Microbiology Lab Quiz #2

Ferment lactose produce

B glactoside permease and b galactosidase

Imagine this situation: Species #1 and Species #2 are unrelated, but each produces an enzyme capable of hydrolyzing soybean oil. How can this reconciled with the fact that enzymes are highly specific to their substrates?

Because they have a specific active site where the substrate binds and this site and the substrate shape are complementary to each other.

Malonate Utilization Test dark blue vs. yellow

Blue: mallonate utilized green/ yellow/ no color: malonate not utilized

Citrate test results Blue No color change; growth No color change; no growth

Citrate utilized citrate utilized citrate not utilized

Lipase Test Results

Clearing in agar around growth; Lipase is present

Results of coagulase test

Clumping of cells; plasma has been coagulated + No cluping; plasma has not been coagulated

Which of the two tests of the MR and VP tests would likely produce more false negatives with a shorter incubation time and why?

False negative. Culture comes back negative but not really negative. VP. Have to let organism run its metabolism for awhile.

red color after A and B

NO3 to NO2

nitrate rductase

NO3- to NO2- nitrate to nitrite

Late lactose fermenters for non fermenters distingushed w/

ONPG

A positive result for the DNA hydrolysis test does not distinguish between Staphylococcus DNase and the DNase produced by Serratia. If you had the expertise to correct this weakness, would you improve the test's specificity or sensitivity?

Specificity because it would now be capable of discriminating between the two types of DNase.

Why is Tributyrin Agar prepared as an emulsion rather than a solution?

The emulsion gives an opaque field on the agar. With this test you will be looking for a clearing in an otherwise slightly opaque agar that indicates the bacteria produced the lipase to break down the oil. If this were done in solution the results would be extremely difficult to interpret correctly.

Suppose you remove your test cultures from the incubator and notice that one of them- a know fermenter- has a gas bubble in the Durham tube. Knowing that fermenters frequently produce gas, you ignore the bubble and proceed to the next step. Adding reagents produces no change, and neither does adding zinc. Is this occurrence consistent with what you have learned about this test? Why?

The gas bubble is nitrogen. if the reagents & zinc do not produce a change, then the nitrates have been used by the bacteria. If you were looking for aerobic and facultative anaerobic gram-negative microorganisms, then congratulations. A bubble plus colour change would indicate some other kind of bacteria, inconsistent with the test.

Citrate Utilization test does what

ability of organisms to use citrate as their sole carbon source and perform cirate fermentation; citrate permease trasnports citrate into cell and perform fermentation

Phenol Red Broth test

acid production from fermentation lowers pH below neutral range of indicator and turns the medium yellow

Results of urease test 24 hours 24-6 days All pink gelatinase present Partially pink pink Orange or yellow pink orange or yellow orange/ yellow

all rapid urea hydrolysis; strong urease production slow urea hydrolysis; week urease production slow urea hydrolysis; weak urease production no urea hydrolysis; urea is absent

superoxidase dismutase

catalyzes conversion of superoxide radicals to hydrogen peroxide

Casease results

clearing in agar; casease present +

Coagulase tests

coagulatse: extracellular enzyme that reacts w/ CRF; clumping factor type

fermentation

metabolic process by which an organic molecule acts as an electron donor and one of its organic products as the final electron accpeotr

Zinc dust then NO color change

nitrate reduction to nongaseous nitrogenous compounds red: No nitrate reduction (positive control)

denitrification

nitrate to N2

suppose that after 7 days a tube inoculated with a slow liquefier shows no evidence of liquefaction, is this a failure of the test system?

not necessarily, some gelatinase-positive organisms produce the gelatinase enzyme at a slower rate and may need a longer incubation period

why is it advisable to use a positive control along with organisms that you are testing?

o make sure your conditions are correct. If your positive control gives a negative answer, then your conditions were incorrect. If your positive control gives a positive response, then your conditions are usable for testing.

why is it more important to use fresh cultures in the coagulase test than in a test medium such as Milk Agar?

old positive culture may not be able to react with the medium to coagulate

Why is gas production not recognized as nitrate reduction when the organism is a known fermenter?

organisms that can ferment also produce gas. Therefore even if gas is produced on the tube, you can't tell if it's by fermentation or by nitrate reduction.

