BIOL 2420 (Microbiology) LAB EXAM IV

enzyme that the oxidase assay detects

Cytochrome C

positive result of the oxidase assay

solution added to the test applicator turns blueish/purple

function of cytochrome C

component of the electron transport chain

chemicals that make the MAC agar selective

bile salts and crystal violet

group of organisms that can’t be grown on MAC agar

inhibits G+ bacteria (I)

chemicals that make the MAC agar differential

lactose as a fermentable sugar and neutral red as a pH indicator

color of bacteria on MAC agar

pink or pinkish colonies indicate they are capable of fermenting lactose

chemicals that make the EMB agar selective

eosin Y and methylene blue

group of organisms that can’t be grown on EMB agar

inhibits G+ bacteria (II)

chemicals that make the EMB agar differential

combination or fermentable carbon sources (sucrose and lactose) and methylene blue

color of bacteria on EMB agar

metallic green indicates e coli, whereas purple determines a strong fermenter of sugars, and pink determines a weak fermenter of sugars

chemicals that make the Hektoen agar selective

combination of bile salts and bromothymol blue and acid fushcin

group of organisms that can’t be grown on Hektoen agar

inhibits G+ bacteria growth (III)

chemicals that make the Hektoen agar differential

combination of fermentable sugars (lactose, sucrose, and salicin) and the pH indicator bromothymol blue; ferric ammonium citrate

color of bacteria on Hektoen agar

fermenting enteric bacteria (yellow - salmon colored), hydrogen sulfide producers (black), non-fermenters (blue/green)

type of agar CNA is

selective and differential

chemicals that make the CNA agar selective

antibiotics nalidixic acid and colistin

group of organisms that can’t be grown on CNA agar

inhibits G- bacterial growth

blood agar type

differential

hemolysis patterns

partial breakdown of the red blood cells (greenish brown, or alpha), complete breakdown of the blood cells (clear halo, beta) and no breakdown of red blood cells (red, gamma)

coagulase assay test 

tells you if the the organism produces the enzyme coagulase

positive result of a coagulase test

6.5% NaCl tolerance test selects for

determines if the organism is salt-tolerant

6.5% NaCl tolerance kind of test

selective only

positive result of 6.5% NaCl tolerance test

test tube would be turbid (non-clear)

chemicals that make the MSA agar selective

7.5% NaCl

group of organisms that can’t be grown on MSA agar

salt sensitive organisms can’t grow

chemicals that make the MSA agar differential

the fermentable sugar mannitol and the pH indicator phenol red

colors of MSA agar test

mannitol was used by the bacteria (yellow), sugar was not used (pink)

distinguishing characteristics between M. luteus and S. epidermidis

M. luteus will form yellow colonies, while S. epidermidis will form white colonies

bile esculin assay tests for

esculinase

chemical that allows the bile esculin to change color

esculetin will react with the ferric in the medium and then turn black

Bile esculin kind of test

both selective and differential

chemicals that make the Bile esculin agar selective

bile salts selects for organisms that are bile salt tolerant

positive result of bile salt esculinase

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