General Microbiology Exam Review

A comprehensive set of vocabulary flashcards covering foundational terms and definitions in general microbiology, including microbial classification, cell structure, virology, mycology, parasitology, staining techniques, and antimicrobial principles.

Categories of Microorganisms

Major groups include bacteria, archaea, fungi, protozoa, algae, helminths, and viruses.

Prokaryote

Single-celled organism lacking a membrane-bound nucleus and organelles; includes bacteria and archaea.

Eukaryote

Organism whose cells possess a true nucleus and membrane-bound organelles; includes fungi, protozoa, algae, helminths.

Pathogen

Any microbe capable of causing disease in a host.

Normal Microbiota (Benefits of Microbes)

Resident microbes that aid digestion, produce vitamins, protect against pathogens, and stimulate immunity.

Louis Pasteur

Father of microbiology; disproved spontaneous generation with the swan-neck flask experiment and developed pasteurization.

Swan-Neck Flask Experiment

Pasteur’s test showing that sterilized broth remained microbe-free unless exposed to airborne microbes, supporting biogenesis.

Abiogenesis (Spontaneous Generation)

Discredited idea that life arises from nonliving matter.

Biogenesis

Principle that living cells only arise from existing living cells.

Joseph Lister

Introduced aseptic surgery using phenol, drastically reducing postoperative infections.

Organic Compounds

Carbon-based molecules essential to life: carbohydrates, lipids, proteins, nucleic acids.

Carbohydrates

Sugars and polysaccharides; energy source and structural component (e.g., peptidoglycan backbone).

Lipids

Hydrophobic molecules (fats, phospholipids, sterols) forming membranes and energy stores.

Proteins

Polymers of amino acids; serve as enzymes, structural fibers, receptors, and transporters.

Nucleic Acids

DNA and RNA; store and transmit genetic information.

Bacterial Cell Wall

Rigid layer (peptidoglycan) that prevents lysis and determines shape.

Bacterial Shapes

Coccus (sphere), bacillus (rod), spirillum/spirochete (spiral), vibrio (comma-shaped).

Bacterial Arrangements

Patterns of cell grouping: diplo-, strepto-, staphylo-, tetrads, sarcinae.

Flagellum

Long whip-like appendage providing motility in bacteria.

Monotrichous Flagella

Single flagellum at one pole.

Lophotrichous Flagella

Tuft of flagella at one pole.

Amphitrichous Flagella

Single flagellum at each pole.

Peritrichous Flagella

Flagella distributed over the entire cell surface.

Fimbriae

Short, numerous filaments for adhesion to surfaces and biofilm formation.

Pilus (Sex Pilus)

Long hollow tube enabling DNA transfer (conjugation) between bacteria.

Glycocalyx

Sticky outer coating (capsule or slime layer) that aids adhesion, evades immunity, and resists dehydration.

Capsule

Dense, well-organized glycocalyx tightly bound to the cell wall; antiphagocytic.

Slime Layer

Loose, easily washed off glycocalyx that helps form biofilms.

Gram Stain

Differential stain separating bacteria into Gram-positive (purple) and Gram-negative (pink) based on cell wall structure.

Gram-Positive

Thick peptidoglycan, teichoic acids, no outer membrane; stains purple.

Gram-Negative

Thin peptidoglycan, outer membrane with LPS; stains pink and often more drug-resistant.

Gram Stain Steps

1) Crystal violet 2) Iodine mordant 3) Alcohol decolorizer 4) Safranin counterstain.

Antimicrobials for Gram (+) vs. Gram (–)

Penicillins/vancomycin target Gram (+); drugs that cross outer membrane (e.g., cephalosporins, polymyxins) for Gram (–).

Cytoplasmic (Cell) Membrane

Phospholipid bilayer that regulates transport, energy reactions, and signal transduction.

Ribosome (Bacterial 70S)

Site of protein synthesis; target of many antibiotics (e.g., tetracyclines).

Nucleoid

Region containing the bacterial chromosome (circular dsDNA).

Inclusion Bodies

Cytoplasmic storage granules (e.g., glycogen, polyphosphate).

Endospore

Dormant, highly resistant bacterial structure produced by Bacillus and Clostridium species.

Eukaryotic Microbes

Fungi, protozoa, algae, and parasitic helminths possessing membrane-bound organelles.

Nucleus

Membrane-enclosed organelle housing eukaryotic DNA.

Endoplasmic Reticulum (ER)

Rough ER synthesizes proteins; smooth ER synthesizes lipids and detoxifies compounds.

Golgi Apparatus

Stacks of cisternae that modify, package, and ship proteins and lipids.

Mitochondrion

Organelle generating ATP by oxidative phosphorylation; contains its own DNA.

Chloroplast

Photosynthetic organelle in algae and plants, containing chlorophyll and thylakoids.

Fungal Cell Wall

Rigid layer primarily composed of chitin and glucans.

Fungal Nutrition

Heterotrophic; absorb nutrients from organic matter (saprophytic or parasitic).

Fungal Reproduction

Asexual spores (conidia, sporangiospores) or sexual spores; yeasts reproduce by budding or fission.

Protozoan Characteristics

Unicellular, lack cell wall, motile via cilia, flagella, or pseudopods.

