Lab Quiz 3

obligate anaerobe

test for both glucose and lactose in single tube.

contains glucose, lactose, peptone, and pH indicator phenol red.

lactose is 10 times more than glucose

control with no growth

glucose and lactose, fermentation with no gas production

glucose and lactose, fermentation with gas production

glucose fermentation and protein utilization

iron sulfate is added to detect presence of endoenzyme desulfhydrase. contains lactose and glucose in 10:1 ration, and pH phenol red. 

glucose fermentation
no lactose fermentation
no desulfhydrase production
aerobic protein use
no gas production
acid production

glucose fermentation
lactose fermentation
no protein use
acid production
no gas production
no desulfhydrase

if yellow has break

then gas production

glucose fermentation
no lactose
aerobic protein use
desulfhydrase production
no gas production

The MR test employs a pH indicator, methyl red, in order to determine the relative amount of organic acids produced from glucose fermentation by an organism, mixed acid pathway


VP test- test high amounts of neutral products, result of glucose fermentation via butaneidol pathway

to test if high amounts of acetoin are present, pink band will present on top for positive result

determine amount of organic acids produced from glucose fermentation by an organism. bacterium has positive reaction, if entire tube turns red because of methyl red

detect organic and gas production

pH phenol red turns yellow if acid is present. peptone is alternativ energy source.

Red tube- red and clearn. NEGATIVE. glucose not used
Red but cloudy- bacteria uses peptone
YELLOw without bubble- glucose used, but no gas production
yellow with bubble- glucose used, and gas production

lactose is a dimer, if it can ferment lactose and glucose

same results as glucose

if sole carbon source is used , pH indicator thymol blue is incorporated.

if citric acid is utilized, pH decreases, and blue color on right, is positive test for citrate utilization

if it is not used- green tube

exoenzyme- produced inside the bacterial cell and then exported into the environment surrounding the cell where they become catalytically active. Peptidases used in this way are thus exoenzymes
endoenzyme- degradation of these absorbed small peptides and amino acids can then be carried out by endoenzymes.

Further degradation of these absorbed small peptides and amino acids can then.peptidases Endoenzymes are enzymes produced by the bacterium that are catalytically active inside the cell. Endoenzymes involved in the further breakdown of these small protein products may be peptidases or other enzymes that complete the breakdown of amino acids

Another example is Kligler Iron Agar (KIA), which can detect the utilization of sulfur-containing amino acids as a result of the endoenzyme desulfhydrase.

contains amino acid tryptophan

bacteria must produce tryptophanase. endoenzyme.
if indole positive, then tryptophanase positive.

Green or yellow- negative, no tryptophanase
red ring on top- positive, tryptophanase present

microorganism has to produce exoenzyme gelatinase, to hyrdrolyze gelatin into amino acids.
blue on strip becomes visible

if geltain is used- blue color of acetate on strip becomes visible

Catalase is an enzyme that often mediates this degradation, producing water and oxygen gas, gets rid of h202.

cytochrome oxidase- catalyzes oxidation of last cytochrome, in system. present in aerobic bacteria, as well as facultative anaerobes and microaerophiles.

use toothpick rub organism on small area

he appearance of a dark purple color within 20 seconds indicates that the organism is oxidase-positive. Oxidase-negative organisms produce either no color to a yellowish color (the original color of the colony) or change to a very light gray color within the 20-second test perio

one drop of H2O2 solution to the culture sample and watch for the production of bubbles in the suspension. These bubbles are the oxygen gas evolved as a result of catalase activity, as the enzyme catalyzes the breakdown of hydrogen peroxide. If no bubbles are produced, the test is negative for the presence of catalase.

based on plates, organism a grew in aerobic, not in anaerobic so its, obligate aerobe

organism b did not grow in aerobic, and did grow in anaerobic, so its obligate anaerobe

organism c grew on both, its facultative anaerobes

microbe has specific pH range within which it can grow.

determined by pH maximum and pH minimum.
pH optimum-grows best

terminal electron acceptor is not oxygen, use nitrate as final electron acceptor.

red color indicates- organism is nitrate negative

no color- with bubble, organism reduces nitrate either by denitrification(gas) or nitrate reduction(no gas)

in the beginning, after sulfanilic acid and naphthylamine added, turns red, then nitrate reduction occurs also

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