effective control measures, fire blight infections pose a recurrent threat on agricultural production worldwide. Recently, bacterial viruses, or bacteriophages, have been proposed as environmentally friendly natural antimicrobial agents for fire blight control. Here, we isolated a novel bacteriophage Hena1 with activity against E. amylovora. Further analysis revealed that Hena1 is a narrow-host-range lytic phage belonging to Myoviridae family. Its genome consists of a linear 148,842 bp dsDNA (48.42% GC content) encoding 240 ORFs and 23 tRNA genes. Based on virion structure and genomic composition, Hena1 was classified as a new species of bacteriophage subfamily Vequintavirinae. The comprehensive analysis of Hena1 genome may provide further insights into evolution of bacteriophages infecting plant pathogenic bacteria.

scholarly journals Evaluation of Susceptibility of Different Pear Hybrid Populations to Fire Blight (Erwinia amylovora)

2011 ◽  
Vol 39 (1) ◽  
pp. 226 ◽  
Author(s):  
Yasemin EVRENOSOĞLU ◽  
Adalet MISIRLI ◽  
Hikmet SAYGILI ◽  
Emre BİLEN ◽  
Özlem BOZTEPE ◽  
...  
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Open Pollination ◽  
Resistance Level ◽  
Class A ◽  
Class B ◽  
Artificial Inoculations ◽  
Serious Disease ◽  
Blight Disease ◽  
Santa Maria

Fire blight disease caused by pathogenic bacterium Erwinia amylovora, is the serious disease of pear, and there is not a certain chemical management against this disease except antibiotic-type compounds such as streptomycin. It is very important to improve new fire blight resistant cultivars in case of integrated disease management. With this purpose, different crosses have been made between Pyrus communis varieties that have good fruit characteristics and resistant cultigens. Besides, self and open pollination treatments have been carried out in maternal plants. The disease resistance level of the hybrids obtained from these combinations was determined by artificial inoculations by Erwinia amylovora in greenhouse conditions. A total of 3284 hybrids were inoculated, and 2631 of them survived and were distributed to different susceptibility classes. 19.88% of the inoculated hybrids was killed by Erwinia amylovora. Total distribution of the hybrids to susceptibility classes was as 6.18% in class “A- slightly susceptible”, 3.11% in class “B- less susceptible”, 8.89% in class “C- mid-susceptible”, 20.28% in class “D- susceptible”, and 61.54% in class “E- very susceptible”. Majority of class “A- slightly susceptible” hybrids were obtained from ‘Magness’ x ‘Ankara’ combination. ‘Kieffer’ x ‘Santa Maria’, ‘Kieffer’ open pollination, ‘Magness’ x ‘Akça’, ‘Magness’ x ‘Kieffer’, ‘Magness’ x ‘Santa Maria’, ‘Mustafa Bey’ x ‘Moonglow’ treatments displayed good results with respect to “A- slightly susceptible” character. It is very important to evaluate these hybrid pear populations through different fruit and tree characteristics in the future.

scholarly journals Nisin Resistance of Listeria monocytogenes Is Increased by Exposure to Salt Stress and Is Mediated via LiaR

2013 ◽  
Vol 79 (18) ◽  
pp. 5682-5688 ◽  
Author(s):  
Teresa M. Bergholz ◽  
Silin Tang ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Salt Stress ◽  
Listeria Monocytogenes ◽  
Safety Concern ◽  
Response Regulator ◽  
Brain Heart Infusion ◽  
Control Measures ◽  
Protective Effects ◽  
Wild Type ◽  
Content Type ◽  
Type Strains

ABSTRACTGrowth ofListeria monocytogeneson refrigerated, ready-to-eat food is a significant food safety concern. Natural antimicrobials, such as nisin, can be used to control this pathogen on food, but little is known about how other food-related stresses may impact how the pathogen responds to these compounds. Prior work demonstrated that exposure ofL. monocytogenesto salt stress at 7°C led to increased expression of genes involved in nisin resistance, including the response regulatorliaR. We hypothesized that exposure to salt stress would increase subsequent resistance to nisin and that LiaR would contribute to increased nisin resistance. Isogenic deletion mutations inliaRwere constructed in 7 strains ofL. monocytogenes, and strains were exposed to 6% NaCl in brain heart infusion broth and then tested for resistance to nisin (2 mg/ml Nisaplin) at 7°C. For the wild-type strains, exposure to salt significantly increased subsequent nisin resistance (P< 0.0001) over innate levels of resistance. Compared to the salt-induced nisin resistance of wild-type strains, ΔliaRstrains were significantly more sensitive to nisin (P< 0.001), indicating that induction of LiaFSR led to cross-protection ofL. monocytogenesagainst subsequent inactivation by nisin. Transcript levels of LiaR-regulated genes were induced by salt stress, and lmo1746 andtelAwere found to contribute to LiaR-mediated salt-induced nisin resistance. These data suggest that environmental stresses similar to those on foods can influence the resistance ofL. monocytogenesto antimicrobials such as nisin, and potential cross-protective effects should be considered when selecting and applying control measures for this pathogen on ready-to-eat foods.

