Response of Paenibacillus polymyxa to iron: alternations in cellular chemical composition and the production of fusaricidin type antimicrobial compounds

In this work, growth, cellular chemical composition and production of fusaricidin type antimicrobial compounds by P. polymyxa SQR-21 were compared in tryptone broth supplemented with four concentrations of iron (25, 50, 100 and 200 µM). The data revealed that the growth of P. polymyxa SQR-21 was increased by 3-8% with the increase in concentration of ferric ion (Fe3+). The production of fusaricidin type compounds was increased by 33-49% only up to 50 µM Fe3+ and the highest level of Fe3+ was inhibitory. Increase in the liquid culture Fe3+concentration increased the intracellular protein (2%), intracellular carbohydrate (14%), extracellular protein (7%) and polysaccharide contents (18%) while the intracellular lipid contents were increased (11%) only up to 50 µM Fe3+. In addition, the regulatory effects of Fe3+ were also reflected by the increase in total RNA contents and relative expression of the fusaricidin synthetase gene (FusA) by 3-13 and 35-56%, respectively, up to 50 µM Fe3+, after that a continuous decrease was observed.