Explanation on Penicillium

Penicillium is a genus of fungi that are saprophytic (that is, they feed on dead and rotting matter). They are also referred to as green or blue mould. They are essential for the production of cheese, organic acids, and antibiotics, all of which are valuable commodities. They are a major decomposer in the environment and contribute significantly to its health. Penicillium can be found in a wide variety of environments such as dirt, air, decomposing food, and so forth. Penicillin is one of the most significant antibiotics, and it is derived from the bacterium Penicillium sp.

Classification and examples

Penicillium is a genus that belongs to the phylum Ascomycota, also known as Ascomycetes. During sexual reproduction, they produce ascospores, which distinguishes them from other species.Penicillium is a Latin word that means “painter’s brush.” They were given this name because of the existence of conidia chains (which are formed asexually) that look as a brush at the end of the mycelium.

Structure  with diagram

• Penicillium’s vegetative structure is a multicellular mycelium, which means it has many cells.

• The mycelium is composed of hyphae, which are long thread-like filamentous structures that are highly branching, multinucleated, and septate in nature.

• The glucose polysaccharides and chitin that make up the cell wall are responsible for the structure of the cell wall.

• Central pores, which are found in the septa, are responsible for maintaining intracytoplasmic continuity.

• Conidiophores, which are asexual spores produced exogenously, are found at the branch termination, together with spherical conidiospores, which are asexual spores generated exogenously.

• Conidia are generated in a basipetal succession, which means that the youngest conidium is found towards the base of the plant.

• Conidia are formed by specialised cells known as phialide, which are present in the group and give the fungus a brush-like look when viewed from above.

• Ascospores are located in asci that are arranged in ascocarps, and they are sexual spores that are produced by the body.

• Some mycelia go deeper into the substratum in order to obtain nutrients.

• The food is kept in the form of oil globules to prevent spoilage.

Reproduction and life cycle

In addition to vegetative reproduction, Penicillium reproduces through asexual and sexual reproduction.

Vegetative reproduction occurs through fragmentation, and each of the fragments develops independently, resulting in the formation of a whole mycelium.

Asexual reproduction takes place in conidiophores, which are unique structures that are used for this purpose.

• Conidiophores can be either unbranched or branching, and they can differentiate into metulae at any point in their life cycle.

• Conidia occur at the end of each metulae when a number of flask-shaped phialide cells grow.

• Mitotic cell division results in the formation of a conidium in the presence of phialide cells. When the phialide cells divide again, they push the first conidium outward and create the second conidium. When the process is repeated, a chain of conidia is produced, which can be observed in a basipetal succession.

• The conidia can be blue, green, or yellow in colour, and can be oval or elliptical in shape, depending on the species.

• Once the conidia have reached maturity, they are separated from the parent and distributed by the wind.

• They attach themselves to a suitable substratum and begin to germinate.

• Germination occurs as a result of the creation of the germ tube. The nucleus undergoes numerous mitotic divisions in a single cell. All of the nuclei enter the germ tube, which is followed by elongation and the creation of septa, ultimately resulting in the production of a mature and branched mycelium.

The creation of ascospores is responsible for sexual reproduction.

• There are homothallic and heterothallic Penicillium species, as well as hybrids (male and female sex organs present on different thallus)

• It is called antheridium and ascogonium, respectively, for the male and female genital organs.

• One of the cells of the vegetative mycelium grows into an ascogonium, which is a single-celled organism with a single nucleus that is similar to a mushroom. Ascogonium’s nucleus divides repeatedly, resulting in a total of 32 to 64 nuclei in each division.

• During development, the growing antheridium branch coils all around ascogonium, and the apical part of it is split by septa, resulting in a unicellular antheridium with a single nucleus at the tip.

• At some point during maturation, the antheridium bends and comes into contact with the ascogonium wall. At this point, cell wall disintegrates and the cytoplasm of the two cells is mixed together. The procedure is referred to as plasmogamy.

• In the cell, there is an intermediate dikaryon stage, which is defined as a dikaryotic stage in which two nuclei (n+n) are present.

• The ascogonium divides frequently by partitioning the wall, resulting in a large number of binucleate cells placed one above another.

• The terminal dikaryotic cell expands up, resulting in the formation of the ascus mother cell.

• Adiploid cells are formed when there is a karyogamy (fusion of the two nuclei) in the cell (2n)

• The diploid zygote proceeds through two rounds of meiosis and subsequently two rounds of mitosis, resulting in the formation of 8 nuclei. Each ascospore acquires a small amount of cytoplasm, resulting in the creation of 8 ascospores.

• Ascospores are discharged as a result of the disintegration of the ascus wall and attach themselves to a suitable substratum.

• The ascospores develop by producing a germ tube, which then matures into the branched mycelium that is seen in the soil.

Conclusion

Penicillium species are extremely significant in the agricultural industry. They manufacture a wide range of food goods as well as organic acids, antibiotics, and mycotoxins. Cheese production – P. camemberti (which produces Camembert and Brie cheeses) and P. roqueforti (which produces Roquefort cheese) are among the many Penicillium species that are employed in the creation of various types of cheese.Enzymes and organic acid production- There are numerous Penicillium species that are employed in the synthesis of organic acids such as citric acid, gluconic acid, tartaric acid, and enzymes such as amylases, proteases, cellulase, lipase, and pectinase, among other things.Penicillin works by blocking the enzymes that are responsible for the creation of bacteria’s cell walls and activating the enzymes that are responsible for the breakdown of the bacteria’s protective outer layer.As a result of their ability to digest xenobiotic chemicals, Penicillium species are also utilised in mycoremediation, which is a bioremediation procedure that employs fungi to clean up the environment.