Antimicrobial Efficacy of Methanobactin against Bacillus Subtilis

Abstract

Methanobactin is a novel extracellular fluorescent chromopeptide produced by methanotrophys. Its recent characterization has placed it in a new class of compounds, which is now known as chalkophores. They are analogous to iron-binding siderophores. The present study investigated the antimicrobial efficacy of copper-bound methanobactin (Mb-Cu) against Bacillus Subtilis in LB medium. Minimum inhibitory concentrations (MICs) determined that at 24 h for stationary-phase Bacillus Subtilis cultures in liquid LB medium (36° C) via use of a twofold dilutions method, was 5 mg/mL. Minimum bactericidal concentrations (MBC) for Mb-Cu observed in the plate after 72 h at 36° C was 10 mg/mL. Effect of different pH value (2 to 9) on antibacterial activity of Mb-Cu was measured by bacteriostatic circle method; the results showed that there was a non-liner relationship between the antimicrobial activity of Mb-Cu against Bacillus Subtilis and pH. Methanobactin was active in the range of pH 2～9 and has the best antimicrobial activity at near pH 6.0. Growth curve of Bacillus subtilis results showed that the maximum growth rate of Bacillus Subtilis was reduce and the lag phase was extended for 3 h.