Bacterial Cell Morphology and Composition

Vocabulary-style flashcards covering the morphology, composition, and structural differences of prokaryotic and eukaryotic cells as presented in the lecture.

Eukaryotic cells

Plant and animal cells that are more complex and contain many organelles, such as chloroplasts.

Prokaryotic cells

Unicellular organisms like bacteria, blue green algae, microplasmas, and spiral/spiroids.

Histones

Proteins required for mitotic division and DNA coiling which are absent in bacteria.

Binary fission

The process of asexual reproduction through which bacteria reproduce.

Thiomargarita

The largest known bacterium, measuring $350\,\mu\text{m}$.

Nanobacteria

The smallest known bacterium, measuring $0.02\,\mu\text{m}$.

Peptidoglycan

Also known as murein or mucopeptide; a polymer of disaccharides linked by polypeptides that makes up more than $50\%$ of a gram-positive cell wall's dry weight.

$\beta(1,4)$ linkage

The type of linkage between hexagons (glucosamine) in the peptidoglycan subunit that provides strength and is hard to break.

Teichoic Acids

Polymers of glycerol or ribitol joined by phosphates found in gram-positive cell walls; responsible for gram-positivity and inhibiting autolytic enzymes.

Mycolic acids

Waxy lipids found in Mycobacterium responsible for the acid-fast test (AFT).

Periplasmic Space

The gap between the plasma membrane and cell wall in Gram-positive bacteria, or between the plasma membrane and outer membrane in Gram-negative bacteria.

Lipopolysaccharides (LPS)

Components of the gram-negative outer membrane acting as endotoxins responsible for toxicity and symptoms like fever and chills.

Lipid A

The hydrophobic part of LPS embedded in the membrane, composed of $2$ glucosamine residues linked $\beta(1,6)$ with four fatty acids.

O-Antigen

A short polysaccharide extending outward from the LPS core that helps avoid host defenses and varies between bacterial strains.

Braun's lipoprotein

A protein that mediates the interconnection between the outer membrane (OM) and murein in gram-negative bacteria.

Porins

Transmembrane proteins that form small hydrophilic channels allowing the diffusion of neutral and charged solutes with a molecular weight $<\,600\,\text{daltons}$.

Hopanoids

Rigid, planar molecules found in the bacterial cytoplasmic membrane that serve a similar function to cholesterol.

Fluid Mosaic Model

The widely accepted model of the cell membrane showing it as a lipid bilayer where proteins and lipids float freely.

Crescentin

Intermediate filament proteins that help determine cell shape.

FtsZ

A tubulin-like protein in the prokaryotic cytoskeleton involved in cell division.

MreB

An actin-like protein in the prokaryotic cytoskeleton involved in maintaining cell shape.

Mesosomes

Invaginations of the plasma membrane involved in cell septum formation, DNA replication, and sporulation.

Carboxysomes

Polyhedral bodies containing the enzyme ribulose-$1,5$-bisphosphate carboxylase, serving as sites for $CO_2$ fixation in photosynthetic bacteria.

Volutin (Metachromatic granules)

Linear polymers of orthophosphates used as storage reservoirs for phosphates or energy reserves.

Magnetosomes

Intracellular chains of magnetite or pyrite particles that aid in orienting bacteria in the earth's magnetic field.

Capsule

A well-organized, rigid glycocalyx firmly attached to the cell wall that excludes particles like India ink and provides resistance to phagocytes.

Slime layer

A zone of diffused, unorganized, and loose material outside the cell wall that represents a loose association of the glycocalyx.

Conjugation pili

Vehicles for the transfer of genetic information between bacteria, often referred to as bacterial cell mating.

Atrichous

A term used to describe bacteria that have no flagella.

Monotrichous

A flagellar arrangement featuring a single flagellum at one end, resulting in a tumbling or corkscrew movement.

Endospore

A cryptobiotic, highly resistant dormant cell formed by some bacteria as a mechanism for survival in response to environmental stress.