Antagonistic Activities of Epiphytic Bacteria from Soybean Leaves against Pseudomonas syringae pv. glycinea in vitro and in planta

May, Rudolf von; Völksch, Beate; Kampmann, Grit

doi:10.1007/s002489900041

Cited by 48 publications

(48 citation statements)

References 17 publications

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“…and probably other phyllosphere PGPBs (17,28,43,44,48,49), can be used in programs to combat foliar bacterial diseases. For the protection of plants, the displacement of a pathogen by a competing species and the competitor's superior adaptation to an ecological niche may prove to be as effective as direct pathogen inhibition or the induction of systemic resistance.…”

Section: Discussionmentioning

confidence: 99%

“…tomato pathogenicity (20), including the sources of genetic resistance to the pathogen (6,18,33,34,39,50; V. F. Lawson and W. L. Summers, abstr., HortScience 17:503) and the genes which confer resistance to the disease (30, 41), this knowledge has not yet translated into an efficient strategy to control this minor, but occasionally devastating, foliar disease. Disease control is still based on traditional chemical and physical methods (3), and despite some significant successes, achieved mainly by the induction of systemic resistance in plants (1,27,45,52) and the displacement of a pathogen by nonvirulent strains of the same pathogen or by ecologically similar antagonistic strains (28,43,44,48,49), biological control of foliar bacterial pathogens is still largely at the experimental stage.The aim of this study was to measure the fluctuations in the populations of the two bacterial species, belonging to different genera, on the foliage and in the rhizospheres of tomato plants inoculated with one or both species. The effect of the relative sizes of the bacterial populations on the development of bacterial leaf speck disease in tomato plants and on plant growth was monitored.…”

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confidence: 99%

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Protection of Tomato Seedlings against Infection by Pseudomonas syringae pv. Tomato by Using the Plant Growth-Promoting Bacterium Azospirillum brasilense

Bashan¹,

de‐Bashan

2002

Appl Environ Microbiol

122

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Pseudomonas syringae pv. tomato, the causal agent of bacterial speck of tomato, and the plant growthpromoting bacterium Azospirillum brasilense were inoculated onto tomato plants, either alone, as a mixed culture, or consecutively. The population dynamics in the rhizosphere and foliage, the development of bacterial speck disease, and their effects on plant growth were monitored. When inoculated onto separate plants, the A. brasilense population in the rhizosphere of tomato plants was 2 orders of magnitude greater than the population of P. syringae pv. tomato (10 7 versus 10 5 CFU/g [dry weight] of root). Under mist chamber conditions, the leaf population of P. syringae pv. tomato was 1 order of magnitude greater than that of A. brasilense (10 7 versus 10 6 CFU/g [dry weight] of leaf). Inoculation of seeds with a mixed culture of the two bacterial strains resulted in a reduction of the pathogen population in the rhizosphere, an increase in the A. brasilense population, the prevention of bacterial speck disease development, and improved plant growth. Inoculation of leaves with the mixed bacterial culture under mist conditions significantly reduced the P. syringae pv. tomato population and significantly decreased disease severity. Challenge with P. syringae pv. tomato after A. brasilense was established in the leaves further reduced both the population of P. syringae pv. tomato and disease severity and significantly enhanced plant development. Both bacteria maintained a large population in the rhizosphere for 45 days when each was inoculated separately onto tomato seeds (10 5 to 10 6 CFU/g [dry weight] of root). However, P. syringae pv. tomato did not survive in the rhizosphere in the presence of A. brasilense. Foliar inoculation of A. brasilense after P. syringae pv. tomato was established on the leaves did not alleviate bacterial speck disease, and A. brasilense did not survive well in the phyllosphere under these conditions, even in a mist chamber. Several applications of a low concentration of buffered malic acid significantly enhanced the leaf population of A. brasilense (>10 8 CFU/g [dry weight] of leaf), decreased the population of P. syringae pv. tomato to almost undetectable levels, almost eliminated disease development, and improved plant growth to the level of uninoculated healthy control plants. Based on our results, we propose that A. brasilense be used in prevention programs to combat the foliar bacterial speck disease caused by P. syringae pv. tomato.Tomato plants are hosts to Azospirillum brasilense, a plant growth-promoting bacterium (PGPB) (7,8), and Pseudomonas syringae pv. tomato, the causal agent of bacterial speck disease (35,47). This disease is of moderate economic importance to tomato production under greenhouse and field conditions (24). Whereas A. brasilense increases the growth and yield of tomato plants (14), P. syringae pv. tomato decreases production (51). Although A. brasilense is known as a rhizosphere bacterium (7), some strains are ephiphytic (7, 10), and P. syringae pv. tomato is...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Protection of Tomato Seedlings against Infection by Pseudomonas syringae pv. Tomato by Using the Plant Growth-Promoting Bacterium Azospirillum brasilense

