Difference Between Yeast and Mold

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. 

difference between yeast and mold

The Difference Between Yeast and Mold

Cell typeUnicellular eukaryotic organismMulticellular eukaryotic organism
HabitatYeasts 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 temperatureThe ideal temperature for growth is 37℃.The optimum temperature for growth is 28℃.
ShapeYeasts 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. 
SizeThe 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 morphologyYeast 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.  
StructureThe 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.
UsesYeasts 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. 
ReproductionMost yeasts reproduce by asexual methods like budding.Molds reproduce by spores which can be both asexual and sexual. 
SpeciesMore than 1500 species identifiedMore than 1000 species identified
Diseases causedYeast 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 EnergyThe 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.
ExamplesCandida 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.

Ashma Shrestha

Hello, I am Ashma Shrestha. I had recently completed my Masters degree in Medical Microbiology. Passionate about writing and blogging. Key interest in virology and molecular biology.

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