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.
 The United States Government has rights in this invention under Contract No. DE-AC36-08G028308 between the United States Department of Energy and the Alliance for Sustainable Energy, LLC, manager and operator of the National Renewable Energy Laboratory.