What is coagulate? Why does pseudomonas give negative reaction on all the fermen

Question

What is coagulate? Why does pseudomonas give negative reaction on all the fermentation? Why must you have a pure culture for inoculation of sugar fermentation and other biochemical? What would happen if culture was contaminated or mixed? Define IMViC. Is MacConkey agar a diffential medium, a selective medium or both? What is coagulate? Why does pseudomonas give negative reaction on all the fermentation? Why must you have a pure culture for inoculation of sugar fermentation and other biochemical? What would happen if culture was contaminated or mixed? Define IMViC. Is MacConkey agar a diffential medium, a selective medium or both? Why does pseudomonas give negative reaction on all the fermentation? Why must you have a pure culture for inoculation of sugar fermentation and other biochemical? What would happen if culture was contaminated or mixed? Define IMViC. Is MacConkey agar a diffential medium, a selective medium or both?

Explanation / Answer

I have answered question 1,3,4,and 5. Question number 2 needs to be more specific.

1) Coagulate:

It ia a process by which a liquid turns to solid or semisolid state, Clotting of blood and formation of curd are examples of coagulation and the solid/ semisolid mass is called a coagulate.

3) A pure culture is a must in sugar fermentation so as to get maximum product, such as ethanol without any contamination, if the culture used in not pure the the unwanted organisms may release other undesired byproducts which might alter the taste and nature of the end product, which might lead to discardinfg the entire batch of fermented product.

In bichemical tests if culture is not pure it could result in false negatives or false positive in biochemical tests, which could lead to giving a patient an incorrect treatment (example: giving ß-lactam antibiotics when macrolides should be used).

4) IMViC:

The IMViC tests are a group of individual tests used in microbiology lab testing to identify an organism in the coliform group. A coliform is a gram negative, aerobic or facultative anaerobic rod which produces gas from lactose within 48 hours. The presences of some coliforms indicate faecal contamination.

The term "IMViC" is an acronym for each of these tests. "I" is for indole test; "M" is for methyl red test; "V" is for Voges-Proskauer test, and "C" is for citrate test. The lower case "i" is merely for "in", as the Citrate test requires coliform samples to be placed "in Citrate".

5) MacConkey agar:

MacConkey’s Agar is both a selective and differential media; it is selective for Gram negative bacteria and can differentiate those bacteria that have the ability to ferment lactose.MacConkey's is a selective medium that inhibits the growth of Gram-positive bacteria due to the presence of crystal violet and bile salts. Gram-negative bacteria grow well on MAC.

MAC is also a differential, that is, this medium differentiates or distinguishes between groups of bacteria on the basis of a color change reaction. MacConkey’s contains two additives that make it differential; neutral red (a pH indicator) and lactose (a disaccharide). By utilizing the available lactose in the medium, Lac+ (Lactose positive) bacteria such as Escherichia coli, Enterobacter and Klebsiella will produce acid in the medium, which lowers the pH of the agar below 6.8 and results in the appearance of red or pink colonies. The bile salts in the medium precipitate in the immediate neighborhood of the colony, causing the medium surrounding the colony to become hazy appearance. Non-lactose fermenting bacteria such as, Proteus species, Salmonella, Pseudomonas aeruginosa and Shigella cannot utilize lactose in the medium, and will use peptone instead. This results in the formation of ammonia, which raises the pH of the agar, and leads to the formation of white or colorless colonies in the plate.

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