A strain of microorganism lacking the ability to synthesize one or more essential growth factors. 
Organism unable to synthesize an organic molecule which is required for its growth: when the compound is given to the organism with the other nutrients it requires, growth of the organism may occur.
<biology> Mutant that differs from the wild type in requiring a nutritional supplement for growth. A deficiency mutant. ... (02 Jan 1998) ... 
(awk´so-trōf) an auxotrophic organism.
A mutant that has a growth factor requirement (contrast with a prototroph).Mutant that differs from the wild-type in requiring a nutritional supplement for growth. A deficiency mutant.
Type: Term Pronunciation: awk′sō-trōf Definitions: 1. A mutant microorganism that requires some nutrient that is not normally required by the organism (prototroph) from which the mutant was derived.
auxotroph 1. A microorganism that requires nutrients from its environment in order to exist; for example, a mutant strain of an organism, e.g. a bacterium, that has lost the ability to synthesize a specific nutrient growth factor and must obtain it from its environment to survive. 2. A mutant organism, especially a microorganism, that has a nutrit...
nutritional mutant with a loss-of-function mutation in a gene encoding the biosynthesis of a specific nutrient such as an amino acid
a mutant organism, esp. a microorganism, that has a nutritional requirement not shared by the parent organism. Cf. prototroph (def. 1).