Protozoan Nutrition

Chemoheterotrophic; ingest particles or absorb nutrients.

Trophozoite

Active, feeding, motile stage of protozoa.

Cyst (Protozoa)

Dormant, resistant stage formed under adverse conditions.

Helminths

Parasitic worms divided into flatworms (platyhelminths) and roundworms (nematodes).

Flatworms (Trematodes & Cestodes)

Leaflike flukes and tapeworms with flattened bodies.

Roundworms (Nematodes)

Cylindrical, unsegmented worms with complete digestive tracts.

Helminth Life Cycle

Egg → larva → adult; often involves intermediate and definitive hosts.

Virus

Obligate intracellular parasite composed of nucleic acid and a protein coat (capsid).

Capsid

Protein shell enclosing viral genome.

Capsomer

Protein subunit that builds the capsid.

Nucleocapsid

Viral genome plus capsid together.

Envelope (Virus)

Lipid membrane derived from host that surrounds some viruses; contains viral glycoprotein spikes.

Spikes (Peplomers)

Viral proteins projecting from envelope or capsid for host attachment.

Icosahedral Virus

Capsid with 20-sided symmetrical structure.

Helical Virus

Rod-shaped capsid arranged in helix around the genome.

Complex Virus

Irregular shape, e.g., bacteriophages with head-tail structure or poxviruses.

Naked Virus

Virus lacking an envelope; more resistant to drying, acids, detergents.

Enveloped Virus

Virus surrounded by lipid envelope; sensitive to solvents, heat, detergents.

dsDNA Virus

Virus with double-stranded DNA genome (e.g., Herpesviridae).

ssDNA Virus

Virus with single-stranded DNA genome (e.g., Parvoviridae).

(+ )ssRNA Virus

Single-stranded RNA that functions as mRNA (e.g., Picornaviridae).

(–) ssRNA Virus

Single-stranded RNA complementary to mRNA; needs RNA polymerase (e.g., Orthomyxoviridae).

dsRNA Virus

Virus with double-stranded RNA genome (e.g., Reoviridae).

Segmented RNA

Genome divided into separate RNA pieces; allows reassortment (e.g., influenza viruses).

Viral Multiplication Stages

Adsorption → Penetration → Uncoating → Synthesis → Assembly → Release.

Cytopathic Effects (CPE)

Visible structural changes in host cells due to viral infection, such as syncytia, inclusion bodies, cell lysis.

Lysogeny

Integration of viral genome (prophage) into bacterial chromosome, imparting new traits (lysogenic conversion).

Latency (Virus)

Dormant state in host where virus persists without producing virions (e.g., HSV in neurons).

Oncovirus

Cancer-causing virus such as HPV, EBV, HBV, HTLV-1.

Bacteriophage

Virus that infects bacteria.

In Vivo

Experimentation inside a living organism.

In Vitro

Experimentation outside a living organism, e.g., in cell culture or test tubes.

Prion

Infectious misfolded protein causing neurodegenerative diseases (spongiform encephalopathies).

Prion Diseases

Creutzfeldt-Jakob disease, bovine spongiform encephalopathy (mad cow), and kuru.

Satellite Virus

Virus requiring a helper virus to replicate (e.g., hepatitis D virus depends on HBV).

Viroid

Infectious, naked circular RNA molecule that infects plants.

Ideal Antimicrobial Characteristics

Selective toxicity, microbicidal, soluble, potent at low dose, stable, non-allergic, inexpensive, limited resistance development.

Bactericidal

Agent that kills bacteria.

Bacteriostatic

Agent that inhibits bacterial growth without killing cells outright.

Selective Toxicity

Ability of a drug to harm the pathogen without harming the host.

Zone of Inhibition (ZOI)

Clear area around an antimicrobial disk where bacteria fail to grow; larger ZOI indicates greater sensitivity.

Minimum Inhibitory Concentration (MIC)

Lowest concentration of a drug that prevents visible microbial growth; lower MIC denotes higher potency.

Therapeutic Index (TI)

Ratio of toxic dose to effective dose; higher TI indicates greater drug safety.

Antimicrobial Modes of Action

1) Inhibit cell wall synthesis 2) Disrupt cell membrane 3) Inhibit protein synthesis 4) Inhibit nucleic acid synthesis 5) Inhibit metabolic pathways.

β-Lactam Antibiotics

Drugs (penicillins, cephalosporins) that block peptidoglycan crosslinking.

Vancomycin

Glycopeptide antibiotic inhibiting cell wall synthesis in Gram (+) bacteria.

Polyenes (Amphotericin B)

Antifungal drugs binding ergosterol to disrupt fungal membranes.

Azoles

Antifungals that inhibit ergosterol synthesis (e.g., fluconazole).

Quinolones/Fluoroquinolones

Antibiotics inhibiting DNA gyrase and topoisomerase IV.

Metronidazole

Drug generating free radicals to treat anaerobic bacteria and protozoa.

Ivermectin

Antihelminthic drug causing paralysis of parasitic worms.

Drug Resistance Mechanisms

Enzymatic drug inactivation, altered target, decreased permeability, efflux pumps, bypass metabolic pathway.