Fungi and Yeast
The diagram above shows a typical structure of a fungus. A fungus is made of hyphae, which are long tubes, collectively they are called mycellium and form branches that can cover many acres.
On the right we have zoomed in on a hypha, and you can see its structure. It has all the typical features of a cell, but there are some unique aspects. The hypha is a long tube and effectively one cell. However, it could be divided into comparments by septa; the hypha is has many nuclei. The tip is tapered, this is where it is growing outwards and is known as the extension zone.
Fungi grow specialised areas for reproduction called fruiting bodies these can grow very large and be visible to the naked eye where they are known as mushrooms. It is from these that spores are produced.
Yeast are a type of fungi, but unlike most they are made up of only individual cells (unicellular). They reproduce by budding where little bits of new yeast grow and break off.
As a living thing, yeast respire. Unlike human anaerobic respiration where lactic acid is produced, they produce ethanol. Alcoholic drinks such are beer are made by fermenting with yeast, this produces alcohol.
Glucose Ethanol + Carbon Dioxide
C6H12O6 2C2H5OH + 2CO2
As microorganisms, fungi can be pathogenic, fungi like warm and damp environments which they can find in places like between the toes and in the vagina. Have a look at the table below to see some examples of pathogenic fungi.
|Athletes Foot||Trichophyton rubrum||Athletes Foot refers to a fungal infection of the foot and can be caused by many different fungi. The mould or yeast grows on the surface and into the skin and causes itching.|
|Thrush||Candida albicans||Thrush refers to this fungus infecting the vagina and causes itching. However, the same fungus can also infect the penis and mouth, and its infection is generally known as candidiasis. It exists naturally in many people with no symptoms, but irritation of the skin, diabetes and hormone therapy can cause an outbreak.|
|Pneumonia is a general term for infection and inflammation of the lungs. It is important to note that it can be caused by bacteria or virus and that fungal pneumonia is quite rare and only normally occurs in people with AIDS because of their weakened immunity.|
Fungi in Industry
Fungi have many uses in industry that are covered in various areas of this site. They are especially useful in food.
Yeast (see above) is used in fermenting beer and wine to produce alcohol, it is also added to bread to make it rise and alter it's texture. Mushrooms are another culinary use of fungi; truffles are a fungus that is highly prized and expensive that is used in cooking.
Fungi can be useful for producing products in fermenters, the best example of this would be penicillin production.
Returning to food: Quorn is a meat alternative, it is derived from the mould Fusarium venenatum. F. venenatum is grown in oxygenated water and fed glucose and various vitamins. The resulting material is removed and heat treated, bound together with egg albumen and pressed into a mince to give it a texture like meat.
This means where digestion is done outside of the organism. This is seen in saprophytic fungus (saprophytic meaning decomposer). The fungi secretes the enzymes into their surrounding material and then absorb the products.
A way of measuring the activity of amylase is to have an agar plate with starch; make a small well and put in the amylase enzyme. Incubate for a time and then flood the area with iodine. It will show a clear zone where the starch has been digested and hence you can see which is the more effective (diagram below).