Biochemical Tests

Question 1

is used to identify bacterial species based
on the differences in the biochemical reactions of each of
the different types of bacteria

Answer 1

Biochemical test

Question 2

The is used to identify bacteria that
produce cytochrome c oxidase, an enzyme of the
bacterial electron transport chain (ETC)

Answer 2

oxidase test

Question 3

t is based on the principle that
certain bacteria produce indophenol blue from the
oxidation of dimethyl-p-phenylenediamine and anaphtho

Answer 3

Principle of Oxidase tes

Question 4

 Oxidase POSITIVE bacteria:

Answer 4

o Pseudomonas
o Vibro cholerae
o Neisseriae
o Campylobacter
o Helicobacter / Haemophilus
o Aeromonas
o Alcaligene

Question 5

Precaution while performing oxidase test:

Answer 5

o Do not use nickel-base alloy wires containing
chromium and iron wire (nichrome wire).
o Interpret test within 10 seconds.
o Perform test using 5% SBA or on a medium without fermentable sugar

Question 6

maintains osmotic pressure. in tsi

Answer 6

Nacl

Question 7

are the fermentable
carbohydrates

Answer 7

Lactose, Sucrose, and Dextrose

Question 8

S make H2S (Hydrogen sulfide) indicator system

Answer 8

sodium thiosulfate and ferrous sulfate

Question 9

is reduced to H2S by several species of bacteria
and H2S combines and form insoluble black precipitates.
FeSO4 present in the medium

Answer 9

Thiosulfate

Question 10

how long is the incubation for tsi

Answer 10

Incubation is for 18 to 24 hours in order to detect the
presence of sugar fermentation, gas production, and H2S
production

Question 11

It is also used to distinguish the Enterobacteriaceae from other gram-negative intestinal bacilli (by their ability to catabolize glucose, lactose, or sucrose, and to liberate sulfides from ferrous ammonium sulfate or sodium thiosulfate

Answer 11

TSI

Question 12

agar slants contain a 1% concentration of
sucrose and lactose, and 0.1% glucose

Answer 12

TSI

Question 13

IN TSI, it is incorporated into
the medium to detect acid production from
carbohydrate fermentation.

Answer 13

phenol red

Question 14

tsi results color

Answer 14

The indicator is pink at alkaline pH and yellow in acidic pH, at neutral pH it remains red

Question 15

Yellow butt (A) and red slant (K)

Answer 15

• due to fermentation of glucose (phenol indicator turns yellow due to persisting acid formation in the butt)
• The slant remains red (alkaline) (K) because of
  limited glucose in the medium. Therefore, limited acid formation, which does not persist.

Question 16

A yellow butt (A) and slant (A)

Answer 16

due to fermentation of lactose and/or sucrose.

• Yellow slant and butt due to high concentration of these sugars leading to excessive acid formation in the entire medium.

Question 17

o noted by splitting agar.

Answer 17

Gas formation

Question 18

o seen by blackening of agar.

Answer 18

Gas formation (H2S)

Question 19

red butt (K) and slant (K)

Answer 19

introduces that none of the sugars were fermented and neither gas nor H2S produced.

Question 20

Slant Butt Gas H2S

of Escherihia,

Answer 20

Acid (A) Acid (A) Pos (+) Neg (-)

Question 21

Klebsiella,

Slant Butt Gas H2S

Answer 21

Acid (A) Acid (A) Pos (+) Neg (-)

Question 22

Enterobacte

Slant Butt Gas H2S

Answer 22

Acid (A) Acid (A) Pos (+) Neg (-)

Question 23

Slant Butt Gas H2S

shigella

Answer 23

Shigella,

Alkaline (K) Acid (A) Neg (-) Neg (-)

Question 24

Slant Butt Gas H2S

Serratia

Answer 24

Serratia
Alkaline (K) Acid (A) Neg (-) Neg (-)

Question 25

Slant Butt Gas H2S salmonella

Answer 25

Salmonella, Alkaline (K) Acid (A) Pos (+) Pos (+)

Question 26

Slant Butt Gas H2S proteus

Answer 26

Proteus Alkaline (K) Acid (A) Pos (+) Pos (+)

Question 27

Slant Butt Gas H2S Pseudomonas

Answer 27

Pseudomonas Alkaline (K) Alkaline (K) Neg (-) Neg (-)

