Microorganisms and Biotechnology

List the main characteristics of Viruses, Bacteria, and fungi.


  • Viruses are Acellular(do not have a cellular structure) organisms.
  • No specified cell content, so no proper cytoplasm or cellular organelles.
  • They are on the borderline of living and non-living organisms.
  • They consider as living organisms because they contain genetic material that helps to replicate when finding a host(a living organism)
  • Their genetic material consists of a simple protein coat with enclosed nucleic acids, i.e., RNA or DNA. Some viruses contain only DNA, while others contain only RNA as their genetic material.
  • They don’t have characteristics of living things other than reproduction so they are considered as non-living organisms (crystalline shape outside the living body) . Reproduction occurs only inform of replication but with the help of a living host. It means the virus contains some raw material (RNA or DNA) but does not contain machinery to process it. Therefore it can process that raw material only when it gets a living body.
  • Mostly they are parasites and pathogens.
  • They can mutate.
  •  They can only be observed under electronic microscopes.
  • They can exist in many shapes: Rod-shaped, polyhedral, spherical, tadpole-like.
  • They are 10-100 times smaller than bacteria.


The life cycle of the virus consists of the following stages:

  • Attachment: First of all, the virus finds a living organism and get attached to the receptors on the host cell through its protein hooks.
  • Penetration: after attachment virus enters into the body.
  • Uncoating/synthesis: it is the process by which viral capsid is degraded by different enzymes.
  • Replication/assembly: in this process, the fusion of viral protein and genetic material occurs and copies of the viral start making.
  • Virus escapes from the host cell by rupturing it (cell lysis)


  • Lack of membrane-bound organelles.
  • Small, usually microscopic.
  • Shapes can be varied:
    • Bacilli are rod-shaped
    • Cocci are sphere-shaped
    • Spirilla are spiral-shaped

  • A double standard circular DNA is embedded in the cytoplasm.
  • No nucleus is present.
  • Bacteria can respire aerobically and anaerobically.
  • May or may not have flagellum a tail or whip-like structure(locomotory organ).
  • Bacteria can be autotrophic. It means they can make their food with the help of the process of photosynthesis, e.g., cyanobacteria(also called blue-green algae)
  • Some bacteria are heterotrophic that cannot make their food, but they derive energy from organic compounds. According to their habitat and association with other organisms, heterotrophic bacteria can be divided into the following main three groups:
  • Parasitic: they get their food from living organisms. In humans, parasitic bacteria can cause cholera, typhoid, tetanus, whooping cough, diarrhea, tuberculosis.In plants, parasitic bacteria can cause citrus canker, crown gall, the blight of beans.
  • Saprophytic: they feed and live on dead and decaying organic matter. They are the main decomposers of the food chain with fungi. They break down complex organic matter into simpler compounds and assimilate them. They help in nutrient recycling. They decompose dead and decaying plants and animal fragments/leftovers and help in biodegradation.
  • Symbiotic: they live in a symbiotic relationship with other organisms. Rhizobium present in root nodules of legumes is a common example of symbiotic bacteria. These bacteria infect the roots of legumes, causing nodule formation where bacteria are accumulated to fix nitrogen from the air into ammonia that a plant used for its growth. Not all the symbiotic bacteria are pathogenic(disease-causing bacteria), but they are useful, e.g., microbial flora of the human body, present in skin, digestive tract, mucous membranes, and other organs, coexist without harming.
  • Bacteria reproduce by binary fission. In this process, a single bacterium divides into two identical daughter cells. Each identical daughter is the clone of the parent cell.


  • Fungi can be unicellular like yeast.
  • Fungi can be multicellular like bread mould

  • They are eukaryotic means they have a true nucleus is enclosed in a membrane and contain many other membranes bounded organelles.
  • They are non-vascular plants.
  • They reproduce sexually and asexually by spores, haploid cells that undergo mitosis to form multicellular, haploid individuals.
  • Spores are very light, small, and many in numbers. For example, giant puffball mushrooms burst open and release trillions of spores in the air that can disperse by wind or hitching a ride on an animal. Spores remain dormant until they get favorable conditions for growth.

  • Fungi do not have chloroplast, so they are heterotrophs.
  • Most fungi are saprophytic.
  • Cell walls are rigid and made up of chitin(adds structural strength) and glucans(a glucose polymer).
  • Fungi shows two distinctive morphological stages:
    • Vegetative stage: consists of a tangled thread-like structure called hyphae. Mass of hyphae is called mycelium.
    • Reproductive stage: this stage is more conspicuous.
  • Fungi can grow in a moist and slightly acidic environment, and they can grow with and without light.

Write the role of microorganisms in decomposition:

Bacteria and fungi are microorganisms that play an important role in decomposition in ecosystem. Decomposition is the process in which microbes help to convert complex substances into simpler one.They are present on every trophic level in an ecosystem. They can be beneficial in the ecosystem in the following ways:

  • They cause the decay of dead animals, plants and other organisms.
  • They can breakdown of macromolecules like protein, carbohydrates and fats into micro molecules and mix with soil and maks it fertile.
  • They also release salts and mineral ions into the soil that eventually taken up by plants to grow.
  • They breakdown carbohydrates and release carbon dioxide into the environment that is used by plants for photosynthesis.
  • During decomposition, oxygen is also released that is used by living things for breathing/respiration.

Try yourself:

  1. What do you mean by acellular and unicellular organisms?
  2. What are spores?
  3. What are the favorable conditions for spores to become live?
  4. How do spores disperse?
  5. Why are viruses in the boarder-line of living and non-living things?
  6. Why do viruses need to enter a living host cell?
  7. In how many groups can you distinguish bacteria according to their shape?
  8. What is the difference between heterotrophs and autotrophs?
  9. What are legumes?
  10. What are hyphae?
  11. What is mycelium?
  12. Give one example of fungi from your daily life.
  13. How are bacteria important and beneficial for the human body?
  14. In which category we keep the fungi? Animal or plant.
  15. What is decomposition?
  16. What is binary fission?
  17. What type of soil is required for fungi to grow well?
  18. What is the difference between parasites and pathogens?
  19. What are saprophytes?
  20. Name any two sources of carbon dioxide in the environment.