10.09

Question 1

growth patterns in broth

Answer 1

• uniform fine turbidity
• Some organisms float on top of
  the medium and produce a type of surface membrane
  called a pellicle
• sediment
• flocculent (clumps)

Question 2

fastidious

Answer 2

An organism that relies heavily on the
environment to supply ready-made organic compounds
is referred to as fastidious

Question 3

Fluid Thioglycollate Medium esp well adapted for

Answer 3

cultivation of strict an aerobes and

microaerophiles.

Question 4

When inoculating

Thioglycollate Broth, it helps to

Answer 4

dip the loop all
the way to the bottom of the tube and gently mix
the broth with the loop as you remove it

Question 5

anaerobic system purpose

Answer 5

cultivating anaerobic

and microaerophilic bacteria.

Question 6

MSA

Answer 6

Mannitol Salt Agar (MSA) contains the carbohydrate
mannitol, 7.5% sodium chloride (NaCl), and the pH
indicator phenol red. used for isolation and differentiation
of Staphylococcus aureus.

Question 7

phenol red

Answer 7

Phenol red is yellow below pH 6.8,
red at pH 7.4 to 8.4, and pink at pH 8.4 and above. Phenol
red indicates whether fermentation has taken place

Question 8

mannitol

Answer 8

Mannitol provides the substrate for fermentation and

makes the medium differential.

Question 9

NaCl

Answer 9

Sodium chloride makes
the medium selective because its concentration is high
enough to dehydrate and kill most bacteria. Staphylococci
thrive in the medium, largely because of their
adaptation to salty habitats such as human skin.

Question 10

most staphylococci

Answer 10

Most staphylococci are able to grow on MSA, but
do not ferment the mannitol, so the growth appears pink
or red and the medium remains unchanged.

Question 11

s aureus

Answer 11

Staphylococcus
aureus ferments the mannitol, which produces
acids and lowers the pH of the medium (Figure 4-6).
The result is formation of bright yellow colonies usually
surrounded by a yellow halo

Question 12

msa result: poor/no growth

Answer 12

organism inhibited by nacl. not staphyloccocus

Question 13

msa result: good growth

Answer 13

organism not inhibited by nacl. is staphyloccocus

Question 14

msa result: yellow growth or halo

Answer 14

organism produces acid from mannitol fermentation. possible pathogenis s aureus

Question 15

msa result: red, no halo

Answer 15

Organism does not ferment mannitol. No reaction

- Staphylococcus other than s aureus

Question 16

mackonkey agar

Answer 16

a selective and differential medium
containing lactose, bile salts, neutral red, and crystal
violet. used to isolate and differentiate
members of the Enterobacteriaceae based on the ability to ferment lactose

Question 17

bile salts

Answer 17

inhibit growth of

Gram-positive bacteria.

Question 18

crystal violet

Answer 18

inhibit growth of
Gram-positive bacteria.Formulations without
crystal violet allow growth of Enterococcus and some
species of Staphylococcus, which ferment the lactose and
appear pink on the medium.

Question 19

neutral red dye

Answer 19

Neutral red dye is a pH indicator
that is colorless above a pH of 6.8 and red at a pH less
than 6.8. Acid accumulating from lactose fermentation
turns the dye red.

Question 20

lactose fermenters mackonkey agar

Answer 20

Lactose fermenters turn a shade of
red on MacConkey Agar, whereas lactose non fermenters
retain their normal color or the color of the medium

Question 21

mc agar: poor/no growth

Answer 21

Organism is inhibited by crystal violet and/or bile. G+

Question 22

mc agar: good growth

Answer 22

Organism is not inhibited by crystal violet or bile. G-

Question 23

mc agar: pink/red, w/ or w/o bile precipitate

Answer 23

Organism produces acid from lactose fermentation; probable coliform

Question 24

mc agar: “colorless” (not red/pink) growth

Answer 24

org doesn’t ferment lactose. no rxn

- noncoliform

Question 25

coliform

Answer 25

gram-negative rod-shaped bacteria. a subgroup of Enterobacteriaceae (Escherichia coli being the most prominent member) that produce gas from lactose fermentation

Question 26

eosin methylene blue agar

Answer 26

Eosin Methylene Blue (EMB) Agar is a complex (chemically undefined), selective, and differential medium. It contains peptone, lactose, sucrose, and the dyes eosin Y and methylene blue. used for the isolation of fecal coliforms.

Question 27

peptone

Answer 27

The peptone provides a complex | mixture of carbon, nitrogen and other nutritional components.

Question 28

sugars

Answer 28

The sugars are included to encourage growth of enteric bacteria and to differentiate them based on color reactions created when combined with the dyes. Lactose supports coliforms such as Escherichia coli and sucrose supports pathogens such as Proteus or Salmonella species

Question 29

emb agar dyes

Answer 29

The purpose of the dyes is twofold, 1) they inhibit the growth of Gram-positive organisms and 2) they react with vigorous lactose fermenters

Question 30

emb agar: poor/no growth

Answer 30

Organism is inhibited by eosin and methylene blue. G+

Question 31

emb agar: good growth

Answer 31

Organism is not inhibited by eosin and methylene blue. G-

Question 32

emb agar: pink, mucoid growth

Answer 32

Organism ferments lactose with little acid production. possible coliform

Question 33

emb agar: dark growth

Answer 33

Organism ferments lactose and/or sucrose with acid production. PROBABLE coliform

Question 34

emb agar: whats dark growth

Answer 34

purple to black, w/ or w/o metallic sheen

Question 35

emb agar: colorless

Answer 35

Organism does not ferment lactose or sucrose. no rxn | - noncoliform

Question 36

emb agar: whats colorless

Answer 36

no pink, purple, or metallic sheen

Question 37

flavoprotein

Answer 37

One carrier molecule in the ETC called flavoprotein can bypass the next carrier in the chain and transfer electrons directly to oxygen (Figure 5-15). This alternative pathway produces two highly potent cellular toxins— hydrogen peroxide (H2O2) and superoxide radical (O2-)

