Microorganisms (Microbes) and Microbiology

• Microorganisms are organisms that cannot be seen with our eyes and can be observed only under a microscope.
• The cell has four main parts: cell wall, cell membrane, cytoplasm, and cell organelles.
• Microorganisms are present in air, water, soil, food, sewage, garbage, and in the bodies of plants, animals, and humans.

Occurrence of Microorganisms

• Microorganisms are found all around us in the environment.
• They occur in both living and non-living surroundings such as soil, water, food, and waste materials.
• Some microorganisms live in the bodies of plants and animals, including humans.

• Some microorganisms are multicellular, such as the fungus growing on bread and strands of algae in ponds.
• Most microorganisms are unicellular, such as bacteria and viruses.
• Bacteria have a different cellular structure and lack the membrane-bound organelles found in eukaryotic cells.
• Their only components are the plasma membrane, cytoplasm, and nucleoid. Such cells are called prokaryotic cells.

A variety of microbes

Prokaryotic cell 

• Each microorganism needs a specific environment for growth and reproduction.
• Some microorganisms need oxygen for growth, while some can grow without oxygen.
• Some microorganisms survive in extreme and adverse conditions, such as the ocean floor, polar ice, and hot water springs.
• During adverse conditions, microorganisms form a thick covering around themselves and stop their life processes.
• When favourable conditions return, they come out of the covering and continue their life processes.

• Medium: soil, water, decaying matter, etc.
• Temperature: 25°C to 37°C.
• Nutrition: specific nutrients; for example, algae need chlorophyll, and oxygen is required by many microbes.
• Atmosphere: moist, humid, and warm.

Aim:

To observe microorganisms in different environments using a magnifying lens or microscope.

Requirements:

Moistened bread or bhakari, closed box, muddy water or water from a stagnant puddle, yoghurt or buttermilk, glass slides, cover slips, compound microscope, and magnifying lens.

Procedure:

1. Keep a moistened piece of bread or bhakari in a closed box and observe it after 3–4 days using a magnifying lens.
2. Observe a drop of muddy water or stagnant water under a compound microscope.
3. Take a drop of yoghurt or buttermilk on a glass slide and observe it under a compound microscope.
4. Draw sketches of the microbes observed.

Conclusion

• Bread or bhakari shows mould or fungal growth after a few days.
• Muddy water shows tiny protozoa and bacteria under the microscope.
• Yoghurt or buttermilk shows Lactobacillus bacteria responsible for curd formation.