Auxotrophs

Part of speech: noun

Definitions

1. A microorganism that cannot manufacture specific organic compounds essential for growth and must obtain them from its environment
2. A living cell, typically a bacterium or fungus, that lacks the ability to synthesize particular nutrients and therefore requires them to be supplied externally
3. An organism unable to produce certain required organic molecules internally and thus dependent on external sources for those substances to survive

Etymology: Ancient Greek had no word for this. The term is a modern scientific coinage built from two classical roots: "auxein," meaning "to increase" or "to grow," and "trophos," meaning "feeder" or "nourisher," from the verb "trephein," "to nourish." Combined, the parts suggest something that needs an external supply to grow. The name describes a strain of microorganism that has lost the ability to make a nutrient its ancestors could manufacture. Such a strain grows only when that nutrient is supplied in the growth medium, which made these mutants useful to geneticists for tracking which genes control which biochemical steps. The contrasting term, "prototroph," uses the Greek "protos," meaning "first," for the wild-type strain that can synthesize its own nutrients.