Microbiology Chap 4

Question 1

Prokaryote characteristics

Answer 1

One circular chromosome not in membrane
No histones or membrane enclosed organelles
Peptidoglycan cell walls if Bacteria & pseudomurein cell walls if Archaea
Divide by binary fission

Question 2

Eukaryote

Answer 2

Paired chromosomes, in nuclear membrane
Have histones & membrane enclosed organelles
Polysaccharide cell walls
Cell division by mitosis

Question 3

Prokaryotes cell shape

Answer 3

Most bacteria are monomorphic (one shape); few are pleomorphic (many shapes)

• Bacillus (rod-shaped)
• Coccus (spherical)
• Spiral

Question 4

Cocci

Answer 4

Can be round, oval, elongated or flattened on one side
Can be found in
Pairs: diplococci
Chains: streptococci

Question 5

Scientific name: Bacillus

Shape: Bacillus

Answer 5

Can be single, pairs (diplobacilli), chain (streptobacilli) or oval-like (coccobacillus)

Question 6

Spirals

Answer 6

• Have one or more twists & are never straight
• Vibrio: curved rod
• Spirillum: helical shape like corkscrew; have rigid bodies
• Spirochete: helical shape & flexible bodies

Question 7

Prokaryotes structures External to Cell Wall

Answer 7

• Glycocalyx
• flagella
• axial filaments
• fimbriae
• pili

Question 8

Glycocalyx

Answer 8

Sticky layer of polysaccharides outside of cell wall

Question 9

Two types of Glycocalyx

Answer 9

Capsule: neatly organized and firmly attached

Slime layer: unorganized & loose

Question 10

Capsules attribute to virulence by

Answer 10

Allowing cell to attach

Preventing phagocytosis

Question 11

Atrichous

Answer 11

no flagella

Question 12

Peritrichous

Answer 12

flagella all over the cell

Question 13

Polar:

Answer 13

flagella on 1 side

Question 14

Monotrichous:

Answer 14

1 flagellum

Question 15

Amphitrichous

Answer 15

flagella on both sides

Question 16

Lophotrichous

Answer 16

tuft of flagella coming from 1 side

Question 17

Chemotaxis

Answer 17

chemical

Question 18

Phototaxis

Answer 18

light

Question 19

Flagella proteins

Answer 19

are H antigens distinguish among serovars

EXAM

Question 20

Axial Filaments

Answer 20

• Also called endoflagella; found in spirochetes

- Bundles of fibrils that arise at end of cell beneath outer sheath, spiral around; anchored at one end of cell

Question 21

Axial filament rotation

Answer 21

Rotation causes cell to move like corkscrew

Question 22

protein pilin

Answer 22

is arranged in helical structure

Question 23

Fimbriae

Answer 23

: hairlike appendages that allow for attachment

Question 24

Pili

Answer 24

• Involved in motitly & DNA transfer between cells
• Gliding motility: smooth gliding movement
• Twitching motility: pilus extends by addition of more pilin, makes contact & retracts as disassembled
• Conjunction (sex) pilus: F+ cells connects to receptors on another cell & DNA from F+ cell is transferred

Question 25

Cell Wall

Answer 25

Prevents lysis when water pressure inside cell is greater then outside Helps maintain shape, anchor flagella & contributes to virulence

Question 26

Gram-positive Cell Walls

Answer 26

- Thick peptidoglycan - Teichoic acids (2 types) - Lipoteichoic acid links to plasma membrane - Wall teichoic acid links to peptidoglycan - May regulate movement of cations & attribute to antigen specificity - Polysaccharides & teichoic acids provide antigenic specificity

Question 27

Gram-Negative Cell Wall

Answer 27

- Thin peptidoglycan (bonded to lipoproteins) & outer membrane - Periplasmic space filled with periplasm (gel-like fluid); high concentration of degradative enzymes & transport proteins - More prone to mechanical breakage; sensitive to tetracycline

Question 28

Gram-Negative Cell Wall stuff

Answer 28

Outer membrane: consists of lipopolysaccharides (LPS), lipoproteins & phospholipids; protection from phagocytes, complement (lysing cells & phagocytosis) & antibiotics

Question 29

LPS consists of

Answer 29

O polysaccharide antigen: useful in identifying gram-negative, ex. E. coli O157:H7 Core polysaccharide: provides stability Lipid A is endotoxin; causes fever, dilation of blood vessels, shock & blood clotting

Question 30

Gram-stain

Answer 30

Crystal violet-iodine crystals form in cell, which are too large to leave

Question 31

Gram-positive (alcohol)

Answer 31

Alcohol dehydrates peptidoglycan making it more impermeable & CV-I crystals do not leave

Question 32

Gram-negative (alcohol)

Answer 32

Alcohol dissolves outer membrane & leaves holes in peptidoglycan letting CV-I wash out

Question 33

Safranin dyes

Answer 33

both pink but only visible in Gram-negative

Question 34

Gram-positive cell walls

Answer 34

- 2-rings in basal body of flagella - Produce exotoxins - High susceptibility to penicillin - Disrupted by lysozyme

Question 35

Gram-negative cell walls

Answer 35

- 4-rings in basal body of flagella - Produce endotoxins & exotoxins - Low susceptibility to penicillin

Question 36

Acid-fast cell walls

Answer 36

``` Like gram-positive Waxy lipid (mycolic acid) bound to peptidoglycan ```

Question 37

Mycoplasmas

Answer 37

- Lack cell walls | - Sterols in plasma membrane

Question 38

Archaea

Answer 38

Wall-less or walls of pseudomurein (lack NAM & D-amino acids)

Question 39

Cell envelope layers

Answer 39

Outer membrane Cell wall Plasma membrane

Question 40

Cell envelope

Answer 40

``` -Gram-negative All 3 -Gram-positive -Missing the outer membrane -Mycoplasma Only have the plasma membrane ```

Question 41

Damage to Cell Wall

Answer 41

- Lysozyme digests disaccharide in peptidoglycan - Found in sweat, tears & saliva - Penicillin inhibits peptide bridges in peptidoglycan - Protoplast is wall-less cell - Spheroplast is wall-less gram-positive cell - Protoplasts & spheroplasts are susceptible to osmotic lysis - L forms are wall-less cells that swell into irregular shapes