Question

Question 18 out of 7 points You have been given a special project to design a new selective and differential solid media that needs to select Gram (-) organisms and differentiate organisms by their ability to forment sucroso. Fill in the following tables based on your media. Selective ingredient Mode of Action U Differential ingredients [D] IC) Growth and Appearance Organism Klebsiella aerogenes (Sucrose (+)) Escherichia coli (Sucrose (-) Staphylococcus aureus (Sucrose (+) FI [G]

thats the whole question, so i dont know what to add here

Answer 1

A) selective ingredient - Bile salt or crystal violet

B) mode of action- prevent or inhibit the growth of Gram positive bacteria and enhance the growth of Gram negative bacteria

Differential ingredients- C) sucrose d) neutral red or any other acid base indicator.

Since the media to be prepared is to test the ability of bacteria to perform sucrose fermentation, the source of sugar should be sucrose. Fermentation results in decrease of pH i.e., acidic pH, so an acid base indicator should be used to find the difference.

Klebsiella aerogenes- sucrose fermentor- E) It is Gram negative so growth with pink or red colour colonies as sucrose is fermented forming acid byproducts.

E coli - sucrose non fermentors- F) Gram negative so growth is seen but colourless colonies as sucrose is not fermented, pH do not change. the bacteria might have used any other source such as peptones for growth.

S aureus- sucrose fermentor- G) no growth as it is Gram positive bacteria