Phage control mechanisms

Another reason for concluding that peptide antibiotics are not synthesized by the kind of template mechanism that is operative in protein formation is that variation of amino acids in the environment can shift the proportion of the molecular species of peptides that are being produced. In protein synthesis, specificity of amino acid sequence is under direct genetic control and single amino acid substitutions in such proteins as hemoglobin, tryptophane synthetase, or phage coat proteins are attributed to alteration in the nucleotide sequence of structural genes rather than to environmental variation (Mach and Tatum, 1964). 

---