New potential bacterial antagonists for the biocontrol of fire blight disease (Erwinia amylovora) in Morocco

2018 ◽  
Vol 117 ◽  
pp. 7-15 ◽  
Author(s):  
Smail Ait Bahadou ◽  
Abderrahmane Ouijja ◽  
Abdelkarim Karfach ◽  
Abdessalem Tahiri ◽  
Rachid Lahlali
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Bacterial Antagonists ◽  
Blight Disease

scholarly journals Chromosomally Encodedhok-sokToxin-Antitoxin System in the Fire Blight PathogenErwinia amylovora: Identification and Functional Characterization

2019 ◽  
Vol 85 (15) ◽  
Author(s):  
Jingyu Peng ◽  
Lindsay R. Triplett ◽  
Jeffrey K. Schachterle ◽  
George W. Sundin
Keyword(s):  
Noncoding Rna ◽  
Pathogenic Bacteria ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Functional Characterization ◽  
Pathogenic Bacterium ◽  
Type I ◽  
Plant Pathogenic Bacterium ◽  
Content Type ◽  
Protein Toxin

ABSTRACTToxin-antitoxin (TA) systems are genetic elements composed of a protein toxin and a counteracting antitoxin that is either a noncoding RNA or protein. In type I TA systems, the antitoxin is a noncoding small RNA (sRNA) that base pairs with the cognate toxin mRNA interfering with its translation. Although type I TA systems have been extensively studied inEscherichia coliand a few human or animal bacterial pathogens, they have not been characterized in plant-pathogenic bacteria. In this study, we characterized a chromosomal locus in the plant pathogenErwinia amylovoraEa1189 that is homologous to thehok-soktype I TA system previously identified in theEnterobacteriaceae-restricted plasmid R1. Phylogenetic analysis indicated that the chromosomal location of thehok-soklocus is, thus far, unique toE. amylovora. We demonstrated that ectopic overexpression ofhokis highly toxic toE. amylovoraand that the sRNAsokreversed the toxicity ofhokthroughmok, a reading frame presumably translationally coupled withhok. We also identified the region that is essential for maintenance of the main toxicity of Hok. Through ahok-sokdeletion mutant (Ea1189Δhok-sok), we determined the contribution of thehok-soklocus to cellular growth, micromorphology, and catalase activity. Combined, our findings indicate that thehok-sokTA system, besides being potentially self-toxic, provides fitness advantages toE. amylovora.IMPORTANCEBacterial toxin-antitoxin systems have received great attention because of their potential as targets for antimicrobial development and as tools for biotechnology.Erwinia amylovora, the causal agent of fire blight disease on pome fruit trees, is a major plant-pathogenic bacterium. In this study, we identified and functionally characterized a unique chromosomally encodedhok-soktoxin-antitoxin system inE. amylovorathat resembles the plasmid-encoded copies of this system in otherEnterobacteriaceae. This study of a type I toxin-antitoxin system in a plant-pathogenic bacterium provides the basis to further understand the involvement of toxin-antitoxin systems during infection by a plant-pathogenic bacterium. The new linkage between thehok-soktoxin-antitoxin system and the catalase-mediated oxidative stress response leads to additional considerations of targeting this system for antimicrobial development.

scholarly journals Effects of Exposure Time and Biological State on Acquisition and Accumulation of Erwinia amylovora by Drosophila melanogaster

2019 ◽  
Vol 85 (15) ◽  
Author(s):  
Matthew Boucher ◽  
Rowan Collins ◽  
Kerik Cox ◽  
Greg Loeb
Keyword(s):  
Drosophila Melanogaster ◽  
Exposure Time ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Current Knowledge ◽  
Selective Medium ◽  
Nutritional State ◽  
Biological Factors ◽  
Content Type ◽  
Disease Cycle

ABSTRACT Fire blight, caused by the bacterium Erwinia amylovora, is a disease devastating the production of rosaceous crops, primarily apple and pear, with worldwide distribution. Fire blight begins in the spring when primary inoculum is produced as ooze, which consists of plant sap, E. amylovora, and exopolysaccharides. Ooze is believed to be transferred to healthy tissues by wind, rain, and insects. However, the mechanisms by which insects locate and transmit ooze are largely undocumented. The goals of this study were to investigate the biological factors affecting acquisition of E. amylovora from ooze by a model dipteran, Drosophila melanogaster, and to determine whether flies are able to mechanically transfer this bacterium after acquisition. We found that the percentage of positive flies increased as exposure time increased, but nutritional state, mating status, and sex did not significantly alter the number of positive individuals. Bacterial abundance was highly variable at all exposure times, suggesting that other biological factors play a role in acquisition. Nutritional state had a significant effect on E. amylovora abundance, and food-deprived flies had higher E. amylovora counts than satiated flies. We also demonstrated that D. melanogaster transmits E. amylovora to a selective medium surface and hypothesize that the same is possible for plant surfaces, where bacteria can persist until an opportunity to colonize the host arises. Collectively, these data suggest a more significant role for flies than previously thought in transmission of fire blight and contribute to a shift in our understanding of the E. amylovora disease cycle. IMPORTANCE A recent hypothesis proposed that dissemination of Erwinia amylovora from ooze by flies to native rosaceous trees was likely key to the life cycle of the bacterium during its evolution. Our study validates an important component of this hypothesis by showing that flies are capable of acquiring and transmitting this bacterium from ooze under various biotic conditions. Understanding how dipterans interact with ooze advances our current knowledge of its epidemiological function and provides strong evidence for an underappreciated role of flies in the disease cycle. These findings may be especially important as they pertain to shoot blight, because this stage of the disease is poorly understood and may involve a significant amount of insect activity. Broadly, this study underscores a need to consider the depth, breadth, and origin of interactions between flies and E. amylovora to better understand its epidemiology.

Sign in / Sign up

Export Citation Format

Share Document