Question 28

If an Enterobacteriaceae contains amino acid decarboxylase, amines produces by decarboxylae action cause an ________ pH, and _________

Answer 28

Amino acid decarboxylation alkaline ph bromocresol purple

Question 29

Amino acid decarboxylation result

Answer 29

alkaline = purple = positive/amino acid is decarboxylated acidic = yellow/glucose fermentation acidifie s broth

Question 30

Decarboxylation patterns are essential for the genus identification of

Answer 30

Klebsiella, Enterobacter, Eschericia, and Salmonella Enterobacter aerogenes, E. cloacae, Proteus mirabilis, and Shigella sonnei

Question 31

Aim: To differentiate gram-negative bacilli based on decarboxylation or deamination of the lysine and the formation of hydrogen sulfide (H2S).

Answer 31

Lysine Iron Agar

Question 32

Lysine decarboxylation is indicated by an increase in

Answer 32

alkaline (purple) medium

Question 33

 Lysine deamination is detected by a

Answer 33

red slant.

Question 34

Dextrose fermentation is indicated by a

Answer 34

purple slant and a yellow butt lia

Question 35

deaminate lysine which results in a distinctive red slant over an acid (yellow) butt. give example

Answer 35

Proteus and Providencia spp.

Question 36

To determine the ability of microbe to degrade amino acid tryptophan.

Answer 36

Indole Production Test

Question 37

indole production test result

Answer 37

: Development of cherry red colour at the interface of the reagent and the broth, within seconds after adding the Kovacs’ reagent indicates the presence of indole and the test is positive. If no color change is observed, then the test is negative and so organisms are not capable of producing tryptophanase

Question 38

To differentiate E. coli and E. aerogene

Answer 38

mr e. coli + e. aerogenes -

Question 39

determine the ability of microbes to oxidize glucose with production and stabilization of high content of acid end product.

Answer 39

mr

Question 40

differentiate the E.coli and E. aerogenes by the production of 2,3-butanediol and acetoin via glucose fermentation

Answer 40

VP e. coli - e. aerogenes +

Question 41

RESULT IN VP

Answer 41

nterpretation: Development of crimson red color indicates positive test for E. aerogenes; and no color indicates negative test

Question 42

Principle: This test determines the capability of some organisms to produce non-acidic or neutral end products, such as acetyl methyl corbinol (acetoin), from the organic acid that results from glucose metabolism

Answer 42

vp

Question 43

Aim: To determine the ability of the microbes to ferment citrate as sole carbon source

Answer 43

Citrate Test

Question 44

cARBON AND NITROGEN SOURCE IN CITRATE TEST

Answer 44

Sodium citrate as the carbon source, Ammonium (NH4 +) as a nitrogen source

Question 45

CITRATE TEST RESULT

Answer 45

+ = BLUE - = NO COLOR

Question 46

UREASE TEST RESULT

Answer 46

+ = REDDISH PINK TO RED - = YELLOW

Question 47

The hydrolysis of urea is catalysed by specific enzyme urease to yield

Answer 47

2 moles of ammonia, water, CO2.

Question 48

o determine the ability of microbes to ferment sugars with the production of an acid and/or gas

Answer 48

Sugar Fermentation Test

Question 49

If fermenting bacteria are grown in a liquid culture medium containing the carbohydrate, they may produce ______as by-products of the fermentation.

Answer 49

If fermenting bacteria are grown in a liquid culture medium containing the carbohydrate, they may produce organic acids as by-products of the fermentation.

Question 50

Gases produced during the fermentation process can detect by using a small, inverted tube (Durham tube) within the liquid culture medium

Answer 50

Sugar Fermentation TesT

Question 51

Sugar Fermentation TesT RESULT

Answer 51

Interpretation: o If the medium changes from colorless to yellow and gas bubble is found in Durham’s tube then it indicates acid and gas production. o If no change observed in the color of medium then sugar is not degraded by the organism

Question 52

To determine the ability of some microbes to reduce nitrate (NO3 - ) to nitrites (NO2 - ) or beyond the nitrite stage

Answer 52

NITRATE REDUCTION

Question 53

RESULT OF NITRATE REDUCTION

Answer 53

+ = RED