[NiFe] hydrogenase is a type of hydrogenase, which is an oxidative enzyme that reversibly converts molecular hydrogen in prokaryotes including Bacteria and Archaea. The catalytic site on the enzyme provides simple hydrogen-metabolizing microorganisms a redox mechanism by which to store and utilize energy via the reaction shown in Figure 1. This is particularly essential for the anaerobic, sulfate-reducing bacteria of the genus Desulfovibrio as well as pathogenic organisms Escherichia coli and Helicobacter pylori. The mechanisms, maturation, and function of [NiFe] hydrogenases are actively being researched for applications to the hydrogen economy and as potential antibiotic targets.