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auxotroph aux·o·troph (ôk'sə-trŏf', -trōf')
A mutated microorganism having nutritional requirements that differ from those of unmutated microorganisms from the same strain.
auxotrophic aux·o·troph·ic (awk-sō-trŏf'ĭk)
Requiring one or more specific substances for growth and metabolism that the parent organism was able to synthesize on its own. Used with respect to organisms, such as strains of bacteria, algae, or fungi, that can no longer synthesize certain growth factors because of mutational changes.