scholarly journals The Pseudomonas syringae avrRpt2 Gene Contributes to Virulence on Tomato

2005 ◽  
Vol 18 (7) ◽  
pp. 626-633 ◽  
Author(s):  
Melisa T. S. Lim ◽  
Barbara N. Kunkel
Keyword(s):  
Pseudomonas Syringae ◽  
Virulence Factors ◽  
Host Defense ◽  
Virulence Gene ◽  
Bacterial Virulence ◽  
Host Tissue ◽  
Native Strain ◽  
Phytopathogenic Bacteria ◽  
Gram Negative ◽  
Mutant Derivative

In order to cause disease on plants, gram-negative phytopathogenic bacteria introduce numerous virulence factors into the host cell in order to render host tissue more hospitable for pathogen proliferation. The mode of action of such bacterial virulence factors and their interaction with host defense pathways remain poorly understood. avrRpt2, a gene from Pseudomonas syringae pv. tomato JL1065, has been shown to promote the virulence of heterologous P. syringae strains on Arabidopsis thaliana. However, the contribution of avrRpt2 to the virulence of JL1065 has not been examined previously. We show that a mutant derivative of JL1065 that carries a disruption in avrRpt2 is impaired in its ability to cause disease on tomato (Lycopersicon esculentum), indicating that avrRpt2 also acts as a virulence gene in its native strain on a natural host. The virulence activity of avrRpt2 was detectable on tomato lines that are defective in either ethylene perception or the accumulation of salicylic acid, but could not be detected on a tomato mutant insensitive to jasmonic acid. The enhanced virulence conferred by the expression of avrRpt2 in JL1065 was not associated with the suppression of several defense-related genes induced during the infection of tomato.

scholarly journals FplA FromFusobacterium nucleatumis a Type Vd autotransporter phospholipase with a proposed role in altered host signaling and evasion of autophagy

2017 ◽  
Author(s):  
Michael A. Casasanta ◽  
Christopher C. Yoo ◽  
Hans B. Smith ◽  
A. Jane Duncan ◽  
Kyla Cochrane ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Outer Membrane ◽  
Virulence Factors ◽  
Biochemical Characterization ◽  
Bacterial Virulence ◽  
Chemical Probes ◽  
Gram Negative ◽  
Enzyme Family ◽  
Host Signaling

ABSTRACTFusobacterium nucleatumis a pathogenic oral bacterium that is linked to multiple human infections and colorectal cancer. While most Gram-negative pathogens utilize secretion systems for cellular invasion and infection,F. nucleatumlacks Type I, II, III, IV, and VI secretion. By contrast,F. nucleatumstrains are enriched in Type V secreted autotransporters, which are Gram-negative bacterial virulence factors critical for binding and entry into host cells. Here we present the first biochemical characterization of aF. nucleatumType Vd phospholipase class A1 autotransporter (strain ATCC 25586, gene FN1704) that we hereby renameFusobacteriumphospholipase autotransporter (FplA). FplA is expressed as a full-length 85 kDa outer membrane embedded protein, or as a truncated phospholipase domain that remains associated with the outer membrane. Using multiple FplA constructs we characterized lipid substrate specificity, potent inhibitors, and chemical probes to detect and track this enzyme family. While the role of FplA is undetermined inF. nucleatumvirulence, homologous phospholipases from intracellular pathogens are critical for vacuole escape, altered host signaling, and intracellular survival. We hypothesize that upon intracellular invasion of the host, FplA could play a role in phagosomal escape, subversion of autophagy, or eicosanoid-mediated inflammatory signaling, as we show that FplA binds with high affinity to host phosphoinositide signaling lipids critical to these processes. Our identification of substrates, inhibitors, and chemical probes for FplA, in combination with anfplAgene deletion strain, encompass a powerful set of tools for the future analysis of FplAin vivo. In addition, these studies will guide the biochemical characterization of additional Type Vd autotransporter phospholipases.IMPORTANCEF. nucleatumis an emerging pathogen that is linked to the pathogenesis of colorectal cancer, yet there is a critical knowledge gap in the mechanisms used by this bacterium to elicit changes in the host for intracellular entry and survival. As phospholipases are critical virulence factors for intracellular bacteria to initiate vacuole lysis, cell-to-cell spread, and evasion of autophagy, we set out to characterize a unique Type Vd secreted phospholipase A1 enzyme fromF. nucleatum. Our results show a potential role for modulating host signaling pathways through cleavage of phosphoinositide dependent signaling lipids. These studies open the door for further characterization of this unique enzyme family in bacterial virulence, host-pathogen interactions, and forF. nucleatum, in colorectal carcinogenesis.

