Microorganisms: Friend and Foe - Summary Notes
Microorganisms: Friends and Foes
Introduction
Microorganisms (or microbes) are tiny living organisms around us that we normally cannot see.
They can be observed through a magnifying glass or microscope.
Classification of Microorganisms
Microorganisms are classified into four major groups:
Bacteria
Fungi
Protozoa
Algae
Viruses are also microscopic but reproduce only inside the cells of a host organism (bacterium, plant, or animal).
Common Ailments and Diseases
Viruses cause common ailments like cold, influenza (flu), and most coughs.
Serious diseases like polio and chickenpox are also caused by viruses.
Protozoa cause diseases like dysentery and malaria.
Bacteria cause diseases like typhoid and tuberculosis (TB).
Where Microorganisms Live
Microorganisms can be single-celled (bacteria, some algae, and protozoa) or multicellular (many algae and fungi).
They live in all types of environments: ice-cold climates, hot springs, deserts, and marshy lands.
They are also found inside the bodies of animals, including humans.
Some grow on other organisms, while others exist freely.
Friendly Microorganisms
Used for various purposes, including the preparation of curd, bread, and cake.
Lactobacillus bacterium promotes the formation of curd by multiplying in milk and converting it.
Used in making cheese, pickles, and other food items.
Helpful in the fermentation of rice idlis and dosa batter.
Used in cleaning up the environment by breaking down organic wastes into harmless substances.
Used in the preparation of medicines and in agriculture to increase soil fertility by fixing nitrogen.
Making of Curd and Bread
Milk is turned into curd by bacteria.
Yeast reproduces rapidly and produces carbon dioxide during respiration.
Bubbles of the gas fill the dough and increase its volume.
This is the basis of the use of yeast in the baking industry for making breads, pastries, and cakes.
Commercial Use of Microorganisms
Used for the large-scale production of alcohol, wine, and acetic acid (vinegar).
Yeast is grown on natural sugars present in grains like barley, wheat, rice, and crushed fruit juices for the commercial production of alcohol and wine.
Fermentation: The process of conversion of sugar into alcohol.
Medicinal Use of Microorganisms
Antibiotics are medicines produced from microorganisms that kill or stop the growth of disease-causing microorganisms.
Examples: Streptomycin, tetracycline, and erythromycin.
Antibiotics are manufactured by growing specific microorganisms and are used to cure a variety of diseases.
Antibiotics are not effective against cold and flu as these are caused by viruses.
Vaccines introduce dead or weakened microbes into a healthy body, which then produces antibodies to fight the invader.
This is how a vaccine works, protecting the body from the disease-causing microbes forever.
Several diseases, including cholera, tuberculosis, smallpox, and hepatitis, can be prevented by vaccination.
Increasing Soil Fertility
Some bacteria can fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility.
These microbes are commonly called biological nitrogen fixers.
Cleaning the Environment
Microorganisms decompose dead organic waste of plants and animals, converting them into simple substances.
These substances are again used by other plants and animals.
Microorganisms can be used to degrade harmful and smelly substances, thereby cleaning up the environment.
Harmful Microorganisms
Some microorganisms cause diseases in humans, plants, and animals and are called pathogens.
Some microorganisms spoil food, clothing, and leather.
Disease-Causing Microorganisms in Humans
Pathogens enter our body through the air we breathe, the water we drink, or the food we eat.
They can also get transmitted by direct contact with an infected person or carried by an animal.
Microbial diseases that can spread from an infected person to a healthy person through air, water, food, or physical contact are called communicable diseases.
Examples: cholera, common cold, chickenpox, and tuberculosis.
Insects and animals can act as carriers of disease-causing microbes (e.g., housefly, female Anopheles mosquito).
Disease-Causing Microorganisms in Animals
Several microorganisms cause diseases in animals.
Anthrax is a dangerous human and cattle disease caused by a bacterium.
Foot and mouth disease of cattle is caused by a virus.
Disease-Causing Microorganisms in Plants
Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple, and others.
