Question

In the earlier class u had prepared the soln of dry yeast for observation of yeast

Answer 1

What is Yeast?

Yeast cells are members of the Fungus Kingdom. They are single celled microorganisms (eukaryotic) classified under phyla Ascomycota (sac fungi) and Basidiomyota (higher fungi) both of which fall under the subkingdom Dikarya.

Yeast Cells

Kingdom - Fungus

Subkingdom - Kikarya

Phyla - Ascomycota and Basidiomycota

Yeast are very diverse (over 1,500 species) with most forming the phylum Ascomycota while only a few are classified as Basidiomycota. Yeast reproduce through budding or binary fission which are both methods of asexual reproduction (Horst, 2010).

Budding - A new cell is formed through mitotic cell division and remains attached as a bud on the old cell until it splits and becomes independent. Here, the parent cell produces an outgrowth that finally splits to become an independent identical cell as the parent cell.

Binary fission - In binary fission, no outgrowth (bud) is formed. Rather, through mitosis, the genome replicates and divides followed by thehttp://commons.wikimedia.org/wiki/File:Binary_fission.png

Binary Fission

* Some of the fungi referred to as dimorphic tend to alternate between the yeast and hyphal phase which means that they can also grow as hyphae (thread like)

Habitat

Because they are very diverse, yeast can be found in a wide variety of habitats particularly in environments with sugar-rich materials. They are likely to be found on flowers, plant leaves, and fruits as well as on soil, deep-sea environments, skin surface and even intestinal tracts of animals (warm blooded).

While they can be found in many environments, yeast require moist environments with sufficient amounts of simple and soluble nutrients to support growth and multiplication (Horst, 2010).

While such yeast as the Candica can cause infections (Candidiasis) there are useful yeast such as:

Baker’s Yeast

Nutritional Yeast

Brewer’s Yeast

Distiller’s and Wine Yeast

Yeast Under the Microscope

Requirements

Water

Yeast cake

Dropper

Glass slides and cover slips

Stains (stated below)

Yeast cake contains Saccharomyces Cerevisiae (sugar-eating fungus) and can therefore be used to obtain the yeast to observe under the microscope. The following is a procedure that can be used to prepare the specimen for observation.

Obtain yeast cake (this can be bought from bakery specialty stores or a supermarket)

Cut a small piece of yeast cake and mix with water to form a pasty texture

Add a little more water to form a solution

Using a dropper, collect and place a drop of the solution on a microscope slide

Place a microscope cover slip and observe under high power objective

Observation

With Brightfield Microscopy

When viewing the specimen under high magnification (1000x and above) one will see oval (egg shaped) organism, which are the yeast. It is also possible to observe the buds, which can be seen on some of the cells.

If the solution had some sugar, one will also notice some bubbles in the specimen, which are as a result of the fermentation process by the microorganisms.

Answer 2

Role of Yeast Fermentation

Explanation:

• Saccharomyces cerevisiae is the budding yeast utilized for bread-production, where the carbon dioxide produced by development in the batter makes the bread rise
• Basically comparative yeasts, however now given different species names, are utilized for creation of beers, wines and other alcoholic drinks
• Single cell can develop into a scarcely obvious settlement in one day
• The development conduct of yeast cultures is like that of microorganisms