Microbio Test 1 - Cell walls

What is the cell membrane composition?

phospholipids bilayer(hydrophilic heads and hydrophobic tail) and membrane proteins(determine what can come in and out)

What is the cell membranes function?

1. permeability barrier

2. energy production

3. transport

4. enzymatic processes

5. murein synthesis (peptidoglycan)

6. chemotaxis

What is the cell wall’s function?

1. target site for viruses/antibiotics

2. role in pathogenesis (causing disease)

3. distinguish types of bacteria (thickness)

4. required for viability

What is Peptidogylcan?

1. provides structural strength

2. deal with osmotic pressure

3. mesh-like structure

What are the structural characteristics of gram positive cells?

1. Capsule

2. Thick cell wall (peptidoglycan)

3. Teichoic acid molecules span the cell wall

4. Plasma membrane

What is a teichoic acid?

1. only in gram-positive

2. role in cell division, adhesion, and cell shape

What are the characteristics of gram positive cells?

1. more sensitive to antibiotics (because of thick peptidoglycan)

2. not sensitive to physical disruption ( thick peptidoglycan, structural strength )

3. sensitive to lysozomes (not as much protection/more peptidoglycan to eat up)

What is the structure of gram negative cells?

1.capsule

2.outer membrane

3.periplasm

4. small layer of peptidoglycan

5.periplasm

6.inner membrane

gram negative characterisitcs

1. not as sensitive to antibiotics (because of thin layer of peptidoglycan)

2. 2 layers of periplasm (above/below peptido)

3. LPS (outer membrane)

4. porins (outer membrane)

5. more sensitive to physical disruption (peptide is thin)

What is the periplasm?

1. space located between cytoplasmic and outer membrane

2. house proteins

What is the LPS and what does it do?

1. lipopolysaccharide

2. permeability barrier

3. recognition molecule for the immune system during infection( it releases to trigger the system

4. (can be endotoxin during infection)

What are porins?

channels for movement of hydrophilic low-molecular-weight substances

What is simple staining?

single color (stain)

stain all cells one color to make morphology visible

What is differential staining?

using multiple stain colors to differentiate` between two types of cells

What is gram staining?

differentiating bacteria into Gram-positive and Gram-negative, leaving them different colors

gram staining process

1. Flood heat-fixed smear with crystal violet for 1 min

   1. crystal violet bind to peptidoglycan

2. Add iodine solution for 1 min

   1. Binds to crystal violet and traps it

3. Decolorize with Alc for about 20 secs

   1. Gram pos cells are purple and gram neg are colorless (destroy outer membrane)

4. Counterstain with safranin for 1 min

   1. Gram pos cells stay purple and gram neg become pink

What are the gram staining products?

1. gram positive-purple (retains crystal violet because of thick peptidoglycan)

2. gram-negative- pink (violet washes due to thin peptidoglycan and new stain (pink) remains)

exception to gram +/-

gram variables (prokaryotes that lack thick cell walls)

1. mycoplasmas- pathogenic bacteria

2. mycobacterium- complicated cell envelope