Exam 1

What is microbiology?

The study of organisms too small to be seen with the naked eye.

Name the three domains of life.

Bacteria, Archaea, Eukarya.

Define normal microbiota.

Microbes that permanently live in or on our bodies and benefit us.

Define transient microbes.

Temporary microbes that are removed by washing or immune defense.

Define opportunistic pathogen.

Microbes that cause disease when immunity is weak or they move to another body site.

What are some emerging infectious diseases(EIDS).

SARS-CoV-2, Zika, Ebola, Candida auras, MRSA.

What pathogen is a Gram positive cocci in clusters that produces toxins and causes MRSA?

Staphylococcus aureus

Name three main chemical bonds and give an example.

• Ionic- transfer of electrons (NaCl).

• Covalent- sharing electrons (H2O).

• Hydrogen- weak attraction (DNA base pairs).

Properties of water important to biology.

Polar, temperature buffer, excellent solvent, hydrogen bonding.

What does pH measure?

The concentration of hydrogen ions(H+).

List the 4 macromolecules of life.

Carbohydrates, lipids, proteins, nucleic acids.

Carbohydrate examples:

Glucose, starch, glycogen, peptidoglycan.

Lipid examples:

Fats, phospholipids(membranes), steroids.

Protein functions:

Enzymes, structure, movement, transport, toxins.

What causes protein denaturation?

Heat, pH changes, chemicals.

DNA VS RNA differences

DNA: deoxyribose, bases A-T-C-G, double stranded.

RNA: ribose, bases A-U-C-G, single stranded.

ATP structure and role

Adenine + ribose + 3 phosphates; energy currency of the cell.

Pathogen: gram positive spore former, anaerobe, causes gas gangrene.

Clostridium perfringes - treat with penicillin G.

Total magnification formula?

Ocular lens X objective lens.

Define resolution

The ability to distinguish fine detail or separate two points clearly.

Which microscope is best for live, unstained microbes?

Darkfield or phase-contrast.

What’s the purpose of heat fixing?

Kills microbes, sticks them to slide, preserves shape.

Difference between simple stain and differential stain.

Simple stain= one dye, shows shape and arrangement. Differential stain= multiple dyes, distinguishes cell types.

What are the steps of Gram stain in order?

1. Crystal violet (primary stain)

2. Iodine (mordant)

3. Alcohol (decolorizer)

4. Safranin (counterstain)

What is a Gram-positive cells final color?

Purple

What is a Gram-negative cells final color?

Pink

What is the role of iodine in Gram stain?

Binds crystal violet inside cell walls (Gram+ holds it tightly).

Acid-fast stain detects what bacteria?

Mycobacterium, Nocardia (waxy mycolic acid)

Capsule stain appearance.

Clear halo around cell.

Endospore stain results.

Spores= green

Cells= pink

Flagella stain use.

Mordant thickens flagella to be visible.

Morphology and characteristics of Helicobacter pylori.

Gram-negative spiral rod, multiple flagella, urease positive.

Diseases caused by Helicobacter pylori?

Gastritis, peptic ulcers, gastric cancer risk.

Diagnostic test for Helicobacter pylori.

Urease breath test.

Treatment for Helicobacter pylori.

H+ pump inhibitor, amoxicillin, clarithromycin.

What are the main differences between prokaryotes and Eukaryotes?

Prokaryotes: no nucleus, single circular chromosome, peptidoglycan cell wall, divide by binary fission.

Eukaryotes: True nucleus, paired linear chromosomes, organelles, divide by mitosis.

Which cell type has 70s ribosomes and which has 80s?

Prokaryotes: 70s

Eukaryotes: 80s (except mitochondria and chloroplasts, which have 70s).

What is the glycocalyx?

A sugar coating external to the cell wall that provides protection and attachment.

Two types of glycocalyx and differences.

• Capsule: neatly organized, firmly attached → prevents phagocytosis.

• Slime layer: unorganized, loosely attached → helps form biofilms.

Why are capsules important for virulence?

They help bacteria evade the immune system by preventing phagocytosis.

What is biofilm?

A community of microbes attached to a surface and encased in a slime layer.
Example: dental plaque.

What is the function of the bacterial flagella?

Motility(movement)

Four flagellar arrangements.

• Monotrichous: one flagellum.

• Lophotrichous: tuft at one end.

• Amphitrichous: one flagellum at each end.

• Peritrichous: flagella over entire surface.

What is taxis?

Movement in response to stimuli.

• Chemotaxis: toward/away from chemicals.

• Phototaxis: toward/away from light.

Where are axial filaments found?

In spirochetes

What’s the difference between fimbriae and pili?

• Fimbriae: allow attachment to surfaces.

• Pili: transfer DNA between bacteria (conjugation).

What is the function of bacterial cell wall?

Maintains shape and prevents lysis (bursting).

