Question

how reducing potential that occur in hydrogen bacteria?

Answer 1

Hydrogen oxidizing bacteria are those bacteria which are facultative autotrophs which can use hydrogen as an electron donor. They are classified into aerobes and anaerobes. The aerobes use hydrogen as an electron donor and oxygen as an acceptor.

Reduction or oxidation potential also known as redox potential is a measure of the tendency of a molecule to acquire or loose electrons to an electrode and getting reduced or oxidised respectively. Redox potential is measured in volts (V).

In case of hydrogen oxidizing bacteria, this special property of molecular hydrogen , that is the redox potential is used with the help of the presence of hydrogenases.

Hydrogen is the most widespread element on earth . It is used as energy source in many biological processes sue to its highly negative redox potential (E₀’= -0.414 V) .

To be a little elaborate, in the case of hydrothermal vent bacteria. H₂ is an important electron donor in hydrothermal vents. In this environment oxidation of hydrogen originates energy , enough to conduct ATP synthesis and leading to autotrophic CO₂ fixation. In hydrothermal vents,along with other chemosynthetic reactions, the oxidation of the sulphide and the hydrogen play very important roles. For the autotrophic carbon fixation, hydrogen oxidation metabolism is more favored than the sulfide/thiosulfate oxidation. This is because to fix a mole of carbon by the hydrogen oxidation, one third of the energy necessary for the sulphide oxidation is used. This is possible due to the redox potential of hydrogen, which is more negative than NAD (P)/H.