Aerobic Hydrogen Production via Nitrogenase in Azotobacter vinelandii CA6.
The diazotroph Azotobacter vinelandii possesses three distinct nitrogenase isoenzymes, all of which produce molecular hydrogen as a by-product. In batch cultures, A. vinelandii strain CA6, a mutant of strain CA, displays multiple phenotypes distinct from its parent: tolerance to tungstate, impaired growth and molybdate transport, and increased hydrogen evolution. Determining and comparing the genomic sequences of strains CA and CA6 revealed a large deletion in CA6's genome, encompassing genes related to molybdate and iron transport and hydrogen reoxidation. A series of iron uptake analyses and chemostat culture experiments confirmed iron transport impairment and showed that the addition of fixed nitrogen (ammonia) resulted in cessation of hydrogen production. Additional chemostat experiments compared the hydrogen-producing parameters of different strains: in iron-sufficient, tungstate-free conditions, strain CA6's yields were identical to those of a strain lacking only a single hydrogenase gene. However, in the presence of tungstate, CA6 produced several times more hydrogen. A. vinelandii may hold promise for developing a novel strategy for production of hydrogen as an energy compound.
Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA.
Jesse
J
Noar
USDA ARS-NCSU, Raleigh, North Carolina, USA.
Telisa
T
Loveless
Department of Automatic and Systems Engineering, Polytechnic University of Valencia, Valencia, Spain.
José Luis
JL
Navarro-Herrero
Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA.
Jonathan W
JW
Olson
Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA jbbarcen@ncsu.edu.
José M
JM
Bruno-Bárcena
D000332:Aerobiosis; D016948:Azotobacter vinelandii / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D016680:Genome, Bacterial; D006859:Hydrogen / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000235:genetics; D009591:Nitrogenase / Q000378:metabolism*; D017973:Tungsten Compounds / Q000378:metabolism
D017973:Tungsten Compounds; D006859:Hydrogen; D007501:Iron; D009591:Nitrogenase; C045951:tungstate