show Abstracthide AbstractRecently, five distinct clades of Escherichia have been recovered from the aquatic environments, and they are believed to be environmentally adapted. We collected more than 4000 strains from the various environment of Hong Kong and isolated 10 environmentally adapted E. coli isolates from freshwater sediment and freshwater periphyton. We will try to find how these strains have evolved and whether they are ecologically different from E. coli sensus stricto. These findings will expand our understanding of the ecology and the role of genetic traits, recombination, horizontal gene transfer and natural selection on the adaptation of E. coli population to different niches.