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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGY AND MANAGEMENT OF SOILBORNE DISEASES OF HORTICULTURAL CROPS Title: TonB Dependent Receptors of Pseudomonas fluorescens Pf-5 and Siderophore Uptake

Authors
item Hartney, Sierra -
item Loper, Joyce

Submitted to: International Plant Growth Promoting Rhizobacteria Workshop
Publication Type: Abstract Only
Publication Acceptance Date: April 15, 2009
Publication Date: May 17, 2009
Citation: Hartney, S., Loper, J.E. 2009. TonB dependent receptors of Pseudomonas fluorescens Pf-5 and siderophore uptake. International Plant Growth Promoting Rhizobacteria Workshop. p.30.

Technical Abstract: TonB-dependent receptors (TBDRs) are outer membrane proteins with essential roles in iron uptake by Gram-negative bacteria. The biological control strain Pseudomonas fluorescens Pf-5 has 45 predicted TBDRs in its genome, which far exceeds the number of TBDRs in most published bacterial proteomes. Bioinformatic analysis confirmed all 45 TBDRs have conserved domains with shared functionality, such as the plug and receptor domains. Eighteen TBDRs were found to have the N-terminal extension domain characteristic of transducers, a subclass of TBDRs that typically initiate a signaling pathway involving anti-sigma factors and extracytoplasmic function (ECF) sigma factors. The remaining 27 TBDRs lack the N-terminal extension domain and linked sigma factors, but may function as receptors for a variety of substrates. Phylogenetic analysis of the transducers and receptors aid in assigning putative functions and implicate horizontal gene transfer as a mechanism for acquisition by Pf-5. Five of the 18 putative transducers are related to TBDRs that function in the uptake of ferric-pyoverdines, the fluorescent siderophores produced by Pseudomonas spp.; these are being tested as ferric-pyoverdine receptors in Pf-5. Cross-feeding assays between different strains of Pseudomonas and Pf-5 receptor mutants in a pyoverdine-pyochelin deficient background indicate specificity of receptors for different pyoverdine structures. Additionally, Pf-5 is able to utilize other siderophores and iron containing compounds not made by Pseudomonads. TonB dependent receptors may have important roles influencing the environmental fitness of P. fluorescens Pf-5.

Last Modified: 10/23/2014
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