A fraction from Escherichia coli with anti-Aspergillus properties

The products of various strains of Escherichia coli (BL21, DH5 alpha, HB101 and XL Blue) were investigated for antimycotic properties using pathogenic isolates of Aspergillus. Co-culture experiments revealed that E coli strains exhibited variable activity against Aspergillus fumigatus. The lysates prepared from DH5 alpha, HB101 and XIL Blue strains of E coli showed inhibitory activity against A. fumigatus in the protein concentration range of 62.50 to 250.00 mu g ml(-1). The highest activity was seen in the lysate of BL21, which inhibited the growth of A. fumigatus and Aspergillus flavus completely at a concentration of 31.25 mu g protein ml(-1). The MIC of BL21 lysate against Aspergillus niger was found to be 62.50 mu g ml(-1). The in vitro toxicity of BL21 lysate was evaluated using a haemolytic assay. A BL21 lysate protein concentration of 1250.00 mu g ml(-1) was found to be nontoxic to human erythrocytes. The standard drug amphotericin B lysed 100 % of erythrocytes at a concentration of 37.50 mu g ml(-1). SIDS-PAGE showed the presence of at least 15 major proteins in the lysate of BL21. Ion-exchange chromatography resolved the BL21 lysate into five fractions and fraction III was found to be endowed with anti-Aspergillus properties. The MIC of this fraction was found to be 3.90 mu g ml(-1). Further work on the purification of the active molecule and its characterization is in progress.