Hydrogen oxidizing bacteria

Hydrogen oxidizing bacteria, or sometimes Knallgas-bacteria, are bacteria that oxidize hydrogen as a source of energy with oxygen as final electron acceptor. See microbial metabolism (hydrogen oxidation). These bacteria include Hydrogenobacter thermophilus, Hydrogenovibrio marinus, and Helicobacter pylori. There are both Gram positive and Gram negative knallgas bacteria.

Most grow best under microaerophilic conditions. They do this because the hydrogenase enzyme used in hydrogen oxidation is inhibited by the presence of oxygen, but oxygen is still needed as a terminal electron acceptor.

The word "Knallgas" is Swedish and German for "bang-gas" and means a mixture of hydrogen and oxygen: see oxyhydrogen.