BIO 1550 Final Exam Study Guide: Key Microbiology Concepts and Infections

Molecules of Microbiology

Macromolecules: Proteins, Lipids, Nucleic Acids, and Carbohydrates

Macromolecules are large, complex molecules essential for life. They include proteins, lipids, nucleic acids, and carbohydrates, each with distinct structures and functions.

• Proteins: Polymers of amino acids; function as enzymes, structural components, and signaling molecules.

• Lipids: Hydrophobic molecules; include fats, phospholipids, and steroids; important for membrane structure and energy storage.

• Nucleic Acids: DNA and RNA; store and transmit genetic information.

• Carbohydrates: Sugars and polysaccharides; provide energy and structural support.

• Example: Starch (a carbohydrate) stores energy in plants; hemoglobin (a protein) transports oxygen in blood.

Enzymes

Enzymes are biological catalysts that speed up chemical reactions without being consumed.

• Active Site: Region where substrate binds and reaction occurs.

• Specificity: Each enzyme acts on a specific substrate.

• Example: DNA polymerase synthesizes new DNA strands during replication.

Dynamics of Microbial Growth

Conditions and Nutritional Requirements for Bacterial Growth

Bacteria require specific environmental and nutritional conditions for optimal growth.

• Temperature: Psychrophiles (cold-loving), mesophiles (moderate), thermophiles (heat-loving).

• pH: Most bacteria prefer neutral pH (6.5–7.5).

• Oxygen: Obligate aerobes, obligate anaerobes, facultative anaerobes, microaerophiles, aerotolerant anaerobes.

• Nutrients: Carbon, nitrogen, sulfur, phosphorus, trace elements, and growth factors.

Bacterial Growth Curve

The bacterial growth curve describes population changes over time in a closed system.

• Lag Phase: Adaptation, no division.

• Log (Exponential) Phase: Rapid cell division.

• Stationary Phase: Growth rate slows; nutrients deplete.

• Death Phase: Cells die due to lack of nutrients and waste accumulation.

Biofilms

Biofilms are structured communities of microorganisms attached to surfaces and embedded in a self-produced matrix.

• Protection: Biofilms protect bacteria from antibiotics and immune responses.

• Example: Dental plaque is a common biofilm.

Prokaryotic Cell Structures & Functions

Gram-Positive vs. Gram-Negative Cell Walls

Bacterial cell walls differ in structure, affecting staining and antibiotic susceptibility.

• Gram-Positive: Thick peptidoglycan layer, teichoic acids, stains purple.

• Gram-Negative: Thin peptidoglycan, outer membrane with lipopolysaccharide (LPS), stains pink.

• Clinical Relevance: Gram-negative bacteria are often more resistant to antibiotics due to the outer membrane.

Microbial Infections – Classification and Pathogenesis

Streptococcus: Cell Wall Components and Classification

• M Protein: Surface protein that helps evade immune response; found in Streptococcus pyogenes.

• Carbohydrate Antigens: Used for Lancefield classification (Groups A, B, etc.).

Lancefield Classification

System based on cell wall carbohydrate antigens; important for identifying pathogenic streptococci.

Hemolysis Patterns

• Alpha Hemolysis: Partial hemolysis, greenish color (e.g., Streptococcus pneumoniae).

• Beta Hemolysis: Complete hemolysis, clear zone (e.g., Streptococcus pyogenes).

• Gamma Hemolysis: No hemolysis (e.g., Enterococcus faecalis).

Microbial Infections – Respiratory System

Upper vs. Lower Respiratory Tract

• Upper: Nose, pharynx, larynx.

• Lower: Trachea, bronchi, lungs.

• Clinical Relevance: Infections differ in severity and causative agents.

Influenza Virus and Its Genome

• Genome: Segmented, negative-sense single-stranded RNA.

• Types: Influenza A, B, and C; A is most variable and causes pandemics.

Antigenic Drift and Shift

• Antigenic Drift: Minor mutations in viral genes; causes seasonal epidemics.

• Antigenic Shift: Major genetic reassortment; can lead to pandemics.

• Reason for Annual Change: High mutation rate and reassortment in influenza viruses.

Microbial Infections – Digestive System

Clostridioides difficile (C. diff) Infection

• Cause: Disruption of normal gut flora, often after antibiotics.

• Prevention: Judicious antibiotic use, infection control in healthcare settings.

• Difficult to Treat: Spore formation, resistance to many antibiotics.

• Identification: Toxin detection (e.g., radioactive immunoassay).

Helicobacter pylori (H. pylori)

• Role: Causes gastritis, peptic ulcers, and is linked to gastric cancer.

• Detection: Urease test—H. pylori produces urease, which converts urea to ammonia, increasing pH.

Microbial Infections – Urogenital System

Urinary Tract Infections (UTIs)

• Details: Commonly caused by Escherichia coli; symptoms include dysuria, frequency, urgency.

• Risk Groups: Women, elderly, catheterized patients, those with urinary tract abnormalities.

Human Papillomavirus (HPV)

• Cause: Sexually transmitted virus; some types cause warts, others cause cancer.

• Prevention: Vaccination (e.g., Gardasil), safe sex practices.

• Types: Over 100 types; high-risk types (e.g., 16, 18) linked to cancer.

Herpes Simplex Virus (HSV1 and HSV2)

• HSV1: Causes oral herpes (cold sores).

• HSV2: Causes genital herpes.

• Vaccine: No effective vaccine currently available.

Microbial Infections – Nervous System

Clostridium botulinum

• Role: Produces botulinum toxin, causing botulism (flaccid paralysis).

Microbial Infections – Respiratory System (continued)

Tuberculosis (TB)

• Organism: Mycobacterium tuberculosis.

• Specificity: Infects lungs primarily; can affect other organs.

Viruses, Viroids, & Prions

Hepatitis Viruses (A, B, C)

• Hepatitis A: Fecal-oral transmission; acute infection; vaccine available.

• Hepatitis B: Bloodborne; chronic infection possible; vaccine available.

• Hepatitis C: Bloodborne; often chronic; no vaccine.

Virus	Transmission	Chronicity	Vaccine
Hepatitis A	Fecal-oral	No	Yes
Hepatitis B	Blood, sexual	Yes	Yes
Hepatitis C	Blood	Yes	No

HIV and AIDS

HIV Genome and Reverse Transcriptase

• Genome: Two copies of single-stranded RNA.

• Reverse Transcriptase: Enzyme that synthesizes DNA from RNA template.

HIV Life Cycle

1. Attachment to CD4+ T cells

2. Fusion and entry

3. Reverse transcription of RNA to DNA

4. Integration into host genome

5. Transcription and translation

6. Assembly and budding of new virions

Transmission and Treatment

• Spread: Blood, sexual contact, mother-to-child.

• Treatment: Antiretroviral therapy (ART) targets multiple stages of the life cycle.

HIV vs. AIDS

• HIV: Infection with the human immunodeficiency virus.

• AIDS: Advanced stage of HIV infection with severe immune suppression and opportunistic infections.

Diseases Associated with HIV Infection

• Opportunistic Infections: Tuberculosis, Pneumocystis pneumonia, Kaposi's sarcoma, candidiasis, etc.

Additional info: Some explanations and examples were expanded for clarity and completeness based on standard microbiology curricula.