Nitrogen-fixing bacteria associated with leguminous and non-leguminous plants

Biological nitrogen fixation is one of the most important nutrient processes in the ecosystem. Many studies have estimated the variations in soil diazotrophic communities across the globe. To understand the dynamics of nitrogen fixing bacterial communities and their response to the environmental changes, it is important to study the temporal variability of these communities. Using DNA fingerprinting method, denaturing gradient gel electrophoresis and real time polymerase chain reaction of the nifH gene, we have found that the agricultural land harbored unique nitrogen fixing communities that revealed different temporal patterns and abundance. Variation in soil moisture, organic carbon content, ammonium and nitrate concentrations may be the main factors which influenced the diazotrophic community composition and nifH gene abundance. Azospirillum species were more dominant in the agricultural soil. Unique environmental factors and agricultural practices were responsible for the temporal shifts in bacterial community structures and nifH transcripts level. Our study expands understanding of the influence of environmental factors on diazotrophic population that contributes to the nitrogen pool.

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“…and Pseudacidovorax sp. were also observed in samples [29]. All the taxas reported during the study, belong to proteobacteria phyla.…”

Section: Resultssupporting

confidence: 52%

Temporal Variations in Diazotrophic Communities and nifH Transcripts Level Across the Agricultural and Fallow Land at Jaipur, Rajasthan, India

Sharma

Singh

2016

Indian J Microbiol

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“…Bacterial species belonging to Bacteroidetes contain genes involved in denitrification indicating a possible involvement in N cycling (Van Spanning et al, 2005). Cyanobacteria have been shown to colonize plant roots (Gantar et al, 1991;Lundberg et al, 2012), promote plant growth (Prasanna et al, 2009) and are an important plant source for inorganic N due to their ability to fix N (Franche et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…Similarly, during bolting and flowering, functional genes expressed in the rhizosphere align to PGPRs such as Bacillus licheniformis (Gutiérrez-Mañ ero et al, 2001) or Burkholderia ambifaria (Chiarini et al, 2006), free N-fixers such as Cyanothece sp. (Junier et al, 2009), as well as symbiotic N-fixing bacteria (Bradyrhizobium) (Stacey et al, 1995) or Herbaspirillum which is involved in endophytic N fixation (Elbeltagy et al, 2001;Franche et al, 2009). It should be noted that in addition to fixing N through legume symbiosis, Bradyrhizobium promotes plant growth of nonleguminous plants (Antoun et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

Rhizosphere microbiome assemblage is affected by plant development

2013

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There is a concerted understanding of the ability of root exudates to influence the structure of rhizosphere microbial communities. However, our knowledge of the connection between plant development, root exudation and microbiome assemblage is limited. Here, we analyzed the structure of the rhizospheric bacterial community associated with Arabidopsis at four time points corresponding to distinct stages of plant development: seedling, vegetative, bolting and flowering. Overall, there were no significant differences in bacterial community structure, but we observed that the microbial community at the seedling stage was distinct from the other developmental time points. At a closer level, phylum such as Acidobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria and specific genera within those phyla followed distinct patterns associated with plant development and root exudation. These results suggested that the plant can select a subset of microbes at different stages of development, presumably for specific functions. Accordingly, metatranscriptomics analysis of the rhizosphere microbiome revealed that 81 unique transcripts were significantly (Po0.05) expressed at different stages of plant development. For instance, genes involved in streptomycin synthesis were significantly induced at bolting and flowering stages, presumably for disease suppression. We surmise that plants secrete blends of compounds and specific phytochemicals in the root exudates that are differentially produced at distinct stages of development to help orchestrate rhizosphere microbiome assemblage.

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“…Bradyrhizobium can infect the soybean root to form root nodules that supply soybean with more than 50 % of its required nitrogen (Franche et al 2009). Azospirillum-known as important plant growth promoting rhizobacteria (PGPR)-can enhance root growth and nodulation of soybean (Molla et al 2001).…”

Section: Community Structure Of Nfbmentioning

confidence: 99%

Responses of soil nitrogen-fixing, ammonia-oxidizing, and denitrifying bacterial communities to long-term chlorimuron-ethyl stress in a continuously cropped soybean field in Northeast China

Zhang

et al. 2013

Ann Microbiol

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Chlorimuron-ethyl is a type of long-residual herbicide applied widely to soybean fields in China, but little information is available about the long-term impact of this herbicide on soil nitrogen-transforming microbial communities. Soil samples (0-20 cm) were collected from three treatments (no, 5-year and 10-year application of chlorimuron-ethyl) in a continuously cropped soybean field. Plate count (CFU), most probable number (MPN) count, and clone library analyses were conducted to investigate the abundance and composition of nitrogen-fixing, ammonia-oxidizing, and denitrifying bacterial communities, and a chlorate inhibition method was adopted to measure the soil nitrification potential. Long-term chlorimuron-ethyl application reduced the abundance of soil culturable nitrogenfixing, ammonia-oxidizing, and denitrifying bacteria. Moreover, chlorimuron-ethyl decreased the diversity of nitrogenfixing and ammonia-oxidizing bacteria but promoted that of denitrifying bacteria. Chlorimuron-ethyl restrained some uncultured nitrogen-fixing bacteria, ammonia-oxidizing bacteria Nitrosospira sp. cluster 3a and 3d, and some novel or putative denitrifying bacteria. The nitrogen-fixing bacteria were closely related to Bradyrhizobium sp., ammoniaoxidizing bacteria Nitrosospira sp. cluster 3b and 3c, and most denitrifying bacteria were resistant to chlorimuronethyl. There was a negative correlation between the nitrification potential and the residual amount of soil chlorimuronethyl (R 2 =0.88, n=3, P<0.05). Therefore, long-term application of chlorimuron-ethyl in the continuously cropped soybean field could seriously disturb soil N-transforming communities, and might impact soybean soil biological quality and soybean growth. Further studies should address rational amendment models of this herbicide to reduce the possible ecological risks of long-term application of this herbicide to soybean fields.

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Nitrogen-fixing bacteria associated with leguminous and non-leguminous plants

Cited by 662 publications

References 192 publications

Temporal Variations in Diazotrophic Communities and nifH Transcripts Level Across the Agricultural and Fallow Land at Jaipur, Rajasthan, India

Temporal Variations in Diazotrophic Communities and nifH Transcripts Level Across the Agricultural and Fallow Land at Jaipur, Rajasthan, India

Rhizosphere microbiome assemblage is affected by plant development

Responses of soil nitrogen-fixing, ammonia-oxidizing, and denitrifying bacterial communities to long-term chlorimuron-ethyl stress in a continuously cropped soybean field in Northeast China

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