YEAST

Yeast

Classification:

Domain        -  Eukaryota
Kingdom      - Fungi
Phylum         - Ascomycota
Subphylum  - Saccharomycotina
Class            - Saccharomycetes
Order            - Saccharomycetales
Family          - Saccharomycetaceae
Genus           - Saccharomyces
Species        - S. cerevisiae (Brewer's/Baker's yeast)

Definition of yeast:

• A yeast is a unicellular fungus which consists of a single nucleus.
• There are about 1500 species most of which are in the phylum Ascomycota and a few being in phylum Basidiomycota
• It can reproduce sexually through spore formation or asexually by budding and transverse division.
• The shape of the yeast is spherical to egg-shaped.
• Yeast cells are larger than bacteria.
• Flagella and cilia are non-existent in yeast.
• Yeast grow as smooth colonies on agar plates much like bacteria.

Saccharomyces cerevisiae:

• S. cerevisiae is a commonly used yeast.
• It is ovum cell shaped.
• It's diameter varies between 5-10 micrometers.
• This yeast can be cultivated easily and quickly.
• It can multiply within 1.5 -2 hours at 30°C.
• The maintenance is cheap and efficient.
• It is used in beer, bread and fermented wine industries. 

Reproduction of Saccharomyces cerevisiae:

S. cerevisiae reproduces at haploid and diploid states.

      As long as nutrients remain plentiful, haploid and diploid cells undergo mitosis to produce haploid and diploid daughter cells, respectively. Each daughter cell leaves a scar on the mother cell as it separates and the daughter cells bud only from unscarred regions of the cell wall. When a mother cell has no more unscarred cell wall remaining, it will no longer be able to reproduce and will die (senesce).

     When nutrients are limited, diploid S. cerevisiae cells undergo meiosis to produce four haploid that remain bound within a common cell wall called the ascus. Upon, the addition of nutrients, two haploid cells of opposite mating types come into contact and fuse to create a diploid. Generally, only cells of opposite mating types can fuse and this process is tightly regulated by the action of pheromones.

Advantages:

1. Yeast grows rapidly, is a common host species and can be easily handled in the laboratory.
2. Its a healthy mix of bacteria in your gut.
3. It can fight pathogens and help to absorb the vitamins and minerals.
4. It supports the nervous system and enhances immunity.
5. It promotes hair, skin and nail health.
6. It keeps your digestive system healthy and working.
7. Yeast extract is an aqueous extract of brewer's yeast
8. Yeast extract is a good source of B vitamins, nitrogen and carbon. 

Diseases :

Candidiasis

According to the CDC, Candidiasis is a yeast infection caused by Candida (a type of yeast). Some species of Candida like Candida albicans can cause infection in people. Candida normally lives inside the body (in places such as the mouth, throat, gut, and vagina) and on skin without causing any problems. 

Sometimes Candida can multiply and cause an infection if the environment inside the vagina changes in a way that encourages its growth. Candidiasis in the vagina is commonly called a “vaginal yeast infection.” Other names for this infection are “vaginal candidiasis,” “vulvovaginal candidiasis,” or “candidal vaginitis.” 

Sometimes, Candida can multiply and cause an infection if the environment inside the mouth, throat, or esophagus changes in a way that encourages fungal growth.

Candidiasis in the mouth and throat is also called thrush or oropharyngeal candidiasis. Candidiasis in the esophagus (the tube that connects the throat to the stomach) is called esophageal candidiasis or Candida esophagitis. Esophageal candidiasis is one of the most common infections in people living with HIV/AIDS.

Antifungal medicines get rid of yeast infections in most people. If you have a weak immune system, treatment might be more difficult.