Antimicrobial activity from endophytic fungi isolated from plant leaves in Dipterocarpous forest at Viengsa district Nan province, Thailand

Eleven fungal endophytes representing different morphotaxa were characterized from 68 cultures, which were isolated from 4 species of Dipterocapous trees (Dipterocarpus tuberculatus Roxb., Shorea obtusa Wall., Shorea siamensis Miq. and Dalbergia oliveri Gamble.) growing in the Dipterocapous forest at Viengsa district, Nan province. Species of Phyllosticta spp. (15 isolates), Nodulisporium spp. (13 isolates) and Xylaria sp.1 (10 isolates) were the most frequently found. All endophytic fungal isolates were tested for potential production of bioactive metabolites. They were tested for antimicrobial activity against pathogenic microorganisms such as Staphylococcus aureus, Bacillus subtilis, Pseudomonas aerogenosa, Escherichia coli and Candida albicans by the paper disk susceptibility test. They inhibited the growth of Gram positive bacteria more than Gram negative bacteria. Candida albicans was inhibited only by Nodulissporium sp. (DT6) and Xylaria sp.1 (DO9)

Solubilization and transformation of insoluble zinc compounds by fungi isolated from a zinc mine

Fungi were isolated from zinc-containing rocks and mining soil. They were screened for the ability to solubilize and transform three insoluble zinc compounds: ZnO, Zn3(PO)4, and ZnCO3. Fungi were plated on potato dextrose agar (PDA) medium which was supplemented with 0.5% (w/v) of insoluble zinc compounds. Of the strains tested, four fungal isolates showed the highest efficiency for solubilizing all the insoluble zinc compounds, producing clearing zone diameters > 40 mm. These were identified as a Phomopsis spp., Aspergillus sp.1, Aspergillus sp.2, and Aspergillus niger. Zinc oxide was the most easily solubilized compound and it was found that 87%, 52%, and 61% of the tested fungi (23 isolates) were able to solubilize zinc oxide, zinc phosphate, and zinc carbonate, respectively. Precipitation of zinc-containing crystals was observed in zinc oxide-containing agar medium underneath colonies of Aspergillus sp.1, and these were identified as zinc oxalate. It is suggested that these kinds of fungi have the potential application in bioremediation practices for heavy metal contaminated soils