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

Molecules of Microbiology

Macromolecules: Proteins, Lipids, Nucleic Acids, and Carbohydrates

• Proteins: Polymers of amino acids; perform structural, enzymatic, and regulatory functions in cells.

• Lipids: Hydrophobic molecules including fats, phospholipids, and steroids; essential 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.

• Enzymes: Biological catalysts, usually proteins, that speed up chemical reactions by lowering activation energy.

• Example: DNA polymerase is an enzyme that synthesizes DNA from nucleotides.

Dynamics of Microbial Growth

Conditions and Nutritional Requirements for Bacterial Growth

• Bacteria require specific nutrients (carbon, nitrogen, minerals, vitamins) and environmental conditions (temperature, pH, oxygen) for growth.

• Temperature Preferences:

  • Psychrophiles: Grow best at low temperatures (0–20°C).

  • Mesophiles: Grow best at moderate temperatures (20–45°C).

  • Thermophiles: Thrive at high temperatures (45–80°C).

  • Psychrotrophs: Grow at low temperatures but have higher optimums than psychrophiles.

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

Bacterial Growth Curve

• Bacterial populations grow in four phases:

  1. Lag Phase: Adaptation, little to no cell division.

  2. Log (Exponential) Phase: Rapid cell division and population growth.

  3. Stationary Phase: Growth rate slows; nutrients deplete, waste accumulates.

  4. Death Phase: Cells die faster than they divide.

• Example: E. coli in nutrient broth shows a classic growth curve over 24 hours.

Biofilms

• Biofilms: Structured communities of bacteria adhering to surfaces and embedded in a self-produced extracellular matrix.

• Biofilms protect bacteria from environmental stress and antibiotics.

• Example: Dental plaque is a biofilm on teeth.

Prokaryotic Cell Structures & Functions

Gram-Positive vs. Gram-Negative Cell Walls

• Gram-Positive: Thick peptidoglycan layer, teichoic acids, no outer membrane; stains purple in Gram stain.

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

• Significance: Affects susceptibility to antibiotics and immune response.

Microbial Infections - Skin and Eyes

Streptococcus Infections

• Streptococcus: Genus of Gram-positive cocci; some species cause pharyngitis, impetigo, and other infections.

• Carbohydrate and M Protein: M protein on cell wall inhibits phagocytosis; carbohydrates used for classification.

• Lancefield Classification: Groups Streptococcus species based on cell wall carbohydrates (e.g., Group A: S. pyogenes).

• Hemolysis Types:

  • Alpha (α): Partial hemolysis, greenish color (e.g., S. pneumoniae).

  • Beta (β): Complete hemolysis, clear zone (e.g., S. pyogenes).

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

Microbial Infections - Respiratory System

Upper and Lower Respiratory Tract

• Upper Respiratory Tract: Nose, pharynx, larynx; common site for infections like pharyngitis.

• Lower Respiratory Tract: Trachea, bronchi, lungs; infections include pneumonia and tuberculosis.

Influenza Virus

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

• Antigenic Drift: Minor changes in viral antigens due to mutations; causes seasonal epidemics.

• Antigenic Shift: Major changes due to reassortment of genome segments; can cause pandemics.

• Annual Variation: High mutation rate and reassortment lead to new strains each year.

Microbial Infections - Digestive System

Clostridioides difficile (C. diff) Infection

• C. diff: Gram-positive, spore-forming anaerobe causing antibiotic-associated diarrhea and colitis.

• Prevention: Judicious antibiotic use, hand hygiene, environmental cleaning.

• Difficult to Treat: Forms spores resistant to many disinfectants; recurrent infections common.

• Identification: Radioimmunoassay for toxins, PCR, or enzyme immunoassay; radioactive test detects toxin presence.

Helicobacter pylori (H. pylori)

• H. pylori: Gram-negative spiral bacterium; causes gastritis, ulcers, and is linked to gastric cancer.

• Detection: Urease test (biopsy or breath test); H. pylori produces urease, converting urea to ammonia and CO2.

• Urease Test Detail: Rapid color change in medium indicates urease activity.

Microbial Infections - Urogenital System

Urinary Tract Infections (UTIs)

• UTI: Infection of urinary tract, commonly caused by Escherichia coli.

• Prone Populations: Women, elderly, catheterized patients, those with urinary tract abnormalities.

Human Papillomavirus (HPV)

• HPV: DNA virus causing warts and cancers (cervical, anal, oropharyngeal).

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

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

Herpes Simplex Virus (HSV)

• HSV-1: Causes oral herpes (cold sores); can cause genital herpes.

• HSV-2: Primarily causes genital herpes.

• Vaccine: No approved vaccine for HSV-1 or HSV-2 as of now.

Microbial Infections - Nervous System

Clostridium botulinum

• C. botulinum: Gram-positive, spore-forming anaerobe; produces botulinum toxin causing flaccid paralysis (botulism).

Microbial Infections - Respiratory System (continued)

Tuberculosis (TB)

• Organism: Mycobacterium tuberculosis; acid-fast bacillus.

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

Viruses, Viroids, & Prions

Hepatitis Viruses

• Hepatitis A: RNA virus; transmitted fecal-oral; acute infection; vaccine available.

• Hepatitis B: DNA virus; transmitted via blood/body fluids; chronic infection possible; vaccine available.

• Hepatitis C: RNA virus; transmitted via blood; often chronic; no vaccine.

• Prevention: Vaccines for Hepatitis A and B; none for C.

HIV and AIDS

• HIV: Human Immunodeficiency Virus; retrovirus with two copies of single-stranded RNA genome.

• Genome: Contains genes for structural proteins, enzymes (reverse transcriptase, integrase, protease), and regulatory proteins.

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

• Life Cycle: Entry into host cell, reverse transcription, integration into host genome, transcription/translation, assembly, budding.

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

• Treatment: Antiretroviral therapy (ART) using drug combinations to suppress viral replication.

• HIV vs. AIDS: HIV is the virus; AIDS is the advanced disease stage with severe immune deficiency.

• Associated Diseases: Opportunistic infections (e.g., Pneumocystis pneumonia, Kaposi's sarcoma, tuberculosis).

Table: Comparison of Hepatitis Viruses

Virus	Genome Type	Transmission	Chronic Infection	Vaccine
Hepatitis A	RNA	Fecal-oral	No	Yes
Hepatitis B	DNA	Blood, body fluids	Yes	Yes
Hepatitis C	RNA	Blood	Yes	No

Table: Bacterial Temperature Preferences

Type	Temperature Range (°C)	Example
Psychrophile	0–20	Pseudomonas fluorescens
Mesophile	20–45	Escherichia coli
Thermophile	45–80	Bacillus stearothermophilus
Psychrotroph	0–30	Listeria monocytogenes

Table: Types of Hemolysis in Streptococcus

Type	Hemolysis	Example Species
Alpha (α)	Partial (greenish)	S. pneumoniae
Beta (β)	Complete (clear zone)	S. pyogenes
Gamma (γ)	None	Enterococcus faecalis

Key Equations

• Bacterial Growth (Exponential Phase): $N = N_0 \times 2^n$ Where $N$ = final cell number, $N_0$ = initial cell number, $n$ = number of generations.

• Urease Reaction (H. pylori detection): $\text{Urea} + \text{H}_2\text{O} \xrightarrow{\text{urease}} 2\text{NH}_3 + \text{CO}_2$

• Reverse Transcription (HIV): $\text{RNA} \xrightarrow{\text{reverse transcriptase}} \text{DNA}$

Additional info: Academic context and examples have been added to clarify and expand on the brief points in the original study guide.