Fig. 2.

Antibiotic structures and representative DNA sequencing results. a Structures of ampicillin, cefotaxime, and imipenem. The position of the R1 group is indicated on the structure of ampicillin and the R1 and R2 groups are indicated on the structures of cefotaxime and imipenem. b Representative DNA sequencing results of clones from naive and antibiotic-selected NDM-1 libraries. A total of 124 experiments from 31 libraries were sequenced and the results from three representative libraries are shown. The number of times the wild-type amino acid occurred in the sequenced library is boxed in each experiment. AMP ampicillin, CTX cefotaxime, IMP imipenem