Patent ID: 7981844

Claim:
A method for screening an environmental nucleic acid library comprising uncharacterized nucleic acids for the presence of a nucleic acid encoding an enantioselective enzyme that can catalyze a reaction on a chiral substrate molecule to yield a factor essential for growth of a cell, wherein the factor essential for growth of the cell must be of a specific chirality to induce growth of the cell and the enantioselective enzyme can catalyze the reaction in both the forward and reverse directions, comprising: (a) providing an environmental nucleic acid library comprising a plurality of uncharacterized polypeptide-encoding nucleic acids; (b) providing a plurality of cells, wherein the cells lack an active form of the enantioselective enzyme and lack the factor essential for growth of the cells, wherein the factor must be of a specific chirality to induce growth of the cells; (c) inserting the nucleic acid library of step (a) into the cells of step (b) and incubating the cells under conditions wherein polypeptides encoded by the uncharacterized polypeptide-encoding nucleic acids of step (a) are expressed; (d) incubating the cells in a growth medium lacking the factor essential for cell growth, and providing the chiral substrate, wherein step (c) and step (d) are not carried out in any particular order or are done together; and (e) screening the cells for growth, wherein growth of the cells identifies the nucleic acid library as comprising a nucleic acid that encodes the enantioselective enzyme.