A fungus secreting antibiotics that kill bacteria is an example of:
Antibiotic secretion by a fungus that suppresses nearby bacteria is a standard example of amensalism, specifically antibiosis, when the fungus is treated as unaffected and the bacteria are harmed. The fungal metabolite inhibits bacterial cell-wall synthesis, protein synthesis, membrane function, or another essential process, depending on the compound. Penicillin, for instance, blocks transpeptidation during peptidoglycan assembly, causing susceptible growing cells to lyse. Ecological sign notation represents this simplified outcome as (0, −): no measurable effect on the producer and a negative
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 8-13