The endophytic fungus A. austroafricanus strain was isolated under aseptic conditions from fresh, healthy leaves of E. crassipes. The fresh plant was gathered at the end of 2014 close to the shore of the Nile branch in Mansoura, Egypt. Cocultivation Experiment of A. austroafricanus with B. subtilis 168 trpC2: Fermentation of the fungus with the bacteria in coculture was conducted in an Erlenmeyer flask (1 L) on solid rice medium. Fifteen Erlenmeyer flasks (5 flasks for axenic A. austroafricanus, 5 for cocultures of A. austroafricanus and B. subtilis, and 5 for axenic B. subtilis) containing 60.0 mL of distilled water and 50.0 g of commercially available milk rice (Milch-Reis, ORYZA) each were autoclaved before inoculating the fungus and the bacterium. An overnight culture of B. subtilis grown in lysogeny broth (LB) was used to inoculate prewarmed LB medium (1:20), which was then incubated at 37 ℃ with shaking at 200 rpm to mid exponential growth phase (optical density at 600 nm of 0.2-0.4). To the rice medium was added 10 mL of the bacterial culture followed by incubation for 4 days at 37 ℃. After 4 days five pieces (1 cm × 1 cm) of A. austroafricanus growing on malt agar were added to the flasks that had been preincubated with B. subtilis. Fungal and bacterial controls were grown axenically on solid rice medium. Cocultures and axenic cultures of A. austroafricanus and B. subtilis were kept at 23 ℃ under static conditions until they reached their stationary phase of growth (2 weeks for controls of A. austroafricanus and bacteria; 4 weeks for cocultures). Cocultivation Experiment of A. austroafricanus with S. lividans TK24: Fifteen Erlenmeyer flasks (5 flasks for axenic A. austroafricanus, 5 for coculture of A. austroafricanus and S. lividans, and 5 for axenic S. lividans) containing 60.0 mL of yeast malt (YM) medium and 50.0 g of commercially available milk rice (Milch-Reis, ORYZA) each were autoclaved before inoculating the fungus and the bacterium. An overnight culture of S. lividans was used to inoculate prewarmed YM medium (1:20), which was then incubated at 30 ℃ with shaking at 200 rpm to mid exponential growth phase. This preculture was then incubated in fresh YM medium overnight to reach mid exponential growth phase. After that, to the rice medium was added a 10 mL volume of the bacterial culture, followed by incubation for 6 days at 30 ℃; then, the same steps as previously described under B. subtilis 168 trpC2 were taken. The fungal strain was cultivated axenically on solid rice medium, prepared by autoclaving 100 g of rice and 100 mL of water in a 1 L Erlenmeyer flask. Fermentation was carried out in five Erlenmeyer flasks for 21 days at 25 ℃ under static conditions. After 21 days' fermentation, the fungal culture in each flask was exhaustively extracted with ethyl acetate overnight (3 × 500 mL) followed by filtration and solvent evaporation under reduced pressure.

The endophytic fungus was isolated from fresh, healthy rhizomes of Aristolochia paucinervis collected in January 2006 from the mountains of Beni-Mellal, Morocco. Cocultivation Experiment of F. tricinctum with B. subtilis 168 trpC2: Growth of fungus and bacteria in coculture for isolation and identification of metabolites was carried out in Erlenmeyer flasks (1 L). The fungal and bacterial strains were cultivated on solid rice media. Twenty-four Erlenmeyer flasks (eight flasks for F. tricinctum alone, eight for coculture of F. tricinctum and B. subtilis, and eight for B. subtilis alone) containing 60 mL of distilled water and 50 g of commercially available milk rice (Milch-Reis, ORYZA) each were autoclaved before inoculating the fungus and the bacterium. B. subtilis was grown in lysogeny broth (LB). An overnight culture of B. subtilis was used to inoculate prewarmed LB medium (1:20), which was then incubated at 37 ℃ with shaking at 200 rpm to mid exponential growth phase (optical density at 600 nm (OD600) of 0.2-0.4). A 10 mL amount of the bacterial culture was added to the rice medium, which was further incubated for 6 days at 37 ℃ After this preincubation, F. tricinctum grown on malt agar (5 pieces, 1 cm × 1 cm) was added to the rice medium containing bacteria (after 6 days incubation) under sterile conditions. Fungal and bacterial controls were grown axenically on rice medium. Coculture and axenic cultures of F. tricinctum or B. subtilis were kept under static conditions at 23 ℃ until they reached their stationary phase of growth (2 weeks for controls of F. tricinctum and 3 weeks for cocultures).

Hence, the production of (-)-citreoisocoumarin induced by coculture of F. tricinctum and B. subtilis might be a result of the competition for nutrients between fungus and bacterium.

Fungal material: Houttuynia cordata was grown in a local garden at Willich, Germany. Fresh roots were harvested in April 2016 and washed with sterilized water, surface sterilized with 70% ethanol for 1 min, and cut into small pieces (around 1 × 1 × 1 cm) using a flame sterilized blade. These pieces were put on malt agar plates (15 g/L malt extract, 15 g/L agar, and 0.2 g/L chloramphenicol in distilled water, pH 7.4-7.8 with sodium hydroxide or hydrochloric acid), and then incubated at room temperature for several days. Fermentation and co-cultivation: Fermentation of the fungus was conducted in 11 Erlenmeyer flasks on solid rice medium (100 g rice in 110 mL water followed by autoclaving) at 20 ℃ at static conditions. After 33 days each flask was extracted with 600 mL EtOAc. Co-cultivation experiment with Bacillus subtilis (ATCC168) was conducted on solid rice medium. A total of 15 flasks was prepared (5 axenic fungal cultures as controls, 5 co-cultures with bacteria and 5 axenic bacterial cultures as controls). After addition of 10 mL bacteria solution to each flask, the flasks were incubated at 30 ℃ for three days. Then a constant number of pieces from agar plates containing Trichocladium sp. were transferred to the co-culture flasks. All flasks were inoculated at 20 ℃ under static conditions. After 33 days 600 mL EtOAc was added to each flask in order to terminate the cultivation. OSMAC experiments: In addition to rice, peas (Pisum sativum, from Mullers Muhle, Germany) were used as medium (100 g of peas in 110 mL of H₂O followed by autoclaving). The cultivation procedure was the same as described for cultivation on rice medium. For the feeding experiment using tryptophan, the rice medium was spiked with 2% tryptophan prior to autoclaving.

Addition of tryptophan to the rice medium which was done trying to mimic the higher protein content of peas vs. rice caused the accumulation of the new compound 13-N-(2-Carboxyphenyl)colletoketol which in addition to colletoketol includes anthranilic acid, the latter probably being a fungal biotransformation product of added tryptophan.