The objective of this study was to investigate the effect of a lysine biosynthesis insertion mutation on the growth response and phenotype of Escherichia coli. The lysA gene encodes the last enzyme in the lysine biosynthetic pathway in most bacteria. This E coli insertion mutant exhibited altered growth physiology and phenotype of the recipient E coli. The constructed mutant could grow in the absence of lysine supplementation although the extent of growth after 7 h incubation in the presence of most lysine concentration was significantly (p < 0.05) decreased compared to that observed with the parent E coli strain. The mutant was also less able to utilize carbon and nitrogen substrates than the parent E coli strain as determined by using phenotype arrays. These results suggest that the carbon and nitrogen phenotype profiles of E coli when measured on phenotype arrays are altered after targeted insertion mutagenesis in the lysA gene. Creation of altered phenotypes may have potential for pharmaceutical and biotechnological applications of lysine E coli metabolism. (C) 2003 Elsevier Science Ltd. All rights reserved.