Chapter 4: Bacteria and Archaea Vocabulary

Vocabulary practice flashcards covering bacterial structures, appendages, cell envelopes, internal organelles, and characteristics from Chapter 4.

Pleomorphism

Variations in size and shape among cells of a single bacterial species due to nutritional or slight genetic differences.

Thiomargarita namibiensis

A large bacterium ranging in size from $100\text{ to }750\,\mu m$, making it visible to the naked eye.

Sarcina

A cellular arrangement consisting of a cubical packet of $8$, $16$, or more cocci cells.

Monotrichous

A flagellar arrangement featuring a single flagellum attached at one end of the cell.

Lophotrichous

A flagellar arrangement characterized by small bunches or tufts of flagella emerging from the same site.

Amphitrichous

A flagellar arrangement featuring flagella attached at both poles of the cell.

Peritrichous

A flagellar arrangement where flagella are dispersed randomly over the surface of the cell.

Periplasmic flagella (axial filaments)

Two or more long, coiled threads located in the periplasm of spirochetes that impart a corkscrew movement allowing the bacterium to flex through tissue.

Pilus

An appendage used for drawing another bacterium close in order to transfer DNA in a process called conjugation.

Nanowires (nanotubes)

Thin tubular membrane extensions that allow bacteria to transmit electrons or nutrients to other bacteria or onto environmental surfaces.

S layer

A protective single layer composed of thousands of copies of a single protein linked together, produced only in hostile environments.

Capsule vs. Slime Layer

A capsule is a dense, tightly bound coating that helps bacteria avoid phagocytosis and enhances virulence, while a slime layer is loose, easily removed, and protects against loss of water and nutrients.

Biofilms

Microbial habitats where microorganisms live in cooperative associations bound together by sticky extracellular matrix deposits on moist surfaces.

Cell envelope

The multi-layered protective outer structure of a bacterium composed of the cell wall, cytoplasmic membrane, and in Gram-negative bacteria, an outer membrane.

Peptidoglycan

A unique macromolecule in bacterial cell walls consisting of alternating strands of N-acetyl glucosamine (G) and N-acetyl muramic acid (M) cross-linked by short peptide chains.

Teichoic and lipoteichoic acids

Acidic polysaccharides located in Gram-positive cell walls that function in cell wall maintenance, enlargement during cell division, and imparting an acidic charge to the surface.

Lipopolysaccharide (LPS)

The complex molecule located in the outer membrane layer of Gram-negative bacteria made of Lipid A (endotoxin) and O polysaccharide (O antigen).

Lipid A

The endotoxin component of lipopolysaccharide in Gram-negative bacteria that stimulates fever and medical shock.

Porins

Membrane channel proteins in the Gram-negative outer membrane that alter their size to control the passage of materials such as antibiotics.

Mycolic acid

A unique long fatty acid chain (cord factor) present in the cell wall of acid-fast bacteria like Mycobacterium and Nocardia that contributes to pathogenicity and chemical resistance.

Mycoplasmas

True bacteria that naturally lack a cell wall and possess a cell membrane resistant to lysis.

Nucleoid

The dense area within a bacterial cell containing condensed DNA molecules and a single circular chromosome without a nuclear membrane.

Plasmid

A double-stranded circle of extra-chromosomal DNA containing nonessential genes.

Prokaryotic Ribosome

A $70S$ structure composed of protein and RNA, made of a $50S$ large subunit and a $30S$ small subunit, responsible for protein synthesis.

Inclusions

Membrane-bound intracellular packets used to store energy-rich nutrients deposited during times of abundance.

Granules

Non-membrane-bound dense crystalline deposits inside bacterial cells storing inorganic compounds such as phosphate or sulfur.

Bacterial microcompartments

Protein-coated packets used to localize enzymes and other proteins in the cytoplasm.

Endospore

A dormant, highly resistant body formed within certain Gram-positive bacteria that enables survival under hostile environmental conditions.

Sporulation

The process of spore formation induced in endospore-forming bacteria by adverse environmental conditions.

Serotype (serovar)

Representatives of a bacterial species that stimulate a distinct pattern of antibody responses due to specific surface molecules.