The organism that results from a close association between single-celled algae and fungi is called a lichen.

Here's a breakdown of the relationship:

* Algae: The photosynthetic partner, providing food through photosynthesis.

* Fungi: The structural partner, providing support, water absorption, and protection.

This symbiotic relationship is mutually beneficial, meaning both organisms benefit from the association. The algae benefit from the protection and moisture provided by the fungus, while the fungus benefits from the food produced by the algae.