Identification of DNA Regions Homologous to Nitrogen Fixation Genes nifE, nifUS and fixABC in Azospirillum brasilense Sp7

The rpoN (ntrA) gene (encoding sigma 54) of Azospirillum brasilense Sp7 was isolated by using conserved rpoN primers and the polymerase chain reaction, and its nucleotide sequence was determined. The deduced amino acid sequence of the RpoN protein was found to share a high degree of homology with other members of the sigma 54 family. Two additional open reading frames were found in the Azospirillum brasilense rpoN region, with significant similarity to equivalent regions surrounding the rpoN locus in other bacteria. An rpoN mutant of Azospirillum brasilense Sp7 was constructed by gene replacement and found to be defective in nitrogen fixation, nitrate assimilation, and ammonium uptake. Lack of ammonium uptake was also found in previously isolated Azospirillum brasilense ntrB and ntrC mutants, further supporting the role of the ntr system in this process. In addition, the rpoN mutant was found to be nonmotile, suggesting a role of RpoN in Azospirillum brasilense flagellar biosynthesis.Key words: Azospirillum brasilense, sigma factor, nitrogen fixation, ammonium assimilation, motility.

Download Full-text

A mutant of Azospirillum brasilense Sp7 impaired in flocculation with a modified colonization pattern and superior nitrogen fixation in association with wheat.

Applied and Environmental Microbiology ◽

10.1128/aem.61.5.1987-1995.1995 ◽

1995 ◽

Vol 61 (5) ◽

pp. 1987-1995 ◽

Cited By ~ 57

Author(s):

S Katupitiya ◽

J Millet ◽

M Vesk ◽

L Viccars ◽

A Zeman ◽

...

Keyword(s):

Nitrogen Fixation ◽

Azospirillum Brasilense ◽

Colonization Pattern ◽

Azospirillum Brasilense Sp7

Download Full-text

Molybdenum incorporation in denitrifying Azospirillum brasilense Sp7

Canadian Journal of Microbiology ◽

10.1139/m92-171 ◽

1992 ◽

Vol 38 (10) ◽

pp. 1042-1047 ◽

Cited By ~ 2

Author(s):

Christian Chauret ◽

Wilfredo L. Barraquio ◽

Roger Knowles

Keyword(s):

Nitrate Reductase ◽

Key Words ◽

Nitrate Reduction ◽

Gel Electrophoresis ◽

Azospirillum Brasilense ◽

Paracoccus Denitrificans ◽

Free Medium ◽

Azospirillum Brasilense Sp7

Nondenaturating disc gel electrophoresis revealed that 99Mo was incorporated into the nitrate reductase of Azospirillum brasilense grown in the absence but not in the presence of tungstate. Under denitrifying conditions, A. brasilense grown in tungsten-free medium steadily accumulated 99Mo for 12 h. In contrast, Paracoccus denitrificans grown under the same conditions ceased uptake after 1 h. However, both bacteria were incapable of accumulating significant amounts of 99Mo in media containing 10 mM tungstate, even though nitrate was reduced by A. brasilense. Aerobically grown A. brasilense cells transported 99Mo more efficiently than anaerobically grown cells. Key words: Azospirillum brasilense, tungsten, molybdenum incorporation, nitrate reduction.

Download Full-text

Role of a Fasciclin domain protein in photooxidative stress and flocculation in Azospirillum brasilense Sp7

Research in Microbiology ◽

10.1016/j.resmic.2021.103875 ◽

2021 ◽

pp. 103875

Author(s):

Ashutosh Prakash Dubey ◽

Parul Pandey ◽

Shivangi Mishra ◽

Parikshit Gupta ◽

Anil Kumar Tripathi

Keyword(s):

Azospirillum Brasilense ◽

Photooxidative Stress ◽

Azospirillum Brasilense Sp7 ◽

Domain Protein

Download Full-text

Expression of the nodulation and nitrogen fixation genes in Rhizobium meliloti during development

Genome ◽

10.1139/g89-054 ◽

1989 ◽

Vol 31 (1) ◽

pp. 354-360 ◽

Cited By ~ 2

Author(s):

San Chiun Shen ◽

Shui Ping Wang ◽

Guan Qiao Yu ◽

Jia Bi Zhu

Keyword(s):

Nitrogen Fixation ◽

Rhizobium Meliloti ◽

Abnormal Development ◽

Wild Type ◽

Free Living ◽

Nod Genes ◽

Nodule Initiation ◽

Fix Genes ◽

Nitrogen Fixation Genes

Genes that specify nodulation (nod genes) are only active in the free-living rhizobia or in the nodule initiation state of rhizobia. As soon as the repression of nod genes occurs in the bacteroids of the nodule, nifA is induced, while ntrC is inactivated and thus the nifA-mediated nif/fix genes are turned on. Limitation of available oxygen brings about the induction of nifA, which reflects the actual status of nif/fix gene activities in symbiotic state of rhizobia. Oxygen thus appears to be a major symbiotic signal to the expression of bacteroid nif/fix genes. Mutation of nifA or shortage of nifA product in wild-type rhizobia caused by the inhibition of multicopy nifH/fixA promoters leads to an abnormal development of nodules and premature degradation of bacteroids in nodules.Key words: nitrogen fixation, nodulation, nif/fix regulation, nifA mutant.

Download Full-text