Question 38

superoxide dismutase

Answer 38

catalyzes conversion of superoxide radicals (the more lethal of the two compounds) to hydrogen peroxide

Question 39

catalase

Answer 39

Catalase converts hydrogen peroxide into | water and gaseous oxygen

Question 40

Bacteria that produce catalase can be detected easily

Answer 40

using typical store-grade hydrogen peroxide. When hydrogen peroxide is added to a catalase-positive culture, O2 gas bubbles form immediately . If no bubbles appear, the organism is catalase-negative.

Question 41

Flavoproteins, iron-sulfur proteins, | and cytochromes

Answer 41

important ETC molecules unable | to donate protons.

Question 42

compelx IV

Answer 42

The last enzyme in the chain, Complex IV, is called cyto chrome c oxidase because it makes the final electron transfer of the chain from cytochrome c, residing in the periplasm, to oxygen inside the cell

Question 43

chromogenic reducing agent

Answer 43

Chromogenic reducing agents are chemicals that develop color as they become oxidized

Question 44

The oxidase test is designed to identify the presence | of cytochrome c oxidase. It is able to do this because

Answer 44

cytochrome c oxidase has the unique ability to not only oxidize cytochrome c, but to catalyze the reduction of cytochrome c by a chromogenic reducing agent called tetramethyl-p-phenylenediamine.

Question 45

oxidase test results n intepretations

Answer 45

1. dark blue w/in 20s: cytochrome c oxidase present | 2. no color change to dark blue w/in 20s: not present

Question 46

what do u do in oxidase test

Answer 46

In the oxidase test, the reducing reagent is added directly to bacterial growth on solid media, or (more conveniently) a bacterial colony is transferred to paper saturated with the reagent

Question 47

starch agar

Answer 47

simple plated medium of beef extract, | soluble starch, and agar

Question 48

When organisms that produce alpha-amylase and oligo-1,6-glucosidase are cultivated on starch agar,

Answer 48

they hydrolyze the starch in the areasurrounding their growth.

Question 49

iodine

Answer 49

Because both starch and its sugar subunits are virtually invisible in the medium, the reagent iodine is used to detect the presence or absence of starch in the vicinity around the bacterial growth. Iodine reacts with starch and produces a blue or dark brown color; therefore, any microbial starch hydrolysis will be revealed as a clear zone surrounding the growth. Iodine will not color the agar where the growth is, only the area surrounding the growth.

Question 50

amylase test results n predictions

Answer 50

clearing around growth = amylase present, n vice versa

Question 51

casease

Answer 51

Casease is an enzyme that some bacteria produce to hydrolyze the milk protein casein, the molecule that gives milk its white color. When broken down into smaller fragments, the ordinarily white casein loses its opacity and becomes clear.

Question 52

casein hydrolysis test results

Answer 52

clearing in agar = casease present, n vice versa

Question 53

milk agar

Answer 53

The presence of casease can be detected easily with the test medium Milk Agar. When plated Milk Agar is inoculated with a casease-positive organism, secreted casease will diffuse into the medium around the colonies and create a zone of clearing where the casein has been hydrolyzed.

Question 54

Gelatinase Test Results and Interpretations

Answer 54

gelatin liquid = gelatinase present. solid = not present

Question 55

gelatin

Answer 55

Gelatin is a protein derived from collagen—a component of vertebrate connective tissue. Gelatinases comprise a family of extracellular enzymes produced and secreted by some microorganisms to hydrolyze gelatin. Subsequently, the cell can take up individual amino acids and use them for metabolic purposes.

Question 56

nutrient gelatin

Answer 56

The presence of gelatinases can be detected using Nutrient Gelatin, which differs from most other solid media in that the solidifying agent (gelatin) is also the substrate for enzymatic activity. Consequently, when a tube of Nutrient Gelatin is stabinoculated with a gelatinase-positive organism, secreted gelatinase (or gelatinases) will liquefy the medium.

Question 57

A slight disadvantage of Nutrient Gelatin is that it

Answer 57

melts at 28°C (82°F). Therefore, inoculated stabs are typically incubated at 25°C along with an uninoculated control to verify that any liquefaction is not temperaturerelated.

Question 58

hemolysin

Answer 58

Several species of Gram-positive cocci produce exotoxins called hemolysins, which are able to destroy red blood cells (RBCs) and hemoglobin.

Question 59

3 types of hemolysis

Answer 59

beta: the complete destruction of RBCs and hemoglobin, results in a clearing of the medium around the colonies alpha: partial, greenish discoloration of the agar around the colonies gamma: non-hemolysis; simple growth w/ no change to medium

Question 60

streak stab technique

Answer 60

. In this procedure the Blood Agar plate is streaked for isolation and then stabbed with a loop. The stabs encourage streptolysin activity because of the reduced oxygen concentration of the subsurface environment

Question 61

Blood Agar is used for

Answer 61

isolation and cultivation of many types of fastidious bacteria. It also is used to differentiate bacteria based on their hemolytic characteristics, especially within the genera Streptococcus, Enterococcus, and Aerococcus.

Question 62

streptolysins

Answer 62

Hemolysins produced by streptococci are called streptolysins. O: oxygen-labile and expresses maxi- mal activity under anaerobic conditions S: oxygen-stable but expresses itself optimally under an aerobic conditions as well.