Microbiology: Bacteria Characteristics and Types

Characteristics:
- Prokaryotic cells (no nucleus or membrane-bound organelles)
- Cell walls composed of peptidoglycan (also known as murein)
- Can be gram-positive (thick peptidoglycan layer) or gram-negative (thin peptidoglycan layer)
Types:
- Aerobic (require oxygen) vs. anaerobic (do not require oxygen)
- Autotrophic (produce own food) vs. heterotrophic (obtain food from environment)
Importance:
- Decomposition and nutrient cycling
- Food production (e.g., yogurt, cheese, bread)
- Human health (e.g., gut microbiome, disease causation)

Characteristics:
- Not considered living cells (do not metabolize, grow, or respond to stimuli)
- Composed of genetic material (DNA or RNA) surrounded by a protein coat (capsid)
- Can replicate only inside host cells
Types:
- DNA viruses (e.g., herpesviruses, adenoviruses)
- RNA viruses (e.g., influenza, HIV)
- Retroviruses (e.g., HIV, which reverse-transcribes RNA into DNA)
Importance:
- Human disease causation (e.g., common cold, influenza, AIDS)
- Vaccine development
- Cancer research (e.g., oncoviruses)

Immune System:
- First line of defense: physical barriers (skin, mucous membranes)
- Second line of defense: innate immunity (e.g., neutrophils, macrophages)
- Adaptive immunity (acquired through exposure): humoral (antibodies) and cell-mediated responses
Immune Responses:
- Primary response: initial exposure to antigen
- Secondary response: subsequent exposure to antigen (faster, stronger response)
Dysfunction:
- Immunodeficiency (e.g., HIV/AIDS)
- Autoimmune disorders (e.g., rheumatoid arthritis, lupus)
- Hypersensitivity reactions (e.g., allergies, anaphylaxis)

Characteristics:
- Eukaryotic organisms (nucleus and membrane-bound organelles)
- Obtain nutrients by feeding on host tissues or fluids
- Can be extracellular (e.g., tapeworms) or intracellular (e.g., Plasmodium)
Types:
- Protozoa (e.g., Plasmodium, Giardia)
- Helminths (e.g., tapeworms, hookworms)
Importance:
- Human disease causation (e.g., malaria, schistosomiasis)
- Zoonotic diseases (transmitted from animals to humans)
- Public health significance in developing countries

Cell Characteristics:
- Lack of nucleus and membrane-bound organelles (prokaryotic cells)
- Cell walls composed of peptidoglycan (murein)
Types of Bacteria:
- Aerobic (require oxygen) vs. anaerobic (do not require oxygen)
- Autotrophic (produce own food) vs. heterotrophic (obtain food from environment)
Gram Staining:
- Gram-positive (thick peptidoglycan layer) vs. gram-negative (thin peptidoglycan layer)
Importance of Bacteria:
- Decomposition and nutrient cycling
- Food production (e.g., yogurt, cheese, bread)
- Human health (e.g., gut microbiome, disease causation)

Viral Characteristics:
- Not considered living cells (do not metabolize, grow, or respond to stimuli)
- Composed of genetic material (DNA or RNA) surrounded by a protein coat (capsid)
- Can replicate only inside host cells
Types of Viruses:
- DNA viruses (e.g., herpesviruses, adenoviruses)
- RNA viruses (e.g., influenza, HIV)
- Retroviruses (e.g., HIV, which reverse-transcribes RNA into DNA)
Importance of Viruses:
- Human disease causation (e.g., common cold, influenza, AIDS)
- Vaccine development
- Cancer research (e.g., oncoviruses)

Immune System:
- First line of defense: physical barriers (skin, mucous membranes)
- Second line of defense: innate immunity (e.g., neutrophils, macrophages)
- Adaptive immunity (acquired through exposure): humoral (antibodies) and cell-mediated responses
Immune Responses:
- Primary response: initial exposure to antigen
- Secondary response: subsequent exposure to antigen (faster, stronger response)
Dysfunction of the Immune System:
- Immunodeficiency (e.g., HIV/AIDS)
- Autoimmune disorders (e.g., rheumatoid arthritis, lupus)
- Hypersensitivity reactions (e.g., allergies, anaphylaxis)

Parasite Characteristics:
- Eukaryotic organisms (nucleus and membrane-bound organelles)
- Obtain nutrients by feeding on host tissues or fluids
- Can be extracellular (e.g., tapeworms) or intracellular (e.g., Plasmodium)
Types of Parasites:
- Protozoa (e.g., Plasmodium, Giardia)
- Helminths (e.g., tapeworms, hookworms)
Importance of Parasites:
- Human disease causation (e.g., malaria, schistosomiasis)
- Zoonotic diseases (transmitted from animals to humans)
- Public health significance in developing countries