exam 1

What is quorum sensing?

• Cell-to-cell chemical communication (autoinducers) that lets bacteria sense population size and coordinate gene activity (e.g., biofilms).

What is magnification?

Making something look bigger than its actual size.

What is resolution (resolving power)?

The ability to clearly distinguish two separate points; for light microscopy ≈ 0.2 µm.

What is the main difference between prokaryotes and eukaryotes?

-Prokaryotes: no nucleus/organelles.

-Eukaryotes: nucleus + organelles. Both have DNA, membranes, ribosomes.

What is the binomial system?

Scientific naming using two parts: Genus species (italicized), e.g., Staphylococcus aureus.

What are pili (fimbriae) and what do they do?

Short, hairlike protein tubes; help bacteria stick to surfaces/host cells (e.g., Neisseria gonorrhoeae).

What is a conjugation (sex) pilus?

A longer pilus that forms a bridge to transfer DNA (plasmids) between bacteria.

What are prokaryotic flagella and what is their function?

Hollow, rigid filaments of flagellin; rotate like propellers for motility and chemotaxis.

What are endoflagella?

Flagella wrapped inside spirochetes; rotation twists the entire cell (e.g., Treponema pallidum).

What is the glycocalyx?

Outer polysaccharide layer:

• Capsule = thick, organized

• Slime layer = thin, loose
  Functions: protects from phagocytosis, helps attachment, prevents drying.

What is the role of the bacterial cell wall?

Protects from lysis, maintains shape, balances water; main component is peptidoglycan.

What is unique about Gram-positive cell walls?

Thick peptidoglycan, teichoic acids, no LPS/endotoxin.

What is unique about Gram-negative cell walls?

Thin peptidoglycan, outer membrane with LPS, Lipid A = endotoxin, no teichoic acids.

What is peptidoglycan?

A strong, mesh-like polymer that forms the bacterial cell wall backbone.

What is lipopolysaccharide (LPS)?

Outer membrane molecule of Gram-negative bacteria; made of Lipid A, core, and O-antigen.

What is Lipid A?

The toxic part of LPS; an endotoxin that can trigger fever or septic shock.

What is the difference between endotoxins and exotoxins?

-Endotoxin = Lipid A of Gram-negatives; heat-stable, weakly toxic.

-Exotoxin = Secreted proteins (Gram±); very potent, specific effects.

What are plasmids?

Small, circular DNA molecules in bacteria; may carry antibiotic resistance or virulence genes; can transfer by conjugation.

What is binary fission?

Asexual reproduction: DNA replicates → septum forms → two identical daughter cells.

What are the four phases of bacterial growth?

Lag (adjustment), Log (exponential growth), Stationary (growth = death), Death (decline).

What is a psychrophile?

Cold-loving microbe; grows best below 15 °C.

What is a mesophile?

Moderate-temperature microbe; grows best 10–45 °C (includes human pathogens).

What is a thermophile?

Heat-loving microbe; grows best around 60 °C.

What is a hyperthermophile?

Extreme heat-loving; grows above 80 °C (mostly Archaea in vents).

What is a halophile?

Salt-loving microbe; thrives in high NaCl.

What is an acidophile?

Microbe that grows best in acidic environments (low pH).

What is an obligate aerobe?

Requires oxygen to grow.

What is an obligate anaerobe?

Oxygen is toxic; cannot grow with O₂.

What is a facultative anaerobe?

Can grow with or without oxygen (prefers O₂).

What is an aerotolerant anaerobe?

Doesn’t use O₂ but can tolerate it.

What is a capnophile?

Requires low O₂ and high CO₂ to grow.

What is an obligate intracellular parasite?

Microbe that must live and replicate inside a host cell.

What are the three domains of life?

Bacteria, Archaea, Eukarya.

What are Archaea?

Prokaryotes found in extreme conditions (heat, salt, acid); none cause human disease.

What are basic dyes?

Positively charged; stain cells (which are negatively charged).

What are acidic dyes?