Oxidation Fermentation Test Sealed: unsealed green or blue any yellow yellow yellow throughout slightly yellow at top yellow at top green or blue green/ blue

oxidation O oxidation and fermentation or fermentation only O-F or F Oxidation and slow fermentation or slow fermentation only OF or F No sugar metabolism, organism is nonsaccharolytic N

Urea broth test results pink orange

pink: reapid urea hydrolysis; strong urease production No urea hydrolysis: norganisms does not produce urease or cannot live in broth

oxidase test

presence of cytochrome c oxidase; catalyzes the reduction of cytochrome c by tetra methyl p phenylenediamine

Mineral oil

prevents diffusion of oxygen into the medium and promotes anaerobic growth

Urea

product of decarboxyation of certain AAs and primary ntirogenous waste in the urine of many land animals

how would you interpret a negative slide test and a positive tube test using the same origin?

the slide test detects bound coagulate, the tube test detects both bound and free. a negative slide test indicated absence of bound coagulase, but a positive tube test indicated presence of free coagulase

reduction potential

the tendency (in volts) of molecules to donate electrons

why is the uninoculated sector relatively unnecessary in this test?

there is typically enough medium that is not cleared to show "no reaction"

Urea hydrolysis

to ammonia by urease positive; overcome buffer in the medium and change it from orange to pink

Functions of the ETC

transport electrons down a chain of molecules w/ increasingly positive reductio potentials to the terminal electron acceptor Generate a proton motive force by pumping H out of the cell thus creating an ionic imbalance that will drive the production of ATP by way of membrane ATPases

DNase test and results

tryptose agar glearing in agar/ loss of green color around growth= DNAse is present

oxidative organisms

carbohydrate to co2 and h2o and energy

Gelatinase Test results

gelain liquie; gelatinase present solid/ control; no gelatinase present

oxidation

loss of electrons

in what ways can a DNase (+) organism use the products of DNA hydrolysis

* The end products of DNA hydrolysis can be used in biosynthsis of nucleic acids through salvage pathway * Recycling of the active components can be done through hydrolysis of DNA. In many organisms, DNase enzymes cleave DNA molecules present in cell free body fluids, reduce their viscosity, and make them available for biosynthetic processes.

Would you change your answer if control btorh didn't change color after addition of reagents? Control broth changed only after addition of reagents and zinc?

3. Gas bubbles are produced during fermentation process. If the organism produces nitrite from nitrate it can be deduced from nitrate reduction test, where nitrite produced reacts with sulphanilic acid and alpha naphthaline to produce a red color. If red color is produced it is Nitrate positive. If no red coloris produced we can interupt in two ways Nitrate negative Or the organism has reduced nitrite to other products like nitrous oxide and nitrogen - Nitrate positive. The second step is addition of zinc powder. If the organism is nitrate negative , zinc reduces nitrate to nitrite and forms red color. If the organism is nitrate positive no color will be formed. Zinc reacts only with nitrate and not with other nitrogen products. From the above explanation we find that the organism present in #2 is nitrate positive and the organism given in #3 is nitrate negative. So we cannot change #3 as #2.

Aerobic ETCs 5.7 diagram 5.23???

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why inoculate ONPG tubes w/ growth from triple sugar iron agar cultures?

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Consequence of inoculating ONPG medium w/ ONPG positive organism grown on nutrient agar instead of kligler iron agaar or triple sugar iron agar

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positive vs. negative control

A negative control is part of a well-designed scientific experiment. The negative control group is a group in which no response is expected. It is the opposite of the positive control, in which a known response is expected.

