Aspergillus niger metabolic gene clusters activation using microbial interactions

Fungi are prominent producers of a large variety of secondary metabolites (Nielsen et al., 2009). These small molecules also named natural products are highly variable in structure and bioactivity, the encoding genes are generally organized in clusters. Fungal secondary metabolites have greatly contributed to human health with for instance clinical drugs like the antibiotic penicillins, the cholesterol-lowering statins, the immunosuppressive cyclosporins. Organic acids such as citric or itaconic acids are important industrially produced molecules for food, cosmetics, cleaning and chelating agent. While industrial fermentations for higher yield production of these molecules is mainly done with a single fungus, in their natural environment, fungi grow with other fungi and bacteria. Fungi produce secondary metabolites for protection against predation or harsh environmental conditions, communication or competition with other microorganisms (Macheleidt et al., 2016) and several secondary metabolites are toxins (e.g. fumonisins, ochratoxins) (Liang et al., 2014). Some of these natural products have been well characterized however a majority is yet to be discover and the biosynthetic gene clusters to be identified. A bottleneck in the discovery of new metabolites is that most of the gene clusters remain silent in laboratory conditions. In this study, we focus on the industrial work horse Aspergillus niger and the use of bacteria to trigger the production of secondary metabolites. A. niger has been grown with bacterial species from soil, the first screening consisted in stationary liquid co-cultures. We will present a comparative analysis by mass spectrometry of the metabolome profiles from the mixed cultures.