Fungi are a group of eukaryotic spore-bearing fungi lacking chlorophyll. The fungi require organic compounds for nutrition. They are heterotrophic organisms that require organic compounds for food. Mycology is the study of fungi. Fungi are of two types; yeast and molds.
A mold is a multicellular fungus growing in filaments called hyphae. The hyphae are multicellular and have many genetically identical nuclei, but it forms a single organism. However, yeast is a unicellular fungus; that is, the thallus (body of fungi) comprises of a single cell.
Although yeast and mold have many differences, they possess similarities. One being the phylum and another being their cell wall has chitin.
The Difference Between Yeast and Mold
| Properties | Yeast | Mold |
|---|---|---|
| Cell type | Unicellular eukaryotic organism | Multicellular eukaryotic organism |
| Habitat | Yeasts can grow in multiple environments like fruits and berries, in the guts and skin of mammals, etc. | Molds require damp and moist places for growth. |
| Growth temperature | The ideal temperature for growth is 37℃. | The optimum temperature for growth is 28℃. |
| Shape | Yeasts usually have egg-shape, but some are elongated and some spherical. | The mycelium appears as a fluffy thread-like structure. The dusty or fuzzy appearance of mold is due to spores at the end of hyphae. The spores have different colors like orange, purple, pink black, brown, etc., which gives the mold a distinct appearance. |
| Size | The size of yeast varies widely. The width ranges from 1-5 µm and length from 5 to 30 µm. | The hyphae are 5-10 µm wide. |
| Colony morphology | Yeast colonies are similar to bacterial colonies but are colorless and are usually non-mucoid or dry in consistency. | Mold colonies look fluffy or fuzzy with uneven ends. They change into different colors, starting from the center. |
| Structure | The thallus (body) of yeast has one cell. A true cell wall composed of cellulose, chitin, or hemicellulose surrounds the cell. | The thallus of mold has two parts; mycelium and spores. The mycelium consists of several filaments called hyphae. The hypha is a tube-like wall that surrounds a cavity called the lumen. The wall of a hypha is made up of chitin or hemicellulose. The spores are single-celled and diverse in shapes and colors. |
| Uses | Yeasts are used in ethanol production, bakeries, vitamin supplements, and the study of cells. | Molds are used to produce some food like cheese, oncom (a byproduct of tofu), etc. |
| Reproduction | Most yeasts reproduce by asexual methods like budding. | Molds reproduce by spores which can be both asexual and sexual. |
| Species | More than 1500 species identified | More than 1000 species identified |
| Diseases caused | Yeast cause infections in people with compromised immune systems. | Molds can cause respiratory disease and allergic reactions in healthy as well as immune-compromised individuals. |
| Source of Energy | The energy source is alcoholic fermentation, which produces ethanol and carbon dioxide as the end product of carbohydrate metabolism. | The molds produce a hydrolytic enzyme that degrades the biopolymers like starch and cellulose into simpler carbohydrates. These simpler compounds are then absorbed by the cell. |
| Examples | Candida albicans, Cryptococcus neoformans, etc., | Penicillium, Aspergillus, Rhizopus, etc. |
Another type of fungi in yeast, as well as mold, forms are the dimorphic fungi. It converts into the mold when the temperature is 20-25℃ and into yeast at 37℃. It is responsible for causing many diseases in humans and animals. Examples of dimorphic fungi are Histoplasma capsulatum, Blastomyces dermatitidis, Coccidiodes immitis, etc.
References and detailed study
Pelczar Jr., M., Chan, E., & Krieg, N. (2007). Microbiology (5th ed., pp. 333-362). Tata McGraw-Hill.