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Molds and Yeasts

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Introduction to mold and yeast

The study of eukaryotes is incomplete without taking into account mould and yeast. They both belong to the Fungi kingdom and are visible to the naked eye in a colony or network. However, their functioning falls under the discipline of microbiology. Despite the commonness of family between yeast and mold, they differ largely; the biggest difference is that while yeast is unicellular, mold is multicellular. The network of the tubular branching hyphae of mold is regarded as a singular organism. Besides these, there are numerous points that help us understand the dissimilarities between these two groups. We shall study the differentiation in detail.  

Basics of Mold

Molds form a taxonomically diverse group in fungi. The spores and filaments present in molds help in their classification against other types of fungi like yeast and mushroom. They are very adaptable to the surroundings and form colonies, even on the least biodegradable organic materials like wood and paper. Mold can be seen growing on books, leftover food and fruits kept outside the refrigerator and on wooden furniture, doors etc. 

Atmospheric moisture and dampness are the necessary conditions for mold to grow. Even if we wipe the affected wooden surfaces and clean the grown mold, we can see a noticeable discoloration or unevenness due to the degrading action of the mold. Molds are of particular interest for mycologists due to the production of enzymes that can break down even some of the toughest organic molecules in the process of degradation. 

What are Yeasts?

Yeasts are other types of fungi and the lowest in the number of species of fungi. They have perplexed evolutionary biologists due to the fact that they have evolved back into unicellular organisms from multicellular organisms. Unlike molds, yeasts do not have differentiable body parts like filament, spore or hypha; they are single cells. 

Their visibility is due to their formation of colonies by budding into clusters and chains. Some species also show multicellular characteristics with the formation of strings by connecting the budded cells; it resembles a hypha and is called pseudohyphae. Yeasts are of particular interest for mycologists due to their ability to convert carbohydrates into ethyl alcohol in the process of fermentation.

Difference Between Yeast and Mold

Both mold and yeast do not have chlorophyll and therefore do not produce their own energy and are heterotrophic beings, just like any other types of fungi. Some molds appear green but are not capable of carrying out photosynthesis. There are more functional, structural, morphological and anatomical differences between the two. The following table gives a detailed differentiation. 

Comparison and Difference Between Yeast and Mold





Form a network called mycelium which is regarded as a single organism

Live Independently however form colonies by budding

Found in damp places

Found on fruits and vegetables and on the skin of several animals

Have several filaments in the mycelium

Have oval or spherical shapes

Have true filaments known as hyphae in individual cells

No true hyphae present; pseudohyphae are formed with budding

Make an approximate number of 100,000 species of fungi

Constituting around 1%, i.e., of all discovered fungal species

Reproduce with sporing, i.e., either asexually by mitosis or sexually by meiosis

Asexual reproduction is the commonest form by budding; however, sexual reproduction is observed in a small number too.

Mostly colourful

Mostly colourless or white

Produce hydrolytic enzymes to help the degradation of biopolymers like starch, lignin and cellulose into simple chemicals as food for absorption. 

Ferment carbohydrate-based products and make alcohol and release carbon dioxide in the process

Penicillium chrysogenum is used in the production of penicillin. Some molds are used in the production of cheese

Used for the fermentation of bread, scone etc., and for the production of alcohol like ethanol in various forms like wine, beer etc. 

Can cause respiratory problems due to allergic reactions

Is known to cause certain infections in human beings and other creatures


Both mold and yeast have microscopic functioning. Earlier, they were part of the plant kingdom under clade Fungus; however, they form a separate kingdom now. While yeast is a unicellular organism, mold is regarded as a multicellular organism because it forms a single network called mycelium. However, when it comes to studying the workings of its individual filaments or smaller anatomical parts, it is regarded as a topic of microbiology.

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FAQs on Molds and Yeasts

Do moulds and yeasts produce the same types of enzymes?

The mechanism of biodegradation of both yeast and mold is the same; i.e., the use of enzymes to convert organic matter into energy. Both molds and yeasts are heterotrophs, just like any other type of fungus. However, they work in different environmental conditions. Molds require humidity or dampness and degrade even tough biopolymers like wood and paper. Yeasts, on the other hand, are seen growing on surfaces of living organisms like the outer layer of certain fruits and skins of certain animals; therefore, even if the layer is tough, there is an internal source of water.

What are the modes of reproduction in yeasts and molds?

Both molds and yeasts show both sexual and asexual types of reproduction; however, their courses are different. Molds procreate by the process of sporogenesis, i.e., the formation of spores. These spores are either the products of mitosis or meiosis; i.e., either asexual or sexual, respectively. 

Yeasts majorly procreate through asexual reproduction by the method of budding. Usually, in conditions like starvation or lack of nutrition, the haploid cells die and the diploid cells undergo sporulation, which leads to sexual reproduction by the method of meiosis.

What are some of the uses of yeast?

Yeast has various uses, specifically due to its ability to ferment carbohydrate-based products and convert them into consumables. This process of fermentation is used in alcohol breweries in the production of beer, wine and other such spirits. Similarly, yeast is also used in the baking of bread, scones, cake, and other such bakery products using the same fermentation process.

Does yeast reproduce sexually?

The most common form of yeast reproduction is budding, but some forms of yeast do reproduce sexually. This is performed by a way of signalling, which is commonly known as the mating factor pathway. Here, two haploid cells combine to form a diploid cell. One cell attracts the other cell by way of the mating factor molecule.

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