Microarray technology allows co-regulated genes to be identified. In order to identify genes that are controlled by specific regulators, gene expression can be compared in mutant and wild-type bacteria. However, there are a number of pitfalls with this approach; in particular, the regulator may not be active under the conditions in which the wild-type strain is cultured. Once co-regulated genes have been identified, proteinbinding motifs can be identified. By combining these data with a map of promoters, or operons (the operome), the regulatory networks in the cell (the regulome) can start to be built up.