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  • 1
    Digitale Medien
    Digitale Medien
    Utilization of nitrate by bacteroids of Bradyrhizobium japonicum in the soybean root nodule (1988)
    Springer
    Planta 174 (1988), S. 51-58 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Bacteroid ; Bradyrhizobium ; Glycine (N2 fixation) ; Nitrate reductase ; Nitrite reductase ; Nitrogen fixation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Bacteroids of Bradyrhizobium japonicum strain CB1809, unlike CC705, do not have a high level of constitutive nitrate reductase (NR; EC 1.7.99.4) in the soybean (Glycine max. Merr.) nodule. Ex planta both strains have a high activity of NR when cultured on 5 mM nitrate at 2% O2 (v/v). Nitrite reductase (NiR) was active in cultured cells of bradyrhizobia, but activity with succinate as electron donor was not detected in freshly-isolated bacteroids. A low activity was measured with reduced methyl viologen. When bacteroids of CC705 were incubated with nitrate there was a rapid production of nitrite which resulted in repression of NR. Subsequently when NiR was induced, nitrite was utilized and NR activity recovered. Nitrate reductase was induced in bacteroids of strain CB1809 when they were incubated in-vitro with nitrate or nitrite. Increase in NR activity was prevented by rifampicin (10 μg· ml-1) or chloramphenicol (50 μg·ml-1). Nitrite-reductase activity in bacteroids of strain CB1809 was induced in parallel with NR. When nitrate was supplied to soybeans nodulated with strain CC705, nitrite was detected in nodule extracts prepared in aqueous media and it accumulated during storage (1°C) and on further incubation at 25°C. Nitrite was not detected in nodule extracts prepared in ethanol. Thus nitrite accumulation in nodule tissue appears to occur only after maceration and although bacteroids of some strains of B. japonicum have a high level of a constitutive NR, they do not appear to reduce nitrate in the nodule because this anion does not gain access to the bacteroid zone. Soybeans nodulated with strains CC705 and CB1809 were equally sensitive to nitrate inhibition of N2 fixation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00394873
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  • 2
    Digitale Medien
    Digitale Medien
    Denitrification in Rhodopseudomonas sphaeroides f. denitrificans (1985)
    Springer
    Archives of microbiology 141 (1985), S. 57-62 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Rhodopseudomonas sphaeroides f. denitrificans ; Photodenitrifier ; Denitrification ; Nitrate reductase ; Nitrite reductase ; Nitrous oxide reductase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Rhodopseudomonas sphaeroides f. denitrificans grown photosynthetically with NO 3 - under anaerobic conditions accumulated NO 2 - in the culture medium. In washed cells succinate, lactate, fumarate, citrate and malate, were effective electron donors for the reduction of NO 3 - , NO 2 - and N2O to N2 gas. Nitrate reductase was inhibited by amytal and potassium thocyanate. Nitrite reductase activity was severely restricted by potassium cyanide, sodium diethyldithiocarbamate, Amytal and 2-n-heptyl-4-hydroxyquinoline-N-oxide whereas N2O reductase was inhibited by NaN3, C2H2 and KCNS. Cells incubated with either K15NO3 or K15NO2 produced 15N2O and 15N2. A stoichiometry of 2:1 was recorded for the reduction of either NO 3 - or NO 2 - to N2O and N2 and for N2O to N2 it was 1:1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00446740
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