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Renin Angiotensin Mechanism.

Importance and Cultivation of Fungi

Introduction:

  • Fungi is a group of non motile eukaryotes which exist as Saprophytes, parasites and symbiotics.

  • Fungi plays a very important role in the ecosystem, their importance is further elaborated.

Importance of Fungi:

  1. First antibiotic “penicillin” was isolated from “Penicillium notatum” and till date Fungi represent an important class which produces antibiotics.

  2. Fungi are a rich source of enzymes, e.g. Amylase is produced from Aspergillus species.

  3. Some fungi are used to modify the taste, texture and palatability of some food products, e.g. Penicillium species is used to ripen some cheese.

  4. Mushrooms are an important source of nutrients.

  5. Yeasts are used in brewing and bakery industries..

  6. In industrial alcohol production e.g. Fusarium species.

  7. Many fungi are saprophytic in nature and also has capacity to break down complex carbon organic molecules.

Culture Media for Fungi:

  • A wide range of media are used for growing fungi. 

  • Most mycologists develop preferences for certain types of media based on experience and peculiarities of the type of fungi that are routinely grown. 

  • Media will affect colony morphology and color, whether particular structures are formed or not, and may affect whether the fungus will even grow in culture. For example, some fungi lack the necessary enzymes to utilize different carbon sources. 

  • All fungi require several specific elements for growth and reproduction.

  • The requirements for growth are generally less stringent than for sporulation, so it is often necessary to try several types of media when attempting to identify a fungus in culture.

  • Most fungi thrive on Potato Dextrose Agar (PDA), but this can be too rich for many fungi, so that excessive mycelial growth is obtained at the expense of sporulation. 

  • The introduction of pieces of tissue, such as filter paper, wheat straw, rice, grains, leaves or dung, often produces good sporulation dependent on the organism grown.

  • Constituents of Media:

    • Media generally contain a source of carbon, nitrogen and vitamins. Glucose (dextrose) is the most widely utilizable carbon source, and hence is the most commonly used in growth media.

    • Nitrogen sources include peptone, yeast extract, malt extract, amino acids, ammonium and nitrate compounds. Casamino Acids, acid-hydrolyzed casein, a mixture of amino acids. It is a good general source of nitrogen but is vitamin free. 

    • Salts, including Fe, Zn and Mn, are often added to ‘defined’ media, but are usually not added to the common media used for routine culture. 

    • Fungi have natural deficiencies for vitamins that are satisfied at µM to nM concentrations. 

    • The most common naturally occurring vitamin deficiencies are thiamin and biotin. 

    • Deficiency of both is quite common among the Ascomycota. 

  • Isolation media e.g. Water Agar, Antibiotic Agar and Acidified Cornmeal Agar.

  • Growth media e.g. Cornmeal Agar, Malt Extract Agar ,  Potato Carrot Agar and Potato Dextrose Agar.

Commonly Used Media and their uses:

  1. Water Agar (WA)--use for isolating fungi from surface-sterilized substrates.

  2. Antibiotic Agar (AA)--use for isolating fungi from substrates not readily surface sterilized, or to clean up a culture contaminated with bacteria.

  3. Acidified Cornmeal Agar (ACMA)--use for isolating fungi from substrates that are likely to be contaminated with bacteria. Not a substitute for AA, but the acidity inhibits bacteria and the medium supports the growth of a wide range of fungi.

  4. Cornmeal Agar (CMA)--use for growing a wide range of fungi, particularly members of the Fungi imperfecti; provides a good balance of mycelial growth and sporulation.

  5. Potato Carrot Agar (PCA)--considered a relatively weak medium somewhat comparable to CMA, good for some Fungi imperfecti.

  6. Malt Agar (MA)--lacks peptone, and is useful for culturing many Ascomycota; sporulation in some species is inhibited by peptone.

  7. Malt Extract Agar (MEA)--a good growth medium for soil fungi, fungi isolated from wood, basidiomycetes, etc. An all-purpose type of medium.

  8. Potato Dextrose Agar (PDA)--a relatively rich medium for growing a wide range of fungi.

  9. Potato Dextrose-Yeast Extract Agar (PDYA)---good for growing cultures derived from mushrooms. 
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