Question

You are measuring the growth and competition of Ps. fluorescence and B. megaterium. They are mixed in a culture together. The culture is then added to a PEA plate and to a EMB plate. What is the expected hypothesis?

Answer 1

Pseudomonas fluorescence is a gram negative bacteria and Bacillus megaterium is a gram postive bacteria. When they are mixed in a culture together and added to PEA plate which is a selective medium for the growth of Gram postive baterias and the active ingredient phenylethyl alcohal reduces the growth of gram negative bacteria thus helps in distinguishing the Ps. fluroscence from B. megaterium while EMB plate helps in inhibiting the growth of gram postive bacteria and promotes the growth of gram negative bacteria Ps. fluroscence . The mechanism behind the process is that when the cultures are mixed together and are plated on different agar mediums we are able to distinguish between different strains of bacteria as PEA allows Gram positive bacteria and EMB allows Gram Negative bacteria. Moreover, their formation of colony patterns also hepls in differentiate between them. As Bacillus megaterium forms dark purple complexes and  Pseudomonas fluorescence and appear red in colour.