Horizontal gene transfer in glycosyl hydrolases inferred from codon usage in Escherichia coli and Bacillus subtilis

Glycosyl hydrolase (GH) genes from Escherichia coli and Bacillus subtilis w ere used to search for cases of horizontal gene transfer. Such an event was inferred by G+C content, codon usage analysis, and a phylogenetic congruen cy test. The codon usage analysis used is a procedure based on a distance d erived from a Pearson linear correlation coefficient determined from a pair wise codon usage comparison. The distances are then used to generate a dist ance-based tree with which we can define clusters and rapidly compare codon usage. Three genes (yagH from E. coil and xynA and xynB from B. subtilis) were determined to have arrived by horizontal gene transfer and were locate d in E. coli CP4-6 prophage, and B. subtilis prophages 6 and 5, respectivel y. In this study, we demonstrate that with codon usage analysis, the propos ed horizontally transferred genes can be distinguished from highly expresse d genes.