Casease nad Amylase differences

Casease is an enzyme that is formed by some bacteria that decomposes casein and is used in ripening cheese. Amylase is any of a group of enzymes that catalyze the hydrolysis of starch and glycogen or their intermediate hydrolysis products.

What does the enzyme casease have in common with amylase?

Casease is an enzyme that is formed by some bacteria that decomposes casein and is used in ripening cheese. Amylase is any of a group of enzymes that catalyze the hydrolysis of starch and glycogen or their intermediate hydrolysis products. They are both exoenzymes. Simply, we can say that Casease hydrolyzes casein while Amylase hydrolyzes starch.

In theory on the first page of this exercise, the disassembly of DNA was described as a "depolymerization". What other terms applies to this process?

Catabolism Hydrolysis

In the Theory, we mention that some organisms are slow gelatin liquefiers. What about an organism might make it slow gelatin liquefier?

Gelatin hydrolysis test is used to identify the ability of an organism to produce gelatinase. Gelatinase is the enzyme that hydrolyzes the gelatin and converts into liquid. This test is used to identify and differentiate between the species of bacteria. Some of the organisms act as slow gelatin liquefiers because of limited production of enzymes and low affinity of enzyme to substance. The other reasons for organism being slow gelatin liquefier are as follows: Increase in temperature Change in pH Secretion of proteinase This is because microorganisms grow best at optimum temperature and pH. The examples of gelatin liquefiers are Bacillus subtilis, Clostridium perfringens, Proteus vulgaris, Staphylococcus aureus, and Bacillus cereus.

Some microbiologists recommend incubating this medium at 37C, along with an uninoculated control, and then transferring all tubes to the refrigerator prior to reading them. Why might this be the preferred technique in some situations? What potential problems can you see with this method?

Gelatin is liquid at 37 degrees. gelatin is positive if liquified. Slow reaction. Grow organism at optimum temperature. Problems: Gelatin breaking down, enzyme denaturing.

Some microbiologists recommend reincubating organisms producing methyl red negative results for an additional 2-3 days. WHy do you think this i done?

Gives organism enough time to lower pH to make sure we don't get a false negative result.

sensitivity vs. specificity

In medical diagnosis, test sensitivity is the ability of a test to correctly identify those with the disease (true positive rate), whereas test specificity is the ability of the test to correctly identify those without the disease (true negative rate).

Why is the methyl red test read immediately and the VP read after 60 mins?

MR tells us if its basic or acid. VP had to wait for chemical to react which is why we gave it some time.

The cell has hundreds of succinate dehydrogenase enzymes. How do you suppose malonate concentration affects cell growth?

Malonate is a competitive inhibitor of succinate dehydrogenase. The attachment of malonate to the succinate dehydrogenase enzyme prevents the attachment of succinate and, thus, the conversion of succinate to fumarate. Malonate concentration affects cell growth: Buildup of succinate in the cell shuts down the Krebs cycle and will kill the organism unless the organism can utilize malonate to ferment and utilize it to produce energy.

when testing microaerophiles some microbiologists prefer to use a semisolid nitrate medium that contains a small amount of agar . Why do you think this is done?

Microaerophiles requires oxygen in lower concentration (facultative anaerobe) , moreover they requires high concentration of carbon dioxide. So they are preferably grown in semi solid agar so that they can grow underneath the agar medium where the concentration of CO2 is high and availability of oxygen is less.

When flavoprotein transfers electrons directly to the final electron acceptor hydrogen peroxide is produced. What other consequences might result from electron carriers in the electron transport chain being bypassed?

One carrier molecule in the ETC called flavoprotein can bypass the next carrier in the chain and transfer electrons directly to oxygen. This alternate pathway produces two very potent cellular toxins

Think about the 20-second time limit on the oxidase test. What happens to the oxidase reagent after 20 seconds? Does this only happen after 20 seconds? If not, why is a 20-second time limit set?

