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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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Kinetics of cyanide synthesis and accumulation in the different pseudomonad strains.The data shows highest cyanide accumulation in CHAO and PAO1 with an increased synthesis during late log phase and early stationary phase. The data is the mean±SD of 3 replicates and the experiment was repeated on two independent occasions.
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pone-0002073-g002: Kinetics of cyanide synthesis and accumulation in the different pseudomonad strains.The data shows highest cyanide accumulation in CHAO and PAO1 with an increased synthesis during late log phase and early stationary phase. The data is the mean±SD of 3 replicates and the experiment was repeated on two independent occasions.

Mentions: Based on our earlier direct and indirect compartment plate bioassay results, we speculated that the primary root growth inhibition of A. thaliana Col-0 by different pseudomonad strains was due to cyanide production by these bacterial strains. Therefore, to check whether these strains produce cyanide in cultures, we estimated the total cyanide produced in the cultures of different strains of P. aeruginosa and P. fluorescens. The cyanide in the culture filtrate as CN− ion was estimated using a specific cyanide ion electrode at different time intervals from 0 to 36 hours during the growth period. The results presented in Figure 2 show a significantly higher amount of cyanide production in the culture of P. fluorescens strain CHAO followed by P. aeruginosa strains PAO1 and PA14. However, significantly less cyanide production was observed in the cyanide mutants PAO6344, CHAO77 compared to the respective parental (PAO1 and CHAO) strains (Figure 2). The production of CN− directly correlated with the root inhibition data described in Figure 1A&B. In most of the strains tested, the trend for cyanide accumulation in the cultures was highest in the early exponential phase followed by early stationary phase and accumulation declined in the late stationary phase.


Cyanogenic pseudomonads influence multitrophic interactions in the rhizosphere.

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

Kinetics of cyanide synthesis and accumulation in the different pseudomonad strains.The data shows highest cyanide accumulation in CHAO and PAO1 with an increased synthesis during late log phase and early stationary phase. The data is the mean±SD of 3 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-g002: Kinetics of cyanide synthesis and accumulation in the different pseudomonad strains.The data shows highest cyanide accumulation in CHAO and PAO1 with an increased synthesis during late log phase and early stationary phase. The data is the mean±SD of 3 replicates and the experiment was repeated on two independent occasions.
Mentions: Based on our earlier direct and indirect compartment plate bioassay results, we speculated that the primary root growth inhibition of A. thaliana Col-0 by different pseudomonad strains was due to cyanide production by these bacterial strains. Therefore, to check whether these strains produce cyanide in cultures, we estimated the total cyanide produced in the cultures of different strains of P. aeruginosa and P. fluorescens. The cyanide in the culture filtrate as CN− ion was estimated using a specific cyanide ion electrode at different time intervals from 0 to 36 hours during the growth period. The results presented in Figure 2 show a significantly higher amount of cyanide production in the culture of P. fluorescens strain CHAO followed by P. aeruginosa strains PAO1 and PA14. However, significantly less cyanide production was observed in the cyanide mutants PAO6344, CHAO77 compared to the respective parental (PAO1 and CHAO) strains (Figure 2). The production of CN− directly correlated with the root inhibition data described in Figure 1A&B. In most of the strains tested, the trend for cyanide accumulation in the cultures was highest in the early exponential phase followed by early stationary phase and accumulation declined in the late stationary phase.

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