Microorganisms: prokaryotic vs eukaryotic

Prokaryotes (Bacteria)

Nucleus: Absent (Nucleoid region; no nuclear membrane)

Genome: Single, circular DNA chromosome

Ribosomes: 70S (50S + 30S)

Cell Wall: Contains Peptidoglycan

Cell Membrane: Does not contain sterols (Exception: Mycoplasma)

Organelles: Absent (No mitochondria, Golgi, or ER)

Reproduction: Asexual (Binary fission)

Eukaryotes (Fungi, Parasites, Human Cells)

Nucleus: Present (True nucleus with nuclear membrane)

Genome: Multiple, linear DNA chromosomes

Ribosomes: 80S (60S + 40S)

Cell Wall: Fungi: Chitin; Humans: No cell wall

Cell Membrane: Contains sterols (Fungi: Ergosterol; Humans: Cholesterol)

Organelles: Present

Reproduction: Sexual (Meiosis) and As*xual (Mitosis)

Cellular Membrane

Phospholipid bilayer; follows Fluid Mosaic Model

Gas Vacuole

• - Not present in all; present in cyanobacteria

• - For floating/buoyancy effect

Cytoplasm

Fluid matrix of the prokaryotic cell

Nucleus/Nucleoid

Composed of genetic material of the cell

Ribosomes

Site of protein synthesis (30s, 50s)

Endospore

Dormant/resistant form of bacteria

Sporogenesis

Spore-staining

Dormant/resistant form of bacteria

Bacillus (G+) and Clostridium (G-)

Sporogenesis

Happens when environment is lacking/deficient of nutrients

Spore-staining

Primary stain: Malachite green; VR: Green

• Bacillus: Non-swollen • Clostridium: Swollen

Plasmids

Extrachromosomal genetic material for advantages

“R Plasmid

Responsible for most of antimicrobial resistance

F plasmids

Genes to form Sex Pilus, which is essential for bacterial genetic transfer

Teichoic Acid

• Only found in G (+) bacteria

• Lies outside cell membrane

Wall Teichoic Acid (WTA)

embedded in peptidoglycan

Membrane Teichoic Acid/Lipoteichoic Acid (MTA)

embedded in membrane

Function

• Antigen: Responsible for antibody production

• Negative surface of G (+) bacteria (where Crystal violet reacts)

Cell wall

Primary component: Peptidoglycan (Murein)

• Penicillin Binding Proteins

• N-acetylmuramic acid (NAM)

• N-acetylglucosamine (NAG)

Gram (+)

Thicker peptidoglycan layer

Gram (-)

• Thinner (1-2 layers)

• More complex (Outer membrane, periplasmic space, lipopolysaccharide A)

Periplasmic Space

• o G (-) bacteria

• o Contains hydrolytic enzymes (which may destroy antibiotics) = harder to treat

Glycocalyx

Extracellular polysaccharide materials that surrounds the cell membrane

Capsule

• Firmly attached to the bacterial cell

• Excludes particle

• Organized structure

• Function: Bacterial virulence

• Able to escape phagocytosis (Neutrophils: acute; Macrophage: chronic)

• Harder to treat

Slime Layer

• Slime Layer

• Loosely attached

• Does not exclude particle

• Unorganized structure

• Function: • Bacterial attachment • Ex. P. aeruginosa, S. epidermidis

Glycocalyx: General functions

• Virulence (capsule)

• Attachment (slime layer)

• Protection

• Food reservoir

Flagella

• Used for movement/locomotion

• Monotrichous: single, polar flagella at one end

• Lophotrichous: tuft of flagella at one end

• Amphitrichous: single, polar flagella at both ends

• Peritrichous: flagella all over the cell

Pili

Rigid, hairlike structures that are usually found in G (-) bacteria

• Ordinary Pili (Fimbriae): Attachment

• Sex Pili: Bacterial Conjugation

Axial Filament

• For spiral motion

• Found in spirochetes

• Treponema pallidum: Syphilis

• Leptospira interrogans: Leptospirosis

• Borrelia burgdorferi: Lyme disease

• Borrelia recurrentis: Relapsing fever

Reproduction

Binary Fission: Primary means of Asexual Reproduction for prokaryotic cell

PROKARYOTES

NUCLEOID REGION (Genetic Material Storage):

• DNA floats freely in cytoplasm (no membrane boundary)

• Concentrated area called nucleoid (not membrane-bound)

• Single, circular chromosome (most prokaryotes)

• May contain “plasmid” (small, circular DNA) • No histones (unlike eukaryotes)

Domain Bacteria

• Small in size does not possess important organelles (golgi apparatus, mitochondria, nuclear membrane, endoplasmic reticulum)

• Possess a cell wall: PEPTIDOGLYCAN (aka Murein)

• Protection against osmotic gradient

Domain Archaea

• Does not possess a cell wall

• Nonpathogenic

• Live in extreme environments

EUKARYOTES

• Membrane-bound nucleus (nuclear envelope = double membrane)

• Multiple membrane-bound organelles

• Multiple, linear chromosomes (vs. prokaryotic single circular chromosome)

• Larger cell size: 10-100 μm diameter

• Compartmentalization of cellular functions

Kingdom Fungi

• Mostly multicellular (except yeasts, which are unicellular).

• Heterotrophic, primarily saprophytic (decomposing organic matter).

• Possess cell walls made of chitin.

Kingdom Plantae (Plants/Algae)

• Multicellular organisms.

• Autotrophic (photosynthetic) using chlorophyll.

• Possess cell walls made of cellulose.

• Generally non-motile.

Kingdom Animalia

• Multicellular organisms.

• Heterotrophic (obtain food by consuming other organisms).

• Lack cell walls.

• Most are motile at some stage of their life cycle.

Kingdom Protista

• Mostly unicellular, but some are multicellular.

• Can be autotrophic or heterotrophic.

• Very diverse group with varying characteristics.