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R R Walcott - One of the best experts on this subject based on the ideXlab platform.
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genetically distinct Acidovorax citrulli strains display cucurbit fruit preference under field conditions
Phytopathology, 2020Co-Authors: Mei Zhao, Saul Burdman, Bhabesh Dutta, Xuelin Luo, R R WalcottAbstract:Strains of Acidovorax citrulli, the causal agent of bacterial fruit blotch (BFB) of cucurbits, can be assigned to two groups, I and II. The natural association of group I and II strains with different cucurbit species suggests host preference; however, there are no direct data to support this hypothesis under field conditions. Hence, the objective of this study was to assess differences in the prevalence of group I and II A. citrulli strains on cucurbit species in the field. From 2017 to 2019, we used group I and II strains to initiate BFB outbreaks in field plots planted with four cucurbit species. At different times, we collected symptomatic tissues and assayed them for group I and II strains using a group-specific PCR assay. Binary distribution data analysis revealed that the odds of melon, pumpkin, and squash foliage infection by group I strains were 21.7, 11.5, and 22.1 times greater, respectively, than the odds of watermelon foliage infection by the group I strain (P < 0.0001). More strikingly, the odds of melon fruit infection by the group I strain were 97.5 times greater than watermelon fruit infection by the same strain (P < 0.0001). Unexpectedly, some of the group II isolates recovered from the 2017 and 2019 studies were different from the group II strains used as inocula. Overall, data from these experiments confirm that A. citrulli strains exhibit a preference for watermelon and melon, which is more pronounced in fruit tissues.
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show me your secret ed weapons a multifaceted approach reveals a wide arsenal of type iii secreted effectors in the cucurbit pathogenic bacterium Acidovorax citrulli and novel effectors in the Acidovorax genus
Molecular Plant Pathology, 2020Co-Authors: Irene Jimenez Guerrero, Gustavo Mateus Da ,silva, Francisco Perezmontano, Naama Wagner, Dafna Shkedy, Mei Zhao, Lorena Pizarro, Maya Bar, R R WalcottAbstract:The cucurbit pathogenic bacterium Acidovorax citrulli requires a functional type III secretion system (T3SS) for pathogenicity. In this bacterium, as with Xanthomonas and Ralstonia spp., an AraC-type transcriptional regulator, HrpX, regulates expression of genes encoding T3SS components and type III-secreted effectors (T3Es). The annotation of a sequenced A. citrulli strain revealed 11 T3E genes. Assuming that this could be an underestimation, we aimed to uncover the T3E arsenal of the A. citrulli model strain, M6. Thorough sequence analysis revealed 51 M6 genes whose products are similar to known T3Es. Furthermore, we combined machine learning and transcriptomics to identify novel T3Es. The machine-learning approach ranked all A. citrulli M6 genes according to their propensity to encode T3Es. RNA-Seq revealed differential gene expression between wild-type M6 and a mutant defective in HrpX: 159 and 28 genes showed significantly reduced and increased expression in the mutant relative to wild-type M6, respectively. Data combined from these approaches led to the identification of seven novel T3E candidates that were further validated using a T3SS-dependent translocation assay. These T3E genes encode hypothetical proteins that seem to be restricted to plant pathogenic Acidovorax species. Transient expression in Nicotiana benthamiana revealed that two of these T3Es localize to the cell nucleus and one interacts with the endoplasmic reticulum. This study places A. citrulli among the 'richest' bacterial pathogens in terms of T3E cargo. It also revealed novel T3Es that appear to be involved in the pathoadaptive evolution of plant pathogenic Acidovorax species.
