|Hartney, Sierra -|
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: March 19, 2009
Publication Date: June 1, 2009
Citation: Hartney, S., Loper, J.E. 2009. TonB dependent receptors of Pseudomonas fluorescens Pf-5: Roles in siderophore and iron uptake. Phytopathology. 99(6S):52. 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. Eighteen TBDRs have the N-terminal extension domain characteristic of transducers, a subclass of TBDRs that typically initiate a signaling pathway and function in siderophore uptake. Phylogenetic analysis indicated that 5 of the 18 putative transducers are related to TBDRs that function in the uptake of ferric-pyoverdines, a structurally-diverse group of fluorescent siderophores produced by Pseudomonas spp. Mutants deficient in each of the five transducers were derived and their capacities to obtain iron from a diverse set of pyoverdines were assessed. Each of the five transducers recognized a specific subset of pyoverdine siderophores, highlighting their specificities for certain pyoverdine structures. Other transducers identified in the Pf-5 genome have predicted specificities for siderophores (enterobactin, aerobactin, ferrichrome, and ferrioxamine) produced by diverse groups of fungi and bacteria, and Pf-5 was shown to utilize each of these siderophores as sources of iron. These transducers may contribute to the environmental fitness of P. fluorescens Pf-5 by facilitating iron acquisition from siderophores produced by its coinhabitants in soil and on plant surfaces.