Effect of Denitrification on Nitrogen Fixation in Light in a Photodenitrifier, Rhodopseudomonas sphaeroides forma sp. denitrificans |
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Authors: | Satoh Toshio; Shimazaki Tomoshiro |
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Institution: | Department of Biology, Tokyo Metropolitan University Fukazawa 2-1-1, Setagaya-ku, Tokyo 158, Japan |
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Abstract: | The effect of denitrification on N2 fixation was studied ina denitrifying photosynthetic bacterium, Rhodopseudomonas sphaeroidesforma sp. denitrificans. KNO3 inhibited diazotrophic growthin light, but NC3-dependent diazotrophic growth in darknesswas found. NO3 inhibited C2H2 reduction activity in lightin cells grown with NO3. NO3-dependent C2H2 reductionactivity in darkness also was present in cells grown with N2plus NO3, but not in cells grown on glutamate with NO3.NO3 repressed the synthesis of nitrogenase in light.This repression was not overcome by the addition of methioninesulfoximine. The inhibitory and repressive effect of NO3 was not mediatedby the NO2 produced from NC3 nor by the NH4+ excretedinto the medium. But, as N2 fixation is controlled by O2 (redoxcontrol) it seems to be mediated through the denitrificationprocesses. Much of the glutamine synthetase was adenylylatedin cells grown with NO3 and its adenylylation state closelyparallelled nitrogenase activity in the cells. (Received September 4, 1982; Accepted December 11, 1982) |
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