Bacteria

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Prokaryote Noun

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[pro-kar-ee-oht]

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Prokaryote

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A unicellular organism lacking a nucleus and membrane-bound organelles, classified within the domains Archaea or Bacteria.

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Example: This diagram shows the structure of a bacterium, a key example of a prokaryote. It highlights the nucleoid area, where DNA is located without a surrounding nucleus.

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Archaea Noun

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[ahr-kee-uh]

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Archaea

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A domain of single-celled prokaryotes with a distinct evolutionary history and unique biochemistry compared to bacteria.

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Example: This diagram shows the labeled parts of an archaean cell, including its DNA in the nucleoid, ribosomes, cell wall, and a flagellum for movement.

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Bacteria Noun

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[bak-teer-ee-uh]

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Bacteria

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A domain of diverse, single-celled prokaryotic microorganisms that are the most abundant organisms on Earth.

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Example: This image shows the three main shapes of bacteria: spherical (cocci), rod-shaped (bacilli), and spiral (spirilla), which is a key way to classify them.

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Spirilli Noun

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[spy-ril-ee]

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Spirilli

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A classification for prokaryotic cells that are characterized by their helical or spiral shape.

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Example: This diagram shows that Spirilli are spiral-shaped bacteria that are rigid and have a wavy or corkscrew appearance, often with flagella for movement.

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Cocci Noun

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[kok-sahy]

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Cocci

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A classification for prokaryotic cells that are characterized by their spherical or round shape.

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Example: This image shows the spherical (ball-like) shape of cocci bacteria, which is their main identifying feature.

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Bacilli Noun

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[buh-sil-ahy]

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Bacilli

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A classification for prokaryotic cells that are characterized by their rod-like shape.

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Example: This diagram shows a bacillus, a type of bacterium with a rod-like shape, and labels its key parts like the cell wall and flagellum.

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Gram staining Noun

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[gram steyn-ing]

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Gram staining

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A laboratory technique used to differentiate bacteria into two groups based on their cell wall composition.

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Example: Gram staining is a lab technique that uses dyes to show a key difference between types of bacteria, staining Gram-positive bacteria purple and Gram-negative pink.

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Gram-positive Adjective

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[gram poz-i-tiv]

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Gram-positive

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Describing bacteria with a thick cell wall that retains a purple dye during the Gram staining procedure.

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Example: Gram-positive bacteria have a thick outer layer of peptidoglycan above their cytoplasmic membrane, which helps them retain a specific stain.

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Gram-negative Adjective

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[gram neg-uh-tiv]

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Gram-negative

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Describing bacteria with a thin cell wall and outer membrane that stains red in a Gram stain.

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Example: This diagram shows the layers of a Gram-negative bacterium's cell wall, which has a thin peptidoglycan layer between an inner and outer membrane.

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Cell Wall Noun

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[sel wawl]

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Cell Wall

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A rigid protective layer located outside the plasma membrane of prokaryotic cells, providing structural support and protection.

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Example: This diagram shows the cell wall as the rigid outer layer that provides structure and a fixed, boxy shape to these onion (plant) cells.