text: Loss of gene activity leads to a nutritional requirement (auxotrophy) not exhibited by the wildtype (prototrophy).
  Amino acids:
  *ala = alanine
  *arg = arginine
  *asn = asparagine
  Some pathways produce metabolites that are precursors of more than one pathway. Hence, loss of one of these enzymes will lead to a requirement for more than one amino acid. For example:
  *ilv: isoleucine and valine
  Nucleotides:
  *gua = guanine
  *pur = purines
  *pyr = pyrimidine
  *thy = thymine
  Vitamins:
  *bio = biotin
  *nad = NAD
  *pan = pantothenic acid