Limits...
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.

Show MeSH

Related in: MedlinePlus

Suppression of B. subtilis biofilm formation on A. thaliana Col-0 roots by indirect exposure of the pseudomonad strains and cyanide (A) and the effect of indirect exposure of the pseudomonad strains and cyanide on single cell growth of B. subtilis (B).The images show complete suppression of B. subtilis biofilm formation when exposed to the indirect exposure of the strains PAO1, PA14, CHAO and HCN when compared to control plants not exposed to either bacterial culture or HCN and ΔhcnB mutants PAO6344 and CHAO77. The data also shows extensive colonization and biofilm formation by B. subtilis with indirect bacterial exposure from the hcnB mutants PAO6344 and CHAO77. The images were representative of the roots from six independent plants imaged.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2315799&req=5

pone-0002073-g005: Suppression of B. subtilis biofilm formation on A. thaliana Col-0 roots by indirect exposure of the pseudomonad strains and cyanide (A) and the effect of indirect exposure of the pseudomonad strains and cyanide on single cell growth of B. subtilis (B).The images show complete suppression of B. subtilis biofilm formation when exposed to the indirect exposure of the strains PAO1, PA14, CHAO and HCN when compared to control plants not exposed to either bacterial culture or HCN and ΔhcnB mutants PAO6344 and CHAO77. The data also shows extensive colonization and biofilm formation by B. subtilis with indirect bacterial exposure from the hcnB mutants PAO6344 and CHAO77. The images were representative of the roots from six independent plants imaged.

Mentions: Since the pseudomonads are common soil bacteria, we suspected that apart from their effect on plant roots, they might also influence other rhizospheric processes such as beneficial bacteria-root associations. Therefore, we studied the possible effects of pseudomonad cyanogenesis on B. subtilis colonization and biofilm formation on Arabidopsis. B. subtilis, a biocontrol PGPR (plant growth-promoting rhizobacteria), forms biofilms on A. thaliana roots and protects the plant from pathogenic infections [37], [39]. The experiment was conducted in vitro; in six well plates using 10-day-old A. thaliana seedlings grown in MS liquid medium with 1% sucrose (see materials and methods). The results presented in Figure 5 show a complete suppression of B. subtilis FB17 biofilm formation on the roots subjected to indirect exposure with P. aeruginosa strains PAO1/PA14, P. fluorescens strain CHAO and HCN (KCN+HCL) (Figure 5A). The control which did not receive any bacterial culture, and the treatments, with bacterial cultures of cyanide impaired mutants PAO6344, and CHAO77 formed extensive biofilms. Although indirect exposure of the pseudomonad strains and cyanide caused complete suppression of B. subtilis biofilm formation on Arabidopsis roots, they did not however, affect the single cell growth of B. subtilis in the Arabidopsis culture medium as indicated by FB17 colony forming units (CFU) data (Figure 5B). These results clearly indicated that apart from the inhibition of plant primary root growth, pseudomonad cyanogenesis also affects other rhizospheric processes such as biofilm formation by a beneficial biocontrol PGPR such as B. subtilis.


Cyanogenic pseudomonads influence multitrophic interactions in the rhizosphere.

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

Suppression of B. subtilis biofilm formation on A. thaliana Col-0 roots by indirect exposure of the pseudomonad strains and cyanide (A) and the effect of indirect exposure of the pseudomonad strains and cyanide on single cell growth of B. subtilis (B).The images show complete suppression of B. subtilis biofilm formation when exposed to the indirect exposure of the strains PAO1, PA14, CHAO and HCN when compared to control plants not exposed to either bacterial culture or HCN and ΔhcnB mutants PAO6344 and CHAO77. The data also shows extensive colonization and biofilm formation by B. subtilis with indirect bacterial exposure from the hcnB mutants PAO6344 and CHAO77. The images were representative of the roots from six independent plants imaged.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0002073-g005: Suppression of B. subtilis biofilm formation on A. thaliana Col-0 roots by indirect exposure of the pseudomonad strains and cyanide (A) and the effect of indirect exposure of the pseudomonad strains and cyanide on single cell growth of B. subtilis (B).The images show complete suppression of B. subtilis biofilm formation when exposed to the indirect exposure of the strains PAO1, PA14, CHAO and HCN when compared to control plants not exposed to either bacterial culture or HCN and ΔhcnB mutants PAO6344 and CHAO77. The data also shows extensive colonization and biofilm formation by B. subtilis with indirect bacterial exposure from the hcnB mutants PAO6344 and CHAO77. The images were representative of the roots from six independent plants imaged.
Mentions: Since the pseudomonads are common soil bacteria, we suspected that apart from their effect on plant roots, they might also influence other rhizospheric processes such as beneficial bacteria-root associations. Therefore, we studied the possible effects of pseudomonad cyanogenesis on B. subtilis colonization and biofilm formation on Arabidopsis. B. subtilis, a biocontrol PGPR (plant growth-promoting rhizobacteria), forms biofilms on A. thaliana roots and protects the plant from pathogenic infections [37], [39]. The experiment was conducted in vitro; in six well plates using 10-day-old A. thaliana seedlings grown in MS liquid medium with 1% sucrose (see materials and methods). The results presented in Figure 5 show a complete suppression of B. subtilis FB17 biofilm formation on the roots subjected to indirect exposure with P. aeruginosa strains PAO1/PA14, P. fluorescens strain CHAO and HCN (KCN+HCL) (Figure 5A). The control which did not receive any bacterial culture, and the treatments, with bacterial cultures of cyanide impaired mutants PAO6344, and CHAO77 formed extensive biofilms. Although indirect exposure of the pseudomonad strains and cyanide caused complete suppression of B. subtilis biofilm formation on Arabidopsis roots, they did not however, affect the single cell growth of B. subtilis in the Arabidopsis culture medium as indicated by FB17 colony forming units (CFU) data (Figure 5B). These results clearly indicated that apart from the inhibition of plant primary root growth, pseudomonad cyanogenesis also affects other rhizospheric processes such as biofilm formation by a beneficial biocontrol PGPR such as B. subtilis.

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