Bashan¹,

de‐Bashan

2002

Appl Environ Microbiol

122

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“…E. amylovora strains were grown on LB agar for 24 h and then resuspended and diluted to an OD 600 of 1.0 in sterile demineralized water. Apple plants were inoculated by the prick technique (47). Each bacterial strain was inoculated into one shoot each of a minimum of five single plants.…”

Section: Methodsmentioning

confidence: 99%

AraC/XylS Family Stress Response Regulators Rob, SoxS, PliA, and OpiA in the Fire Blight Pathogen Erwinia amylovora

2014

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bTranscriptional regulators of the AraC/XylS family have been associated with multidrug resistance, organic solvent tolerance, oxidative stress, and virulence in clinically relevant enterobacteria. In the present study, we identified four homologous AraC/ XylS regulators, Rob, SoxS, PliA, and OpiA, from the fire blight pathogen Erwinia amylovora Ea1189. Previous studies have shown that the regulators MarA, Rob, and SoxS from Escherichia coli mediate multiple-antibiotic resistance, primarily by upregulating the AcrAB-TolC efflux system. However, none of the four AraC/XylS regulators from E. amylovora was able to induce a multidrug resistance phenotype in the plant pathogen. Overexpression of rob led to a 2-fold increased expression of the acrA gene. However, the rob-overexpressing strain showed increased resistance to only a limited number of antibiotics. Furthermore, Rob was able to induce tolerance to organic solvents in E. amylovora by mechanisms other than efflux. We demonstrated that SoxS from E. amylovora is involved in superoxide resistance. A soxS-deficient mutant of Ea1189 was not able to grow on agar plates supplemented with the superoxide-generating agent paraquat. Furthermore, expression of soxS was induced by redox cycling agents. We identified two novel members of the AraC/XylS family in E. amylovora. PliA was highly upregulated during the early infection phase in apple rootstock and immature pear fruits. Multiple compounds were able to induce the expression of pliA, including apple leaf extracts, phenolic compounds, redox cycling agents, heavy metals, and decanoate. OpiA was shown to play a role in the regulation of osmotic and alkaline pH stress responses.

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“…E. amylovora norM mutant Ea1189-34 and the parent strain Ea1189, grown on LB agar plates for 48 h, were resuspended and diluted in sterile demineralized water for inoculation. Apple plants were inoculated by the prick technique described by May et al (31). Five microliters of a bacterial suspension (10 2 to 10 6 CFU/ml) was placed onto each wound on a shoot tip.…”

Section: Methodsmentioning

confidence: 99%

NorM, an Erwinia amylovora Multidrug Efflux Pump Involved in In Vitro Competition with Other Epiphytic Bacteria

Burse

Weingart

Ullrich

2004

Appl Environ Microbiol

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Blossoms are important sites of infection for Erwinia amylovora, the causal agent of fire blight of rosaceous plants. Before entering the tissue, the pathogen colonizes the stigmatic surface and has to compete for space and nutrient resources within the epiphytic community. Several epiphytes are capable of synthesizing antibiotics with which they antagonize phytopathogenic bacteria. Here, we report that a multidrug efflux transporter, designated NorM, of E. amylovora confers tolerance to the toxin(s) produced by epiphytic bacteria cocolonizing plant blossoms. According to sequence comparisons, the single-component efflux pump NorM is a member of the multidrug and toxic compound extrusion protein family. The corresponding gene is widely distributed among E. amylovora strains and related plant-associated bacteria. NorM mediated resistance to the hydrophobic cationic compounds norfloxacin, ethidium bromide, and berberine. A norM mutant was constructed and exhibited full virulence on apple rootstock MM 106. However, it was susceptible to antibiotics produced by epiphytes isolated from apple and quince blossoms. The epiphytes were identified as Pantoea agglomerans by 16S rRNA analysis and were isolated from one-third of all trees examined. The promoter activity of norM was twofold greater at 18°C than at 28°C. The lower temperature seems to be beneficial for host infection because of the availability of moisture necessary for movement of the pathogen to the infection sites. Thus, E. amylovora might employ NorM for successful competition with other epiphytic microbes to reach high population densities, particularly at a lower temperature.

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Antagonistic Activities of Epiphytic Bacteria from Soybean Leaves against Pseudomonas syringae pv. glycinea in vitro and in planta

Cited by 48 publications

References 17 publications

Protection of Tomato Seedlings against Infection by Pseudomonas syringae pv. Tomato by Using the Plant Growth-Promoting Bacterium Azospirillum brasilense

Protection of Tomato Seedlings against Infection by Pseudomonas syringae pv. Tomato by Using the Plant Growth-Promoting Bacterium Azospirillum brasilense

AraC/XylS Family Stress Response Regulators Rob, SoxS, PliA, and OpiA in the Fire Blight Pathogen Erwinia amylovora

NorM, an Erwinia amylovora Multidrug Efflux Pump Involved in In Vitro Competition with Other Epiphytic Bacteria

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