Page 103 - MNUmicrobiology practical 2025

General Microbiology & Immunology (PM 401) second level Semester 4 2024/2025

Certain bacteria grow on this media causing lactose fermentation with production of

acid which will change the color of the indicator (neutral red) and the bacterial colony

appear pink color. Example: E. coli

Other organisms such as Salmonella can grow on the media but not cause lactose

fermentation. So their colonies will not take the pink color

Simmon’ citrate media

• This media used to test the ability of the organism to

utilize citrate as a source of Carbon. This media has a pH

indicator called Bromothymol Blue added that detects the

change in pH. In acidic pH indicator is green and in

alkaline a pH the color is blue

• Upon citrate utilization the PH of the media will be

reduced causing change in color of the media into blue

General Microbiology & Immunology (PM 401) Practical note Page 92