text: * F: Formylation (optional)
  * A: Adenylation (required in a module)
  * PCP: Thiolation and peptide carrier protein with attached 4'-phospho-pantetheine (required in a module)
  * C: Condensation forming the amide bond (required in a module)
  * Cy: Cyclization into thiazoline or oxazolines (optional)
  * Ox: Oxidation of thiazolines or oxazolines to thiazoles or oxazoles (optional)
  * Red: Reduction of thiazolines or oxazolines to thiazolidines or oxazolidines (optional)
  * E: Epimerization into D-amino acids (optional)
  * NMT: N-methylation (optional)
  * TE: Termination by a thio-esterase (only found once in a NRPS)
  * R: Reduction to terminal aldehyde or alcohol (optional)
  * X: Recruits cytochrome P450 enzymes (optional)