Final answer:
Among the given options, NADH is not considered a growth factor for microbes as it is produced internally by cells, unlike the other substances which they need to obtain from their environment.
Step-by-step explanation:
The correct answer to the question which states, "all of the following are examples of growth factors used by microbes except" with the options (A) vitamins, (B) amino acids, (C) NADH, (D) heme, and (E) calcium is (C) NADH. Growth factors for microbes are essential compounds that the organism cannot synthesize on its own, and these include vitamins, amino acids, and heme which are vital for various cellular functions.
However, NADH is not considered a growth factor as it is a cofactor synthesized by cells during metabolic processes rather than being an exogenous substance that must be obtained from the environment as in the case of growth factors required by fastidious bacteria.