Bacteria are everywhere and can eat just about anything, including such unappetizing fare as petroleum sludge. Therefore, they must possess the enzymes (and the genes encoding the enzymes) that catabolize hydrocarbons. In the past, the challenge has been to identify and cultivate the desired species; advances in technology have made it feasible to bypass cultivation and to browse for specific genes (enzyme activities) in metagenome (expression) libraries. Uchiyama et al. take the next step in devising a method of sorting the library contents on the basis of substrate specificity and then searching for genes of interest. Their approach succeeds because bacteria rely on gene regulatory networks (and even riboswitches) that, in many cases, are induced or repressed by small molecules--either the substrate itself or chemically related compounds. Starting with a metagenome library made from petroleum-contaminated groundwater, they end up with a P450 enzyme that catalyzes hydroxylation (which makes hydrocarbons more polar and amenable to catabolism) of 4-hydroxybenzoate. -- GJC
Nature Biotechnol. 23, 88 (2005).
