DATE : 2016/08/12

GROWTH AND NUTRITION OF

FUNGIBinod PokhrelB.V.Sc & A.HAFU,Rampur

Growth

Growth is defined as the irreversible increase in the dry mass of an organism. It is brought about by an increase in cell size or number.

How growth takes place in Fungi?

Mycelial fungi - extension growth of hyphae(tip).

Unicellular fungi (e.g. yeasts) - increase in individual cell volume.

Yeast like fungi grow partly as yeast and partly as chain of elongated budding cells joined end to end .

Moulds or filamentous fungi with multiple cells forming typically a thread-like mass with many branches grows by branching and tip elongation

Optimal condition for growth

Presence of water: 80–90% of the fungi is composed of water by mass, and requires excess water for absorption due to the evaporation of internally retent water.

Presence of oxygen Neutral-acidic pH : Optimum pH

5.0

Contd…

Low-medium temperature: ranges between 1 °C and 35 °C, with optimum growth at 25 °C.

The majority of nutrients must be able to provide carbon, proteins, vitamins and cases, ions. Due to the carbon composition of the majority of organisms, dead and organic matter provide rich sources of disaccharides and polysaccharides such as maltose and starch and of the monosaccharide glucose.

In terms of nitrogen-rich sources, saprotrophs require combined protein for the creation of proteins, which is facilitated by the absorption of amino acids, and usually taken from rich soil. Although both ions and vitamins are rare, thiamine or ions such as potassium, phosphorus, and magnesium aid the growth of the mycelium.

How Fungi is grown on lab?

1. Liquid bath culture2. Liquid continuous culture3. Culture on solid media

Liquid bath culture

If we wanted to estimate the growth of a mycelial fungus growing in a LIQUID medium, we might first have to filter off the liquid medium and then determine the dry mass of the mycelium.

Liquid continuous culture

An alternative to the liquid batch culture system is CONTINUOUS CULTURE in a liquid medium:

This involves the CONTINUOUS ADDITION OF FRESH CULTURE MEDIUM to the vessel and the WITHDRAWAL (by means of an overflow devise) of a corresponding volume of OLD, SPENT MEDIUM, which will contain some of the microbial cells.

The apparatus used is called a chemostat

Solid Media

While it's relatively easy to determine the biomass of a fungus growing in a liquid medium, it's more difficult to estimate biomass when a fungus is growing in all three dimensions over and through a solid medium.

For this reason we usually express the growth of a colony in terms of the RADIAL EXTENSION OF THE COLONY (i.e. we measure colony radius).

NUTRITION In FUNGI

ALL fungi are CHEMOHETEROTROPHIC (chemo-organotrophic) - synthesising the organic compounds they need for growth and energy from pre-existing organic sources in their environment, using the energy from chemical reactions.

They lack chlorophyll pigments and are incapable of photosynthesis.

Fungi absorb their food, rather than ingesting it as their protoplasm is surrounded by rigid wall.

SMALL MOLECULES (e.g. simple sugars, amino acids) in solution can be absorbed directly across the fungal wall and plasma membrane..

Contd..

LARGER, MORE COMPLEX MOLECULES (e.g. polymers such as polysaccharides and proteins) must be first broken down into smaller molecules, which can then be absorbed. This degradation takes place outside the fungal cell or hypha and is achieved by enzymes which are either released through or are bound to the fungal wall. Because these enzymes act outside the cell they are called extracellular enzymes.

Since water is essential for the diffusion of extracellular enzymes and nutrients across the fungal wall and plasma membrane, actively growing fungi are usually restricted to relatively moist (or humid) environments.

Fungi are more resistant to high osmotic pressure than bacteria.

Fungi require less nitrogen than bacteria to grow and can grow at PH of 5.

Process of Nutrition intake As matter decomposes within a medium in which a

saprotroph is residing, the saprotroph breaks such matter down into its composites.

Proteins are broken down into their amino acid composites through the breaking of peptide bonds by proteases.

Lipids are broken down into fatty acids and glycerol by lipases.

Starch is broken down into pieces of simple disaccharides by amylases.

These products are re-absorbed into the hypha through the cell wall via endocytosis and passed on throughout the mycelium complex. This facilitates the passage of such materials throughout the organism and allows for growth and, if necessary, repair.

Thanks for your

concentration