scholarly journals Dual Role of Auxin in Regulating Plant Defense and Bacterial Virulence Gene Expression During Pseudomonas syringae PtoDC3000 Pathogenesis

2020 ◽  
Vol 33 (8) ◽  
pp. 1059-1071 ◽  
Author(s):  
Arnaud T. Djami-Tchatchou ◽  
Gregory A. Harrison ◽  
Chris P. Harper ◽  
Renhou Wang ◽  
Michael J. Prigge ◽  
...  
Keyword(s):  
Gene Expression ◽  
Pseudomonas Syringae ◽  
Bacterial Growth ◽  
Plant Pathogens ◽  
Virulence Gene ◽  
Bacterial Virulence ◽  
Auxin Signaling ◽  
Host Defenses ◽  
In Planta ◽  
Virulence Gene Expression

Modification of host hormone biology is a common strategy used by plant pathogens to promote disease. For example, the bacterial pathogen strain Pseudomonas syringae DC3000 (PtoDC3000) produces the plant hormone auxin (indole-3-acetic acid [IAA]) to promote PtoDC3000 growth in plant tissue. Previous studies suggest that auxin may promote PtoDC3000 pathogenesis through multiple mechanisms, including both suppression of salicylic acid (SA)-mediated host defenses and via an unknown mechanism that appears to be independent of SA. To test if host auxin signaling is important during pathogenesis, we took advantage of Arabidopsis thaliana lines impaired in either auxin signaling or perception. We found that disruption of auxin signaling in plants expressing an inducible dominant axr2-1 mutation resulted in decreased bacterial growth and that this phenotype was suppressed by introducing the sid2-2 mutation, which impairs SA synthesis. Thus, host auxin signaling is required for normal susceptibility to PtoDC3000 and is involved in suppressing SA-mediated defenses. Unexpectedly, tir1 afb1 afb4 afb5 quadruple-mutant plants lacking four of the six known auxin coreceptors that exhibit decreased auxin perception, supported increased levels of bacterial growth. This mutant exhibited elevated IAA levels and reduced SA-mediated defenses, providing additional evidence that auxin promotes disease by suppressing host defense. We also investigated the hypothesis that IAA promotes PtoDC3000 virulence through a direct effect on the pathogen and found that IAA modulates expression of virulence genes, both in culture and in planta. Thus, in addition to suppressing host defenses, IAA acts as a microbial signaling molecule that regulates bacterial virulence gene expression.

scholarly journals Dual role of auxin in regulating plant defense and bacterial virulence gene expression during Pseudomonas syringae PtoDC3000 pathogenesis

2019 ◽  
Author(s):  
Arnaud T. Djami-Tchatchou ◽  
Gregory A. Harrison ◽  
Chris P. Harper ◽  
Renhou Wang ◽  
Michael J. Prigge ◽  
...  
Keyword(s):  
Gene Expression ◽  
Pseudomonas Syringae ◽  
Bacterial Growth ◽  
Plant Pathogens ◽  
Virulence Gene ◽  
Bacterial Virulence ◽  
Auxin Signaling ◽  
Host Defenses ◽  
In Planta ◽  
Virulence Gene Expression

