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Cyanogenic pseudomonads influence multitrophic interactions in the rhizosphere.

Rudrappa T, Splaine RE, Biedrzycki ML, Bais HP - PLoS ONE (2008)

Bottom Line: Additionally, pseudomonad cyanogenesis also affected other beneficial rhizospheric processes such as Bacillus subtilis colonization by biofilm formation on A. thaliana Col-0 roots.The effect of cyanogenesis on B. subtilis biofilm formation was further established by the down regulation of important B. subtilis biofilm operons epsA and yqxM.Our results show, the functional significance of pseudomonad cyanogenesis in regulating multitrophic rhizospheric interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America.

ABSTRACT
In the rhizosphere, plant roots cope with both pathogenic and beneficial bacterial interactions. The exometabolite production in certain bacterial species may regulate root growth and other root-microbe interactions in the rhizosphere. Here, we elucidated the role of cyanide production in pseudomonad virulence affecting plant root growth and other rhizospheric processes. Exposure of Arabidopsis thaliana Col-0 seedlings to both direct (with KCN) and indirect forms of cyanide from different pseudomonad strains caused significant inhibition of primary root growth. Further, we report that this growth inhibition was caused by the suppression of an auxin responsive gene, specifically at the root tip region by pseudomonad cyanogenesis. Additionally, pseudomonad cyanogenesis also affected other beneficial rhizospheric processes such as Bacillus subtilis colonization by biofilm formation on A. thaliana Col-0 roots. The effect of cyanogenesis on B. subtilis biofilm formation was further established by the down regulation of important B. subtilis biofilm operons epsA and yqxM. Our results show, the functional significance of pseudomonad cyanogenesis in regulating multitrophic rhizospheric interactions.

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Effect of indirect exposure of the pseudomonad strains and cyanide on the transcription of the yqxM operon in B. subtilis.Strain Marburg thrC::yqxM-lacZ (NRS1531) was grown in biofilm medium under biofilm formation conditions at 37°C with or without exposure to pseudomonad strains and HCN. Growth (A) and β-galactosidase activity (B) were measured at regular intervals and plotted as a function of time. These experiments were repeated on at least 3 independent occasions and a representative plot is shown. Data is the mean±SD of 12 replicates and the experiment was repeated on two independent occasions.
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pone-0002073-g007: Effect of indirect exposure of the pseudomonad strains and cyanide on the transcription of the yqxM operon in B. subtilis.Strain Marburg thrC::yqxM-lacZ (NRS1531) was grown in biofilm medium under biofilm formation conditions at 37°C with or without exposure to pseudomonad strains and HCN. Growth (A) and β-galactosidase activity (B) were measured at regular intervals and plotted as a function of time. These experiments were repeated on at least 3 independent occasions and a representative plot is shown. Data is the mean±SD of 12 replicates and the experiment was repeated on two independent occasions.

Mentions: While pseudomonads and cyanide suppressed the ability of B. subtilis to form biofilms, it did not suppress the single cell growth. Therefore, we hypothesized that pseudomonads and cyanide may inhibit biofilm formation through limiting the induction of one (or both) of two key loci required for biofilm formation, the epsA-O and yqxM-sipW-tasA operons [40]–[45]. To test this hypothesis, we used the transcriptional fusions of the promoter regions for both the epsA and yqxM operons to β-galactosidase and monitored the expression profile in the presence and absence of PAO1, CHAO, PAO6344, CHAO77 and cyanide. Treatment with PAO1, cyanide and CHAO suppressed the induction of epsA by more than 40% (Figure 6B) and yqxM by about 50% (Figure 7B) when compared to the untreated control and cyanide mutants. The suppression of transcription induction in each case occurred from the late log phase and continued through the stationary phase (see Figure 6A&7A for growth), suggesting that there may be a receptor that is actively produced in the late log-phase to late stationary phase in B. subtilis that could perceive the presence of cyanide. These data clearly showed the specificity of cyanide and cyanide producing pseudomonads in down regulation of B. subtilis biofilm operons.