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ferric uptake regulator fura is required for Acidovorax citrulli virulence on watermelon
Phytopathology, 2019Co-Authors: Jun Liu, Yanli Tian, Yuqiang Zhao, Rong Zeng, Baohui Chen, R R WalcottAbstract:Acidovorax citrulli is the causal agent of bacterial fruit blotch, a serious threat to commercial watermelon and melon crop production worldwide. Ferric uptake regulator (Fur) is a global transcription factor that affects a number of virulence-related functions in phytopathogenic bacteria; however, the role of furA has not been determined for A. citrulli. Hence, we constructed an furA deletion mutant and a corresponding complement in the background of A. citrulli strain xlj12 to investigate the role of the gene in siderophore production, concentration of intracellular Fe2+, bacterial sensitivity to hydrogen peroxide, biofilm formation, swimming motility, hypersensitive response induction, and virulence on melon seedlings. The A. citrulli furA deletion mutant displayed increased siderophore production, intracellular Fe2+ concentration, and increased sensitivity to hydrogen peroxide. In contrast, biofilm formation, swimming motility, and virulence on melon seedlings were significantly reduced in the furA mutant. As expected, complementation of the furA deletion mutant restored all phenotypes to wild-type levels. In accordance with the phenotypic results, the expression levels of bfrA and bfrB that encode bacterioferritin, sodB that encodes iron/manganese superoxide dismutase, fliS that encodes a flagellar protein, hrcN that encodes the type III secretion system (T3SS) ATPase, and hrcC that encodes the T3SS outer membrane ring protein were significantly downregulated in the A. citrulli furA deletion mutant. In addition, the expression of feo-related genes and feoA and feoB was significantly upregulated in the furA mutant. Overall, these results indicated that, in A. citrulli, FurA contributes to the regulation of the iron balance system, and affects a variety of virulence-related traits.
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further characterization of genetically distinct groups of Acidovorax citrulli strains
Phytopathology, 2017Co-Authors: M Zivanovic, R R WalcottAbstract:Bacterial fruit blotch of cucurbits (BFB) is caused by the gram-negative bacterium Acidovorax citrulli, whose populations can be distinguished into two genetically distinct groups, I and II. Based on visual assessment of BFB severity on cucurbit seedlings and fruit after inoculation under greenhouse conditions, group I A. citrulli strains have been reported to be moderately to highly virulent on several cucurbit hosts, whereas group II strains have exhibited high virulence on watermelon but low virulence on other cucurbits. Additionally, group I strains are recovered from a range of cucurbit hosts, while group II strains are predominantly found on watermelon. The goal of this research was to develop tools to characterize and rapidly distinguish group I and II A. citrulli strains. We first sought to determine whether quantification of A. citrulli colonization of cucurbit seedling tissue reflects the differences between group I and II strains established by visual assessment of BFB symptom severity. Spray inoculation of melon seedlings with cell suspensions containing approximately 1 × 104 CFU/ml resulted in significantly higher (P = 0.01) population growth of M6 (group I; mean area under population growth curve [AUPGC] = 43.73) than that of AAC00-1 (group II; mean AUPGC = 39.33) by 10 days after inoculation. We also investigated the natural spread of bacterial cells and the resulting BFB incidence on watermelon and melon seedlings exposed to three group I and three group II A. citrulli strains under mist chamber conditions. After 5 days of exposure, the mean BFB incidence on melon seedlings exposed to representative group II A. citrulli strains was significantly lower (25 and 3.98% in experiments 1 and 2, respectively) than on melon seedlings exposed to representative group I strains (94.44 and 76.11% in experiments 1 and 2, respectively), and on watermelon seedlings exposed to representative group I and II strains (70 to 93.33%). Finally, we developed a polymerase chain reaction assay based on the putative type III secretion effector gene, Aave_2166, to rapidly distinguish group I and II A. citrulli strains. This assay will be important for future epidemiological studies on BFB.
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pathways of bacterial invasion and watermelon seed infection by Acidovorax citrulli
Plant Pathology, 2015Co-Authors: Bhabesh Dutta, K L Johnson, J T Lessl, Utku Avci, A C Sparks, R R WalcottAbstract:This study explored the pathways of ingress of Acidovorax citrulli, the causal agent of bacterial fruit blotch of cucurbits, into watermelon seeds. Up until 7 days post-inoculation (DPI), a significantly higher percentage of watermelon seeds was infected with A. citrulli when the bacteria were applied (c. 1 × 106 colony-forming units) to stigmas versus ovary pericarps of female flowers. Immunofluorescence microscopy showed that, with stigma inoculation, A. citrulli colonized style and ovary tissues by 1 DPI, and the bacteria co-localized with pollen germ tubes in these tissues. With ovary pericarp inoculation, A. citrulli cells penetrated the epicarp and mesocarp tissues by 1 DPI but did not reach endocarp until 4 DPI. Finally, manual pollination followed by stigma inoculation led to >53% A. citrulli-infected seed lots, while A. citrulli was not detected in seeds/ovules generated by stigma inoculation without pollination (chemically induced parthenocarpy). These results show that stigma inoculation results in faster colonization of watermelon ovules by A. citrulli than pericarp inoculation, even though there is no difference in the levels of infection in mature seeds. The data also indicate that pollen germ tubes play an important role in A. citrulli ingress into watermelon seeds via stigmas.
