Bacterial Morphology Flashcards

Comprehensive vocabulary flashcards covering bacterial morphology, including shapes, arrangements, ultrastructures, and classification based on cell wall composition.

Cocci

Spherical shaped bacteria that appear as round berries (meaning “berries”) and vary in arrangement depending on genus.

Diplococcus

Bacterial cells that come in pairs.

Streptococcus

Bacterial cells arranged in chains.

Staphylococcus

Bacterial cells arranged in irregular clusters, often resembling grapelike clusters.

Sarcina

Cubical packets of cocci bacteria.

Pediococcus

Bacterial cells that form tetrads (groups of four).

Bacilli

Rod shaped or cylindrical shaped bacteria (meaning “little staff”).

Coccobacilli

Bacteria characterized by a broad and long cell that resembles cocci.

Streptobacilli

Bacteria arranged in short or long chains of bacilli.

Palisade arrangement

Bacilli cells that are lined side by side, such as in Corynebacterium diphteriae.

Rosette arrangement

Bacilli arranged like the claw of a cat, such as in Caulobacter.

Spirilla

Spiral or helical-shaped bacteria that are rigid like a corkscrew.

Spirochetes

Flexible, spiral bacteria capable of movement via contraction of flagellum or axial filaments.

Pleiomorphic

Bacteria that possess varied cell shapes.

Micrometer ($\mu m$)

A unit of measurement for bacteria; $1\,\mu m = 10^{-3}\,mm$.

Flagellum

A slender, threadlike structure providing motility; it can propel bacteria at speeds up to $100\,\mu m/second$.

Mordant

A substance used for fixing stain that can also increase the diameter of the flagellum to make it visible under a light microscope.

Monotrichous

A type of flagellation where one flagellum is attached at one end of the cell, such as in Pseudomonas.

Amphitrichous

A type of flagellation where one flagellum is attached at each end of the cell, such as in Spirillum.

Lopotrichous

A type of flagellation where several flagella are attached at one end of the cell.

Peritrichous

A type of flagellation where flagella are attached at any part of the cell, such as in Escherichia coli.

Fimbriae

Shorter, straighter filamentous appendages used for adhesion to other cells or surfaces.

Pili

Appendages that are usually longer and fewer than fimbriae, functioning in the transfer of DNA between cells during conjugation.

Capsule

A slimy layer made of polysaccharides that surrounds the cell wall; it aids in adherence, protects from drying, and prevents engulfment by white blood cells.

Cell wall

A structure accounting for $10 - 40\%$ of a cell’s dry weight that gives shape, rigidity, and protection from osmotic lysis.

Osmosis

The diffusion of water through a selectively permeable membrane.

Isotonic

A medium with equal solutes in the cell and the environment.

Hypotonic

A medium with more solutes inside the cell than in the environment.

Hypertonic

A medium with less solutes inside the cell than in the environment, such as concentrated salt or sugar solutions.

Peptidoglycan (Murein)

A polysaccharide polymer of N-acetylglucosamine and N-acetylmuramic acid that serves as the major structural component of bacterial cell walls.

Gram negative (-) bacteria

Bacteria with a thin cell wall ($10 - 15\,nm$) and a bilayered membrane containing phospholipids and lipopolysaccharides.

Gram positive (+) bacteria

Bacteria with a thicker cell wall ($20 - 25\,nm$) caused by a high amount of peptidoglycan and no outer membrane.

Mesosomes

Invaginations of the cytoplasmic membrane forming tubules used for cell division, DNA replication, enzyme secretion, or photosynthesis.

Nuclear area (Nucleoid)

The region near the center of the bacterial cell consisting of a single, circular chromosome.

Spores

Thick-walled, highly refractile structures resistant to heat, drying, and chemicals; they are metabolically inactive and used for survival rather than reproduction.

Cysts

Dormant, thick-walled structures found in Azotobacter that can resist drying but not high heat.