Cyanogenic pseudomonads influence multitrophic interactions in the rhizosphere.

Rudrappa T, Splaine RE, Biedrzycki ML, Bais HP - PLoS ONE (2008)

Effect of indirect exposure of the pseudomonad strains and cyanide on the transcription of the yqxM operon in B. subtilis.Strain Marburg thrC::yqxM-lacZ (NRS1531) was grown in biofilm medium under biofilm formation conditions at 37°C with or without exposure to pseudomonad strains and HCN. Growth (A) and β-galactosidase activity (B) were measured at regular intervals and plotted as a function of time. These experiments were repeated on at least 3 independent occasions and a representative plot is shown. Data is the mean±SD of 12 replicates and the experiment was repeated on two independent occasions.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2315799&req=5

pone-0002073-g007: Effect of indirect exposure of the pseudomonad strains and cyanide on the transcription of the yqxM operon in B. subtilis.Strain Marburg thrC::yqxM-lacZ (NRS1531) was grown in biofilm medium under biofilm formation conditions at 37°C with or without exposure to pseudomonad strains and HCN. Growth (A) and β-galactosidase activity (B) were measured at regular intervals and plotted as a function of time. These experiments were repeated on at least 3 independent occasions and a representative plot is shown. Data is the mean±SD of 12 replicates and the experiment was repeated on two independent occasions.
Mentions: While pseudomonads and cyanide suppressed the ability of B. subtilis to form biofilms, it did not suppress the single cell growth. Therefore, we hypothesized that pseudomonads and cyanide may inhibit biofilm formation through limiting the induction of one (or both) of two key loci required for biofilm formation, the epsA-O and yqxM-sipW-tasA operons [40]–[45]. To test this hypothesis, we used the transcriptional fusions of the promoter regions for both the epsA and yqxM operons to β-galactosidase and monitored the expression profile in the presence and absence of PAO1, CHAO, PAO6344, CHAO77 and cyanide. Treatment with PAO1, cyanide and CHAO suppressed the induction of epsA by more than 40% (Figure 6B) and yqxM by about 50% (Figure 7B) when compared to the untreated control and cyanide mutants. The suppression of transcription induction in each case occurred from the late log phase and continued through the stationary phase (see Figure 6A&7A for growth), suggesting that there may be a receptor that is actively produced in the late log-phase to late stationary phase in B. subtilis that could perceive the presence of cyanide. These data clearly showed the specificity of cyanide and cyanide producing pseudomonads in down regulation of B. subtilis biofilm operons.

Bottom Line: Additionally, pseudomonad cyanogenesis also affected other beneficial rhizospheric processes such as Bacillus subtilis colonization by biofilm formation on A. thaliana Col-0 roots.The effect of cyanogenesis on B. subtilis biofilm formation was further established by the down regulation of important B. subtilis biofilm operons epsA and yqxM.Our results show, the functional significance of pseudomonad cyanogenesis in regulating multitrophic rhizospheric interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America.

ABSTRACT
In the rhizosphere, plant roots cope with both pathogenic and beneficial bacterial interactions. The exometabolite production in certain bacterial species may regulate root growth and other root-microbe interactions in the rhizosphere. Here, we elucidated the role of cyanide production in pseudomonad virulence affecting plant root growth and other rhizospheric processes. Exposure of Arabidopsis thaliana Col-0 seedlings to both direct (with KCN) and indirect forms of cyanide from different pseudomonad strains caused significant inhibition of primary root growth. Further, we report that this growth inhibition was caused by the suppression of an auxin responsive gene, specifically at the root tip region by pseudomonad cyanogenesis. Additionally, pseudomonad cyanogenesis also affected other beneficial rhizospheric processes such as Bacillus subtilis colonization by biofilm formation on A. thaliana Col-0 roots. The effect of cyanogenesis on B. subtilis biofilm formation was further established by the down regulation of important B. subtilis biofilm operons epsA and yqxM. Our results show, the functional significance of pseudomonad cyanogenesis in regulating multitrophic rhizospheric interactions.

Show MeSH
Related in: MedlinePlus