Fungal Parasites and Pathogens

Free Response

Why can superficial mycoses in humans lead to bacterial infections?


Dermatophytes that colonize skin break down the keratinized layer of dead cells that protects tissues from bacterial invasion. Once the integrity of the skin is breached, bacteria can enter the deeper layers of tissues and cause infections.

Explain how the Red Queen Hypothesis describes the continuously evolving relationship between red grapes and Botrytis cinerea.


The Red Queen Hypothesis describes the biological stalemate between a predator and prey. The two populations are constantly applying evolutionary pressure on each other, forcing each population to adapt to counter an adaptation of the other population. In the case of the fungi B. cinerea and the red grape plant, the grapes are the prey and the fungi are the predator in the Red Queen Hypothesis. The grapes develop defenses to prevent infection by the fungi, ensuring that the B. cinerea that survive to colonize the red grapes have developed adaptations to overcome the plant defenses. The red grapes that then survive the infection are the plants that have additional adaptations that limit the pathogenicity of B. cinerea. This cycle continues to repeat unless one population evolves an adaptation that cannot be countered by the other population, which would wipe out the later population.