Bacteriology- overview

Question 1

Understand and differentiate the morphology of common bacteria: Cocci, bacilli, spirochete

Answer 1

Cocci: round

Bacilli: rod-shaped

Spirochete: corkscrew

Question 2

Know the difference between a prokaryotic and eukaryotic cell

Answer 2

Prokaryotic

• CELL WALL
• no membrane bound organelles
• no nuclear membrane
• dna- single (often round plasmid)
• replicate by binary fission

Eukaryotic

• NO CELL WALL
• membrane bound organelles
• nuclear membrane and nucleolus
• dna-chromisome
• replicate by mitosis

Question 3

Bacterial cell structure: name and describe elements of…

• Appendages (2)
• Cell envelope (3)
• Cytoplasmic content (2)

Answer 3

Bacterial Cell Structure

Appendages (not present in all bacteria)

• Flagella-long and flowy and present in motile bact.
• Pili (fimbriae)- short and hair-like and help cell adhere to stuff

Cell envelope= entire outer part of cell

• capsule-outer most layer of cell. protects cell. polysaccharide
• cell wall-middle outer layer. rigidity
• plasma membrane- inner outer layer. permeability barrier

Cytoplasmic content

• chromisomes- genetic material of cell in nucleoid
• ribosomes- protein synthesis

Question 4

Describe differences in cell wall structure between gram positive and negative bacteria

Answer 4

Gram-positive cell wall

• layer 1: capsule
• layer 2: thick layer of peptidogylcan (murein)
• layer 3. plasma membrane
• techoic acids: run perpendicular to petidoglycan sheets

Gram-negative cell wall

• layer 1: capsule
• layer 2: phospholipid-lipopolysaccharide outer membrane
• layer 3: thin peptidoglycan sheet
• layer 4: plasma membrane

***the space between outer membrane and plasma membrane where peptidoglycan layer is is called periplasm.

Question 5

Know details about LPS

• location
• structure
• function

Answer 5

LPS = endotoxin = Lipopolysaccharide

Location- outer membrane of gram-negative cell wall

Structure- lipid head (inside membrane) with polysaccharide tail (outside cell)

• Lipid A- toxic portion of molecule. causes fever, hemmorage and shock.
• polysaccharide- responsible for antigenic properties (how immune system will respond)

** O-specific polysaccharide may be part that provides adherence

Question 6

Discuss bacterial chromosomes

Answer 6

Bacterial Chromisomes

• haploid circular chromosome of DNA (nucleoid)
• small extrachromosomal pieces of DNA= plasmids
• chromisome is genetic control center of cell

Question 7

Endospore

(structure/function)

Answer 7

Endospore= dormant form of a bacteria.

Structure (outer to inner)

• Exosporium
• Spore coat
• Cortex
• Core wall-dipicolinic acid
• INSIDE- ribosomes and chromisome

Function

• dormant form that bacteria can take on when conditions are not correct
• allows some bacteria to stay dormant for years before regermination
• the dehydrated core contains chromosome and ribosomes

Question 8

Capsule function

Answer 8

Capsule function

• adherence
• resistance to phagocytic cells
• antibody and drug resistance
• reserve of nutrients
• protection against drying

Question 9

How would you technically determine gram+ or gram-?

Answer 9

evaluate the components of the cell wall.

Gram +

• Thick wall
• 1 layer
• lots of peptid
• techoic acids
• NO LPS
• sensative to penicillin
• sensative to lysozyme

Gram -

• Thin wall
• 2 layers
• less peptid
• NO techoic acids
• LPS
• not sensative to penicillin
• not sensative to lysozyme

Question 10

Cell wall function

Answer 10

Cell wall function

• prevents damage to PROTOPLAST
• contains receptor sites for drugs and ligands for adherence
• components responsible for symptoms
• provides immonological distinction among strains of bact.
• lends rigitity and structure to cell
• contains MUREIN (distinctive of bacteria)

Question 11

Draw disease triad

Answer 11