Oxidase reagent consists of N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride or p-aminodimethylaniline in distilled water. This reagent is abble to oxidise itself after a short interrval of time. So complete the reaction 20 minutes are enough. If we will leave the test reaction for more than 20 seconds then the strip will oxidise itself and will give the false positive result. On the other hand if we will give less than 20 seconds to this reactio then the reaction will not complete and we will again get the false negative. therefore the optimim time to get the correct result is 20 seconds which allow the complete reaction without self oxidation of the oxidase reagent.

ONPG test yellow

Produces B galactosidase vs. no color doesn't produce it

Explain how an organism that possesses the citrase enzyme might not test positively on Simmons Citrate Agar. Is this a false negative result? Why or why not?

Simmon's Citrate agar is used to determine an organism's ability to use citrate as a sole carbon source.Simon's citrate agar is a defined medium in which sodium citrate is the sole carbon source, and ammonium is the sole nitrogen source. Bromothymol blue (BTB) is included as a pH indicator The medium is initially at pH 6.9, at which BTB is green; at a pH greater than 7.6 BTB turns a deep blue. The pH change is induced by CO2, which is given off as a by-product of citrate utilization. When it reacts with Na and H2O in the agar it raises the pH above 7.6 The organism must contain the enzyme citrase to degrade citrate (citrase) Citrate --------->CO2 + Na HCO + H2O I (blue color change) Now, coming to how a citrate test may give false results. There are only 2 ways that can happen. - Failure to incubate with loose caps may result in a false-negative results. - Avoid using a large inoculum to streak the strand; an inoculum that is too heavy may result in a false-positive test.

Suppose you had poured iodine on your plate and noticed clearings in the uninoculated area, as well as around both of your transferred cultures. What are some possible explanations for this occurrence? Was integrity of this exercise compromised? What kinds of things might be done to avoid this problem in future exercises?

Starch Hydrolysis test: It is an important microbial analysis technique, by conducting this test one can identify whether the test organism can digest complex compounds, like starch or not. Starch agar medium used for starch hydrolysis test, which contains starch and nutrient agar. The test reagent, which is used for the Starch hydrolysis is Iodine reagent. It reacts with complex starch molecule and form a blue-black color in the culture medium. Hence, if the organism has the ability to digest starch by producing α-amylase, then after adding Iodine to the test plate it cannot give blue-black color appearance. The possible explanations for this occurrence are as follows: So, if you had poured iodine on your plate and noticed clearings in the uninoculated area, it is because of "improper mixing of starch in the culture." Clearings advocate contamination not seen before iodine was added. Yes, the integrity of this exercise has been compromised and needs to be redone. The things might be done to avoid this problem in future exercises are proper preparation of starch agar medium, maintenance of proper temperature in the incubator and following of test procedure properly without compressing, etc.

examine the structural formulas below. ordinarily, in biochemical reactions there is specificity between an enzyme and its substrate. that is, enzymes typically attach to one substrate exclusively. explain why it is possible for succinate dehydrogenase to bind to two different substrates. be specific.

Succinate dehydrogenase is the enzyme that catalyses the conversion of sucinate to fumarate. The substrate concentration plays a crucial role in this reaction. This is because the enzyme can bind with both the substrates malonate and succinate. Malonate is the competitor inhibitor of the enzyme succinate dehydrogenase. The affinity of the enzyme for substartes depends on their concentration. If malonate concentration is more, then enzyme binds to malonate and inhibits the conversion into fumarate. If succinate concentration is more, then the enzyme successfully converts succinate into fumarate. The active site of the enzyme contains two confirmation states by which, alternatively either substrate can bind to the enzyme. Thus, it is possible for succinate dehydrogenase to bind to two different substrates.

suggest a reason why this test is read after 24 hours while other tests (e.g gelatinase test) may take a week. what would be the likely consequences of incubating DNase Agar for a week?

