Unit 4: General Characteristics of Bacteria

Comprehensive vocabulary flashcards covering the general characteristics, morphology, cell structure, transport mechanisms, and appendages of bacteria based on the Unit 4 lecture notes.

Eukaryotes

Organisms whose DNA is found in the cell's nucleus separated by a nuclear membrane, associated with chromosomal proteins called histones, and arranged in multiple chromosomes.

Prokaryotes

Organisms where DNA is not enclosed within a membrane and is usually a singular circularly arranged chromosome, lacking membrane-enclosed organelles like mitochondria or Golgi apparatus.

Binary Fission

The process by which prokaryotes usually divide, involving DNA copying and the cell splitting into two cells.

Peptidoglycan (Murein layer)

A complex polysaccharide macromolecule found in the cell walls of almost all prokaryotes that gives the cell shape and strength.

Bacterial Size Range

Most clinically relevant bacterial species range from $0.25$ to $1\,\mu m$ in width and $1$ to $3\,\mu m$ in length.

Cocci

Bacteria with a circular morphology, such as Staphylococci.

Bacillus

Bacteria that are rod-shaped, for example Bacillus anthracis.

Pleomorphic

Bacteria that have no defined shape, often due to variations in their cell envelope or weak cell walls.

Outer Membrane

A bilayered structure found only in gram-negative bacteria composed of lipopolysaccharide that acts as a primary permeability barrier.

Porins

Water-filled protein structures scattered throughout the lipopolysaccharide that control the passage of nutrients and other solutes through the outer membrane.

Murein Lipoproteins

Proteins that facilitate the attachment of the outer membrane to the peptidoglycan layer in gram-negative microorganisms.

Lipopolysaccharide (LPS) Regions

Composed of three regions: O-specific polysaccharide (antigenic), Core polysaccharide ($KDO$ and heptose), and Lipid A (endotoxin).

Lipid A

The inner, major constituent of LPS responsible for producing fever and shock conditions in patients infected with gram-negative bacteria.

N-acetyl-D-glucosamine (NAG) and N-acetyl-D-muramic acid (NAM)

The alternating disaccharide-pentapeptide subunits that compose the structure of the murein layer.

Mycolic Acid

A strong hydrophobic molecule consisting of glycolipids and fatty acids that forms a lipid shell around Mycobacterium and Nocardia, determining their acid-fast staining reaction.

Teichoic Acid

Glycerol or ribitol phosphate polymers anchored to the peptidoglycan (NAM) in gram-positive cell walls.

Lipoteichoic Acid

A component of gram-positive cell walls that is anchored to the plasma membrane.

Periplasmic Space

A gel-like matrix found only in gram-negative bacteria between the outer and inner membranes containing nutrient-binding proteins and enzymes.

L-forms

Gram-positive and gram-negative cells that have lost their cell walls and grow in media supplemented with serum or sugar to prevent osmotic rupture.

Simple Diffusion

A passive transport process relying on a concentration gradient for the entry of very few nutrients like oxygen, carbon dioxide, and water.

Symport

A type of ion-coupled active transport involving the simultaneous transport of two substrates in the same direction by a single carrier.

Antiport

The simultaneous transport of two like-charged compounds in opposite directions by a common carrier.

Bacterial Ribosomes

The site of protein biosynthesis, measuring $70S$ in size and separating into $50S$ and $30S$ subunits.

Plasmid

An extrachromosomal, double-stranded DNA element associated with virulence, antibiotic resistance, and toxin production.

Babes-Ernst bodies

Specific polyphosphate granules found in Corynebacterium diphtheriae that serve as a storage form of inorganic phosphates.

Endospores

Small, dormant structures produced within vegetative cells of some Gram-positive bacteria, composed of calcium dipicolinate, meant for survival against external conditions.

Capsule

An organized glycocalyx firmly attached to the cell wall that protects bacteria from phagocytosis and desiccation.

Flagellin

The globular protein arranged in intertwining chains that forms the filament of the bacterial flagellum.

Monotrichous

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

Peritrichous

A flagellar arrangement where the entire cell surface is covered with flagella.

Axial Filaments (Endoflagella)

Bundles of fibrils that arise at the ends of the cell beneath an outer sheath and allow spirochetes to move in a spiral motion.

Brownian Movement

The rapid back and forth bouncing of bacteria caused by the bombardment of water molecules, distinguished from true motility.

Pili (Fimbria)

Hair-like proteinaceous microfibrils composed of pilins that serve as adhesins for attachment to host cell surfaces.

Sex Pilus

A hollow conduit that facilitates the passage of DNA from a donor (F-positive) cell to a recipient (F-negative) cell during conjugation.