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Paenibacillus strains with nitrogen fixation and multiple beneficial properties for promoting plant growth.

ABSTRACT: Paenibacillus is a large genus of Gram-positive, facultative anaerobic, endospore-forming bacteria. The genus Paenibacillus currently comprises more than 150 named species, approximately 20 of which have nitrogen-fixation ability. The N2-fixing Paenibacillus strains have potential uses as a bacterial fertilizer in agriculture. In this study, 179 bacterial strains were isolated by using nitrogen-free medium after heating at 85 °C for 10 min from 69 soil samples collected from different plant rhizospheres in different areas. Of the 179 bacterial strains, 25 Paenibacillus strains had nifH gene encoding Fe protein of nitrogenase and showed nitrogenase activities. Of the 25 N2-fixing Paenibacillus strains, 22 strains produced indole-3-acetic acid (IAA). 21 strains out of the 25 N2-fixing Paenibacillus strains inhibited at least one of the 6 plant pathogens Rhizoctonia cerealis, Fusarium graminearum, Gibberella zeae, Fusarium solani, Colletotrichum gossypii and Alternaria longipes. 18 strains inhibited 5 plant pathogens and Paenibacillus sp. SZ-13b could inhibit the growth of all of the 6 plant pathogens. According to the nitrogenase activities, antibacterial capacities and IAA production, we chose eight strains to inoculate wheat, cucumber and tomato. Our results showed that the 5 strains Paenibacillus sp. JS-4, Paenibacillus sp. SZ-10, Paenibacillus sp. SZ-14, Paenibacillus sp. BJ-4 and Paenibacillus sp. SZ-15 significantly promoted plant growth and enhanced the dry weight of plants. Hence, the five strains have the greater potential to be used as good candidates for biofertilizer to facilitate sustainable development of agriculture.

SUBMITTER: Liu X

PROVIDER: S-EPMC6761918 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Paenibacillus strains with nitrogen fixation and multiple beneficial properties for promoting plant growth.

Liu Xiaomeng X Li Qin Q Li Yongbin Y Guan Guohua G Chen Sanfeng S

PeerJ 20190923

Paenibacillus is a large genus of Gram-positive, facultative anaerobic, endospore-forming bacteria. The genus Paenibacillus currently comprises more than 150 named species, approximately 20 of which have nitrogen-fixation ability. The N2-fixing Paenibacillus strains have potential uses as a bacterial fertilizer in agriculture. In this study, 179 bacterial strains were isolated by using nitrogen-free medium after heating at 85 °C for 10 min from 69 soil samples col ...[more]

PMID: 31579563

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Project description:Plant growth-promoting rhizobacteria (PGPR) may provide a biological alternative to fix atmospheric N2 and delay N remobilisation in maize plant to increase crop yield, based on an understanding that plant-N remobilisation is directly correlated to its plant senescence. Thus, four PGPR strains were selected from a series of bacterial strains isolated from maize roots at two locations in Malaysia. The PGPR strains were screened in vitro for their biochemical plant growth-promoting (PGP) abilities and plant growth promotion assays. These strains were identified as Klebsiella sp. Br1, Klebsiella pneumoniae Fr1, Bacillus pumilus S1r1 and Acinetobacter sp. S3r2 and a reference strain used was Bacillus subtilis UPMB10. All the PGPR strains were tested positive for N2 fixation, phosphate solubilisation and auxin production by in vitro tests. In a greenhouse experiment with reduced fertiliser-N input (a third of recommended fertiliser-N rate), the N2 fixation abilities of PGPR in association with maize were determined by 15N isotope dilution technique at two harvests, namely, prior to anthesis (D50) and ear harvest (D65). The results indicated that dry biomass of top, root and ear, total N content and bacterial colonisations in non-rhizosphere, rhizosphere and endosphere of maize roots were influenced by PGPR inoculation. In particular, the plants inoculated with B. pumilus S1r1 generally outperformed those with the other treatments. They produced the highest N2 fixing capacity of 30.5% (262 mg N2 fixed plant-1) and 25.5% (304 mg N2 fixed plant-1) of the total N requirement of maize top at D50 and D65, respectively. N remobilisation and plant senescence in maize were delayed by PGPR inoculation, which is an indicative of greater grain production. This is indicated by significant interactions between PGPR strains and time of harvests for parameters on N uptake and at. % 15Ne of tassel. The phenomenon is also supported by the lower N content in tassels of maize treated with PGPR, namely, B. pumilus S1r1, K. pneumoniae Fr1, B. subtilis UPMB10 and Acinetobacter sp. S3r2 at D65 harvest. This study provides evidence that PGPR inoculation, namely, B. pumilus S1r1 can biologically fix atmospheric N2 and provide an alternative technique, besides plant breeding, to delay N remobilisation in maize plant for higher ear yield (up to 30.9%) with reduced fertiliser-N input.

