1. Identify the purpose of each ingredient in each medium. What will bacteria th

Question

1. Identify the purpose of each ingredient in each medium. What will bacteria that grow on this medium use each ingredient to produce? Please be specific in terms of macromolecules needed to produce cells, and the macronutrients and micronutrients used for these purposes.

NA: Peptone

meat extract

agar

dH2O

GSA: Glucose

sodium chloride

magnesium sulfate

ammonium phosphate

potassium phosphate

agar

dH2O

2. When growing, many bacteria produce acid byproducts as a result of their metabolism. Too much acidity can inhibit bacterial growth. As such, media often includes some buffering capacity to limit the change in pH. Which components of the recipes for NA and GSA do you think help accomplish buffering of each medium? Hint: see Nester chapter 4.

Explanation / Answer

Nutrient agar

Peptone: rich in organic nitrogen, Amino acids, and proteins. It is needed for the synthesis of proteins and nucleic acids

Meat extract: Carbon, amino acids and nitrogen. It is essential for the synthesis of carbohydrates and proteins

Agar: solidifying agent

dH20: Essential for all metabolic pathways, source of hydrogen and oxygen. Essential for the formation of cytoplasm and proteins

GSA

Glucose: Rich source of carbohydrates. Essential for the energy production

Sodium chloride: Required for osmotic balance

Magnesium sulfate: Magnesium acts as a cofactor for enzymes involved in DNA replication and protein synthesis

Ammonium phosphate: Ammonia is a source of nitrogen. It is essential for the synthesis of amino acids and proteins. Phosphate group is required for the synthesis of DNA.

Potassium phosphate: Potassium maintain the pH of the cell and the phosphate group is required for the synthesis of DNA.

Agar: Solidifying agent

dH20: required for all metabolic reactions. Souce of Hydrogen and oxygen. Essential for the activity of enzymes and it is required for the development of cytoplasm.

2. In nutrient agar, water acts as a buffering agent.

In GSA agar, Ammonium phosphate and potassium phosphate acts as buffering agent.

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