Cells and Microorganisms

Microorganisms: Cells and Organisms

Learning Objective

• Explore the different types of microorganisms.
• Understand that all organisms are made of cells and microorganisms are typically single-celled.

Types of Microorganisms

• Prokaryotes
• Bacteria
• Fungi
• Viruses

Viruses

• A microscopic particle that gets inside a cell and often destroys the cell.
• Viruses are tiny.
  • Smaller than the smallest bacteria.
  • Change rapidly.
  • So small and change so often that scientists don't know exactly how many types exist.
  • These properties make viruses difficult to fight.

Virus Size Comparison

• E. coli (bacterium): 1000 nm \times 3000 nm
• Red blood cell: 10,000 nm in diameter
• Poliovirus: 30 nm
• Bacterial ribosomes: 25 nm
• Bacteriophage MS2: 24 nm
• Bacteriophage T4: 50 nm \times 225 nm
• Smallpox virus: 200 nm \times 300 nm
• Tobacco mosaic virus: 15 nm \times 300 nm

Are Viruses Living?

• Like living things, viruses contain protein and genetic material.
• But viruses don't act like living things.
  • Can't eat, grow, or break down food.
  • Can't use oxygen.
  • Cannot function on its own.
• Can only reproduce inside a living cell that serves as a host.
  • Host: an organism from which a parasite takes food or shelter.
  • Virus uses host's cell as a tiny factory and forces host to make viruses rather than healthy new cells.

Classifying Viruses

• Can be grouped together by:
  • Their shape
  • Type of disease they cause
  • Life cycle
  • Kind of genetic material they contain

Basic Shapes of Viruses

• Crystals
  • The polio virus is shaped like crystals.
• Cylinders
  • The tobacco mosaic virus is shaped like a cylinder and attacks tobacco plants.
• Spheres
  • Influenza viruses look like spheres. HIV is another virus that has this structure.
• Spacecraft
  • One group of viruses attacks only bacteria. Many of these look almost like spacecraft.

Viruses: Living vs. Non-Living

• Borderline between living and non-living.
• Inside host:
  • Use host machinery for multiplication.
• Outside the host:
  • Inactive.
  • No activity.
• Burst the host cell.
• Infect other cells.
• Person falls sick.

Tasks

• Task 1: Prepare a comprehensive PowerPoint presentation/poster that highlights the role, characteristics, and classification of microorganisms. The presentation should include key information on types of microorganisms (bacteria, fungi, and viruses), their significance in various environments (such as their role in medicine, agriculture, and ecosystems).
• Task 2: Differentiate between Bacteria, Fungi, and Viruses.

Difference Between Fungi, Bacteria, and Virus

Bacteriophage Life Cycle

• Step 1: Virus attaches to the cell surface of a bacterium.
• Step 2: Penetration - Phage DNA enters the bacterial cell.
• Step 3: Replication - Phage DNA is replicated; phage proteins are synthesized.
• Step 4: Assembly - Phage components are assembled into mature viruses.
• Step 5: Release - The bacterial cell lyses and releases many phages that can then infect other cells.