the meaningful notes of chapter 2 of 8th class the microbial word types of microbial characteristics of microbial mean of microbial
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What are Microbes?
Microbes or microorganisms are tiny organisms which are so small that we cannot see them with an unaided eye. Some microorganisms can be seen with the help of a magnifying glass (such as fungus that grows on bread) while some can only be seen when you use a microscope (such as bacteria and protozoa). Microorganism were first observed by Anton Van Leeuwenhoek.
Viral, Bacterial, and Protozoan Diseases
Causes Diseases
Viruses
Common Ailments: Cold, Cough, and Influenza (or Flu)
Serious Diseases: Polio, Chicken Pox, Measles etc
Bacteria
Typhoid and Tuberculosis (TB) etc
Protozoans
Dysentery and Malaria etc
Table 1: Microbial Diseases
Microorganisms
There are four major types of microorganisms:
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.
Types of Bacteria (based on their Shapes) and their Examples
Shape of Bacteria Example Image
Comma-shaped Bacteria
Vibrio Cholera
Vibrio Cholerae
Spherical-shaped Bacteria (Cocci)
treptococcus
Staphylococcus and Streptococcus
Rod-shaped Bacteria (Bacilli)
Salmonella
E.coli and Salmonella
Spiral-shaped Bacteria (Spirilla)
Borrelia
Fungi: These are non-green plants and hence, cannot make their own food. They either live as parasites (deriving nutrition from host organisms, for example, Puccinia which causes wheat leaf rust) or grow on the organic matter (such as bread mould).
Puccinia triticina
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.
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.
Where do Microorganisms Live?
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).
Microorganisms and Us
Some microorganisms are beneficial to us while others are harmful and cause diseases.
Microorganisms and Us
How are bacteria useful to us?
How is curd formed?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.
Common Methods of preserving food are:
Common Methods of preserving food are:
Nitrogen Fixation
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.
Nitrogen Fixation
Nitrogen Cycle
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.
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