Inducing perylenequinone production from a bambusicolous fungus Shiraia sp. S9 through co-culture with a fruiting body-associated bacterium Pseudomonas fulva SB1

Abstract

Abstract Background Fungal perylenequinonoid (PQ) pigments from Shiraia fruiting body have been well known as excellent photosensitizers for medical and agricultural uses. The fruiting bodies are colonized by a diverse bacterial community of unknown function. We screened the companion bacteria from the fruiting body of Shiraia sp. S9 and explored the bacterial elicitation on fungal PQ production. Results A bacterium Pseudomonas fulva SB1 isolated from the fruiting body was found to stimulate the production of fungal PQs including hypocrellins A, C (HA and HC), and elsinochromes A–C (EA, EB and EC). After 2 days of co-cultures, Shiraia mycelium cultures presented the highest production of HA (325.87 mg/L), about 3.20-fold of that in axenic culture. The co-culture resulted in the induction of fungal conidiation and the formation of more compact fungal pellets. Furthermore, the bacterial treatment up-regulated the expression of polyketide synthase gene (PKS), and activated transporter genes of ATP-binding cassette (ABC) and major facilitator superfamily transporter (MFS) for PQ exudation. Conclusions We have established a bacterial co-culture with a host Shiraia fungus to induce PQ biosynthesis. Our results provide a basis for understanding bacterial–fungal interaction in fruiting bodies and a practical co-culture process to enhance PQ production for photodynamic therapy medicine.

Keywords

• Shiraia
• Fruiting body
• Associated bacteria
• Co-culture
• Perylenequinones
• Hypocrellin A