Key components of peptidoglycan.

NAG (N-acetylglucosamine) + NAM (N-acetylmuramic acid) linked by peptide cross-bridges.

Gram-positive cell wall features.

• Thick peptidoglycan layer.

• Teichoic acids for structure and stability.

• Stains purple in Gram stain.

Gram-negative cell wall features.

• Thin peptidoglycan layer.

• Outer membrane with lipopolysaccharides (LPS).

• LPS includes O antigen (ID marker) and Lipid A endotoxin (toxic).

• Stains pink in Gram stain.

Which type of bacteria are more resistant to antibiotics like penicillin?

Gram-negative bacteria because of their outer membrane barrier.

What’s the function of the plasma membrane?

Selectively permeable barrier that controls what enters/leaves the cell.

Define nucleoid.

Region containing the bacterial chromosome and plasmids (extra circular DNA).

What is the function of plasmids?

Carry extra genes, such as for antibiotic resistance.

Prokaryotic ribosome size.

70s (30s + 50s subunits)

What is the function of inclusions?

Storage of nutrients like lipids, phosphate, or gas vesicles for buoyancy.

What is the function of endospores?

Survival structures that are highly resistant to heat, chemicals, and radiation.

Two key genera that form endospores.

Clostridium and Bacillus

Define sporulation.

Process of forming an endospore when conditions are unfavorable.

Define germination.

Return of an endospore to a vegetative (active) state when conditions improve.

Morphology and characteristics of Klebsiella pnueumoniae.

• Gram-negative rod.

• Has a prominent capsule.

• Non-motile.

Diseases caused by Klebsiella pneumoniae.

• Pneumonia (especially in alcoholics and immunocompromised individuals)

• UTIs

• Nosocomial infections

Unique symptom of Klebsiella pneumonia.

Pink/red sputum “currant jelly”

Why is klebsiella pneumonia difficult to treat?

It has multiple drug resistance mechanisms due to its capsule and plasmids.

Common treatment for Klebsiella pneumonia.

Third generation cephalosporins (ceftriaxone, cefotaxime).

Compare fimbriae, pili, and flagella.

• Fimbriae: attachment.

• Pili: DNA transfer.

• Flagella: Motility (movement).

Compare Gram-positive and Gram-negative walls.

• Gram+ = thick peptidoglycan, teichoic acids, purple stain.

• Gram– = thin peptidoglycan, outer membrane with LPS, pink stain.

Which structure provides antibiotic resistance genes?

Plasmids

What is generation time?

Time it takes for a bacterial population to double.

List the four phases of bacterial growth curve.

1. Lag phase- adjusting, no division.

2. Log (exponential) phase- rapid growth.

3. Stationary phase- growth slows, nutrients used up.

4. Death phase- cells die faster than they divide.

Define obligate aerobe.

Requires oxygen to grow.

Define obligate anaerobe.

cannot grow in oxygen; oxygen is toxic.

Define facultative anaerobe.

Grows with or without oxygen, grows better with oxygen.

Define aerotolerant anaerobe.

Does not use oxygen but tolerates its presence.

Define microaerophile.

Needs oxygen at a lower concentration than in air.

Selective vs Differential media.

• Selective: suppresses unwanted microbes, promotes desired ones.

• Differential: distinguishes microbes based on visible changes.

Example of direct vs indirect measurement of microbial growth.

Direct: plate counts, microscopic counts.

Indirect: turbidity (spectrophotometer).

What are the three main physical factors that influence microbial growth?

temperature, pH, osmotic pressure.

Define psychrophiles, mesophiles, and thermophiles.

• Psychrophiles: cold loving microbes

• Mesophiles: moderate temperature loving microbes (most human pathogens)

• Thermophiles: heat loving microbes.

What are extreme thermophiles (hyperthermophiles)?

Microbes that thrive in very high heat, such as hot springs.

What pH do most bacteria grow best at?

Neutral pH (6.5-7.5)

Define acidophiles.

Microbes that grow in very acidic environments.

Define alkaliphiles.

Microbes that grow in basic(alkaline) environments.

Define osmotic pressure.

The force exerted by water as it moves across a semipermeable membrane.

Differentiate between facultative halophiles and extreme halophiles.

• Facultative halophiles: tolerate high salt but do not require it.

• Extreme halophiles: require very high salt to grow (e.g., Dead Sea microbes).

Name the six key chemical elements microbes need for growth.

Carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen.

What is the role of carbon in microbial growth?

Used as the main structural component and energy source for cells.

What is the role of nitrogen in microbes?

Needed for proteins, DNA, and RNA.

What is the role of sulfur?

Found in some amino acids and vitamins.

Define trace elements and give examples.

Small amounts of mineral like iron, zinc, copper, used as enzyme cofactors.

What are organic growth factors?

Essential compounds microbes cannot make and must get from the environment like vitamins.