ABSTRACTModification of host hormone biology is a common strategy used by plant pathogens to promote disease. For example, the bacterial pathogen Pseudomonas syringae strain PtoDC3000 produces the plant hormone auxin (Indole-3-acetic acid, or IAA) to promote PtoDC3000 growth in plant tissue. Previous studies suggest that auxin may promote PtoDC3000 pathogenesis through multiple mechanisms, including both suppression of salicylic acid (SA)-mediated host defenses and via an unknown mechanism that appears to be independent of SA. To test if host auxin signaling is important during pathogenesis, we took advantage of Arabidopsis thaliana lines impaired in either auxin signaling or perception. We found that disruption of auxin signaling in plants expressing an inducible dominant axr2-1 mutation resulted in decreased bacterial growth, demonstrating that host auxin signaling is required for normal susceptibility to PtoDC3000, and this phenotype was dependent on SA-mediated defenses. However, despite exhibiting decreased auxin perception, tir1 afb1 afb4 afb5 quadruple mutant plants lacking four of the six known auxin co-receptors supported increased levels of bacterial growth. This mutant also exhibited elevated IAA levels, suggesting that the increased IAA in these plants may promote PtoDC3000 growth independent of host auxin signaling, perhaps through a direct effect on the pathogen. In support of this, we found that IAA directly impacted the pathogen, by modulating expression of bacterial virulence genes, both in liquid culture and in planta. Thus, in addition to suppressing host defenses, IAA acts as a microbial signaling molecule that regulates bacterial virulence gene expression.

Application of commercial test-systems to identify gram-negative facultatively anaerobic bacteria

2016 ◽  
Vol 3 (1) ◽  
pp. 43-48 ◽  
Author(s):  
V. Patyka ◽  
L. Butsenko ◽  
L. Pasichnyk
Keyword(s):  
Erwinia Amylovora ◽  
Anaerobic Bacteria ◽  
Biochemical Properties ◽  
Test System ◽  
Phytopathogenic Bacteria ◽  
Gram Negative ◽  
Test Systems ◽  
Facultatively Anaerobic ◽  
Microbiological Methods

Aim. To validate the suitability of commercial API 20E test-system (bioMerieux) for the identifi cation and characterization of facultative gram-negative phytopathogenic bacterial isolates. Methods. Conventional mi- crobiological methods, API 20E test-system (bioMerieux) according to the manufacturer’s instructions. Re- sults. The identifi cation results for Erwinia amylovora, Pectobacterium carotovorum and Pantoea agglome- rans isolates were derived from the conventional and API 20E test systems, which, were in line with the literature data for these species. The API 20E test-system showed high suitability for P. agglomerans isolates identifi cation. Although not all the species of facultatively anaerobic phytopathogenic bacteria may be identi- fi ed using API 20E test-system, its application will surely allow obtaining reliable data about their physiologi- cal and biochemical properties, valuable for identifi cation of bacteria, in the course of 24 h. Conclusions. The results of tests, obtained for investigated species while using API 20E test-system, and those of conventional microbiological methods coincided. The application of API 20E test-system (bioMerieux) ensures fast obtain- ing of important data, which may be used to identify phytopathogenic bacteria of Erwinia, Pectobacterium, Pantoea genera.

Virulence factors associated with organisms causing asymptomatic bacteriuria in pregnant females attending a tertiary care hospital

2017 ◽  
Vol 6 (05) ◽  
pp. 5373
Author(s):  
Prabha Ponnusamy* ◽  
Radhika Katragadda ◽  
Thyagarajan Ravinder
Keyword(s):  
Virulence Factors ◽  
Host Defense ◽  
Virulence Factor ◽  
Tertiary Care Hospital ◽  
Tertiary Care ◽  
Asymptomatic Bacteriuria ◽  
Phenotypic Expression ◽  
Care Hospital ◽  
Cross Sectional ◽  
Pregnant Females

Asymptomatic bacteriuria (ASB), most common during pregnancy is endangering as it may lead to maternal and fetal complications. Various organisms causing ASB combats the host defense mechanisms through virulence factors exhibited by them. In order to understand the pathogenesis and sequelae of infections, virulence factors like hemolysin production, gelatinase production, haemagglutination, biofilm production and many more should be identified. Hence, we aimed at studying the distribution of virulence factors among each organism causing asymptomatic bacteriuria in pregnant females attending a tertiary care hospital. Materials and Methods: This cross-sectional study was conducted in Department of Microbiology over a period of one year and six months (January 2014 to June 2015) at a tertiary care teaching hospital. A total of 1000 urine samples were included in study taken from pregnant women with asymptomatic bacteriuria. Isolation, identification of organisms was done according to standard microbiological techniques and virulence factors for individual organisms by phenotypic method were tested. Results: Out of 1000 samples screened for ASB, organisms were isolated in following frequency distribution: Escherichia coli, the commonest 54/118 (45.76%), Klebsiella pneumoniae 21/118 (17.80%), Staphylococcus aureus 19/118 (16.10%), Staphylococcus saprophyticus 10/118 (8.45%), Enterococcus faecalis 9/118 (7.63%), Pseudomonas aeruginosa 3/118 (2.54%) and Proteus mirabilis 2/118 (1.69%). Virulence factors for individual organisms and biofilm detection for all organisms were done. Conclusion: Multifactorial mechanisms determine the pathogenicity of an organism and it needs to be explored by analyzing each virulence factor and mechanism of invasion in combating the host defense systems. Hence analyzing the phenotypic expression of each virulence factor helps in better understanding about the complications of ASB.

