Microbiology – Exam 2 Vocabulary Review

A comprehensive set of vocabulary flashcards covering microbial nutrition, growth conditions, enzymology, metabolism, antimicrobial control, drug mechanisms, resistance, epidemiology, and infection terminology for Exam 2 preparation.

Autotroph

Organism that uses inorganic CO₂ as its carbon source.

Heterotroph

Organism that must obtain carbon in organic form.

Phototroph

Microbe that gains energy from light by photosynthesis.

Chemotroph

Microbe that gains energy from chemical compounds.

Photoautotroph

Uses light for energy and CO₂ for carbon.

Chemoautotroph

Uses inorganic chemicals for energy and CO₂ for carbon.

Photoheterotroph

Uses light for energy and organic compounds for carbon.

Chemoheterotroph

Uses organic compounds for both energy and carbon.

Psychrophile

Grows best at 0–15 °C; cannot grow above 20 °C.

Mesophile

Optimum growth at 20–40 °C; includes most human pathogens.

Thermophile

Grows optimally at 45–80 °C; lives in hot soil/water.

Barophile

Requires very high hydrostatic pressure for growth.

Halophile

Requires high salt concentrations (9–25 % NaCl) for growth.

Enzyme

Biological catalyst that lowers activation energy and speeds reactions.

Activation Energy

Energy barrier that must be overcome for a reaction to proceed.

Substrate

Reactant molecule on which an enzyme acts.

Apoenzyme

Protein portion of an enzyme without its cofactor.

Cofactor

Non-protein ion (e.g., Fe, Cu, Co) that activates or assists an enzyme.

Coenzyme

Organic cofactor (often vitamin-derived) that transfers groups between substrates.

Holoenzyme

Complete, active enzyme composed of apoenzyme plus cofactors/coenzymes.

Lag Phase

Adjustment period of a culture; little or no cell division.

Exponential (Log) Phase

Rapid, geometric increase in cell numbers under favorable conditions.

Stationary Phase

Rates of cell growth and death are equal; nutrients become limited.

Death Phase

Cells die exponentially as limiting factors intensify.

Competitive Inhibition

Look-alike molecule occupies enzyme’s active site, blocking substrate.

Noncompetitive Inhibition

Regulatory molecule binds to a site other than the active site and inactivates the enzyme.

NADH

Primary electron carrier generated mainly in the Krebs cycle (6 per glucose).

ATP

Adenosine triphosphate—cellular energy currency for storage and use.

Glycolysis

Anaerobic breakdown of glucose to 2 pyruvate, yielding 2 ATP and 2 NADH.

Krebs Cycle

Cyclic pathway that oxidizes acetyl-CoA, generating 2 ATP, 6 NADH, 2 FADH₂ per glucose.

Electron Transport Chain

Series of membrane carriers that generate ~34 ATP using NADH/FADH₂ electrons.

Aerobic Respiration

Glycolysis + Krebs + ETC using O₂; yields 36–38 ATP, CO₂, H₂O.

Anaerobic Respiration

Glycolysis + Krebs + ETC with non-oxygen final acceptor; 2–36 ATP.

Fermentation

Glycolysis only; converts pyruvate to acids/alcohols; regenerates NAD⁺; yields 2 ATP.

Aerobe

Organism able to use oxygen in metabolism.

Obligate Aerobe

Cannot grow without oxygen.

Facultative Anaerobe

Uses O₂ when present; can switch to anaerobic metabolism when absent.

Microaerophile

Requires small amounts of oxygen; does not grow at atmospheric levels.

Anaerobe

Cannot use oxygen for metabolism.

Obligate Anaerobe

Dies in the presence of oxygen.

Aerotolerant Anaerobe

Does not use O₂ but can survive limited exposure.

Obligate Acidophile

Requires an acidic environment to grow.

Alkalinophile

Thrives in environments with high alkaline pH.

Disinfection

Physical or chemical destruction of vegetative pathogens on inanimate objects; not endospores.

Sterilization

Complete removal/destruction of all microbial life on inanimate objects.

Antisepsis / Degermation

Disinfection of living tissue to reduce pathogen numbers.

Decontamination / Sanitization

Mechanical removal of microbes to safe levels on animate or inanimate objects.

Bactericide

Agent that kills bacteria (not necessarily endospores).

Bacteriostatic

Agent that inhibits bacterial reproduction without killing.

