Test for E. coli Observations Conclusions/ Interpretations (you must include mor
ID: 261647 • Letter: T
Question
Test for E. coli
Observations
Conclusions/ Interpretations (you must include more than simply positive or negative for full credit)
6) Glucose Ferm.(liquid broth test)
7) Lactose Ferm. (liquid broth test)
8) Sucrose Ferm.(liquid broth test)
9) Gelatin Hydrolysis
10) Indole
11) Methyl Red
12) Voges Proskauer
13) Citrate
Test for E. coli
Observations
Conclusions/ Interpretations (need to include more than simply positive or negative)
14) Triple Sugar Iron (TSI)
15) Urea Hydrolysis
16) Oxidase (see professor to obtain your dry slide)
17) Motility
18) Catalase
19) MacConkey Agar
Growth observed?________
Gram ? ___________
Lactose fermented?________
20) Eosin Methylene Blue agar (EMB)
Growth observed?________
Gram? ___________
Lactose fermented?________
21) Mannitol Salt (MSA)
Mannitol fermented?____________
Test for E. coli
Observations
Conclusions/ Interpretations (you must include more than simply positive or negative for full credit)
6) Glucose Ferm.(liquid broth test)
7) Lactose Ferm. (liquid broth test)
8) Sucrose Ferm.(liquid broth test)
9) Gelatin Hydrolysis
10) Indole
11) Methyl Red
12) Voges Proskauer
13) Citrate
Explanation / Answer
This test is used to see if the microbe can ferment the carbohydrate sucrose as a carbon source or not.
Bacteria grown on this medium has not produced the enzyme citrate-permease ,which is capable of converting citrate to pyruvate.
When the bacteria metabolizes citrate, the ammonium salts are broken down to ammonia increasing the alkalinity. The shift in pH turns the bromthymol blueindicator in the medium from green to blue above pH 7.6.
Tests for E.coli Observations Conclusion/ Interpretation 6) Glucose Ferm (Liquid broth test) pH indicator turns yellow Result is positive , organism is capable of fermenting the sugar glucose, so acidic byproducts are formed and the pH indicator turns yellow. E. coli is capable of fermenting glucose . 7) Lactose Ferm(Liquid broth test) culture will chang to yellow in the presence of acids (indicating a positive test) shows positive for e.coli, to see if the microbe can ferment the carbohydrate (sugar) lactose as a carbon source. 8) Sucrose ferm (Liquid broth test) Is variable for E.coli,This test is used to see if the microbe can ferment the carbohydrate sucrose as a carbon source or not.
9) Gelatin Hydrolysis The control tube and the test tube both remains completely solidified. Test -ve for E.coli, The test is used to determine the ability of an organism to produce extracellular proteolytic enzymes gelatinases which hydrolyze gelatin. but here it is -ve for E.coli. 10) Indole Formation of a pink to red color (cherry-red ring) in the reagent layer on top of the medium within seconds of adding the reagent. It is positive for E.coli,This test shows the ability of the bacteria to decompose the amino acid tryptophane to indole, which gets accumulates in the medium. Indole production test is important in the identification of E. coli. 11) Methyl red Red color produced Tests positive for E.coli, The color developes due to strong acid production from dextrose fermentation / It is used to detect aciditywhen an organism ferment glucose. 12) Vogus prokauer Yellow color produced Tests -ve for E.coli/ organism not used Butylene glycol pathway and not produced acetonin 13) Citrate No growth or trace of growth Test -ve for E.coli, No growth indicatesBacteria grown on this medium has not produced the enzyme citrate-permease ,which is capable of converting citrate to pyruvate.
When the bacteria metabolizes citrate, the ammonium salts are broken down to ammonia increasing the alkalinity. The shift in pH turns the bromthymol blueindicator in the medium from green to blue above pH 7.6.
14)Triple sugar iron Growthyellow slant, yellow butt, gas is positive, no H 2 S is produced An acid/acid (yellow slant/yellow butt) reaction indicates the fermentation of dextrose, lactose and/or sucrose. A blackening of the medium occurs in the presence of H 2 S. Bubbles or cracks in the agar indicate the production of gas. 15) Urea hydrolysis No color change occurs. negative for E.coli,urease test is used to see the ability of an organism to split urea, by the production of the enzyme urease. but negative organisms produce no color change or yellow due to production of acid. 16) Oxidase No purple-blue colour/No colour change. It shows it is -ve.The oxidase test detects the presence of cytochrome oxidase system which catalyses the transport of electrons between electron donors in the bacteria and a redox dye- tetramethyl-p-phenylene-diamine. in case of positive result, the dye is reduced to deep purple color. but in e.coli it's -ve. 17) Motility Motile Tests positive for E.coli 18) Catalase Copious bubbles are produced. positive for e.coli, it shows presence of catalase enzyme , catalase helps in the release of oxygen from hydrogen peroxide (H2O2).Bacteria by this protects themselves from the lethal effect of Hydrogen peroxide which gets accumulated as an end product of aerobic carbohydrate metabolism. 19) Mac konkey agar Growth occurs, having colonies pink to red with bile salt precipitate surrounding the colonies Result is positive,isolated colonies of lactose-fermenting bacteria looks pink to red in color and are surrounded by a zone of bile salt precipitation.helps to test the GM-ve bacteria. 20) Mannitol salt (MSA) No growth Mannitol Salt Agar (MSA) is used to determine if the bacteria is halophilic (salt loving) and is the bacteria can ferment mannitol. If the bacteria is able to grow then it is a halophilic bacteria, due to it's ability to grow in a high salt environment. A positive result for mannitol fermentation is the formation of a yellow halo around the bacterial colony, indicating production of acid from the breakdown of mannitol. but here no growth so it is -ve.Related Questions
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