N2O reduction by Vibrio succinogenes

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Vibrio succinogenes is an anaerobic bacterium.
• Formate oxidation is a known metabolic pathway.
• Nitrous oxide (N2O) can act as a terminal electron acceptor in anaerobic respiration.

Purpose of the Study:

• To investigate the anaerobic growth of Vibrio succinogenes.
• To determine the role of nitrous oxide (N2O) as a terminal oxidant for Vibrio succinogenes.
• To elucidate the metabolic pathways involved in N2O and nitrate reduction by this bacterium.

Main Methods:

• Culturing Vibrio succinogenes under anaerobic conditions with formate as the electron donor.
• Supplementing cultures with nitrous oxide (N2O) as a terminal oxidant.
• Assessing the effect of acetylene (C2H2), an inhibitor of N2O reduction, on bacterial growth.
• Analyzing the reduction products of nitrate under varying formate availability.

Main Results:

• Vibrio succinogenes demonstrated anaerobic growth fueled by formate oxidation, with N2O quantitatively reduced to dinitrogen (N2).
• The presence of acetylene (C2H2) completely inhibited growth, confirming the essential role of N2O reduction.
• Nitrate was reduced to nitrite or ammonia, with N2 not being a product of nitrate reduction. The reduction of nitrate to ammonia appeared to be coupled to energy-yielding reactions.

Conclusions:

• Nitrous oxide (N2O) is a crucial terminal oxidant for the anaerobic respiration and growth of Vibrio succinogenes.
• The bacterium possesses an efficient N2O reductase system, converting N2O to N2.
• Nitrate reduction pathways in Vibrio succinogenes differ from N2O reduction, producing nitrite or ammonia but not dinitrogen.