The Bacterial Cell

Vocabulary flashcards covering key terms related to bacterial cell structure, genetics, envelopes, appendages, and physiology.

Cell Theory

Idea that all living things are made of cells and all cells arise from pre-existing cells.

Prokaryotic Cell

Cell lacking a membrane-bound nucleus and organelles; bacteria and archaea.

Eukaryotic Cell

Cell with a membrane-bound nucleus and organelles; plants, animals, fungi, protists.

Nucleoid

Dense, non-membrane region in bacteria where the single circular chromosome is located.

Plasmid

Small circular DNA molecule in bacteria that carries non-essential but often advantageous genes.

Genetic Recombination

Exchange of genetic material that creates new gene combinations on a chromosome.

Vertical Gene Transfer

Passing of genes from parent to daughter cells during binary fission; no recombination.

Horizontal Gene Transfer

Movement of genes between independent bacterial cells; involves recombination.

Transformation

Uptake of free DNA from the environment by a competent bacterial cell.

Conjugation

Direct plasmid DNA transfer between bacteria via a pilus.

Pilus (pl. pili)

Rigid tubular appendage used mainly for DNA transfer during conjugation.

Bacteriophage

Virus that infects bacteria; can mediate DNA transfer (transduction).

Transduction

Horizontal gene transfer in which a bacteriophage carries DNA from one bacterium to another.

Competent Cell

Bacterium capable of taking up extracellular DNA during transformation.

Antibiotic Resistance Gene (R Factor)

Plasmid-borne gene that enables bacteria to survive antibiotic treatment.

Virulence Gene

Gene that enhances a pathogen’s ability to cause disease (e.g., toxin gene).

Cocci

Spherical bacterial cells.

Bacilli

Rod-shaped bacterial cells.

Spirilla

Rigid spiral-shaped bacteria, usually with flagella.

Coccobacilli

Very short rods that resemble spheres.

Vibrios

Slightly curved rod-shaped bacteria (comma-shaped).

Spirochetes

Flexible, corkscrew-shaped bacteria with internal flagella.

Glycocalyx

Polysaccharide/protein coating outside bacterial cell wall; includes capsules and slime layers.

Slime Layer

Loose, unorganized glycocalyx easily washed off.

Capsule

Dense, well-organized glycocalyx firmly attached to the cell wall.

Biofilm

Community of microbes attached to a surface and embedded in a self-produced matrix.

Peptidoglycan

Mesh-like polymer of sugars and amino acids forming the bacterial cell wall.

Gram-Positive Bacteria

Bacteria with thick peptidoglycan cell wall; retain crystal violet stain (purple).

Gram-Negative Bacteria

Bacteria with thin peptidoglycan layer and outer membrane; stain pink with safranin.

Teichoic Acids

Polymers in Gram-positive walls that reinforce structure and aid adherence.

Porins

Protein channels in the outer membrane of Gram-negative bacteria that allow molecule passage.

Periplasmic Space

Region between inner and outer membranes in Gram-negative cells containing enzymes and peptidoglycan.

Cell Membrane (Plasma Membrane)

Phospholipid bilayer with proteins that regulates entry and exit of substances.

Endospore

Dormant, highly resistant bacterial structure formed under harsh conditions.

Sporulation

Process of endospore formation.

Germination

Return of an endospore to active vegetative growth when conditions improve.

Flagellum

Long helical appendage that rotates to provide bacterial motility.

Run and Tumble

Movement pattern where counter-clockwise rotation causes straight runs and clockwise rotation causes tumbles.

Taxis

Directed bacterial movement toward or away from a stimulus.

Chemotaxis

Movement in response to chemical gradients.

Phototaxis

Movement in response to light.

Thermotaxis

Movement in response to temperature changes.

Fimbriae

Short, bristle-like protein appendages that help bacteria adhere to surfaces and each other.

Ribosome (Prokaryotic)

70S particle composed of 30S and 50S subunits; site of protein synthesis.

Thylakoid (in Cyanobacteria)

Plasma membrane fold containing chlorophyll for photosynthesis.

Inclusion Bodies

Non-membrane storage granules for nutrients such as glycogen or gas vesicles.

Cytoplasm

Gel-like interior of the cell composed of water, salts, sugars, and proteins.

Cell Envelope

Collective term for glycocalyx, cell wall, and cell membrane surrounding a bacterium.