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Citrobacter diversus is capable of fermenting lactose, therefore it would test positive for lactose fermentation in biochemical tests. This bacterium produces acid and gas during lactose fermentation, which can be detected using appropriate methods such as the MacConkey agar test.
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Describe the effect a repressor has on the lac operon when lactose is present?
When lactose is present, it binds to the repressor protein, causing a conformational change that prevents the repressor from binding to the operator region of the lac operon. As a result, RNA polymerase can transcribe the structural genes of the lac operon, leading to the production of enzymes involved in lactose metabolism.
What does starch agar select for?
Starch agar selects for bacteria that can produce the enzyme amylase, which breaks down starch into smaller sugars. Bacteria that are able to grow on starch agar can hydrolyze starch, forming a clear zone around their colonies due to starch digestion.
What bacteria produces green colony with white puffy margin on Macconkey agar plates?
The bacteria that produces green colonies with white, puffy margins on MacConkey agar plates is typically Escherichia coli. This appearance is due to the fermentation of lactose, which leads to the production of acids and gases, causing the characteristic color change and morphology on the agar plate.
What are the MacConkey test results for s epidermidis?
Staphylococcus epidermidis is a gram-positive bacterium and does not ferment lactose. Therefore, on a MacConkey agar plate, S. epidermidis would appear as colorless, indicating a negative result for lactose fermentation. Additionally, there would not be any pink or red colonies representing acid production.
Why are some organisms positive in the ONPG Test but negative when tested for the ability to metabolize lactose?
In the ONPG test, organisms may be positive due to the presence of beta-galactosidase enzyme, which cleaves ONPG and produces a yellow color. However, in the lactose fermentation test, some organisms may lack other necessary enzymes or transport systems to fully metabolize lactose, resulting in a negative result despite having beta-galactosidase.
What happens when you make curd from milk?
When you make curd from milk, the milk ferments due to the introduction of good bacteria like Lactobacillus. This bacteria converts the lactose in the milk into lactic acid, which thickens the milk and gives it a tangy flavor. The result is a creamy, tangy product known as curd or yogurt.
Which bacteria gives raffinose utilization test?
The bacteria Escherichia coli gives a positive result for the raffinose utilization test. This test is used to differentiate between bacterial species based on their ability to ferment raffinose, a trisaccharide sugar. If an organism can ferment raffinose, it will produce acid and gas, causing a drop in pH and the release of bubbles in the medium.
Which of the following involves a chemical change combinding an acid and a base dew forming or souring milk?
Souring milk involves a chemical change where lactic acid is produced by the fermentation of lactose in milk by bacteria. This is not the result of combining an acid and a base, but rather the conversion of lactose (a sugar) into lactic acid.
What are coliform bacteria?
A coliform count is a microbiological assay of the number of coliform-type bacteria living in a certain sample. This is often used as a measure of fecal contamination of water supplies.
Ability of bacteria to produce insulin was result of?
Genetic engineering of the bacteria.
Does lactose can give a positive result in xanthoprotein test?
nitration of the benzene ring and gives positive
What is the positive result for mucic acid test?
A positive result for a mucic acid test shows the presence of mucic acid in the sample being tested. This result may indicate certain metabolic disorders or conditions such as mucopolysaccharidoses or pentosuria. Additional testing and evaluation by a healthcare provider would be needed to determine the underlying cause of the positive result.
What happens if your lactosentolerent?
Lactose intolerance results from the body's inability to produce an enzyme necessary to break down lactose found in most dairy products. Consumption of such foods can result in nausea, diarrhea and cramping. There is a racial preponderance for lactose intolerance, with African-American and Asian populations having as much as 70% lactose intolerance in their populations.
What is difference between lactic acid and lactose?
Lactic acid is a chemical compound produced during anaerobic respiration in muscles, while lactose is a sugar found in milk. Lactic acid contributes to muscle fatigue, while lactose can cause digestive issues in individuals with lactose intolerance.
Describe the effect a repressor has on the lac operon when lactose is present?
When lactose is present, it binds to the repressor protein, causing a conformational change that prevents the repressor from binding to the operator region of the lac operon. As a result, RNA polymerase can transcribe the structural genes of the lac operon, leading to the production of enzymes involved in lactose metabolism.
What does starch agar select for?
Starch agar selects for bacteria that can produce the enzyme amylase, which breaks down starch into smaller sugars. Bacteria that are able to grow on starch agar can hydrolyze starch, forming a clear zone around their colonies due to starch digestion.
In examples of chemical changes the odor of sour milk indicates a chemical change has taken place true or false?
True. The souring of milk is a chemical change caused by the breakdown of lactose sugars into lactic acid by bacteria. The change in odor is a result of this chemical reaction.
