Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/21/2006
Publication Date: 8/25/2006
Citation: Krasnoff, S.B., Sommers, C.H., Moon, Y., Donzelli, B., Vandenberg, J.D., Churchill, A., Gibson, D.M. 2006. Production of mutagenic metabolites by metarhizium anisopliae. Journal of Agricultural and Food Chemistry. 54:7083-7088. Interpretive Summary: Fungi in the genus Metarhizium can infect many insect pests, making them useful for development as insect biological control agents. For microbial strains already in use or under evaluation as biocontrol agents, it is especially important to identify all possible bioactive chemistries that are present in the organism, both from a regulatory standpoint as well as to further understand how various products serve the producing organism. We isolated the two major components of a complex pigment mixture and identified them as NG-391 and NG-393, two compounds previously identified from two undescribed Fusarium species. In this paper, we also present bioassay data indicating that these compounds are mutagenic, but do not exhibit antifungal, antibacterial, or insecticidal activity. The relevance of these findings to the use of M. anisopliae as a biocontrol agent for insect pests is currently unknown. This finding, however, heightens the need to develop a more complete understanding of the factors that regulate expression of these products and to find more efficient ways to fully characterize the metabolic capacity of these fungi.
Technical Abstract: NG-391 (1) and NG-393 (2), previously reported from undescribed Fusarium species as nerve-cell growth stimulants, were identified from fermentation extracts of the entomopathogenic fungus Metarhizium anisopliae. These compounds are 7-desmethyl analogs of fusarin C and (8Z)-fusarin C, mutagenic toxins from Fusarium species that contaminate corn. A mutant strain of M. anisopliae (KO-B1-3) overproduces 1 and 2 by ca. 10-fold relative to the wild-type strain, ARSEF #2575, from which it was derived. Overproduction of these compounds in KO-B1-3 imparts a yellow pigmentation to the culture medium of the fungus. These compounds were inactive in antibacterial, antifungal, and insecticidal assays. However, like their fusarin analogs, 1 and 2 exhibited S9-dependent mutagenic activity in the Salmonella mutagenicity test. Discovery of these mutagenic compounds as products of M. anisopliae raises questions about the use of this fungus as a biological control agent.