Location: Toxicology & Mycotoxin ResearchTitle: Xenobiotic remediation in niche domination of soil-borne mycotoxigenic fungi: The deletion analysis of fungal lactamases in Fusarium verticillioides
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/2/2016
Publication Date: N/A
Interpretive Summary: Beta-lactam antibiotics such as penicillin interfere with synthesis of the bacterial cell wall. Bacteria produce beta-lactamase enzymes that protect themselves from these antibiotics by degrading and inactivating them. Fungi also have many genes that encode beta-lactamases even though their cell wall synthesis is not affected by beta-lactam antibiotics. Earlier we showed that one lactamase enzyme, encoded by FDB1-ORF5 (FVEG_08291), was responsible for detoxification of the maize benzoxazinone phytoanticipins, including BOA a gamma lactam. We are in the process of deleting each of the 46 lactamase encoding genes in Fusarium verticillioides by our OSCAR methodology. We hypothesize that these enzymes likely play roles in protection from microbial lactam containing compounds produced by soil microbes competing for resources with F. verticillioides. This presentation gave an update on our progress.
Technical Abstract: Beta-lactamase enzymes are well studied because of their huge impact on medicine. Their prominent role is in resistance to beta-lactam (four membered lactam ring) antibiotics including the first and most famous fungus derived medically important antibiotic, penicillin. These antibiotics primarily function by interfering with bacterial cell wall construction. Fungi also have genes that encode canonical beta-lactamase domains. Very little is known about the function of these enzymes in fungi. Clearly, they likely do not act to protect the fungus from beta-lactams since fungi have completely different walls and tend to be unaffected by these drugs. Fusarium species tend to possess large families of beta-lactamase encoding genes. In our fungus of interest, the fumonisin producer F. verticillioides, there are 46 beta-lactamase genes. In fungi, reports describe the functions of only two beta-lactamase genes, one functioning in the synthesis of a secondary metabolite and the other involved in breakdown of a plant xenobiotic. In the case of biosynthesis it was found that it was not the lactamase portion of the protein that is involved in the biosynthesis but rather a second functional domain. In the second case, F. verticillioides was shown to degrade gamma-lactam maize phytoanticipins. Earlier we showed that one enzyme, encoded by FDB1-ORF5 (FVEG_08291), was responsible for detoxification of the maize benzoxazinone phytoanticipins, including BOA. BOA is a gamma-lactam, with a five membered lactam ring, and is cleaved by this enzyme. This result suggests that fungal lactamases have specificity beyond beta-lactams. We are deep into a family-wide gene deletion project to determine the function of these enzymes, with the hypothesis that they are involved in chemical warfare with antagonistic organisms and that their expansion in the genus Fusarium is a driving force for the ubiquitous nature of F. verticillioides in agricultural soils. This presentation will give an update on our results using undergraduates to generate the deletion set by ATMT with our OSCAR methodology.