Quick Revision:What are Microbes? |
|
Causes | Diseases |
Viruses |
Common Ailments: Cold, Cough, and Influenza (or Flu) |
Bacteria |
Typhoid and Tuberculosis (TB) etc |
Protozoans |
Dysentery and Malaria etc |
Table 1: Microbial Diseases |
There are four major types of microorganisms:
Fig 1: Types of Microorganisms
Bacteria: These are single-celled organisms with a rigid cell wall. They can only be seen under a microscope which enlarges images from 100 to 1000 times.
Fig 2: Ultrastructure of a Bacterial Cell
Shape of Bacteria | Example | Image |
Comma-shaped Bacteria |
Fig 3: Vibrio Cholera |
Vibrio Cholerae |
Spherical-shaped Bacteria (Cocci) |
Fig 3: Streptococcus |
Staphylococcus and Streptococcus |
Rod-shaped Bacteria (Bacilli) |
Fig 4: Salmonella |
E.coli and Salmonella |
Spiral-shaped Bacteria (Spirilla) |
Fig 5: Borrelia |
Treponema and Borrelia |
Table 2: Shapes of Bacteria (with Examples)
Fig 7: Puccinia triticina
Fig 8: Bread Mould
Fungi, like mushrooms, moulds, mildews, and years, are eukaryotic. It means that they have a true nucleus.
The main components of fungi are:
i. Hyphae: They are thread-like filaments which penetrate into substrates, secrete enzymes to break down nutrients into smaller molecules, and absorb them.
ii. Spores are a unit of sexual or asexual reproduction. They can adapt for dispersal and survival for extended periods of time in unfavourable conditions.
Algae : These are simple plant- like organisms which are usually aquatic in nature. They contain a cell wall and chlorophyll and can make their own food by photosynthesis.Algae can be unicellular or multicellular. Some of the common examples are diatoms, Chlamydomonas, and seaweed.
Protozoa: Protozoa are unicellular are organisms. Some of them live independently while others live as parasites. Many of the parasitic protozoans cause diseases in plants, domestic animals, and human beings. Example of some protozoans are Amoeba, Plasmodium and Paramecium
Fig 9: Paramecium
How are Viruses different from other microbes?
Viruses are microscopic organisms but they are different from other microbes because they reproduce only inside the cells of the host organism (which can be a plant, animal, or a bacterium).
Fig 10: Types of Viruses
Viruses are much smaller than bacteria and come in a wide variety of shapes and sizes. A complete virus particle is known as Virion.
Virion consists of a nucleic acid surrounded by 'capsid'. Capsid is a protective coat made of protein. The subunits of this protein called 'Capsomeres'. Viruses can be seen only by an electron microscope as they are ultramicroscopic in size.
Outside the body of a living organism, they do not show any reaction and hence, can be crystallized and stored like non-living things.
Microbes can survive in all kinds of environments – from icy cold climates to hot springs (any kind of temperature); and deserts to marshy lands (any humidity level). Some live independently while others live as parasites – inside the bodies of other organisms (including animals and human beings).
Some microorganisms are beneficial to us while others are harmful and cause diseases.
How are bacteria useful to us?
Bacteria are helpful because:
It decomposes organic wastes (such as vegetable peels, animal remains, and faeces etc.).
It is used in the preparation of medicines.
It increases soil fertility by fixing nitrogen.
It is used in the setting of curd and making cheese, pickles, and other food items.
How is yeast useful to us?
Yeast is used in the baking industry (to make bread, pastries, and cakes) because it helps in fermentation. It reproduces rapidly and produces carbon dioxide during respiration. Bubbles of the carbon-dioxide gas it produces fill the spaces in the dough and increases its volume.
It is also used in the commercial production of alcohol and wine which is done by growing yeast on natural sugars present in fruit juices and grains like rice, wheat, and barley.
What are Antibiotics? What are their uses?
Antibiotics are medicines that can kill or stop the growth of disease-causing microorganisms. For Example, Penicillin.
Antibiotics are used to:
Cure a variety of diseases (such as streptomycin, erythromycin, and tetracycline that are made from bacteria and fungi),
Cure microbial infection in animals (by mixing antibiotics with the feed of livestock and poultry), and
Control several plant diseases.
What precautions should be followed while taking antibiotics and why?
Antibiotics should be taken only on the advice of the doctor, and one must complete the course the doctor prescribes.
Antibiotics taken in wrong doses may make the body resistant to the drug and it may not be effective in the future. Moreover, antibiotics may also kill the beneficial bacteria in the body.
