Abstract: Provided herein are methods for measuring H2 production by a hydrogenase. Also provided are methods for evolving a hydrogenase or hydrogen-sensing system by comparing the level of production of H2 by the hydrogenase to the level Of H2 produced by a wild-type hydrogenase cultured under the same conditions and selecting a microorganism with increased H2 production over the H2 production by a microorganism having a wild-type hydrogenase. Further provided herein are microorganisms and plasmids comprising a hupSL promoter coupled with a reporter gene.