The DNase test agar has three components, namely Tryptone (proteins), emulsion of DNA, agar, sodium chloride and a dye called methyl green. This media has pH 7.3 +/- 0.2 and it is commonly used to test the organisms that produce an enzyme called DNase. The organisms that give positives result for this test are Staphylococcus aureus and Serratia marcescens, etc. In this media, after inoculation of bacteria, it should be allowed to grow in aerobic condition for 18 to 24 hours. If the test or inoculated bacteria have the ability to produce enzyme DNase, then it will give clear zones after the plate is flooded with 1N HCl. This test should be read after 24 hours, because it is a single step process and the synthesis rate of the enzyme DNase is very fast, so it can polymerize the DNA in the media with faster rate when compared to the enzyme gelatinase.

suppose that when you examined your tubes after incubating them that you noticed that the unsealed control contained slight yellowing at the top. suppose further that pair 1 showed complete yellowing of both tubes and pairs 2 amp 3 showed slight yellowing of the unsealed tube. assuming all other tubes were green, what conclusions could you safely make?

The Oxidation-Fermentation Test is used to differentiate bacteria based on their ability to oxidize or ferment specific sugars. Once microbes are inoculated, -One tube is sealed with a layer of sterile mineral oil to promote anaerobic growth and fermentation. -The other tube is left unsealed to allow aerobic growth and oxidation. Organisms able to ferment the carbohydrate or ferment and oxidize the carbohydrate will turn the sealed and unsealed yellow throughout. Organisms able only to oxidize the sugar will turn the unsealed yellow medium and leave the sealed medium green or blue. Slow or weak fermenters will turn both tubes slightly yellow at the top. Organisms not able to metabolize the sugar will either produce no color change or will turn the medium blue due to alkaline products from amino acids degradation. Since Pair #1 showed complete yellowing for sealed and unsealed, these Organisms able to ferment the carbohydrate or ferment and oxidize the carbohydrate. So our interpretation will be that the organism has: Oxidation and fermentation OR fermentation only. For tubes #2 and #3, the sealed tubes were green throughout suggests that they need oxygen for aerobic growth, and the fact that their unsealed tubes showed light yellowing is evidence for oxidation. Sealed - Green and Unseal - Yellow. Our interpretation for these pairs of tubes would be : Oxidation Tube 1 can be either Oxidation and fermentation OR fermentation only. So reliability of this needs to be confirmed more with additional testing. Tubes 2 and 3 are most reliable because they can only be oxidation only and no fermentation.

list possible reasons why the slide test is not appropriate for detecting free coagulase?

The coagulate slide test is used to detect the presence of coagulase, which is normally attached to the bacterial cell walls. This bound coagulase causes the fibrinogen in the plasma to precipitate, and thus causes the cells to agglutinate. The agglutination of the bacteria is use as the indication for the positive coagulates slide test. This is not possible for detecting free coagulase, because though is reacts with fibrinogen, no agglutination forms due to lack of bacteria. So, no agglutination is detected if free coagulase is used.

suppose you could selectively prevent production of amylase or oligo-1,6-glucosidase in an organism that normally hydrolyzes starch. Which enzyme would the organism miss the most?

The correct answer is alpha amylase. a-amylase breaks off a-1-4 linkage of starch to eventually produce maltose and glucose whereas oligo 1-6 glucosidase acts on a 1-6 linkage of isomaltose and dextrin from starch and glycogen. Amylase is responsible for the break down of food immediately after mastication as it is produced by the salivary glands. It is then used to brek down the bolus into smaller pieces as it passes through the small intestine. The pancreas secrete amylase that seeps into the small intestine.

Tributyrin Agar has a shelf life of only a few days before it loses its opacity. With this in mind, explain the importance of positive and negative controls in this test.

