Microorganisms: Bacteria, Fungi, and Protozoa

• Microorganisms are living organisms that are too small to be seen without a microscope.
• Soil and water are full of microorganisms.
• Microorganisms have been used for the production of alcohol since ages.
• Bacteria is also used in the preparation of medicines.
• Microorganisms decompose organic waste into usable substances.
• Microorganisms can be unicellular or multicellular.
• Bacteria, fungi, protozoa, and some algae are the four major groups of microorganisms.
• Viruses are also microorganisms but different in that they reproduce inside a host cell.

Common Microorganism Examples

• Bacteria
• Fungi
• Protozoa
• Algae

Where Microorganisms Live:

• Microorganisms live in various types of environments, hot to cold.
• Some grow on other organisms (including humans), while others exist freely.

Uses of Microorganisms:

• Preparation of curd, bread, and cake.

Lactobacillus

• A bacterium that promotes the formation of curd by multiplying in milk and converting it into curd.

Yeast

• It is used in baking for making breads, pastries, and cakes
• It reproduces rapidly, producing carbon dioxide, which fills the dough and increases its volume.
• It is used for large-scale alcohol, wine, and acetic acid production.
• Conversion of sugar into alcohol by yeast is called fermentation.

Antibiotics:

• Medicines sourced from microorganisms that kill or stop the growth of disease-causing microorganisms.
• Antibiotics should only be taken when prescribed by a qualified doctor.
• Antibiotics are ineffective against cold and flu, which are caused by viruses.
• Taking antibiotics when not needed or in wrong doses can reduce their effectiveness in the future.
• Examples include Streptomycin, tetracycline, and erythromycin.

Alexander Fleming

• Discovered penicillin from a green mould that prevented bacteria growth.

Antibodies:

• Produced by the body to fight disease-carrying microbes.
• The body remembers how to fight the microbe if it enters again.
• Weakened microbes introduced into the body stimulate antibody production, providing protection.

Vaccine:

• Protects humans and animals from several diseases.
• Edward Jenner developed the vaccine for smallpox in 1798.

Biological Nitrogen Fixers:

• Bacteria that fix nitrogen from the atmosphere to enrich the soil.

Cleaning the Environment:

• Some microorganisms decompose dead organic waste of plants and animals into simple substances.
• These substances can be used by other plants and animals.
• Microorganisms degrade harmful and smelly substances, cleaning up the environment.

Pathogens:

• Disease-causing microorganisms.
• They can be transmitted through air, water, food, or direct contact with an infected person or animal.

Communicable Diseases:

• Microbial diseases that can spread from an infected person to a healthy person through air, water, food, or physical contact.
• Examples are cholera, common cold, chicken pox, and tuberculosis.

Carriers of Diseases:

• Insects and animals that carry disease-causing microbes.
• The female Anopheles mosquito carries the parasite of malaria.
• The Aedes mosquito acts as the carrier of dengue virus.

Disease-Causing Bacteria:

• Anthrax is a dangerous human and cattle disease, Foot and mouth disease of cattle.
• Robert Koch discovered bacillus anthracis which caused antrax disease in 1876.

Plant Diseases:

• Microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, and apple.

Food Poisoning:

• It is caused by consuming food spoilt by some microorganisms.
• Microorganisms that grow on our food sometimes produce toxic substances.

Food Preservation:

• Salts and edible oils are common chemicals used to check the growth of microorganisms.
• They are therefore called preservatives.
• Common salt has been used to preserve meat and fish for ages.

Sodium Benzoate and Sodium Metabisulphite:

• Common preservatives used in jams and squashes.

Preservation by Sugar:

• It reduces the moisture content which inhibits the growth of bacteria which spoil food.

Preservation by Oil and Vinegar:

• It prevents spoilage of pickles because bacteria cannot live in such an environment.

Pasteurization:

• A process discovered by Louis Pasteur, in which milk is heated to about 70°C for 15 to 30 seconds and then suddenly chilled and stored.

Rhizobium:

• A bacterium involved in the fixation of nitrogen in leguminous plants.

Nitrogen Cycle:

• Atmospheric nitrogen is converted into compounds in the soil by certain bacteria and blue-green algae.
• Plants utilize these compounds from the soil through their root system.
• Plants use the nitrogen for synthesis of plant proteins and other compounds. Animals feeding on plants obtain these proteins and other nitrogen compounds.
• When plants and animals die, bacteria and fungi convert nitrogenous wastes into nitrogenous compounds.
• Other bacteria convert some of them to nitrogen gas, which goes back into the atmosphere, keeping the percentage of nitrogen relatively constant.