Viruses and Bacteria Quiz

Viruses and Bacteria

• Viruses: Submicroscopic entities that require a host cell to reproduce, consisting primarily of a protein coat (capsid) surrounding nucleic acid (DNA or RNA).

• Virus Shapes: Rod-shaped, polyhedral, enveloped, or bacteriophage-like.

• Specificity (Host Range): Viruses are specific to the cells they infect.

• Viral Replication: Viruses use the host cell's machinery to replicate new viruses, either through a lytic or lysogenic cycle.

• Bacteriophages: Viruses that infect bacteria; they inject their genetic material into the cell.

  • Lytic Cycle: The virus immediately takes over the host cell, replicates, and causes the host cell to burst, releasing newly formed viruses.
    • Viral DNA takes over bacterial cellular machinery
  • Lysogenic Cycle: The viral DNA is integrated into the host bacterial chromosome, and replicated along with the bacterial DNA.

• Animal Viruses: Infect animal cells; these viruses often have an outer lipid envelope derived from the host cell membrane.

  • Viral envelope "spikes" match receptor sites on the host cell, allowing entry.

• Viral Replication in Animals: Viruses merge with the host cell membrane and the new viruses are typically released through exocytosis.

• Viroids: Infectious RNA molecules that cause diseases in plants.

• Prions: Infectious protein particles causing degenerative brain diseases in animals.

  • No cure or vaccine.

• Bacteria: Single-celled prokaryotic organisms without a nucleus or membrane-bound organelles.

  • Cell walls contain peptidoglycan (in Eubacteria).

• Bacterial Shapes: Coccus (spherical), bacillus (rod-shaped), spirillum (spiral-shaped).

• Bacterial Reproduction: Asexual, primarily through binary fission.

• Bacterial Classification: Based on oxygen needs (obligate aerobes, anaerobes, facultative anaerobes), and Gram staining properties (Gram-positive, Gram-negative).

• Gram Staining: Distinguishes bacteria based on the properties of their cell walls. Gram-positive bacteria stain purple; Gram-negative bacteria stain pink.

Bacterial Structure

• Capsule: Extra layer providing protection against host immune factors
• Cell Wall: Provides structural support and shape. Presence or absence of peptidoglycan differentiates Gram-positive and Gram-negative bacteria.
• Plasma Membrane: Regulates passage of molecules into and out of the cell.
• Cytoplasm: Contains ribosomes, DNA in a nucleoid region, and other cellular components.
• Flagella: Whip-like structures for movement.
• Pili: Hair-like appendages used for conjugation (DNA exchange) or attachment.

Bacterial Growth and Reproduction

• Binary Fission: Asexual reproduction method; the cell divides into two identical daughter cells.
• Endospores: Resistant structures formed by some bacteria under harsh conditions to aid in survival.
• Exchange of Genetic Material (Conjugation, Transformation, Transduction): Processes by which bacteria can transfer genetic information between one another.

Bacterial Energy and Nutrition

• Heterotrophic: Obtain nutrients from organic compounds.
• Photoautotrophic: Use sunlight to produce their own food.
• Chemoautotrophic: Obtain energy from inorganic chemical reactions.

Bacterial Diseases in Humans

• Pathogens: Disease-causing bacteria.
• Koch's Postulates: Criteria for proving that a specific microorganism causes a specific disease.
• Methods to Control Bacterial Growth: Sterilization, disinfectants, food storage and processing (temperature control).

Test your knowledge on viruses and bacteria with this quiz. Explore topics such as virus structures, replication cycles, and the unique characteristics of bacteriophages. Challenge yourself to understand how these microorganisms interact with their hosts.