Question

You add 10 g/L of a nutrient to a growing liquid culture of E. coli; after five hours, you observe that in response to the addition of the nutrient, the quantity of cell mass has doubled. The nutrient source of which element is the one you added that most likely yielded this effect?

Answer 1

Carbon

Step-by-step explanation:

Bacteria like E.coli requires several nutrients in the culture medium for its growth. Nutrients are required according to the bacterial cell's elemental composition. E.coli cell primarily consists of carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus, calcium, magnesium and other trace elements like zinc, copper etc.

Out of all the elements, carbon is the major one as it makes up 50% of the dry weight of the E.coli cell. The cell usually obtains it from organic compounds or CO2. Since here the addition of nutrient doubled the E.Coli cell mass, it is most probably the source of Carbon because carbon is the major constituent of the cell.