Penicillium nalgiovense Laxa isolated from Antarctica is a new source of the antifungal metabolite amphotericin B

K Stefan Svahn, Erja Chryssanthou, Björn Olsen, Lars Bohlin, Ulf Göransson

The need for new antibiotic drugs increases as pathogenic microorganisms continue to develop resistance against current antibiotics. We obtained samples from Antarctica as part of a search for new antimicrobial metabolites derived from filamentous fungi. This terrestrial environment near the South Pole is hostile and extreme due to a sparsely populated food web, low temperatures, and insufficient liquid water availability. We hypothesize that this environment could cause the development of fungal defense or survival mechanisms not found elsewhere. We isolated a strain of Penicillium nalgiovense Laxa from a soil sample obtained from an abandoned penguin's nest. Amphotericin B was the only metabolite secreted from Penicillium nalgiovense Laxa with noticeable antimicrobial activity, with minimum inhibitory concentration of 0.125 μg/mL against Candida albicans. This is the first time that amphotericin B has been isolated from an organism other than the bacterium Streptomyces nodosus. In terms of amphotericin B production, cultures on solid medium proved to be a more reliable and favorable choice compared to liquid medium. These results encourage further investigation of the many unexplored sampling sites characterized by extreme conditions, and confirm filamentous fungi as potential sources of metabolites with antimicrobial activity.