scholarly journals Clonal Clusters, Molecular Resistance Mechanisms and Virulence Factors of Gram-Negative Bacteria Isolated from Chronic Wounds in Ghana

Antibiotics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 339
Author(s):  
Denise Dekker ◽  
Frederik Pankok ◽  
Thorsten Thye ◽  
Stefan Taudien ◽  
Kwabena Oppong ◽  
...  
Keyword(s):  
Molecular Epidemiology ◽  
Virulence Factors ◽  
Iron Uptake ◽  
Chronic Wounds ◽  
Sub Saharan Africa ◽  
Gram Negative Bacteria ◽  
Beta Lactamase ◽  
Secretion Systems ◽  
Gram Negative ◽  
E Coli

Wound infections are common medical problems in sub-Saharan Africa but data on the molecular epidemiology are rare. Within this study we assessed the clonal lineages, resistance genes and virulence factors of Gram-negative bacteria isolated from Ghanaian patients with chronic wounds. From a previous study, 49 Pseudomonas aeruginosa, 21 Klebsiellapneumoniae complex members and 12 Escherichia coli were subjected to whole genome sequencing. Sequence analysis indicated high clonal diversity with only nine P. aeruginosa clusters comprising two strains each and one E. coli cluster comprising three strains with high phylogenetic relationship suggesting nosocomial transmission. Acquired beta-lactamase genes were observed in some isolates next to a broad spectrum of additional genetic resistance determinants. Phenotypical expression of extended-spectrum beta-lactamase activity in the Enterobacterales was associated with blaCTX-M-15 genes, which are frequent in Ghana. Frequently recorded virulence genes comprised genes related to invasion and iron-uptake in E. coli, genes related to adherence, iron-uptake, secretion systems and antiphagocytosis in P. aeruginosa and genes related to adherence, biofilm formation, immune evasion, iron-uptake and secretion systems in K. pneumonia complex. In summary, the study provides a piece in the puzzle of the molecular epidemiology of Gram-negative bacteria in chronic wounds in rural Ghana.

Interference of quorum sensing regulated bacterial virulence factors and biofilms by Plumbago zeylanica extract

2021 ◽  
Author(s):  
Faizan Abul Qais ◽  
Iqbal Ahmad ◽  
Fohad Mabood Husain ◽  
Suliman Y. Alomar ◽  
Naushad Ahmad ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Virulence Factors ◽  
Bacterial Virulence ◽  
Plumbago Zeylanica

scholarly journals Folding Control in the Path of Type 5 Secretion

Toxins ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 341
Author(s):  
Nathalie Dautin
Keyword(s):  
Protein Folding ◽  
Virulence Factors ◽  
Secretion System ◽  
Gram Negative Bacteria ◽  
Secretion Systems ◽  
Gram Negative ◽  
Final Destination ◽  
Cell Compartments ◽  
Recent Addition ◽  
Functionally Diverse

The type 5 secretion system (T5SS) is one of the more widespread secretion systems in Gram-negative bacteria. Proteins secreted by the T5SS are functionally diverse (toxins, adhesins, enzymes) and include numerous virulence factors. Mechanistically, the T5SS has long been considered the simplest of secretion systems, due to the paucity of proteins required for its functioning. Still, despite more than two decades of study, the exact process by which T5SS substrates attain their final destination and correct conformation is not totally deciphered. Moreover, the recent addition of new sub-families to the T5SS raises additional questions about this secretion mechanism. Central to the understanding of type 5 secretion is the question of protein folding, which needs to be carefully controlled in each of the bacterial cell compartments these proteins cross. Here, the biogenesis of proteins secreted by the Type 5 secretion system is discussed, with a focus on the various factors preventing or promoting protein folding during biogenesis.

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