Siderophore production in groundnut rhizosphere isolate, Achromobacter sp. RZS2 influenced by physicochemical factors and metal ions

Abstract

Growth and siderophore production of plant growth promoting rhizobacteria (PGPR) are influenced by a variety of physicochemical and environmental factors of the rhizosphere. Any factor that affects the growth of PGPR will also influence the production of siderophore and other metabolites produced by PGPR. In order to provide the optimum conditions for good growth and performance of PGPR, it is necessary to know the best physicochemical conditions. The present study describes the effect of various nutrients, physical parameters and metal ions on growth and siderophore production by Achromobacter sp. RZS2 isolated from groundnut rhizosphere. We report siderophore production by Achromobacter sp. RZS2 in a succinic acid medium (SM). Optimization for the production of siderophores was done by using different nitrogen sources, organic acids, amino acids, sugars, media, metal ions, inoculum level, incubation time, and pH values. The optimum conditions for maximum production of siderophores were SM, 30 h incubation at 28 °C, neutral pH, the presence of urea and low stress of iron. However, the stress condition of iron might be a decisive factor for siderophore production. Low stress of ferric iron supported the growth yield while higher level (600 µM and above) completely repressed siderophores. Isolate continued producing siderophore in presence of other heavy metals. The ability of isolate to utilize urea indicated that the microorganism can grow even in the presence of commonly used inorganic fertilizer such as urea. Use of synthetic pesticides pours various metal ions in the soil, these metal ions get incorporated into our food chain and have been the cause of various health hazards. Growth of isolate at a higher level (up to 600 µM of iron) of iron and moderate concentration (100 µM) of other heavy metals makes it a suitable organism for bioremediation of metal ions from agriculture soil.