Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/30/2011
Publication Date: 6/1/2011
Citation: Hartney, S.L., Mazurier, S., Lemanceau, P., Loper, J.E. 2011. Diversity of TonB-dependent outer-membrane proteins in plant-associated strains of Pseudomonas fluorescens. Phytopathology. 101(6)S:70. Interpretive Summary:
Technical Abstract: Genomic sequences of ten strains of plant-associated Pseudomonas spp. were surveyed for the presence of TonB-dependent outer-membrane proteins (TBDPs), which function in the uptake of substrates from the environment by many Gram-negative bacteria. The ten strains, representing P. fluorescens, P. chlororaphis, and P. synxantha, were isolated from the phyllosphere, rhizosphere or soil. Fourteen to forty-five TBDPs were identified in each strain, and phylogenetic analysis of the TBDPs identified five that are conserved across all ten genomes. Comparisons to proteins with known functions allowed the assignment of putative roles in uptake of heme, vitamin B12, copper, and the siderophore ferrichrome to the conserved TBDPs. Each strain also has multiple TBDPs with predicted functions in the uptake of pyoverdines, a structurally diverse class of siderophores produced by the fluorescent pseudomonads. Strain Pf-5, for example, has six such TBDPs. Using crossfeeding assays, we found that Pf-5 utilized pyoverdines having 17 distinct structures. Mutants of Pf-5 lacking each of the six putative pyoverdine receptors were constructed and tested in crossfeeding assays, which linked the uptake of specific pyoverdines to individual TBDPs. The identification of the core TBDPs present in all genomes as well as the TBDPs unique to each genome highlights functions conserved across the species as well as those specific to the distinctive lifestyles of each strain.