Negatively charged; stain background (cells repel dye).

What is the Gram stain used for?

To distinguish Gram+ (purple) vs Gram– (pink) bacteria by cell wall.

What does the acid-fast stain identify?

Mycobacterium (e.g., M. tuberculosis) with waxy walls; acid-fast cells stain red.

What is an endospore?

• Dormant, resistant structure formed by Bacillus or Clostridium when stressed.

Why are endospores resistant?

Thick coats, dipicolinic acid + Ca²⁺, low water content, special proteins.

What is germination of an endospore?

Return of spore → vegetative (active) cell when conditions improve.

What is mutualism?

Both host and microbe benefit.

What is parasitism?

Microbe benefits, host harmed.

What is pathogenicity?

Likelihood an infection leads to disease.

What is virulence?

Degree of harm/damage caused.

What are signs?

Measurable changes (e.g., fever, rash).

What are symptoms?

Felt by patient (e.g., pain, nausea).

What is a syndrome?

A group of signs + symptoms indicating a disease.

What is a reservoir?

Natural source of a pathogen (animal, human, environment).

What are fomites?

Contaminated objects that transmit microbes.

What is an intermediate host?

Host that carries pathogen but may not show disease.

What is a carrier?

Infected person who spreads disease, may be asymptomatic.

What is a superspreader?

Individual who transmits infection to many more people than usual.

What is horizontal transmission?

Person-to-person spread (touch, fluids, droplets).

What is vertical transmission?

Mother → child (pregnancy, birth, breastfeeding).

What is a mechanical vector?

Pathogen carried on body surface; no replication in vector.

What is a biological vector?

Pathogen grows or replicates inside the vector.

What are respiratory droplets?

5 µm particles; travel short distances (3–6 ft).

What are aerosols?

Tiny particles; stay airborne long; can reach deep lungs.

What is a primary infection?

First infection in a healthy host.

What is a secondary infection?

Infection following a primary one in a weakened host.

What is a local infection?

microbial infection limited to one site.

What is a systemic infection?

Spreads through blood to multiple tissues/organs.

What is bacteremia?

Bacteria present in blood.

What is septicemia?

Bacteria multiplying in blood (“blood poisoning”).

What is sepsis?

Body-wide inflammatory response to infection; can cause organ failure.

What is viremia?

Viruses in blood.

What is toxemia?

Toxins in blood.

What is a cytotoxin?

Exotoxin that kills cells or disrupts metabolism.

What is a neurotoxin?

Exotoxin that blocks nerve signal transmission.

What is an enterotoxin?

Exotoxin that affects the GI tract, causing diarrhea/fluid loss.

What is an exotoxin?

Protein secreted by Gram+ or Gram–; very potent and specific.

What is an endotoxin?

Lipid A portion of LPS (Gram– only); released on lysis; less potent, causes fever/shock.

What is an antitoxin?

Host antibody that neutralizes toxins.

What is coagulase?

Enzyme that clots blood around bacteria; hides them from immunity.

What is streptokinase/staphylokinase?

Enzymes that dissolve clots; help bacteria spread in tissues.

What is hyaluronidase?

“Spreading factor”; breaks down connective tissue (hyaluronic acid).

What is a portal of entry?

Route by which pathogen enters host (skin, respiratory, GI, urogenital, parenteral).

What is a portal of exit?

Route by which pathogen leaves host (respiratory droplets, feces, urine, etc.).

What is infectious dose (ID)?

Minimum number of microbes needed to cause disease.

What are the stages of disease?

Incubation (no symptoms) → Prodromal (mild symptoms) → Acute (peak illness) → Decline → Convalescence.

What does sporadic mean?

Few, irregular cases.

What does endemic mean?

Constant, low-level presence in a region.

What does epidemic mean?

Cases rise above expected baseline in a region.

What does pandemic mean?

Epidemic spreading across countries/continents.

What are HAIs (nosocomial infections)?

Infections acquired in healthcare settings (e.g., catheters, ventilators).