Molds and Yeasts

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

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Basics of Moulds

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

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


What are Yeasts?

Yeasts are other types of fungus and the lowest in the number of species of fungus. They have perplexed evolutionary biologists due to the fact that they have evolved back into unicellular organisms from multicellular organisms. Unlike moulds, 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 Mould

Both mould and yeast have microscopic functioning. Earlier they were part of the plant kingdom under clade Fungus; however, they form a separate kingdom now. They do not have chlorophyll and therefore do not produce their own energy and are heterotrophic beings just like any other types of fungi. Some moulds appear green but are not capable of carrying out photosynthesis. Yeast is a unicellular organism. Mould is regarded as a multicellular organism because it forms a single network called as mycelium; however, when it comes to studying the workings of its individual filaments or smaller anatomical parts, then it is regarded as a topic of microbiology. There are even more functional, structural, morphological and anatomical differences between the two. The following table gives a detailed differentiation. 


Comparison and Difference Between Yeast and Mould

Mould

Yeast

Multicellular

Unicellular

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

Live Independently however form colonies by budding

Found in damp places

Found of 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 fungus

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 moulds 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


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The above diagram shows the different anatomical parts of a mould along with its process of reproduction, i.e., release of spores. 

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The above image shows the lab cultured colony of yeast.

FAQ (Frequently Asked Questions)

1. Do moulds and yeasts produce the same types of enzymes?

The mechanism of biodegradation of both yeast and mould is the same; i.e., the use of enzymes to convert organic matter into energy. Both moulds and yeasts are heterotrophs, just like any other type of fungus. However, they work in different environmental conditions. Moulds 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.

2. What are the modes of reproduction in yeasts and moulds?

Both moulds and yeasts show both sexual and asexual types of reproduction; however, their courses are different. Moulds 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, the diploid cells undergo sporulation which lead to sexual reproduction by the method of meiosis.