Gram positive and negative bacteria 1

Question 1

equation to solve for # bacterial cells present

Answer 1

N= N. x 2^n

n= t/g

t= length of time
N.= inoculum number of cells
g= generation time

Question 2

Viable count procedures

Answer 2

1. serial dilutions of suspension of bacteria- addition of aliquot of specimen to a sterile solution
2. plate onto growth media- spread or pour
   spread- drop of suspension placed onto center agar plate and spread over surface
   pour- suspension added to tubes of molten agar (42-45 C) and poured into petri dish
3. Count colonies

Question 3

significance of record results

Answer 3

10^-1 through -3: TMTC

10^-4: best for accurate count, 30-300 colonies

10^-5 TFTC, only about 21 colonies

Question 4

Spectrophotometer function

Answer 4

records optical density of absorbance units

as population increases, turbidity increases

Question 5

Gram negative cell structure

Answer 5

1 layer of peptidoglycan

outer membrane contains endotoxin, LPS and porins

periplasmic space with beta lactamase

stains pink/red

Question 6

Gram positive cell structure

Answer 6

many layers of peptidoglycan

contains lipoteichoic acid

stains purple

Question 7

Cell wall composition

Answer 7

GlcNAc and Mur2Ac are held together by peptide bonds

Question 8

Gram staining procedure

Answer 8

1. smear
2. air dry
3. heat fix
4. stain with crytal violet- blue cationic dye- sticks to peptidoglycan b/c + to -
5. add iodine- mordent
6. rinse with ethanol- decolorizes
7. rinse with water
8. stain with safranin- red cationic dye- counterstain

Question 9

purpose of spores/ endospores

Answer 9

dormant or resting stage

resistant to dissication, heat and UV light

Question 10

Purpose of glucocalyx

Answer 10

slime layer- not well organized
well organized capsule
gelatinous material
functions of help organism resist environmental insults- dehydration, pH changes
can be virulence factor

Question 11

flagella

Answer 11

made of proteins, used for motility

Question 12

monotrichous

Answer 12

1 at one end

Question 13

lopotrichous

Answer 13

tuft at end

Question 14

amphitrichous

Answer 14

1 and each end

Question 15

peritrichous

Answer 15

all over the place