Recording images of plates using a plate reader. (a) The plate area with the interacting fungus can be defined as containing 96, 24 or 6 “wells” with zero thickness walls that can each be scanned (30 × 30 readings). (b) Scan of a Nunc OmniTray plate (120 × 80 mm) (Thermo Fisher Scientific, Waltham, MA) using a standard flatbed optical document scanner containing the fungus F. graminearum inoculated, with a row of agar plugs cut from a colony, at position 2. P. fluorescens In5 containing a plasmid with nunF-promoter-mCherry construct was inoculated as a streak at position 1 and the bacterium containing a plasmid with the same construct but lacking the promoter was inoculated as another streak at position 3. (c–e) Images constructed from scans by the BMG LABTECH microplate reader (BMG LABTECH, Offenburg, Germany) in different channels of the same row of 6 “wells”. (c) Red fluorescence (Excitation filter 584 nm Emission filter 620–10 nm) recording the mCherry signal. (d) Green fluorescence (Excitation filter 485-12 Emission filter 520) recording the bacterial fluorescent siderophore pyoverdine and also a fungal fluorescent compound. (e) Absorbance 660 nm measuring optical density (OD) used to measure biomass (660 nm is not absorbed by the red fungal pigment).