Beauvericin from the Endophytic Fungus, Fusarium redolens, Isolated from Dioscorea zingiberensis and Its Antibacterial Activity

From the fungal endophyte, Fusarium redolens Dzf2, isolated from rhizomes of the Chinese medicinal plant Dioscorea zingiberensis, beauvericin was obtained by TLC in combination with bioautographic antibacterial assay. The compound was identified by spectroscopic and physicochemical means. The median effective inhibitory concentration (IC50) values of beauvericin against six test bacteria ( Bacillus subtilis, Staphylococcus haemolyticus, Pseudomonas lachrymans, Agrobacterium tumefaciens, Escherichia coli and Xanthomonas vesicatoria) were between 18.4 and 70.7 μg/mL. The beauvericin content of F. redolens Dzf2 mycelia was 9.60 mg/g dw, and beauvericin yield 62.4 mg/L. The obtained results show the potential use of the endophytic fungus for its biological role in providing its host plant with protection, as well as the possible development of beauvericin as an antibacterial.

Adherence of bacteria to leaves

Members of seven genra of bacteria, pathogens and nonpathogens of plants, adhered to young leaves when leaves were suspended in cell suspensions for 10 min. With Pseudomonas lachrymans, the adherence rate (cells applied vs. cells adhering) to host (cucumber) and nonhost (chrysanthemum) leaves was a straight-line, log–log function, as was the adherence of Escherichia coli and Serratia marcescens to cucumber leaves. Adhering cells of these three bacteria were washed with water from cucumber leaves at a straight-line, log–log rate. Adhered cells of P. lachrymans were most commonly found near veins on cucumber leaves. There appeared to be a polymeric surface layer on this bacterium and on the cucumber leaf when leaves bearing bacteria were stained with ruthenium red and viewed in thin section.