Flynn W Picardal - One of the best experts on this subject based on the ideXlab platform.
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induction of nitrate dependent fe ii oxidation by fe ii in dechloromonas sp strain uwnr4 and Acidovorax sp strain 2an
Applied and Environmental Microbiology, 2013Co-Authors: Anirban Chakraborty, Flynn W PicardalAbstract:ABSTRACT We evaluated the inducibility of nitrate-dependent Fe(II)-EDTA oxidation (NDFO) in non-growth, chloramphenicol-amended, resting-cell suspensions of Dechloromonas sp. strain UWNR4 and Acidovorax sp. strain 2AN. Cells previously incubated with Fe(II)-EDTA oxidized ca. 6-fold more Fe(II)-EDTA than cells previously incubated with Fe(III)-EDTA. This is the first report of induction of NDFO by Fe(II).
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enhanced growth of Acidovorax sp strain 2an during nitrate dependent fe ii oxidation in batch and continuous flow systems
Applied and Environmental Microbiology, 2011Co-Authors: Anirban Chakraborty, Eric E Roden, Jurgen Schieber, Flynn W PicardalAbstract:ABSTRACT Microbial nitrate-dependent, Fe(II) oxidation (NDFO) is a ubiquitous biogeochemical process in anoxic sediments. Since most microorganisms that can oxidize Fe(II) with nitrate require an additional organic substrate for growth or sustained Fe(II) oxidation, the energetic benefits of NDFO are unclear. The process may also be self-limiting in batch cultures due to formation of Fe-oxide cell encrustations. We hypothesized that NDFO provides energetic benefits via a mixotrophic physiology in environments where cells encounter very low substrate concentrations, thereby minimizing cell encrustations. Acidovorax sp. strain 2AN was incubated in anoxic batch reactors in a defined medium containing 5 to 6 mM NO3−, 8 to 9 mM Fe2+, and 1.5 mM acetate. Almost 90% of the Fe(II) was oxidized within 7 days with concomitant reduction of nitrate and complete consumption of acetate. Batch-grown cells became heavily encrusted with Fe(III) oxyhydroxides, lost motility, and formed aggregates. Encrusted cells could neither oxidize more Fe(II) nor utilize further acetate additions. In similar experiments with chelated iron (Fe(II)-EDTA), encrusted cells were not produced, and further additions of acetate and Fe(II)-EDTA could be oxidized. Experiments using a novel, continuous-flow culture system with low concentrations of substrate, e.g., 100 μM NO3−, 20 μM acetate, and 50 to 250 μM Fe2+, showed that the growth yield of Acidovorax sp. strain 2AN was always greater in the presence of Fe(II) than in its absence, and electron microscopy showed that encrustation was minimized. Our results provide evidence that, under environmentally relevant concentrations of substrates, NDFO can enhance growth without the formation of growth-limiting cell encrustations.
M Gillis - One of the best experts on this subject based on the ideXlab platform.
