Question

Imagine you did a gram stain and observed a mixture of two species. One is a gram positive cocci and the other is a gram-negative rod. How could you use PEA and EMB to help you get a pure culture of each species?

Answer 1

a pure culture means one species of microorganisms is only growing on a medium. here PEA agar and EMB age are two agar mediums that facilitates the growth of gram Positive and gram negative bacterias. main classes of bacterias are cocci and rod. PEA is a best medi to grow gram positive bacteria cocci. while growth of most gram negative bacterias are inhibited in pea agar. EMB agar also facilitates the growth of gram positive cocci. examples are enterococci, staphylococci etc... gram positive rods are also is facilitated in pea . salmonella is a rod shaped gram negative bacteria, that inhibit growth on EMB agar. the aniline dyes inhibit some of gram Positive and fastidious gram negative growth on EMB agar. to obtain pure culture we should spread bacteria on surface of solid media. it will grow and multiply ina isolated manner.