Final answer:
Lichens, which were once thought to be related to plants, were reclassified as fungi due to their symbiotic fungal component and advanced understanding of their nature.
Step-by-step explanation:
The microorganisms that were reclassified into fungi are lichens. Lichens are not a single organism but rather a symbiotic association of a fungus with a photosynthetic partner, which can be either a green algae or cyanobacteria. Originally, lichens were classified with plants because of their similarities in terms of habitat, but with advances in microbiology and the understanding of their fungal nature, they have been reclassified as fungi. Fungi are eukaryotic organisms known for their heterotrophic lifestyle and saprozoic feeding methods. Unlike bacteria and archaea, which are prokaryotic, fungi have a complex cellular organization. Fungi include both macroscopic organisms like mushrooms, as well as microscopic yeasts and spores.