Micro-Organisms Notes

Topics: Bacteria, Fungus, Food preservation Pages: 8 (2347 words) Published: May 3, 2013
Research how humans interact with micro-organisms and use this information to write a discussion for your report.

Basic structure and function

Explain the parts and how they work for fungi and bacteria

Most fungal species are multicellular. Most fungi do not have flagella in any phase of their life cycle. They move toward food by growing toward it. The main body of most fungi is made up of fine, branching, and usually colourless threads called hyphae. Each fungus will have vast numbers of these hyphae, all intertwining to make up a tangled web called the mycelium. Fungi decompose dead animals and plant matter. Fungi releases carbon dioxide to the air. Bacteria are prokaryotic. Bacterial cells usually come in one of 3 shapes: cocci, bacilli, spirilla. They can be by themselves, in pair, chains, or clusters. They can use either a flagella or pili to move the cell. Bacteria can reproduce by binary fission or by conjugation. Bacteria can get into your body a number of ways: by inhaling those, through cuts, eating contaminated food, or getting bit by an infected insect. Bacteria are either heterotrophic or autotrophic. Bacteria can be helpful in many ways such as making food, medicine, help clean our environment, or make several vitamins in the intestines. Bacteria can also be harmful by causing cavities and gum disease, ulcers, or disease by releasing toxins.

Explain the ideal conditions needed for life processes of feeding and reproduction for fungi and bacteria

Conditions for microbial growth (and also for enzyme action) 1) organic food (proteins, carbohydrates, fats) - same as humans! 2) suitable temperature
3) moisture (water)
4) [if aerobic] air
5) suitable pH 6 – 7.5
Bacteria and fungi thrive in warm, moist conditions, rich in nutrients

Food spoilage and food preservation

Discuss a named example of food spoilage by fungi

Aspergillus flavus

Aspergillus flavus is a fungus. It grows by producing thread like branching filaments known as hyphae. Filamentous fungi such as A. flavus are sometimes called molds. A network of hyphae known as the mycelium secretes enzymes that break down complex food sources. The resulting small molecules are absorbed by the myceilium to fuel additional fungal growth. The unaided eye cannot see individual hyphae, but dense mats of mycelium with conidia (asexual spores) often can be seen. The ear of maize below shows the growth of the fungus covering four maize kernels. When young, the conidia of A. flavus appear yellow green in color. As the fungus ages the spores turn a darker green. The fungus can infect seeds of corn, peanuts, cotton, and nut trees

Discuss how different methods of food preservation can affect the life process of fungi

Drying food preservation
One of the oldest methods of food preservation is by drying, which reduces water activity sufficiently to prevent or delay bacterial growth. Most types of meat can be dried; a good example is beef biltong. Many fruits can also be dried; for example, the process is often applied to apples, pears, bananas, mangoes, papaya, apricot, and coconut. Zante currants, sultanas and raisins are all forms of dried grapes. Drying is also the normal means of preservation for cereal grains such as wheat, maize, oats, barley, rice, millet and rye. Food preservation freezing

Freezing is also one of the most commonly used processes commercially and domestically for preserving a very wide range of food including prepared food stuffs which would not have required freezing in their unprepared state. For example, potato waffles are stored in the freezer, but potatoes themselves require only a cool dark place to ensure many months' storage. Cold stores provide large volume, long-term storage for strategic food stocks held in case of national emergency in many countries. Vacuum packing Food preservation

Vacuum-packing stores food in a vacuum environment, usually in an air-tight bag or bottle. The vacuum...
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