Peter Proksch
Institute of Pharmaceutical Biology and Biotechnology
University of Duesseldorf, Germany
Fungi are promising sources of novel bioactive compounds that are important for drug discovery programs. Several examples from the author´s lab indicate the significance of fungal endophytes for the discovery of new bioactive leads in the field of anti-tumor compounds and of compounds showing activity against Mycobacterium tuberculosis. However, as encountered in terrestrial microorganisms there is a high rate of redundancy that results in the frequent re-discovery of known compounds. Apparently only a part of the biosynthetic genes that are harbored by fungi are transcribed under routine laboratory conditions which involve cultivation of axenic microbial strains. Many biosynthetic genes remain silent and are not expressed in vitro thereby seriously limiting the chemical diversity of microbial compounds that can be obtained through fermentation. In contrast to this, co-cultivation (also called mixed fermentation) of two or more different microorganisms tries to mimic the ecological situation where microorganisms always co-exist within complex microbial communities. The competition or antagonism experienced during co-cultivation is shown to lead to a significantly enhanced production of constitutively present compounds and/or to an accumulation of cryptic compounds that are not detected in axenic cultures of the producing strain. This presentation will highlight the power of co-cultivation for increasing the chemical diversity of fungi drawing mainly on recent studies from the author´s lab.
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