Pasteurization

Heat treatment that removes pathogens (e.g., Salmonella, Mycobacterium) while sparing many harmless microbes.

Autoclave

Steam under pressure (121 °C, 15 psi) device used for moist-heat sterilization.

Halogens

Chlorine, iodine, fluorine, bromine—common, broad-spectrum antimicrobial chemicals.

Sulfonamides

Drugs that block folic-acid synthesis by competing with PABA for dihydropteroate synthase.

PABA

Para-aminobenzoic acid; normal substrate for folic acid pathway blocked by sulfa drugs.

Narrow-Spectrum Drug

Antimicrobial effective against a specific group; e.g., isoniazid.

Broad-Spectrum Drug

Antimicrobial effective against multiple groups; e.g., tetracyclines.

Beta-lactam Drugs

Penicillins/cephalosporins that inhibit cell-wall peptidoglycan synthesis.

Spontaneous Mutation

Random genetic change that can confer drug resistance.

Horizontal Gene Transfer

Acquisition of resistance genes via conjugation, transformation, or transduction.

Plasmid

Small circular DNA that often carries antibiotic resistance factors.

Transposon

Mobile DNA segment that can move resistance genes within or between genomes.

Fomite

Inanimate object that transmits pathogens (e.g., doorknob, phone).

Axenic

State of being free of all living microorganisms; sterile.

Lipopolysaccharide (LPS)

Outer-membrane molecule of Gram-negative bacteria that acts as endotoxin.

Endotoxin

Toxic LPS shed by Gram-negative bacteria causing fever and inflammation.

Incubation Period

Time from contact with pathogen to first symptoms.

Prodromal Stage

Early, vague symptoms signaling onset of illness.

Acute Phase

Height of infection; pathogen multiplies at high levels and causes peak symptoms.

Convalescent Stage

Symptoms decline as host recovers.

Continuation Phase

Pathogen or symptoms persist for months or years in some diseases.

Localized Infection

Microbe confined to a specific tissue or site.

Systemic Infection

Infection spreads to several sites via bloodstream or fluids.

Focal Infection

Begins locally then seeds infection in other tissues.

Mixed Infection

Simultaneous infection by several different microbes.

Primary Infection

First or initial infection in a host.

Secondary Infection

New infection occurring during or after treatment of a primary infection.

Acute Infection

Rapid onset, short duration illness.

Chronic Infection

Long-lasting or persistent infection.

Epidemiology

Study of disease frequency, distribution, and determinants in populations.

Endemic Disease

Disease with steady, predictable frequency in a locale.

Sporadic Disease

Disease that appears irregularly and infrequently.

Epidemic Disease

Sudden, higher-than-expected outbreak in a region.

Pandemic Disease

Epidemic that spreads across continents.

BSL-1

Handles non-pathogenic microbes; minimal biosafety requirements.

BSL-2

Handles moderate-risk agents; lab coats, biosafety cabinets required.

BSL-3

Handles airborne, serious pathogens; controlled access, negative pressure labs.

BSL-4

Handles life-threatening agents with no treatment; full-body suits, isolated facility.

Cell Wall Inhibitors

Drugs such as penicillins and vancomycin that block peptidoglycan synthesis.

Cell Membrane Inhibitors

Drugs such as polymyxins and daptomycin that disrupt membrane integrity.

Folic Acid Synthesis Inhibitors

Sulfonamides and trimethoprim that block tetrahydrofolate formation.

Protein Synthesis Inhibitors

Agents like erythromycin and clindamycin that bind ribosomal subunits.

DNA/RNA Inhibitors

Rifampin and quinolones that obstruct transcription or DNA gyrase.

Penicillin

Prototype beta-lactam antibiotic targeting cell-wall cross-linking enzymes.

Vancomycin

Glycopeptide antibiotic that blocks peptidoglycan elongation; used for MRSA.

Polymyxin

Cyclic peptide that binds LPS and disrupts Gram-negative membranes.

Daptomycin

Lipopeptide that depolarizes Gram-positive cell membranes.

Trimethoprim

Synergistic with sulfonamides; blocks dihydrofolate reductase in folate pathway.

Erythromycin

Macrolide that blocks the 50S ribosomal translocation step.

Clindamycin

Lincosamide that inhibits peptide bond formation on the 50S subunit.

Rifampin

Blocks bacterial RNA polymerase; treats tuberculosis.