Bacterial Cell Anatomy, Ribosomes, Endospores, and Flagellar Motility

Flashcards covering bacterial ribosome sizes, internal organelles, endospore characteristics, flagellar arrangements, and mechanisms of motility.

Prokaryotic Ribosome

A $70\,S$ total ribosome composed of a $50\,S$ large subunit and a $30\,S$ small subunit.

Eukaryotic Ribosome

An $80\,S$ total ribosome composed of a $60\,S$ large subunit and a $40\,S$ small subunit.

Svedberg Units ($S$)

Units of measurement for ribosome subunit sizes that are non-additive, where larger values represent larger subunits.

Nuclear Region (Nucleoid)

The non-membrane-bound cytoplasmic region in a prokaryote containing the major genomic material, typically consisting of one double-stranded circular chromosome.

Plasmids

Small, double-stranded, usually circular pieces of DNA that exist separately from the bacterial chromosome and float freely in the cytoplasm.

Photosynthetic Organelles in Cyanobacteria

Internal membrane-bound structures housing photosynthetic pigments to protect them from degradation by cytoplasmic components.

Nitrogen-Fixing Organelles

Membrane-bound vesicles in nitrogen-fixing bacteria that maintain an oxygen-free environment to prevent oxygen from destroying sensitive nitrogen-fixation enzymes.

Gas Vesicles

Internal membrane structures containing gases or low-density proteins that allow bacteria to regulate buoyancy and float at desired water depths.

Cladosporium

A fungus that co-inhabits flat white vinyl roofs with cyanobacteria and produces enzymes capable of degrading vinyl material.

Endospores

Extremely hardy, heat-resistant, non-reproductive resting state structures produced by a small subset of Gram-positive bacteria to outlast harsh conditions.

Resting State Spore

A survival-focused spore formed at a maximum ratio of one spore per cell, germinating into a single cell without increasing the overall organism count.

Bacillus anthracis

A Gram-positive endospore-forming bacterium that causes anthrax, capable of inducing fatal lung or intestinal infections when its endospores are inhaled or ingested.

Polar Monotrichous

A flagellar arrangement consisting of a single flagellum located at one end of the cell.

Peritrichous

A flagellar arrangement characterized by dozens of flagella distributed across the entire surface of the cell, as seen in Salmonella and Proteus.

Flagellin

The protein subunit that locks together to construct the filament portion of a bacterial flagellum.

Flagellar Motor

A protein-based rotary structure spanning the cell envelope that utilizes hydrogen ions via proton motive force to turn the flagellum.

Run

A bacterial swimming motion produced when the flagellar motor turns in a direction that locks flagellins into a rigid, functional corkscrew shape.

Tumble

A brief, random reorientation event that occurs when the flagellar motor reverses direction, causing the flagellum to bundle up and loosen.

Chemotaxis

Bacterial movement in response to chemical gradients, directing the cell toward nutrients or away from toxic substances.

Phototaxis

Directed movement or positioning of a cell or organism in response to light intensity.