Microorganisms (Microbes) and Microbiology

Microorganisms are tiny living organisms invisible to the human eye. They can only be observed using a microscope. The cell has four main parts: the cell wall, cell membrane, cytoplasm, and cell organelles. Microorganisms are present all around us in the air, water, soil, food, sewage, and garbage, as well as in the bodies of plants and animals, including humans. 

Among the living organisms, microorganisms are the largest in number. Hence, they are classified as follows:

Classification of Microorganisms

With reference to the size of microbes, remember: 

1 meter = 10⁶ micrometres (µm)
1 meter = 10⁹ nanometres (nm)

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

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

3. Procedure

• Bread Experiment: Place a moistened piece of bread or bhakari in a closed box. Observe it with a magnifying lens to check for mould growth after 3-4 days.
• Water Sample Observation: Place a drop of muddy or stagnant water on a glass slide, cover with a cover slip, and observe under the compound microscope.
• Yoghurt/Buttermilk Observation: Place a drop of yoghurt or buttermilk on a glass slide, cover it with a cover slip, and observe under the microscope.
• Recording observations: Draw sketches of the observed microorganisms in your notebook.

4. Conclusion

• Bread/Bhakari: Mould or fungal growth develops after a few days due to microorganisms.
• Muddy Water: Tiny protozoa and bacteria can be seen moving under the microscope.
• Yoghurt/Buttermilk: Lactobacillus bacteria are visible and responsible for curd formation.

Microorganisms are tiny living organisms invisible to the human eye. They come in different types:

1. Multicellular Microorganisms: Some microorganisms, like the mould (fungus) on bread or algae in ponds, are made up of many cells working together. These are similar to larger plants and animals but much smaller in size.
2. Unicellular Microorganisms: Most microorganisms, like bacteria and viruses, are made of only one cell. They are called unicellular organisms because they perform all life functions in just one cell. Bacteria are prokaryotic cells, meaning they don’t have many complex parts like those found in plant or animal cells. The plasma membrane, cytoplasm and nucleoid are their only components.

Prokaryotic cell

Microorganisms need the right environment to grow and reproduce. Different types of microorganisms have different needs:

1. Oxygen requirement: Some microorganisms need oxygen to grow. Others can grow without oxygen.

2. Surviving Extreme Conditions: Some microorganisms live in harsh environments like

• The ocean floor
• Ice in the polar regions
• Hot springs

3. Protective Covering During Adverse Conditions: When conditions become unfavourable, microorganisms form a thick protective covering around themselves. They pause their life processes (like sleeping). When conditions become favourable again, they come out of the covering and resume their activities.

Where do the microorganisms grow?
Medium: Soil, water, decaying matter, etc.
Temperature : 25°C - 37°C
Nutrition: specific nutrients, e.g., algae-chlorophyll, oxygen.
Atmosphere: Moist, humid, warm