BIOL 2460 - Exam #2 Study Guide 2

Microbial Diversity

Habitats and Communities

  • Microbes inhabit diverse environments: soil, water, human body.

  • Key roles:

    • Nutrient cycling

    • Decomposition

    • Symbiotic relationships

Microbiomes

  • Definition: Microbial communities in specific environments.

  • Importance of human microbiome:

    • Aids digestion

    • Supports immunity

    • Competes against pathogens

Types of Symbioses

  • Mutualism: Both organisms benefit

    • Example: Gut bacteria aiding digestion.

  • Commensalism: One organism benefits; the other unaffected

    • Example: Skin microbiota.

  • Parasitism: One organism benefits at the expense of the host

    • Example: Mycobacterium tuberculosis causing tuberculosis.

Taxonomy

  • Gram-negative bacteria:

    • Features: Outer membrane, thin peptidoglycan layer.

    • Includes major pathogens.

  • Gram-positive bacteria:

    • Features: Thick peptidoglycan layer, no outer membrane.

    • Includes endospore-formers.

Major Taxonomic Groups

  • Gram (-) Proteobacteria:

    • Movement: Flagella, pili, gliding.

    • Metabolism: Aerobic and anaerobic; some nitrogen fixers.

    • Habitat: Soil, water, human hosts.

    • Clinical Significance: Pathogens like Escherichia coli, Salmonella, Helicobacter pylori.

  • Gram (-) Nonproteobacteria:

    • Movement: Some with axial filaments (e.g., spirochetes).

    • Metabolism: Aerobic, anaerobic, phototrophic.

    • Habitat: Water, soil, animal hosts.

    • Clinical Significance: Treponema pallidum (syphilis), Borrelia burgdorferi (Lyme disease).

  • Phototrophic Bacteria:

    • Movement: Some motile, some nonmotile.

    • Metabolism: Photosynthesis (oxygenic or anoxygenic).

    • Habitat: Aquatic environments.

    • Clinical Significance: Cyanobacteria (oxygen production, harmful algal blooms).

  • Gram (+) Bacteria:

    • High G+C (Actinobacteria):

      • Movement: Mostly nonmotile.

      • Metabolism: Decomposers, antibiotic producers.

      • Clinical Significance: Mycobacterium tuberculosis, Streptomyces.

    • Low G+C (Firmicutes):

      • Movement: Some motile via flagella.

      • Metabolism: Facultative anaerobes, endospore-formers.

      • Clinical Significance: Clostridium botulinum, Staphylococcus aureus.

  • Archaea:

    • Movement: Flagella or nonmotile.

    • Metabolism: Extremophiles (methanogens, halophiles).

    • Habitat: Harsh environments (hydrothermal vents, salt lakes).

Eukaryotic Microorganisms

Protozoa

  • Movement: Different types (flagella, cilia, pseudopodia).

  • Metabolism: Heterotrophic, some mixotrophic.

  • Habitat: Freshwater, soil, hosts.

  • Clinical Significance: Plasmodium (malaria), Trypanosoma (sleeping sickness).

Helminths (Parasitic Worms)

  • Nematoda (Roundworms):

    • Examples: Ascaris lumbricoides (intestinal parasite), Enterobius vermicularis (pinworm).

  • Platyhelminthes (Flatworms):

    • Trematodes (Flukes): Schistosoma (schistosomiasis).

    • Cestodes (Tapeworms): Taenia species attach via scolex.

Fungi

  • Metabolism: Heterotrophic decomposers.

  • Habitat: Soil, decaying matter, human hosts.

  • Clinical Significance: Candida albicans (yeast infections), Aspergillus (lung infections).

Lichens

  • Symbiosis: Between fungi and algae/cyanobacteria.

  • Role: Important in ecological succession.

Viruses and Acellular Pathogens

General Characteristics

  • Acellular and obligate intracellular parasites.

  • Structure: Capsid (protein coat), genetic material (DNA or RNA), envelope (some viruses), spikes (host recognition).

Transmission

  • Direct contact (respiratory droplets, sexual transmission).

  • Fomites (inanimate objects like doorknobs).

  • Mechanical vectors (flies carrying viruses externally).

  • Biological vectors (mosquitoes transmitting dengue).

Viral Life Cycles

  • Bacteriophages:

    • Lytic cycle: Immediate replication and lysis (e.g., T4 phage).

    • Lysogenic cycle: Integration into host genome (e.g., Lambda phage).

  • Animal Viruses:

    • Entry via endocytosis or membrane fusion.

    • Replication depends on nucleic acid type (e.g., Retroviruses use reverse transcriptase).

Persistent Infections

  • Latent: Virus remains dormant, can reactivate (e.g., herpes virus).

  • Chronic: Continuous virus production (e.g., hepatitis B, HIV).

Acellular Pathogens

  • Viroids: Infectious RNA causing plant diseases.

  • Virusoids: Satellite RNA; requires a helper virus.

  • Prions: Misfolded proteins causing neurodegenerative diseases (e.g., Mad Cow Disease).

Viral Isolation and Cultivation

  • Techniques: Require host cells for culture (in vivo vs. in vitro).

  • HeLa cells: Widely used in virology research.

Detection Methods

  • Cytopathic effects: Observable changes in host cells.

  • Hemagglutination assay: Detect viral particles via RBC clumping.

  • Nucleic Acid Amplification Tests: PCR and RT-PCR for viral genome detection.

  • Enzyme Immunoassays: ELISA for detecting viral antigens/antibodies.

Influenza Vaccine Production

  • Cultured in chicken eggs or cell lines.

  • Annual development of inactivated or live attenuated vaccines based on predicted strains.