G-12 BIOLOGY, UNIT 2, MICROORGANISMS_240919_155114

Unit 2: Microorganisms

1. Introduction to Microorganisms

  • Definition: Microorganisms are tiny life forms that cannot be seen clearly with the naked eye and require microscopes for observation.

  • Microbiology: The study of microorganisms, which includes:

    • Bacteria

    • Archaea

    • Protozoa

    • Viruses

    • Microscopic Algae

    • Microscopic Fungi

    • Helminthes (parasitic worms)

  • Evolutionary Grouping: Organisms are categorized into three domains:

    • Bacteria

    • Archaea

    • Eukarya

2. Eubacteria

  • Definition: Eubacteria refers to true bacteria, which are prokaryotic, unicellular organisms that reproduce through asexual division.

  • Characteristics:

    • Omnipresent in soil, air, and water.

    • Variability in nutritional modes: can be autotrophic or heterotrophic (e.g., parasites, saprophytes, symbiotic).

    • Predominantly lack true chlorophyll; some possess Bacteriochlorophyll.

    • Cell Structure:

      • Thick, rigid cell wall made of peptidoglycan outside the plasma membrane.

      • Absence of organelles such as mitochondria, Golgi apparatus, plastids, and endoplasmic reticulum.

      • Presence of DNA and RNA in the cell.

3. Bacterial Cell Structure

  • Microscopy: Studied under an electron microscope to reveal unique structures, both external and internal.

  • Important External Features:

    • Pili: Short, hair-like structures important for movement, adherence, and virulence.

    • Flagella: Structures that aid in locomotion.

  • Internal Structures Include:

    • Cytoplasm

    • Cell Membrane

    • Nucleoid (contains genetic material)

4. Bacterial Shapes

  • Classification Based on Shape:

    • Cocci (spherical)

    • Bacilli (rod-shaped)

    • Spirochaetes (spiral or corkscrew-shaped)

  • Examples:

    • Cocci: Diplococci, Streptococci

    • Bacilli: Diplobacilli, Streptobacilli

5. Gram Staining Technique

  • Purpose: Differentiates bacteria based on cell wall composition.

  • Types of Bacteria:

    • Gram-Positive: Retain crystal violet stain (purple); thick peptidoglycan layer.

      • Examples: Staphylococci, Streptococci.

    • Gram-Negative: Lose crystal violet and take up red counterstain (thin peptidoglycan layer).

      • Examples: E. coli, Pseudomonas aeruginosa.

  • Gram Staining Steps:

    1. Heat fixing.

    2. Primary stain (crystal violet).

    3. Mordant (Gram's iodine).

    4. Decolorization (alcohol wash).

    5. Counterstaining (safranin).

6. Nutritional Types of Bacteria

  • Autotrophs: Acquire carbon from inorganic sources.

    • Photoautotrophs: Use sunlight.

    • Chemoautotrophs: Obtain energy from inorganic chemicals.

  • Heterotrophs: Get carbon from organic sources.

    • Photoheterotrophs: Use sunlight.

    • Chemoheterotrophs: Obtain energy from organic sources.

7. Reproduction in Bacteria

  • Asexual Reproduction: Mainly through binary fission.

  • Conjugation: Genetic material transfer between two bacterial cells (e.g., E. coli).

    • F Factor: Contains genes for the transfer of DNA and the formation of sex pili.

8. Archaea

  • Characteristics:

    • Prokaryotic, unicellular organisms lacking a membrane-bound nucleus and peptidoglycan in cell walls.

    • Lipids in membranes have branched hydrocarbon chains.

    • Thriving in extreme environments categorized as:

      • Methanogens

      • Extreme halophiles

      • Extreme thermophiles

9. Fungi

  • Definition: Eukaryotic organisms that are spore-bearing, lack chlorophyll, and reproduce sexually and asexually.

  • General Characteristics:

    • Composed of hyphae forming a mycelium.

    • Rigid cell wall made of chitin and glucans.

    • Nutritionally saprophytic, parasitic, or symbiotic.

10. Pathogenic Microorganisms

  • Common diseases caused by bacteria include:

    • Pertussis, Typhoid fever, Cholera (causative agents listed).

  • Protozoan diseases include:

    • Malaria, Giardiasis, Amoebiasis (examples of causative agents).

  • Viral diseases include:

    • Polio, Measles, Rabies (with causative agents and transmission routes).

11. Modes of Disease Transmission

  • Key Methods:

    • Contact

    • Droplet

    • Airborne

    • Common vehicle

  • Prevention: Regular hygiene practices, vaccinations, and proper sanitation techniques.

12. Conclusion

  • Understanding Microorganisms: Essential for utilizing their beneficial roles while controlling disease transmission in various environments, from healthcare to agriculture.

  • Microorganisms: Tiny life forms that cannot be seen clearly with the naked eye and require microscopes for observation.

  • Microbiology: The study of microorganisms, which includes:

    • Bacteria: Prokaryotic unicellular organisms.

    • Archaea: Prokaryotic unicellular organisms without peptidoglycan.

    • Protozoa: Single-celled eukaryotic organisms.

    • Viruses: Infectious agents that replicate only inside living cells.

    • Microscopic Algae: Photosynthetic microorganisms.

    • Microscopic Fungi: Fungi that cannot be seen without a microscope.

    • Helminthes: Parasitic worms.

  • Eubacteria: True bacteria that are prokaryotic and unicellular.

  • Peptidoglycan: A polymer consisting of sugars and amino acids that make up the cell wall of bacteria.

  • Pili: Short, hair-like structures important for movement, adherence, and virulence.

  • Cytoplasm: The fluid contained within the cell membrane, excluding the nucleus.

  • Nucleoid: The region in prokaryotic cells that contains the genetic material.

  • Gram Staining: A technique to differentiate bacterial species based on the characteristics of their cell walls.

  • Auotrophs: Organisms that produce their own food from inorganic sources.

  • Saprophytic: Organisms that obtain their nutrition from decaying organic matter.

  • Symbiotic: Interaction between organisms from different species, often resulting in benefits for both.

  • Chitin: A long-chain polymer that forms the structural component in the cell walls of fungi.