Page 121 - MNUmicrobiology practical 2025

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

• Media: Simmons Citrate Agar- contains sodium citrate as sole carbon source, mineral

salts, and pH indicator Bromothymol blue

• Reagents/indicators: Bromothymol Blue is a pH indicator. Yellow at less than pH 6.0,

green between pH 6.0-7.6, Prussian blue at pH greater than 7.6.

• Mechanism/reactions: Utilization of citrate leaves a sodium residue, increasing pH of the

medium

• Interpretation:

(+) = medium changes color from green to

Prussian blue

(-) = no change, medium remains green

General Microbiology & Immunology (PM 401) Practical note Page 110