The positive result in this case is the clearing of an area from partially opaque to clear. Negative results can look similar to the agar losing its opacity due to end of shelf life. With that in mind it is important to have a negative control to avoid interpreting results as positive when they are actually just end of opacity results. The positive control enables you to know when you have waited long enough to truly call the test results negative. Considering the time you usually wait for your culture to metabolize for any given test it's not difficult to see why it's helpful to have negative and positive controls.

early formulation of this medium used a smaller amount of carbohydrate and occasionally produced false alkaline (pink) result after 48 hours. why do you think is happened? list at least two steps, as a microbiologist, that you could take to prevent the problem

The smaller amount of carbohydrate ferments and undergoes glucose fermentation because glucose is preferentially degraded first. Since the substrate is minimal, the acid thus produced is rapidly oxidized. The presence of peptones in the medium also boost the formation of the alkali. Two steps to prevent the problem: a) Make sure the beef extract (or any other protein sources) used should not contain glucose fermenting enzymes. b) The production of NH3 from the peptones which lead to pseudo pink colouration can be inhibited by maintaining anaerobic conditions, thereby limiting oxidation reactions during the fermentation.

Why run simultaneous test on known ONPG positive organism?

The test is simultaneously run on a phenyl alanine postive and a negative organism so that they serve as postive and negative controls. A positve control ensure that all the reagents are working properly and the test is performed correct. The negative control ensures that that are no false negative results. Both these serve as controls to eliminate false reactions or false reports.

Explain why it is acceptable to record positive test before the suggested incubation time is completed but it is not acceptable to record a negative result early

This would be because the positive reaction has demonstrated that the cells were able to undergo hydrolysis and produce Urease. However, if the incubation time is cut short, this makes your results incomplete because the reaction time may not all react at the same rate and the color indicator may not have developed yet.

Uninoculate tubes and tubes inoculated w/ an orgnaims that is N are negative controls. what info is provided by each?

Unioculated tube means tubes lacking the inoculum (bacterial culture). Generally these serve as negative control. In this tube, the growth of bacteria should not be observed. Tubes inoculated with organism "N" are having the inoculum. These serve as reference tubes. Through these the effect of bacteria on the growing culture is checked. Reference tube will always have the inoculum

Typically, this medium (urea broth) is filter sterilized because autoclaving breaks down the urea. Even unsterilized broth, however rarely produces false positive results. Why do you think this is true?

Urea can be used by few types of bacteria. So, the bacteria that make use of urea only survive in the urea containing medium. This is the reason for even unsterilized medium rarely produces false-positive results.

which test would likely benefit most from a longer incubation time? why?

VP. bc it give organism to build up acetone.

Why were you told to shake the VP tubes after the reagents were added?

We needed oxygen. Color changes better in presence of oxygen.

false positive by poor specificity or poor sensitivity of peroxidase test?

Well since Sensitivity roughly relates to measuring the proportion of actual positives and the reaction to the innoculating loop (assuming it is metal and not plastic or platinum) would result in a false-positve and Specificity measures the proprtions of negatives correctly identified. So if the loop is plastic or platinum and you had a false-positive, i would say it was caused by a poor Sensitivity in the test, ruling out the specificity on the basis the "negative" result is not correctly identified since we know we can rule out the material of the loop.

If the control is solid and an inoculated tube is liquid, is it acceptable to read the result before the complete incubation time as elapsed? Why or why not?

Yes because it tells you liquification is due to the presence of the enzyme and not temperature.

suppose you ran this test with Providencia stuartii,but it took 48 hours to turn pink.Do you think this is a false result? If so, is it a false positive or false negative? if not, why not? Give some possible explanations for this occurence.

Yes it is a false positive reaction. Urease production is indicated by a bright pink color on the slant indicating hydrolysis of urea which should occur in 24 hours of incubation, but as it take 48 hours to show pink colour indicating hydrolysis of proteins in the medium rather than urea hydrolysis.

If the control is solid and tube is also solid, is it acceptable to read the result before the complete incubation time has elapsed? Why?

