Microbiology Chapter 4

Prokaryote

A cell type characterized by a single circular chromosome not enclosed in a membrane, lacking histones and organelles. Binary diffusion division. Comes from the greek word prenucleus.

Eukaryote

A cell type with paired chromosomes enclosed in a nuclear membrane, containing histones and organelles. Polysaccharide cells walls, when present.

Bacteria Shape

Most bacteria are monomorphic, single shaped, but there are a few that are pleomorphic, many shaped.

Bacteria Shape Types

1. Bacillus (Rod-shaped)

2. Coccus (spherical-shaped)

3. Spiral

   1. Vibrio

   2. Spirillum

   3. Spirochete

4. Star-shaped or rectangle

Vibrio

Type of spiral bacteria

Spirillum

Type of spiral bacteria

Spirochete

Type of spiral bacteria

Different arrangements of bacteria

1. Pairs: Diplo

2. Clusters: Staphylo

3. Chains: Strepto

4. Groups of 4: tetrads

5. Groups of 8: sarcinae

Glycocalyx

A viscous and gelatinous layer external to the cell wall, made of polysaccharides and/or polypeptides, contributing to virulence (AKA Prevents death). There are two types

1. Capsule: neatly organized and firmly attached (common)

2. Slime Layer: Unorganized and loose (less common)

Flagella

Filamentous appendages composed of protein flagellin that propel bacteria and facilitate movement. This part allows bacteria to move toward or away from stimuli.

Flagella three parts

1. Filament: outermost region

2. Hook: attached to the filament

3. Basal body: consists of rod and pairs of rings; anchors flagellum to the cell wall and membrane

Fimbriae

Hairlike appendages on bacteria that assist in attachment to surfaces.

Pili

Appendages involved in bacterial motility and DNA transfer through conjugation phili.

Cell Wall

A protective layer that prevents osmotic lysis (cell explosion), primarily made of peptidoglycan in bacteria. This also contributes to the pathogenicity of bacteria. (ability to causes disease)

Cell wall contains Peptidoglycan

A polymer of repeating disaccharides in rows, NAG then NAM. Rows are linked by polypeptides.

Gram positive cell walls

If the cell walls are thick peptidoglycan and have teichoic acids they will show up as this. There are two rings of basal body of flagella and they produced exotoxins. (high susceptibility to penicillin & lysozyme).

Gram negative cell walls

If the cell walls are thin peptidoglycan, have and outer membrane and a periplasmic space they will show up as this. There are 4 rings of basal body flagella and they produce endotoxins and exotoxins. (Low susceptibility to penicillin)

Teichoic Acids

Lipoteichoic acid link cell wall to plasma membrane, wall teichoic acid links the peptidoglycan. These can carry a charge and basiclaly serve as the finger print of the bacteria (antigenic specificity)

Gram-Negative cell walls (Part 2)

Made of polysaccharides, lipoproteins and phospholipids. Protects bacteria from phagocytes, complement and antibiotics.

Porins

Proteins form channels through membranes, mainly found in gram-negative but can be found in gram positive.

Gram-Stain Process

1. Crystal violet-iodine crystals form inside cell.

2. Alcohol added (either derphdrayte peptidoglycan (positive) or dissolves the outer membrane and leave holes in the peptidoglycan

3. CV-I will either get washed out (negative) or stay (positive).

4. Then safranin is added to stain cells red.

Atypical Cell Walls

Acid-fast cell walls, like gram positive cell walls. Waxy lipid bound to peptidoglycan. There are multiple types including mycoplasmas and archaea.

Mycoplasmas

This type of atypical cells walls: Lack cell walls, sterols in plasma membrane.

Archaea

This type of atypical cell wall is either wall-less or walls of pseudomurein, which lacks the d-amino acid.

Damages cells walls

1. Lysozyme: hydrolyzes bonds in peptidoglycan.

2. Penicillin: Inhibits peptide bridges in peptidoglycan.

Transport Proteins

Peripheral proteins on the membrane surface, Integral and transmembrane proteins penetrate the membrane.

Plasma Membrane

A phospholipid bilayer with embedded proteins that regulates selective permeability and ATP production.

Fluid Mosaic Model

The membrane is a thick fluid, where proteins move freely for various functions. Phospholipids rotate and move laterally and can be self sealing.

Plasma membrane function

It is selectively permeability, collectively contains enzymes for ATP Productions and some membranes have photosynthetic pigments on folding called chromatophores

Ways of Transportation

1. Passive processes: Simple diffusion, Facilitated diffusion, Osmosis.

2. Active Processes: require transport protein

Hypotonic Solution

Solute concentration lower outside then inside

Hypertonic Solution

Solute concentration higher outside then inside.

Cytoplasm

The substance within the plasma membrane, consisting of water, proteins, carbohydrates, lipids, and ions.

Nucleoid

The region in prokaryotic cells containing DNA, including the bacterial chromosome and plasmids. Not a membrane bound structure.

Ribosomes

Sites of protein synthesis, composed of protein and rRNA, with a size of 70S in prokaryotes.

Inclusions

Storage structures within prokaryotic cells for various substances like phosphate and energy reserves.

Endospores

Dormant, resistant cells produced by certain bacteria (e.g., Bacillus, Clostridium) when nutrients are scarce.

Sporulation & Germination

1. Sporulation: Endospore formation

2. Germination: Endospore returns to vegetative state

Flagella and Cilia (eukaryotic)

Consist of microtubules made of protein tubulin. Projections in eukaryotic cells for locomotion or moving substances, with a 9+2 microtubule arrangement.

Cell Wall (Eukaryotic Cells)

Found in plants, algae and fungi. Will be made of carbohydrates, Cellulose, chitin, mannan.

Glycocalyx

Carbohydrates bond to proteins and lipids in the plasma membrane, found in animal cells.

Nucleus

The membrane-bound organelle in eukaryotic cells that contains DNA and is involved in cell division. Double membrane strucutre that contains the DNA. Histone proteins in the to form chromatin.

Plasma Membrane Eukaryotic cells

Both have phospholipid bilayer and intergral/perpheral proteins. They are both selective permeability. The difference is this type have sterols and carbohydrates. Another difference is Endocytosis and phagocytosis.

Endoplasmic Reticulum (ER)

An organelle with rough ER for protein synthesis and smooth ER for synthesizing membranes and hormones.

Golgi Complex

An organelle that modifies and transports proteins via vesicles.

Lysosomes

Organelles containing digestive enzymes for breaking down waste materials.

Vacuoles

Storage organelles in eukaryotic cells that help maintain cell shape.

Mitochondria

Organelles responsible for ATP production, featuring a double membrane with cristae and matrix.

Chloroplasts

Organelles in plant cells that conduct photosynthesis, containing thylakoids with chlorophyll.

Peroxisomes

Organelles that oxidize fatty acids and detoxify harmful substances.

Centrosomes

Structures in eukaryotic cells that contain protein fibers and centrioles, essential for forming the mitotic spindle.