0
What else can I help you with?
Explain why the TSI medium contains a lower concentration of glucose than of lactose and sucrose?
When any sugar is metabolized under anaerobic conditions (fermentation), there is increased acid production; thus the butt of the tube remains acid for a longer period of time. When glucose only is fermented, acid is produced throughout the medium but due to the relatively low concentration of glucose in the medium and the aerobic metabolism that is present on the slant, nitrogenous metabolic end products soon change the reaction of the slant to alkaline. These alkaline products neutralize the small amounts of acids present in the slant but are unable to neutralize the large amounts acid present in the butt. Thus, the appearance of an alkaline (red) slant and an acid (yellow) butt after 24 hours incubation indicates that the organism is a glucose fermenter but is unable to ferment lactose and sucrose. Bacteria that ferment lactose or sucrose (or both), in addition to glucose, produce such large amounts of acid that the oxidative deamination of protein that may occur in the slant does not yield enough alkaline products to cause a reversion of pH in that region. Thus, these bacteria produce an acid slant and acid butt. The inclusion of sucrose permits separation of certain Proteus organisms which ferment sucrose from the salmonellae since both of these groups of organisms are lactose-negative and both may produce hydrogen sulfide.AC
Does Enterobacter aerogenes produce gas in the Kligler Iron Agar test?
Yes. Enterobacter aerogenes ferments lactose and glucose as well as producing gas. It does not produce H2S. Occasionally the slant may revert to an alkaline reaction even though lactose has been fermented. Another lactose test should be formed, such as the reaction on MacConkey agar
What is the purpose of lactose in the macconkey agar?
Lactose in MacConkey agar serves as a fermentable carbohydrate that allows for the differentiation of bacteria based on their ability to ferment lactose. Lactose fermentation produces acidic byproducts, which lower the pH of the agar, causing lactose-fermenting bacteria to produce pink/red colonies while non-fermenters appear colorless.
Why isn't a pH indicator needed in the lactose broth fermentation tubes?
A pH indicator is not needed in lactose broth fermentation tubes because the fermentation of lactose by bacteria produces acid as a byproduct, lowering the pH of the broth. This drop in pH can be visually observed as a color change in the medium, indicating lactose fermentation.
How is lac operon different from trp operon?
1. in lac operon; gene activity is induced when lactose is present in the medium, whereas in case of trp operon, repression of the gene activity takes place in presence of tryptophan in the medium. 2. lac operon spans about 4-6kb...whereas trp operon spans abut 7kb. 3. lac operon helps in the breakdown of lactose into glucose and galactose, to generate energy( catabolic pathway ) in case of trp operon, it helps in the synthesis of enzymes required for the formation of the amino acid Tryptophan( anabolic pathway ). 4. lac operon is an example of positive regulation ; and trp operon is an example of negative regulation. Trp operon is also regulated by other mechanism called attenuation while no such even occurs in lac operon . .
Explain why the TSI medium contains a lower concentration of glucose than of lactose and sucrose?
When any sugar is metabolized under anaerobic conditions (fermentation), there is increased acid production; thus the butt of the tube remains acid for a longer period of time. When glucose only is fermented, acid is produced throughout the medium but due to the relatively low concentration of glucose in the medium and the aerobic metabolism that is present on the slant, nitrogenous metabolic end products soon change the reaction of the slant to alkaline. These alkaline products neutralize the small amounts of acids present in the slant but are unable to neutralize the large amounts acid present in the butt. Thus, the appearance of an alkaline (red) slant and an acid (yellow) butt after 24 hours incubation indicates that the organism is a glucose fermenter but is unable to ferment lactose and sucrose. Bacteria that ferment lactose or sucrose (or both), in addition to glucose, produce such large amounts of acid that the oxidative deamination of protein that may occur in the slant does not yield enough alkaline products to cause a reversion of pH in that region. Thus, these bacteria produce an acid slant and acid butt. The inclusion of sucrose permits separation of certain Proteus organisms which ferment sucrose from the salmonellae since both of these groups of organisms are lactose-negative and both may produce hydrogen sulfide.AC
What must happen for transcription of the lac operon genes to take place?
