Anaerobic growth and potential for amino acid production by nitrate respiration in Corynebacterium glutamicum.
Oxygen limitation is a crucial problem in amino acid fermentation by Corynebacterium glutamicum. Toward this subject, our study was initiated by analysis of the oxygen-requiring properties of C. glutamicum, generally regarded as a strict aerobe. This organism formed colonies on agar plates up to relatively low oxygen concentrations (0.5% O(2)), while no visible colonies were formed in the absence of O(2). However, in the presence of nitrate (NO3-), the organism exhibited limited growth anaerobically with production of nitrite (NO2-), indicating that C. glutamicum can use nitrate as a final electron acceptor. Assays of cell extracts from aerobic and hypoxic cultures yielded comparable nitrate reductase activities, irrespective of nitrate levels. Genome analysis revealed a narK2GHJI cluster potentially relevant to nitrate reductase and transport. Disruptions of narG and narJ abolished the nitrate-dependent anaerobic growth with the loss of nitrate reductase activity. Disruption of the putative nitrate/nitrite antiporter gene narK2 did not affect the enzyme activity but impaired the anaerobic growth. These indicate that this locus is responsible for nitrate respiration. Agar piece assays using L-lysine- and L-arginine-producing strains showed that production of both amino acids occurred anaerobically by nitrate respiration, indicating the potential of C. glutamicum for anaerobic amino acid production.
Takeno
Seiki
S
Department of Bioscience and Biotechnology, Faculty of Agriculture, Shinshu University, Nagano, 399-4598, Japan.
Ohnishi
Junko
J
Komatsu
Tomoha
T
Masaki
Tatsuya
T
Sen
Kikuo
K
Ikeda
Masato
M
D000596:Amino Acids / Q000096:biosynthesis*; D001421:Bacteria, Anaerobic / Q000378:metabolism*; D048230:Corynebacterium glutamicum / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology
D000596:Amino Acids; D009566:Nitrates