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Contrasting Regulation of Live Bacillus cereus No.1 and its Volatiles on Shiraia Perylenequinone Production

Summary

This research investigated how bacteria living inside medicinal mushrooms can affect the production of important anticancer compounds. Scientists found that bacterial gases could increase the production of these beneficial compounds, while direct contact with bacteria decreased their production. This discovery has important implications for both medicine and agriculture. Key impacts on everyday life: • Could lead to better methods for producing natural anticancer drugs • May help develop more environmentally friendly crop protection methods • Provides new understanding of how microorganisms interact in nature • Could improve cultivation of medicinal mushrooms • May lead to new biotechnology applications

Background

Fungal perylenequinones (PQs) are photoactivated polyketide mycotoxins produced by plant-associated fungi. Hypocrellins, effective anticancer photodynamic therapy agents, are main bioactive PQs isolated from bambusicolous Shiraia fruiting bodies. Previous research found bacterial communities inhabiting fungal fruiting bodies are diverse but their functions remained unknown. Bacillus was identified as the most dominant genus inside Shiraia fruiting bodies.

Objective

To understand the regulation role of dominant Bacillus isolates on host fungus by investigating the relationship between B. cereus No.1 and host fungus Shiraia sp. S9, comparing the effects of live bacterium and its volatiles on Shiraia PQ production, and elucidating the mechanisms involved.

Results

Bacterial volatiles significantly promoted fungal PQ production including hypocrellin A (HA), HC and elsinochrome A-C through transcriptional regulation. In submerged bacterial volatile co-culture, volatiles enhanced both HA production in mycelium and release into medium, reaching total HA production of 225.9 mg/L (1.87x control). In contrast, live bacteria suppressed PQ production in both confrontation plates and mycelium cultures through direct contact by down-regulating biosynthetic genes and degrading extracellular HA to its reductive product.

Conclusion

This study revealed dual effects of fruiting body-associated B. cereus No.1 on host fungal metabolite production: promotion via bacterial VOCs and inhibition through direct contact. The findings provide new understanding of bacterial-fungal interactions and potential applications in both biotechnology for PQ production and agricultural biocontrol.
  • Published in:Microbial Cell Factories,
  • Study Type:Laboratory Research,
  • Source: 10.1186/s12934-022-01897-z
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