In 2013, a team of microbiologists led by Professor Volker Müller from Goethe University Frankfurt discovered an unusual enzyme in a heat-loving (thermophilic) bacterium: the hydrogen-dependent CO2 reductase HDCR. It produces formic acid (formate) from gaseous hydrogen (H2) and carbon dioxide (CO2), and in the process the hydrogen transfers electrons to the carbon dioxide. That makes this HDCR the first known enzyme which can directly utilize hydrogen. In contrast, all enzymes known until then that produce formic acid take a detour: they obtain the electrons from soluble cellular electron transfer agents, which for their part receive the electrons from the hydrogen with the help of other enzymes.