These diseases reduce the yield of crops.
Food Poisoning
Food poisoning could be due to the consumption of food spoilt by some microorganisms.
Microorganisms that grow on our food sometimes produce toxic substances, making the food poisonous.
Food Preservation
Chemical Method: Salts and edible oils are used to check the growth of microorganisms.
Common preservatives: Sodium benzoate and sodium metabisulphite.
Preservation by Common Salt: Used to preserve meat, fish, amla, raw mangoes, and tamarind.
Preservation by Sugar: Used to preserve jams, jellies, and squashes.
Preservation by Oil and Vinegar: Used to prevent spoilage of pickles, vegetables, fruits, fish, and meat.
Heat and Cold Treatments: Boiling milk kills microorganisms; low temperature inhibits the growth of microbes.
Pasteurisation: The milk is heated to about for 15 to 30 seconds and then suddenly chilled and stored to prevent the growth of microbes.
Storage and Packing: Dry fruits and vegetables are sold in sealed airtight packets to prevent the attack of microbes.
Nitrogen Fixation
Rhizobium is involved in the fixation of nitrogen in leguminous plants (pulses).
Rhizobium lives in the root nodules of leguminous plants, such as beans and peas, with which it has a symbiotic relationship.
Nitrogen Cycle
Our atmosphere has 78% nitrogen gas.
Certain bacteria and blue-green algae present in the soil fix nitrogen from the atmosphere and convert it into compounds of nitrogen.
Plants utilise these compounds from the soil through their root system.
When plants and animals die, bacteria and fungi present in the soil convert the nitrogenous wastes into nitrogenous compounds to be used by plants again.
Certain other bacteria convert some part of them to nitrogen gas, which goes back into the atmosphere, keeping the percentage of nitrogen in the atmosphere more or less constant.
Microorganisms: Friends and Foes
Introduction
Microorganisms (microbes) are tiny organisms we can't see without magnification.
Classification
Microbes are grouped into: Bacteria, Fungi, Protozoa, Algae.
Viruses need a host to reproduce.
Common Ailments and Diseases
Viruses cause colds, flu, and chickenpox.
Protozoa cause dysentery and malaria.
Bacteria cause typhoid and tuberculosis.
Where Microorganisms Live
Microbes can be single-celled or multicellular.
They live everywhere: hot, cold, and inside bodies.
Friendly Microorganisms
Used to make curd, bread, cheese, and clean the environment.
Help in medicine and agriculture by fixing nitrogen.
Making of Curd and Bread
Bacteria turns milk into curd.
Yeast makes bread rise by producing carbon dioxide.
Commercial Use
Used to make alcohol, wine, and vinegar.
Fermentation: Sugar converted to alcohol.
Medicinal Use
Antibiotics from microbes kill harmful microorganisms.
Vaccines use dead/weak microbes to create antibodies and protect from diseases like cholera and smallpox.
Increasing Soil Fertility
Bacteria fix nitrogen in the soil.
Cleaning the Environment
Microbes decompose waste into simple substances.
Harmful Microorganisms
Pathogens cause diseases and spoil food.
Disease-Causing Microorganisms in Humans
Pathogens enter through air, water, food, or contact.
Communicable diseases spread through contact (e.g., cold, chickenpox).
Insects/animals carry microbes (e.g., mosquitoes).
Disease-Causing Microorganisms in Animals
Microbes cause diseases like anthrax and foot/mouth disease.
Disease-Causing Microorganisms in Plants
Microbes harm crops like wheat and rice.
Food Poisoning
Spoiled food contains toxic substances from microbes.
Food Preservation
Use salt, oil, sugar, heat/cold, and packing to prevent microbe growth.
Pasteurization: Heating milk to kill microbes.
Nitrogen Fixation
Rhizobium fixes nitrogen in plants like beans.
Nitrogen Cycle
Bacteria and algae fix atmospheric nitrogen into soil compounds.
Plants use these, and when they die, microbes return nitrogen to the soil and atmosphere.