Please Note: Antibiotics cannot cure cold and flu caused by viruses.
Some Definitions to Remember: Pathogens: Disease-causing microbes are called Pathogens. |
Name some of the diseases which can be prevented by vaccines
Some of the diseases that can be prevented by vaccination are:
Cholera,
Hepatitis,
Smallpox, and
Tuberculosis.
One can get necessary vaccines from nearby hospitals.
How do microbes clean up the environment?
Microbes or microorganisms decompose organic waste and dead remains of plants and animals and convert them into simpler substances (which can again be used by other plants and animals) by the process of biodegradation. Thus, they help us in getting rid of harmful and smelly substances and clean up the environment.
Some Definitions to Remember: Communicable Diseases: These are microbial diseases (diseases caused by microbes) that spread from one infected person to a healthy person through air, water, food or physical contact, such as cholera, chicken pox, common cold and tuberculosis. |
How do houseflies transfer pathogens?
A housefly may sit on the garbage and animal excreta and the pathogens stick to their body. When they sit on uncovered food, these pathogens get transferred to the food. When someone eats this contaminated food, he or she may fall sick.
To avoid this, we must keep the food covered.
Name the carriers of:
Female Anopheles mosquito (carries the parasite of malaria called Plasmodium)
Female Aedes mosquito (carries the dengue virus called Flavivirus)
How to prevent diseases that spread through air or contact?
To prevent diseases that spread through the air, keep the patient in complete isolation and keep his or her personal belongings away from others. Vaccination at the suitable age can prevent the onset of tuberculosis, chicken pox, polio, and measles.
How to prevent diseases that spread through water or food?
To prevent the spread of polio, cholera, typhoid and hepatitis A, vaccination is effective. One should also maintain personal hygiene and good sanitary habits and drink boiled drinking water.
One should also eat properly cooked food to avoid diseases like cholera.
How to prevent diseases that spread through mosquitoes?
We can stop the spreading of diseases caused by mosquitoes (such as malaria and dengue) by not allowing the mosquitoes to breed. We should keep our surroundings clean and dry, and not let water collect anywhere - in coolers, tyres, and flower pots etc.
We should also spray insecticides and use mosquito repellents and mosquito nets to protect ourselves from mosquito bites.
Anthrax: A dangerous disease that affects human and cattle is caused by a bacterium called Bacillus Anthracis.
Foot and mouth disease in Cattle: It is caused by a virus called Foot-and-mouth-disease Virus (FMDV) or Picornavirus.
Microorganisms can cause diseases in plants and reduce crop yield. Some of the plants in which they cause diseases are:
The plants can be protected by using chemicals that kill these microbes.
Common Diseases in Plants caused by Microbes
Citrus Canker is caused by Bacteria and spreads through Air.
Rust of Wheat is caused by Fungi and spreads through Air or Seeds.
Yellow Vein Mosaic of Okra (Bhindi) is caused by Virus and spreads through Insects.
Why do we need to preserve food?
We need to preserve food because microorganisms that grow on food can sometimes produce toxic substances which are poisonous to us. If we consume this spoilt food, we can become seriously ill or die. Hence, we need to preserve food from being spoilt.
Nitrogen constitutes 78% of our atmosphere.
In living organisms, it is found in:
Proteins,
Nucleic Acids,
Chlorophyll, and
Vitamins.
Atmospheric nitrogen cannot be used directly by the plants and animals. It gets fixed by either lightning or natural nitrogen fixers.
A step-by-step explanation of Nitrogen Cycle
Nitrogen Fixation: Atmospheric nitrogen is converted by lightning or certain bacteria like Rhizobium, Azotobacter and blue-green algae (present in soil) into compounds usable by plants.
Nitrification: Ammonia conversion into nitrites by Nitrosomonas and further conversion of nitrites into nitrates by Nitrobacter. Plants take up nitrogen in form of ammonia or nitrates.
Assimilation: Roots of plants absorb these nitrogenous compounds from soils and plants use them to synthesize proteins and other compounds.
Animals feeding on plants get these proteins and nitrogen compounds.
Ammonification: When plants and animals die, bacteria and fungi present in the soil convert the nitrogenous wastes into compounds that can be used by plants again.
Denitrification:Nitrates can be converted into nitrogen gas which is released back in the atmosphere by certain bacteria. Eg. Pseudomonas
Hence, atmospheric nitrogen remains constant.
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