Notes on Fungi - Basics - Dr. J. Merrylin

Food Microbiology | Food Microbiology | Food Microbiology

Molds

• Molds  are  multicellular,  filamentous  fungi  whose  growth  on  food,  with  its  fuzzy  or  cottony  appearance,  sometimes  colored,  and  usually  moldy food is considered unfit to eat.

• Although molds are involved in the spoilage of many kinds of food, special molds are useful in the manufacture of certain foods or ingredients of foods.
• Thus some kids of cheese are mold-ripened. Eg., blue, Roquefort, camembert cheese,  etc.  and  molds  are  used  in  making  Oriental  foods.  Eg.,  soy  sauce, miso, sonti.

• Molds  have  been  grown  as  food  or  feed  and  are  employed  to  produce products used in foods, such as amylase for bread making or citric acid used in soft drinks.

 The body or vegetative structure of a fungus is called thallus. It varies in complexity  and  size,  ranging  from  the  single-cell  microscopic  yeasts  to multicellular molds, macroscopic puffballs, and mushrooms.

                

• The thallus is made of hyphae which are cyclindrical, tube like structure that elongates by growth at tip.
• A mass of hyphae known as mycelium (a tangled mass or tissue like aggregation) is responsible for filamentous nature of mold.
• The thallus of mold is made up of two part; mycelium and spore
• Molds have typical eukaryotic structures and have a cell wall usually composed of chitin, sometimes cellulose, and occasionally both. Furthermore, molds are obligate aerobes and grow by elongation at apical tips of their hyphae and thus are able to penetrate the surfaces on which they begin growing.

Types of hyphae

• The  hyphae  may  be  submerged,  or  growing  within  the  food,  or  aerial,  or growing into the air above the food
• Hyphae may be classified as vegetative and hence involved in the nutrition of the mold, or fertile, involved in the production of reproductive parts.
• In most molds the fertile hyphae are aerial, but in some molds they may be submerged.
• The hyphae of some molds are full and smooth, but the hyphae of others ar characteristically thin and ragged
• In some fungi hyphae is divided into cell or compartment by incomplete septum. Septum has a central pore which allows the movement of cytoplasm from one cell or compartment to another.
• There are three types of hyphae among fungi.

1. Coenocytic or non-septated hyphae
2. Septate hyphae with uninucleated cell
3. Septate hyphae with multinucleated cell

 

• Hyphae can be vegetative or reproductive
• Vegetative hyphae: It penetrates the soil or medium to absorb nutrition and moisture
• Reproductive hyphae: These are aerial hyphae and form spores for reproduction.
• Examples of some mold:
• Rhizopus
• Mucor

Reproduction of Molds

•       Molds reproduce primarily by means of asexual reproductive spores. Some molds also form  sexual spores
•        Asexual spore of molds are produced in large numbers and are small, light and resistant to drying. They are readily spread through the air.

           These include the following.

• A hypha can fragment (by the separation of hyphae through splitting of the cell wall or septum) to  form cells that behave as spores. These cells are called arthroconidia or arthrospores.

• If the cells  are  surrounded  by  a  thick  wall  before  separation,  they  are called chlamydospores.

 

• If the spores develop within a sac (sporangium) at a hyphal tip, they are called sporangiospores. 

• If the spores are not enclosed in a sac but produced at the tips or sides of the hypha, they are termed conidiospores.

• Spores produced from a vegetative mother cell by budding are called blastospores. 

Types of Mold

• Aspergillus: Common indoors, often found on food and dust.
• Penicillium: Found on decaying food and materials; some species are used to make antibiotics.
• Cladosporium: Grows on wood, carpets, and fabrics.
• Stachybotrys (Black Mold): Toxic mold that grows on wet materials like drywall.

Harmful Effects of Mold

• Causes allergies, skin rashes, and respiratory issues.
• Produces mycotoxins, which can be harmful if ingested or inhaled.

Uses of Mold

• Food Industry: Molds are used to make cheese (e.g., blue cheese) and ferment soy products.
• Medicine: Used to produce antibiotics like penicillin.

Learn About Molds in Microbiology

References

1. Martein Probisker,2018, Fundamentals of Microbiology, Jones & Bartlett Learning publication,11^th Ed
2. Frazier W.C. 1988, Food Microbiology - Tata Mc Graw Hill Book Company, 5^th Ed, Bombay.
3. Adams M.R. and Moss M.O.2000, Food microbiology - Royal society of Chemistry publication, 2^nd Ed.
4. Banwart G.T.2004, Basic Food Microbiology - CSS Publishers, 2^nd Ed 

Web Resources

1.  https://byjus.com/biology/kingdom-fungi/
2.  https://www.uou.ac.in/lecturenotes/science/MSCBOT-17/Unit%20%E2%80%9310%E2%80%93%20General%20Characters%20and%20Classification%20of%20Fungi%20by%20Dr.%20Kirtika%20Padalia-converted.pdf
3. https://www.bellarmine.edu/faculty/dobbins/Secret%20Readings/Lecture%20Notes%20113/FungusWO.pdf
   
4. https://www.rlsycollegebettiah.ac.in/wp-content/uploads/2023/02/file_63e39a790ec90.pdf
   
5. https://www.bdu.ac.in/cde/SLM/B.Sc.%20Botany/I%20Year/B.Sc.Botany_Alagi%2CFungi%20%26%20Plant%20Protection%20%28Practical%29_I-Year_SPS.pdf

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