+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Symbiotic and free living denitrification by bradyrhizobium japonicum

Symbiotic and free living denitrification by bradyrhizobium japonicum

Soil Science Society of America Journal 50(2): 349-354

Denitrification by Bradyrhizobium japonicum (formerly Rhizobium japonicum) was characterized in two strains, USDA-110 and USDA-23, to determine the extent of denitrifying enzyme expression during symbiotic growth with soybean [Glycine max (L.) Merr.]. The rhizobia grew in anaerobic batch cultures, depleting NO3- and producing N2O in the presence of C2H2. Specific denitrifying activities of resting cells of rhizobia were compared with those of the common soil denitrifier Pseudomonas fluorescens, and were found to range from 14 to 18% of the P. fluorescens activity. Bacteroid specific activities were less than activities of free-living rhizobial cells, though the ratio depended on the growth stage of the cells. Denitrification was observed in detached whole nodules containing either of the strains, but not in nodules formed by a NO3- reductase mutant of B. japonicum 110. Denitrification rates of nodules were unaffected by the presence of external O2, though the rates were limited by the external NO3- concentration. Denitrification by intact, nodulated soybean plants under aerobic conditions was observed. In the presence of NO3- denitrification and N2 fixation (C2H2 reduction) occurred simultaneously. The estimated ratio of N denitrified to N fixed ranged from 0 to 0.3, depending on assay conditions. The observations suggest that denitrification in soybean nodules in the field can be a continuous process, independent of soil aeration. However, it is likely to be slow relative to N2 fixation under most conditions.

Please choose payment method:

(PDF emailed within 0-6 h: $19.90)

Accession: 006555470

Download citation: RISBibTeXText

DOI: 10.2136/sssaj1986.03615995005000020019x

Related references

Sulfur nutrition of free living and symbiotic Bradyrhizobium japonicum and Bradyrhizobium sp. (Arachis). ACIAR proceedings series: 8) 275, 1987

The presence and relative amounts of a stress protein in free living and symbiotic bradyrhizobium japonicum. Gresshoff, P M , Et Al (Ed ) Nitrogen Fixation: Achievements And Objectives; 8th International Congress on Nitrogen Fixation, Knoxville, Tennessee, Usa, May 20-26, Xix+869p Routledge, Chapman And Hall: New York, New York, Usa; London, England, Uk Illus 522, 1990

Bradyrhizobium japonicum ntr bc gln a and nif a gln a mutants further evidence that separate regulatory pathways govern gln ii expression in free living and symbiotic cells. Molecular Plant-Microbe Interactions 4(3): 254-261, 1991

Expression and functional roles of Bradyrhizobium japonicum genes involved in the utilization of inorganic and organic sulfur compounds in free-living and symbiotic conditions. Molecular Plant-Microbe Interactions 24(4): 451-457, 2011

The complete denitrification pathway of the symbiotic, nitrogen-fixing bacterium Bradyrhizobium japonicum. Biochemical Society Transactions 33(Pt 1): 141-144, 2005

Nitrate reductase activity of free-living and symbiotic uptake hydrogenase-positive and uptake hydrogenase-negative strains of Bradyrhizobium japonicum. Archives of microbiology51(2): 166-170, 1989

Symbiotic efficiency of Hup+, Huphr and Hup- strains of Bradyrhizobium japonicum and Bradyrhizobium elkanii in cowpea cultivars. Pesquisa Agropecuaria Brasileira 34(10): 1925-1931, 1999

Conservation of symbiotic nitrogen fixation gene sequences in Rhizobium japonicum and Bradyrhizobium japonicum. Journal of Bacteriology 163(1): 21-26, 1985

Dissimilatory nitrate reduction in free-living and symbiotic cells of Bradyrhizobium sp. Plant Physiology & Biochemistry 38: s148, 2000

Rhizobitoxine inhibition of hydrogenase synthesis in free-living Bradyrhizobium japonicum. Journal of Bacteriology 172(8): 4505-4509, 1990

Ability of free living cells of bradyrhizobium japonicum to denitrify in soils. Biology & Fertility of Soils 7(3): 219-224, 1989

Glyphosate effects on Bradyrhizobium japonicum on free living form and on symbiosis with soybean. Biologia Plantarum 36(Suppl. ): S344, 1994

Induction of nitrogenase and hydrogenase activities in the free-living state of Bradyrhizobium japonicum. Jarq 27(1): 13-19, 1993

HoxA is a transcriptional regulator for expression of the hup structural genes in free-living Bradyrhizobium japonicum. Molecular Microbiology 23(5): 967-977, 1997