Question

b. MSA plate i. Substrate = ii. Product = C. EMB plate (fda.gov) i. Substrate = ii. Product =
explain what metabollic process, what substrate and product

Answer 1

Answer

According to the given question-

MSA plate- also called mannitol salt agar is selective and differential media. It is used as selective media for gram negative bectreria such as stephylococcus, as well as some gram positive microorganisms such as enterococcus. It is used as differential media for the stephylococcus bacteria because thay have capability of fermenting carbohydrate mannitol.

The medium containing about 7.5% of NaCl. So the bacteria which can tolerate this Salt concentration only those can survive in this medium.

Stephylococcus aureus have enzyme coagulase which catalyses the sugar mannitol into acid and produces yellow colony as indicated by phenol red with pH less than 6.9. those microorganisms cannot ferment mannitol gives pink colony.

Here the substrate are mannitol and product are acidic byproduct which changes the colour of medium.

EMB plate - contains Eosin Y and methylene blue stain or dye used for the selective and differential media for the selection of gram negative microorganisms.

This medium promote the growth of gram negative microorganisms while inhibit the growth of gram positive microorganisms.

Here the substrate are lactose which is converted into lactic acid by the microorganisms that are capable of fermenting lactose such as E.coli and gives metallic green colour.