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#nutritional requirements

2 public questions tagged with this topic.

Microbial genetics

Auxotrophs differ from prototrophs because auxotrophs

Auxotrophs carry mutation in a gene encoding enzyme in biosynthetic pathway, blocking synthesis of specific growth factor such as histidine, leucine, arginine, or tryptophan. Unlike prototrophs that produce everything, auxotrophs need exogenous supplement of that metabolite added to medium to grow. They are isolated after mutagenesis and used to pinpoint pathway steps and map genes. Reversion to prototrophy via back-mutation or recombination confirms gene identity. Conditional growth requirement makes auxotrophs ideal for selection in conjugation, transformation, and complementation experiments for pathway dissection.

Ref: Hartl & Jones, Genetics, 8th ed., Chapter 6: Auxotrophic Mutants and Nutritional Requirements

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Gene Dissection and Complementation

Minimal medium contains

Minimal medium deliberately excludes complex nutrients containing only simple carbon source like glucose or sucrose supplying energy, inorganic salts supplying nitrogen, phosphate and sulfate, trace elements and single vitamin biotin for Neurospora. No amino acids, purines or yeast extract added forcing organism to manufacture all macromolecular precursors endogenously via its own enzymes. This selective medium supports prototrophs but reveals auxotrophs through growth failure, enabling screens for nutritional mutants and ordering of biosynthetic steps via supplementation tests after mutagenesis in microbial genetics experiments.

Ref: Griffiths et al., Introduction to Genetic Analysis, 12th ed., Chapter 7: Minimal versus Complete Medium Design

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