Lac operon is a set of genes that regulates the digestion of lactose. In absence of lactose in the medium, the repressor protein binds to the operator that inhibit the transcription of structural genes such as beta galactosidase, lactose permease and transacetylase. This makes sure to avoid the enzyme synthesis when there is no need!Conversely, when the lactose present in the medium, an isomer of lactose called allolactose bind to the repressor protein, the conformational change in the repressor let it to detach from repressor hence the RNA polymerase can transcribe the structural gene. Although this may be enough for synthesis of structual gene the system is tightly regulated by a protein called CAP (catabolite activator protein) and glucose.Glucose is a preferred source of energy for cell when this desirable source is present, lactose need not be used as a energy resource. What happens is there will be low level of cAMP when there is high amount of glucose and this keeps CAP inactive.When there is low glucose levels, the cAMP would be higher, that binds to CAP to make it active, which in turn binds to the promoter that enhance the transcription of structural genes.Thus, for efficient transcription lac operon structural genes, lactose must be present where glucose must be absent.
Quantity of lactose in levine eosin methylene blue agar?
Levine eosin methylene blue agar does not contain lactose. It is a selective and differential medium used for the isolation and differentiation of gram-negative enteric bacteria based on their ability to ferment lactose. The agar contains lactose as a substrate for fermentation, but the actual quantity of lactose present in the agar may vary depending on the manufacturer and the specific formulation of the medium.
What type of macromolecule is lactose and what is the monomer of that macromolecule?
Lactose is not a macromolecule. It is a disaccharide, that is one molecule of lactose is formed by the elimination of water between two simple sugar molecules, in this case galactose and glucose. Lactose can be made to link up into medium chain molecules, but this is a fairly random process and produces a mixture of products which are not digestible.
What reaction would you predict from an organism growing in litmus milk that has the following results in other media?
Assuming that you are asking about other media such as milk agar, PR lactose broth, purple lactose broth, and PR glucose broth, the answer you are looking for is as follows: A. A clear zone around the growth on a milk agar plate: indicates hydrolysis of casein, so should be clarification of medium present B. A/- in PR lactose broth: indicates lactose fermentation with acid and no gas produced, so should be pink litmus with acid clots and reduction of litmus in lower portion of medium C. A/G in purple lactose broth: indicates lactose fermentation with acid and gas produced, so should have pink litmus on top, acid clot, reduction of litmus, and fissures in the clot D. K in PR glucose broth: indicates peptone degradation with alkaline end products, so litmus should be blue
What is in milk that makes it a good culture medium for production of yogurt?
Lactose
How would the results of the starch hydrolysis change if glucose was added to the medium?
Adding glucose to the starch hydrolysis medium would provide an additional readily available source of energy for the organisms present. This could potentially increase the growth rate and metabolism of those organisms, leading to a faster breakdown of starch into glucose. As a result, the rate of starch hydrolysis may be accelerated in the presence of glucose.
Does Enterobacter aerogenes produce gas in the Kligler Iron Agar test?
Yes. Enterobacter aerogenes ferments lactose and glucose as well as producing gas. It does not produce H2S. Occasionally the slant may revert to an alkaline reaction even though lactose has been fermented. Another lactose test should be formed, such as the reaction on MacConkey agar
Which medium supports the fewest organisms?
Glucose
What is table milksugar?
Milk sugar is Lactose. A table sugar is medium sized granulated.
What bacteria grows in a medium of lactose fermentation?
It is always an unnamed substance that u can call anything
What is use double strength lactose broth?
Double strength lactose broth is used to selectively culture lactose fermenting bacteria. It contains a higher concentration of lactose compared to regular lactose broth, allowing for more efficient differentiation of lactose fermenters from non-fermenters based on acid production. This medium is often used in microbiology laboratories for various tests and experiments.
