Complex chemical stress arises during the production of biofuels. Large-scale mutant fitness profiling was used to identify bacterial and yeast tolerance genes and to model fitness in a complex hydrolysate mixture. The resulting model can be used to engineer more tolerant strains.

This study shows that, in bacteria grown in the laboratory, there is little correlation between when genes are important for fitness and when they are more highly expressed. Most genes thus appear to be regulated by signals that are not related to their function.

Drosophila simulans identification. We thank undergraduate students Damani Fitzgerald, Aaron Johnson, Imani Lowery, and Angela Sehres for technical assistance. This study was supported in parts by NIH R01 DK096907 (PDN), NIH-NIGMS (KMB), and R15ES029673 (AKM).