Question

Someone new is preparing media for lab and adds buffers to the EMB agar that raise the pH to 7.8. The starting pH of EMB plates should be 6.9 – 7.3. No one is aware of the change. The EMB plates are inoculated for identification of unknown bacteria. After the appropriate incubation time, the results are interpreted. Discuss the consequences of the change in starting pH to the interpretation of the results. (The answer is not that no organisms could grow.)

Answer 1

Answer and Explanation:

• Eosin Methylene blue agar or EMB agar consists of sucrose, lactose, methylene blue and Eosin Y. These segments make it a differential medium which permits development of gram-negative microorganisms. Gram positive microscopic organisms develop inadequately on this medium.  

• It is particular for development of gram-negative microscopic organisms. It likewise separates between non-fermenting gram negative enteric microscopic organisms and lactose fermenting.  

• Lactose fermenting gram negative microscopic organisms use lactose to deliver corrosive which changes the shading to dull purple. Some of the lactose fermenter will exhibit dim provinces with green metallic sheen while different settlements with purple focus. Green metallic sheen is because of creation of solid acids.  

• In the event that the beginning pH is 7.8 rather than 6.9-7.3, the color won't change shading regardless of creation of acids. Consequently, it won't be conceivable to separate between lactose fermenter and non-fermenters.