An Asymbiotic Nitrogen-Fixing Bacterium from the Root Environment of Corn
AUTOR(ES)
Raju, P. N.
RESUMO
Examination of root systems and adhering soil associated with unusually green corn plants from nitrogen-deficient areas in fields has revealed higher acetylene-reducing activities than comparable root systems of chlorotic plants that appeared to be nitrogen deficient. From the root systems with acetylene-reducing activity, N2-fixing Enterobacter cloacae were isolated. Pure cultures of the organism grown in a medium lacking added fixed nitrogen reduced acetylene to ethylene and used N2 as a sole source of nitrogen under anaerobic conditions. Acetylene reduction was strikingly inhibited by 0.04 atm or greater partial pressures of O2; however, the bacteria maintained appreciable acetylene-reducing rates in medium exposed to partial pressures of O2 ranging from 0.005 to 0.015 atm. Nitrogenase activity in cell-free extracts of the bacterium was dependent upon Na2S2O4 and an ATP-generating system. Some environmental conditions expected to influence N2 fixation by free-living N2-fixing bacteria on root surfaces of nonlegumes are discussed.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=389796Documentos Relacionados
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