Abstract:
Paenibacillus polymyxa strains produce fusaricidin type compounds that are active against a wide variety of Gram-positive bacteria and fungi. Growth and production of fusaricidin type antifungal compounds by P. polymyxa SQR-21 were compared in tryptone broth supplemented with three concentrations (200, 400 and 600 µM) of lead. The data revealed that the growth of P. polymyxa increased by 7-34 % and fusaricidin type compounds production increased by 15-70 % with the increase in concentration of lead ion (Pb²⁺). The increase in Pb²⁺ concentration, decreased the intracellular carbohydrate contents but increased the intracellular protein and lipid contents, however, higher levels of Pb2+ inhibited the intracellular protein and lipid contents. On the other hand, extracellular protein contents were decreased and extracellular polysaccharide contents were increased with the increase in Pb2+ contents in liquid culture. In addition, the regulatory effects of lead were also reflected by decrease of total RNA and increase of relative expression of the six module-containing nonribosomal peptide synthetase (FusA) when the lead treated experimental samples were compared with the untreated controls. The Pb²⁺ seems to be directly or indirectly correlated with the production of fusaricidin type antifungal compounds. This information will aid in developing fermentation technology for maximum antibiotic production.
