Nutritional factors regulating growth and accumulation of phenazine 1-carboxylic acid by Pseudomonas fluorescens 2-79

Abstract

Pseudomonas fluorescens strain 2-79 (NRRL B-15 132) is a biocontrol agent of take-all of wheat caused by the fungus Gaeumannomyces graminis var. tritici. Strain 2-79 produces the antibiotic phenazine 1-carboxylic acid, which acts as the primary mechanism of disease suppression. As a first step toward designing efficient methods of mass producing and formulating this biocontrol agent, the regulation of growth and antibiotic production by growth factors (including purines, pyrimidines, vitamins) and minerals (supplying B3+, Ca2+, Co2+, Cu2+, Fe2+, Mg2+, Mn2+, Mo6+, Zn2+) was examined in defined liquid culture. Additions of boric acid and sulfates of iron and magnesium enhanced both cell and associated antibiotic accumulation. However, accumulation of the antibiotic alone improved with additions of zinc sulfate, ammonium molybdate, and cytosine, but worsened with addition of adenine. Interactive effects involving the sulfates of iron, magnesium, and zinc were observed, and optimal iron-magnesium and iron-zinc combinations were demonstrated with respect to biomass and antibiotic accumulation, respectively.