Chapter 4: A Survey of Prokaryotic Cells and Microorganisms

Vocabulary flashcards covering key terms and concepts from the lecture notes on prokaryotic cells and microorganisms.

Eukaryotic cells

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

Prokaryotic cells

Cells that lack a true nucleus and membrane-bound organelles; include bacteria and archaea.

Glycocalyx

External coating of sugars and/or proteins on some cells; includes slime layer and capsule; protects the cell and aids in attachment.

Slime layer

A loosely organized, easily detachable glycocalyx that helps in protection and adherence.

Capsule

A tightly organized, firmly attached glycocalyx that can enhance virulence by resisting phagocytosis.

Fimbriae

Fine, hairlike projections used for adhesion to surfaces and other cells.

Pili

Rigid tubes made of pilin protein; primarily for DNA transfer (conjugation) and attachment; largely in Gram-negative bacteria.

Flagellum

A long, whip-like structure used for motility; can be arranged in several patterns on the cell.

Monotrichous

Single flagellum located at one end of the cell.

Lophotrichous

A small cluster of flagella emerging from the same site.

Amphitrichous

Flagella present at both ends of the cell.

Peritrichous

Flagella distributed over the entire surface of the cell.

Chemotaxis

Movement toward or away from chemical stimuli.

Phototaxis

Movement toward light.

Run

Counterclockwise rotation of flagella resulting in a smooth, linear movement.

Tumble

Clockwise rotation of flagella causing reorientation.

Cell membrane

Phospholipid bilayer with embedded proteins; fluid mosaic; selectively permeable; site of energy reactions and transport.

Cell wall

Rigid layer outside the cytoplasmic membrane; provides shape and protection; composition varies by Gram type.

Gram-positive bacteria

Bacteria with a thick peptidoglycan layer and teichoic/lipoteichoic acids; no outer membrane.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer and an outer membrane containing LPS; periplasmic space present; porins in the outer membrane.

Peptidoglycan

A cross-linked polymer of sugars and short peptides forming the rigid layer of most bacterial cell walls.

Teichoic acid

Anionic polymers in Gram-positive cell walls that help maintain wall structure and transport cations.

Lipoteichoic acid

Teichoic acids anchored in the cell membrane of Gram-positive bacteria.

Muramic acid

A component of peptidoglycan found in bacterial cell walls (not in eukaryotic cells).

Periplasmic space

The gap between the inner membrane and the cell wall in Gram-negative bacteria.

Outer membrane

An extra membrane in Gram-negative bacteria containing LPS and porins.

Lipopolysaccharides (LPS)

Endotoxin-containing molecules in the outer membrane of Gram-negative bacteria; can trigger strong immune responses.

Porin proteins

Protein channels in the outer membrane that regulate molecule passage.

Nucleoid

Region in bacteria where the chromosome is located; not enclosed by a membrane.

Chromosome

A single, circular, double-stranded DNA molecule containing the cell’s genetic information.

Plasmids

Small, circular DNA molecules that are not essential for growth but can transfer between cells and are often used in genetic engineering.

Bacterial ribosome

Ribosome in bacteria; composed of rRNA and protein in two subunits; 70S total (50S + 30S).

Inclusions and granules

Intracellular storage bodies that vary in content and help the cell survive nutrient scarcity.

Cytoskeleton

Internal network of protein filaments in some bacteria that supports shape and division.

Endospore

Dormant, highly resistant cell produced by some Gram-positive genera; extremely tough and long-lasting survival.

Sporulation

Formation of endospores in response to adverse conditions.

Germination

Return of an endospore to a metabolically active vegetative cell when conditions improve.

Clostridium

Gram-positive genus that forms endospores.

Bacillus

Gram-positive genus that forms endospores.

Sporosarcina

Gram-positive genus that forms endospores.

Bacterial shapes

Coccus (sphere), Bacillus (rod), Coccobacillus (short/oval), Vibrio (curved), Spirillum (spiral), Spirochete (corkscrew).

Pleomorphism

Variation in cell shape and size within a single species (e.g., Mycoplasma).

Bacterial arrangements

Patterns of division/attachment: singles, diplococci, tetrads, chains, sarcina, diplobacilli, palisades.

Domain Archaea

Archaea; adapted to extreme habitats and diverse nutrition modes.

Domain Bacteria

Bacteria domain; includes phyla such as Proteobacteria (Gram-negative), Firmicutes (Gram-positive), Actinobacteria (Gram-positive).

Proteobacteria

Phylum of Gram-negative bacteria.

Firmicutes

Phylum of mostly Gram-positive bacteria.

Actinobacteria

Phylum of Gram-positive bacteria with high G+C content.

Gram stain

Differential stain distinguishing Gram-positive (purple) from Gram-negative (red/pink) bacteria; aids in classification and treatment.

Acid-fast stain

Stain for Mycobacterium and Nocardia due to mycolic acids in their cell walls; not detected reliably by Gram stain.

Mycobacterium

Genus with mycolic acid in the cell wall; acid-fast and often resilient to chemicals.

Nocardia

Genus with mycolic acids; acid-fast organisms causing infections.

Mycoplasma

Bacteria lacking a cell wall; stabilized by sterols; pleomorphic.

Cord factor

Toxic mycobacterial lipid (trehalose dimycolate) associated with virulence and serpentine “cord” appearance.

Biofilm

Community of microorganisms attached to a surface, embedded in an extracellular matrix including glycocalyx.

Gram staining steps

Sequence: crystal violet, iodine (mordant), alcohol (decolorizer), safranin (counterstain); different retention distinguishes cell walls.

Universal phylogenetic tree

Diagram showing evolutionary relationships among all domains of life.