You cannot read a negative result early because the enzyme might need to be incubated in order to starting breaking down.

Many bacteria that are able to metabolize citrate (as seen in the Krebs cycle) produce negative results in this test. why? be specific.

bacteria that are able to metabolize citrate-as carbon source bacteria shows the citrate permease for metabolism of citrate. bacteria uses the citrate and changes the ammounimu phosphate into ammounimun hydroxide , so the color medium is blue------which positive test. gram negative bacteria does not show color change in medium --negative results

In many tests it is acceptable to read a positive result before the incubation time is completed. Why is this not the case with Starch Agar?

because if the enzyme amylase is present, it needs time to break the starch down to glucose

Differential tests

biochemical tests; differentiate and sometiems identify microorganisms based on specific biochemical characteristics

DNase

breaks DNA into small fragments

peroxidase test

bubbles= catalase is present

catalase

converts hydrogen into water and gaseous oxygen

Results of oxidase test

dark blue/ purple w/in 20 seconds; cytochrome C oxidase present +

Gas formed

denitrification

Methyl Red test

detect mixed acid fermentation; lowers pH by overcoming phosphate buffer; Red is positive, yellow negative

free energy

energy released in metabolic reactions

Casease

enzyme that hydrolyze milk protein casein; gives milk its white color

Gelatinases

enzymes that hydrolyze gelain; inclubated at least 7 days

Voges Proskauer test/ VP test:

ferment flucose then convert acid products to acetoin and 2,3 butanediol; produces red color (reagent A an dB)

Phenol Red Broth yellow w/ bubble yellow w/o bubble red no bubble pink no bubble

fermentation w/ acid and gas end products A/G Fermentation w/ acid end productts; no gas produced A/- No fermentation -/- Degradation of peptone; alkaline end products K

how would you expect the results of this exercise to change if you were to add glucose to the medium?

in starch hydrolysis test, bacteria hydrolysis starch in the medium and dark brown color with iodine.-it is a positive test for starch hydrolysis. if you add glucose to the medium ------gives --positive test result for starch hydrolysis

how do we know that casease is an exoenzyme and not a cytoplasmic enzyme?

it is produced by bacteria and used to hydrolyze casein

Why control tube w/o regular carbohydrate too?

s a control, which, in this case, is a negative control. Since there is no carbohydrate added there will be no bacterial growth. In your tubes which do have some carbohydrate there will be bacterial growth It also ensures that any change in the media is due to the growth of the bacteria and not some external factor. Since both sets of tubes were inoculated but only one set shows some change

Which in table would be reliable carbohydrate 5-3

screenshot on desktop

Amylase test how to and results

streak; iodine flood Halo around: alpha amylase and/or oligo 1,6 glucosidase is present

Nitrate test, no visual evidence of denitrification (gas formation)

sulfanilic acid, reagent A, alpha napthylamine (B); RED COLOR; Zinc catalyzes if no color

energy of formation

the energy contained in a cellular molecule form energy released during reactions involved in its assembly from individual components

why is it advisable to use a positive control along with the organisms that you are testing?

the positive control would indicate that the medium was prepared correctly and makes it more sure that negative results are true negatives

is it acceptable to read a positive test before the incubation time is completes? how about an early negative result?

you can read a positive early, this means the organism has already produced casein, do not read a negative test early, it can just mean the organism is growing slowly and the enzyme did make casein yet

Provide a possible explanation as to why this test identifies the presence of cytochrome c oxidase and not other oxidases

ytochrome C oxidase is unique in its ability not only to oxidize cytochrome C, but also to reduce cytochrome C by a chromogenic reducing agent (the reducing agent is tetramethyl-p-phenylenediamine). Upon oxidation, the chromogenic agent develops color, while the Cyt-C gets reduced. Other cytochrome oxidases can perform the task of oxidation only, they cannot reduce their cytochromes. Hence, only Cyt-C will participate in the reaction.