Project description:Diazotrophic bacteria can reduce N2 into plant-available ammonium (NH4 +), promoting plant growth and reducing nitrogen (N) fertilizer requirements. However, there are few systematic studies on the effects of diazotrophic bacteria on biological N2 fixation (BNF) contribution rate and host plant N uptake and metabolism. In this study, the interactions of the diazotrophic Paenibacillus beijingensis BJ-18 with wheat, maize, and cucumber were investigated when it was inoculated to these plant seedlings grown in both low N and high N soils, with un-inoculated plants as controls. This study showed that GFP-tagged P. beijingensis BJ-18 colonized inside and outside seedlings, forming rhizospheric and endophytic colonies in roots, stems, and leaves. The numbers of this bacterium in the inoculated plants depended on soil N levels. Under low N, inoculation significantly increased shoot dry weight (wheat 86.1%, maize 46.6%, and cucumber 103.6%) and root dry weight (wheat 46.0%, maize 47.5%, and cucumber 20.3%). The 15N-isotope-enrichment experiment indicated that plant seedlings derived 12.9-36.4% N from BNF. The transcript levels of nifH in the inoculated plants were 0.75-1.61 folds higher in low N soil than those in high N soil. Inoculation enhanced NH4 + and nitrate (NO3 -) uptake from soil especially under low N. The total N in the inoculated plants were increased by 49.1-92.3% under low N and by 13-15.5% under high N. Inoculation enhanced activities of glutamine synthetase (GS) and nitrate reductase (NR) in plants, especially under low N. The expression levels of N uptake and N metabolism genes: AMT (ammonium transporter), NRT (nitrate transporter), NiR (nitrite reductase), NR, GS and GOGAT (glutamate synthase) in the inoculated plants grown under low N were up-regulated 1.5-91.9 folds, but they were not obviously changed under high N. Taken together, P. beijingensis BJ-18 was an effective, endophytic and diazotrophic bacterium. This bacterium contributed to plants with fixed N2, promoted plant growth and N uptake, and enhanced gene expression and enzyme activities involved in N uptake and assimilation in plants. However, these positive effects on plants were regulated by soil N status. This study might provide insight into the interactions of plants with beneficial associative and endophytic diazotrophic bacteria.

Project description:BackgroundDiazotrophic (nitrogen-fixing) Gram-positive and endospore-formed Paenibacillus spp. have potential uses as a bacterial fertilizer in agriculture. The transcriptional analysis of nitrogen fixation in Paenibacillus is lacking, although regulation mechanisms of nitrogen fixation have been well studied in Gram-negative diazotrophs.ResultsHere we report a global transcriptional profiling analysis of nitrogen fixation in Paenibacillus sp. WLY78 cultured under N2-fixing condition (without O2 and NH4(+)) and non-N2-fixing condition (air and 100 mM NH4(+)). The nif (nitrogen fixation) gene operon composed of 9 genes (nifBHDKENXhesAnifV) in this bacterium was significantly up-regulated in N2-fixing condition compared to non-N2-fixing condition, indicating that nif gene transcription is strictly controlled by NH4(+) and O2. qRT-PCR confirmed that these nif genes were differently expressed. Non-nif genes specifically required in nitrogen fixation, such as mod, feoAB and cys encoding transporters of Mo, Fe and S atoms, were coordinately transcribed with nif genes in N2-fixing condition. The transcript abundance of suf operon specific for synthesis of Fe-S cluster was up-regulated in N2-fixing condition, suggesting that Sul system, which takes place of nifS and nifU, plays important role in the synthesis of nitrogenase. We discover potential specific electron transporters which might provide electron from Fe protein to MoFe protein of nitrogenase. The glnR whose predicted protein might mediate nif transcription regulation by NH4(+) is significantly up-regulated in N2-fixing condition. The transcription levels of nitrogen metabolism and anaerobic respiration were also analyzed.ConclusionsThe nif gene operon (nifBHDKENXhesAnifV) in Paenibacillus sp. WLY78 is significantly up-regulated in N2-fixing condition compared to non-N2-fixing condition. Non-nif genes specifically required in nitrogen fixation were also significantly up-regulated in N2-fixing condition. Fur and Fnr which are involved in anaerobic regulation and GlnR which might mediate nif gene transcription regulation by NH4(+) were significantly up-regulated in N2-fixing condition. This study provides valuable insights into nitrogen fixation process and regulation in Gram-positive firmicutes.

Project description:The role of microbial volatile organic compounds (MVOCs) in promoting plant growth has received much attention. We isolated Paenibacillus peoriae from mangrove rhizosphere soil, which can produce VOCs to promote the growth of Arabidopsis thaliana seedlings, increase the aboveground biomass of A. thaliana, and increase the number of lateral roots of A. thaliana. The effects of different inoculation amounts and different media on the composition of MVOCs were studied by solid-phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) and headspace sampler/GC-MS. We found that the growth medium influences the function and composition of MVOCs. To survey the growth-promoting functions, the transcriptome of the receptor A. thaliana was then determined. We also verified the inhibitory effect of the soluble compounds produced by P. peoriae on the growth of 10 pathogenic fungi. The ability of P. peoriae to produce volatile and soluble compounds to promote plant growth and disease resistance has shown great potential for application in the sustainability of agricultural production. IMPORTANCE Microbial volatile organic compounds (MVOCs) have great potential as "gas fertilizers" for agricultural applications, and it is a promising research direction for the utilization of microbial resources. This study is part of the field of interactions between microorganisms and plants. To study the function and application of microorganisms from the perspective of VOCs is helpful to break the bottleneck of traditional microbial application. At present, the study of MVOCs is lacking; there is a lack of functional strains, especially with plant-protective functions and nonpathogenic application value. The significance of this study is that it provides Paenibacillus peoriae, which produces VOCs with plant growth-promoting effects and broad-spectrum antifungal activity against plant-pathogenic fungi. Our study provides a more comprehensive, new VOC component analysis method and explains how MVOCs promote plant growth through transcriptome analysis. This will greatly increase our understanding of MVOC applications as a model for other MVOC research.

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Paenibacillus strains with nitrogen fixation and multiple beneficial properties for promoting plant growth.

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<i>Paenibacillus</i> strains with nitrogen fixation and multiple beneficial properties for promoting plant growth.

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