Characterization of Cell Envelope Protein Patterns of Crop Yield Increasing Root-Colonizing Pseudomonas spp

Abstract

Yield reduction in high frequency cropping soil is often caused by unknown deleterious micro-organisms. Such yield depressions can be reduced by seed inoculation with fluorescent Pseudomonas spp., which display in vitro antagonism to other micro-organisms (Geels and Schippers, 1983). To explain the beneficial effect of these Pseudomonas spp. on crop yield a mechanism has been suggested in which, at the root-surface a competition for Fe³⁺ takes place between Pseudomonas spp. and deleterious microorganisms (Kloepper et al., 1980). Under the limiting Fe³⁺ conditions in soil Pseudomonas spp. are thought to produce a high affinity Fe³⁺-uptake system, consisting of (i) siderophores, which are Fe³⁺-chelating agents, and (ii) outer membrane receptor proteins, which have a high affinity and specificity for the matching Fe³⁺-siderophore complex (Neilands, 1982). These siderophores bind Fe³⁺, thereby making this essential element unavailable to other micro-organisms, including deleterious micro-organisms. This results in a reduction of the number of deleterious micro-organisms, thus creating a more favourable environment for the plant.