Effect of amino acids on expression of K99 adherence pili by Escherichia coli

Various common L-amino acids differed in their ability to suppress K99 production in E. coli. Strains of E. coli also varied in their sensitivity to amino acid-mediated suppression of K99. Alanine, methionine, leucine, and valine were the most suppressive amino acids. However, when compared to single amino acids, mixtures of these amino acids were frequently either less suppressive, non-suppressive, or even stimulatory for K99 expression.