Secondary metabolites are key players in microbial interactions, but their production and secretion pose a significant economic and logistical challenge. An evolutionary arms race invariably ensues, leading to complex intra- and inter-cellular metabolic networks. We will explore such networks in the interaction between the fungus Ustilago maydis and the bacterium Pseudomonas. The fungus secretes itaconic acid and derivatives via a metabolic network that strongly involves mitochondrial metabolism. The bacterium can degrade itaconic acid, but it is unclear how it is affected by the derivatives. We will explore these interactions through quantitative modulation of fluxes between (sub)cellular compartments using molecular switches and metabolic models to contextualise the networks with biosensor data and omics analysis.