Patent ID: 6942973

Claim:
A method for isolating a gene encoding an enzyme, comprising: (a) adding a mixture of labeled first nucleic acid probes, isolated from a microbial strain cultured on medium without an inducing substrate, and labeled second nucleic acid probes, isolated from the microbial strain cultured on medium with the inducing substrate, to an array of random genomic DNA fragments of unknown sequence and unknown function of the microbial strain under conditions where the labeled nucleic acids hybridize to complementary sequences of the random genomic DNA fragments in the array, wherein the first nucleic acid probes are labeled with a first reporter and the second nucleic acid probes are labeled with a second reporter, wherein the inducing substrate is selected from the group consisting of cellulose, hemicellulose, lignin, phytic acid, starch, pectin, and protein; (b) examining the array under conditions wherein the relative expression of the genes of the microbial strain is determined by the observed hybridization reporter signal of each spot in the array in which (i) the random genomic DNA fragments in the array that hybridize to the first nucleic acid probes produce a distinct first hybridization reporter signal or to the second nucleic acid probes produce a distinct second hybridization reporter signal indicating induction of a gene by the presence of the inducing substrate in the culture medium of the microorganism, and (ii) the random genomic DNA fragments in the array that hybridize to both the first and second nucleic acid probes produce a distinct combined hybridization reporter signal; and (c) isolating from the microbial strain the gene induced by the presence of the substrate, wherein the gene encodes an enzyme that degrades the substrate.