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Acidovorax valerianellae sp nov a novel pathogen of lamb s lettuce valerianella locusta l laterr
International Journal of Systematic and Evolutionary Microbiology, 2003Co-Authors: Louis Gardan, D E Stead, Catherine Dauga, M GillisAbstract:Bacterial spot disease of lamb’s lettuce [Valerianella locusta (L.) Laterr.] was first observed in fields in 1991. This new bacterial disease is localized in western France in high-technology field production of lamb’s lettuce for the preparation of ready-to-use salad. Nineteen strains isolated in 1992 and 1993 from typical black leaf spots of naturally infected lamb’s lettuce were characterized and compared with reference strains of Acidovorax and Delftia. The pathogenicity of the 19 strains was confirmed by artificial inoculation. Biochemical and physiological tests, fatty acid profiles, DNA–DNA hybridization and other nucleic acid-based tests were performed. A numerical taxonomic analysis of the 19 lamb’s lettuce strains showed a single homogeneous phenon closely related to previously described phytopathogenic taxa of the genus Acidovorax. DNA–DNA hybridization studies showed that the lamb’s lettuce strains were 91–100 % related to a representative strain, strain CFBP 4730 T , and constituted a discrete DNA hybridization group, indicating that they belong to the same novel species. Results from DNA–rRNA hybridization, 16S rRNA sequence analysis and fatty acid analysis studies confirmed that this novel species belongs to the b-subclass of the Proteobacteria and, more specifically, to the family Comamonadaceae and the genus Acidovorax. The name Acidovorax valerianellae sp. nov. is proposed for this novel taxon of phytopathogenic bacteria. The type strain is strain CFBP 4730 T (=NCPPB 4283 T ). Lamb’s lettuce, also known as corn salad [Valerianella locusta (L.) Laterr.], was traditionally cultivated in France for use in salads in autumn and winter. Since 1985, advanced technology has been used for continuous, yearround cultivation; 90 % of French production (representing 75 % of world production) is concentrated in western France, near the Atlantic coast. The lettuce produced is used for sale traditionally, in trays, and for the preparation
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Acidovorax valerianellae sp nov a novel pathogen of lamb s lettuce valerianella locusta l laterr
International Journal of Systematic and Evolutionary Microbiology, 2003Co-Authors: Louis Gardan, D E Stead, Catherine Dauga, M GillisAbstract:Bacterial spot disease of lamb's lettuce [Valerianella locusta (L.) Laterr.] was first observed in fields in 1991. This new bacterial disease is localized in western France in high-technology field production of lamb's lettuce for the preparation of ready-to-use salad. Nineteen strains isolated in 1992 and 1993 from typical black leaf spots of naturally infected lamb's lettuce were characterized and compared with reference strains of Acidovorax and Delftia. The pathogenicity of the 19 strains was confirmed by artificial inoculation. Biochemical and physiological tests, fatty acid profiles, DNA-DNA hybridization and other nucleic acid-based tests were performed. A numerical taxonomic analysis of the 19 lamb's lettuce strains showed a single homogeneous phenon closely related to previously described phytopathogenic taxa of the genus Acidovorax. DNA-DNA hybridization studies showed that the lamb's lettuce strains were 91-100% related to a representative strain, strain CFBP 4730(T), and constituted a discrete DNA hybridization group, indicating that they belong to the same novel species. Results from DNA-rRNA hybridization, 16S rRNA sequence analysis and fatty acid analysis studies confirmed that this novel species belongs to the beta-subclass of the Proteobacteria and, more specifically, to the family Comamonadaceae and the genus Acidovorax. The name Acidovorax valerianellae sp. nov. is proposed for this novel taxon of phytopathogenic bacteria. The type strain is strain CFBP 4730(T) (= NCPPB 4283(T)).
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Acidovorax anthurii sp. nov., a new phytopathogenic bacterium which causes bacterial leaf-spot of anthurium
International Journal of Systematic and Evolutionary Microbiology, 2000Co-Authors: Louis Gardan, Catherine Dauga, M Gillis, Philippe Prior, G S SaddlerAbstract:The bacterial leaf-spot of anthurium emerged during the 1980, in the French West Indies and Trinidad. This new bacterial disease is presently wide spread and constitutes a serious limiting factor for commercial anthurium production. Twenty-nine strains isolated from leaf-spots of naturally infected anthurium were characterized and compared with reference strains belonging to the Comamonadaceae family, the genera Ralstonia and Burkholderia, and representative fluorescent pseudomonads. From artificial inoculations 25 out of 29 strains were pathogenic on anthurium. Biochemical and physiological tests, fatty acid analysis, DNA-DNA hybridization, 16S rRNA gene sequence analysis, DNA-16S RNA hybridization were performed. The 25 pathogenic strains on anthurium were clustered in one phenon closely related to phytopathogenic strains of the genus Acidovorax. Anthurium strains were 79-99 % (Delta T-m range 0.2-1.6) related to the strain CFBP 3232 and constituted a discrete DNA homology group indicating that they belong to the same species. DNA-rRNA hybridization, '165 rRNA sequence and fatty acid analysis confirmed that this new species belongs to the beta-subclass of Proteobacteria and to rRNA superfamily ill, to the family of Comamonadaceae and to the genus Acidovorax. The name Acidovorax anthurii is proposed for this new phytopathogenic bacterium. The type strain has been deposited in the Collection Francaise des Bacteries Phytopathogenes as CFBP 3232(T).
Anirban Chakraborty - One of the best experts on this subject based on the ideXlab platform.
