Would a single medium be likely to function for both selecti

Would a single medium be likely to function for both selection and differential? Why or why not? Would a single medium likely function as an enriched and selective agar? Why or why not? What does the term \"hemolysis\" mean? Which hemolysis pattern would you most likely expect to occur with an extremely virulent pathogen? Explain.

Solution

Answer 1:

A single medium CAN serve for both selection and differentiation for several bacterial species because these species can be isolated in one medium and at the same time, show differential reaction or growth patterns in the same medium. For example, MacConkey’s Agar can be used as selective medium for Gram negative bacteria and same can be used for differentiating those bacteria which can ferment lactose.

Answer 2:

A single medium CANNOT serve as both, enriched as well as selective medium because the enriched media has nutrients added to enhance growth of bacteria whereas the selective medium also has ingredients that inhibit the growth of some bacteria. For example, if a sample from stools were to be cultured on an enrich medium, almost everything will grow on it. A selective media like MacConkey’s Agar would be more useful for selection purpose.

Answer 3:

Breakdown of red blood cells is called hemolysis. It can be witnessed in Staphylococcus cultured on blood agar.

Answer 4:

Virulent strain lyse (breakdown) the blood cells completely with the help of beta lysine. So one can clearly see in the red opaque background of the medium, some semi translucent or small opaque zones that are colonies of these extremely virulent pathogens. These contrast with the less virulent strains which greening of the agar and no marked differentiation form the enriched base in non-virulent strains.