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MCB 301: Biochemical Tests Study Q&A’S Latest Update
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MCB 301: Biochemical Tests Study Q&A’S Latest Update
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MCB 301: Biochemical Tests StudyQ&A’S Latest Update
Score the Methyl Red test: no color change or turns a brown, yellow or black color -
✔✔-
some sugar-fermenting bacteria also produce __________ which remove the carboxyl
group from specific amino acids - ✔✔decarboxylases
lysine decarboxylase removes the carboxyl group from the amino acid lysine to produce
_______________ and _____________ - ✔✔carbon dioxide and cadaverine
foul-smelling polyamine produced by protein hydrolysis during putrefaction of
animal tissue and a toxic diamine - ✔✔cadaverine
the accumulation of cadaverine causes pH to ___________ - ✔✔increase (alkaline)
(Kligler's test) prolonged incubation of hydrogen sulfide produces _____________ -
✔✔entirely black agar medium
brom cresol purple initially turns the medium ________ - ✔✔yellow
What is indole?
,and it accumulates as an _________ - ✔✔- a putrefactive compound
-end product
Indole is used to distinguish between: ______________________________ -
✔✔shigella and salmonella (2 genera that contain human pathogenic species)
Score the lysine decarboxylase test: solution turns purple - ✔✔+
Score the lysine decarboxylase test: solution turns grayish purple - ✔✔need to
check pH by dipping pH strip into culture
pH > 7 means the test is positive
pH < 7 means the test is negative
what molecules in sugar tests can produce an alkaline reaction and cause a color
change in the pH indicator? - ✔✔hydrolysis of amino acids in peptone
placing a small, inverted Durham tube in the test medium allows you to determine if
________ is present - ✔✔gas (H2)
Score the glucose test: yellow and a gas bubble has formed in the Durham tube
- ✔✔A/G
Score the glucose test: medium has turned yellow - ✔✔A (acid produced)
Score the glucose test: medium has turned lime green or yellowish in the
bottom/green at top - ✔✔(A)
, Score the glucose test: no acid or gas has been produced and growth is noted.
the medium is green - ✔✔0+
Score the glucose test: no acid or gas has been produced and growth is noted. the
medium has turned blue due to an alkaline reaction caused by amino acid use as
carbon source - ✔✔0+/B
Score the glucose test:No acid or gas has been produced and no growth is noted -
✔✔0-
how might you get a false negative in the sugar test? - ✔✔some gram-positives
grow slowly and may need a larger inoculum to grow
brom cresol purple pH range - ✔✔5.2 to 6.8
sugar tests use which indicator - ✔✔brom cresol purple
(indole test) if growth is present in tube, add _________________ - ✔✔add Kovac's
reagent (DO NOT MIX)
(indole test) if no growth is present, test results will be _______ - ✔✔not valid and
cannot be used to ID bacteria
(indole test) bright reddish-pink band forms at medium-reagent interface - ✔✔(+)
catalase test is GENERALLY assoc. with what kind of organisms - ✔✔aerobic
(this is not always the case, bacteroids can produce catalase even though it is
an anaerobe)
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