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induction of nitrate dependent fe ii oxidation by fe ii in dechloromonas sp strain uwnr4 and Acidovorax sp strain 2an
Applied and Environmental Microbiology, 2013Co-Authors: Anirban Chakraborty, Flynn W PicardalAbstract:ABSTRACT We evaluated the inducibility of nitrate-dependent Fe(II)-EDTA oxidation (NDFO) in non-growth, chloramphenicol-amended, resting-cell suspensions of Dechloromonas sp. strain UWNR4 and Acidovorax sp. strain 2AN. Cells previously incubated with Fe(II)-EDTA oxidized ca. 6-fold more Fe(II)-EDTA than cells previously incubated with Fe(III)-EDTA. This is the first report of induction of NDFO by Fe(II).
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enhanced growth of Acidovorax sp strain 2an during nitrate dependent fe ii oxidation in batch and continuous flow systems
Applied and Environmental Microbiology, 2011Co-Authors: Anirban Chakraborty, Eric E Roden, Jurgen Schieber, Flynn W PicardalAbstract:ABSTRACT Microbial nitrate-dependent, Fe(II) oxidation (NDFO) is a ubiquitous biogeochemical process in anoxic sediments. Since most microorganisms that can oxidize Fe(II) with nitrate require an additional organic substrate for growth or sustained Fe(II) oxidation, the energetic benefits of NDFO are unclear. The process may also be self-limiting in batch cultures due to formation of Fe-oxide cell encrustations. We hypothesized that NDFO provides energetic benefits via a mixotrophic physiology in environments where cells encounter very low substrate concentrations, thereby minimizing cell encrustations. Acidovorax sp. strain 2AN was incubated in anoxic batch reactors in a defined medium containing 5 to 6 mM NO3−, 8 to 9 mM Fe2+, and 1.5 mM acetate. Almost 90% of the Fe(II) was oxidized within 7 days with concomitant reduction of nitrate and complete consumption of acetate. Batch-grown cells became heavily encrusted with Fe(III) oxyhydroxides, lost motility, and formed aggregates. Encrusted cells could neither oxidize more Fe(II) nor utilize further acetate additions. In similar experiments with chelated iron (Fe(II)-EDTA), encrusted cells were not produced, and further additions of acetate and Fe(II)-EDTA could be oxidized. Experiments using a novel, continuous-flow culture system with low concentrations of substrate, e.g., 100 μM NO3−, 20 μM acetate, and 50 to 250 μM Fe2+, showed that the growth yield of Acidovorax sp. strain 2AN was always greater in the presence of Fe(II) than in its absence, and electron microscopy showed that encrustation was minimized. Our results provide evidence that, under environmentally relevant concentrations of substrates, NDFO can enhance growth without the formation of growth-limiting cell encrustations.
John D. Coates - One of the best experts on this subject based on the ideXlab platform.
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complete genome sequence of the anaerobic perchlorate reducing bacterium azospira suillum strain ps
Journal of Bacteriology, 2012Co-Authors: Kathryne G Byrnebailey, John D. CoatesAbstract:Azospira suillum strain PS (formally Dechlorosoma suillum strain PS) is a metabolically versatile betaproteobacterium first identified for its ability to grow by dissimilatory reduction of perchlorate and chlorate [denoted (per)chlorate]. Together with Dechloromonas species, these two genera represent the dominant (per)chlorate-reducing bacteria in mesophilic freshwater environments. In addition to (per)chlorate reduction, A. suillum is capable of the anaerobic oxidation of humic substances and is the first anaerobic nitrate-dependent Fe(II) oxidizer outside the Diaphorobacter and Acidovorax genera for which there is a completed genome sequence.
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completed genome sequence of the anaerobic iron oxidizing bacterium Acidovorax ebreus strain tpsy
Journal of Bacteriology, 2010Co-Authors: Kathryne G Byrnebailey, Karrie A Weber, Saumyaditya Bose, Traci Knox, Trisha L Spanbauer, Olga Chertkov, John D. CoatesAbstract:Acidovorax ebreus strain TPSY is the first anaerobic nitrate-dependent Fe(II) oxidizer for which there is a completed genome sequence. Preliminary protein annotation revealed an organism optimized for survival in a complex environmental system. Here, we briefly report the completed and annotated genome sequence of strain TPSY.
