Endophytic Nitrogen-fixing Bacteria Research Articles

Structure and Functions of Endophytic Bacterial Communities Associated with Sphagnum Mosses and Their Drivers in Two Different Nutrient Types of Peatlands

Sphagnum mosses are keystone plant species in the peatland ecosystems that play a crucial role in the formation of peat, which shelters a broad diversity of endophytic bacteria with important ecological functions. In particular, methanotrophic and nitrogen-fixing endophytic bacteria benefit Sphagnum moss hosts by providing both carbon and nitrogen. However, the composition and abundance of endophytic bacteria from different species of Sphagnum moss in peatlands of different nutrient statuses and their drivers remain unclear. This study used 16S rRNA gene amplicon sequencing to examine endophytic bacterial communities in Sphagnum mosses and measured the activity of methanotrophic microbial by the 13C-CH4 oxidation rate. According to the results, the endophytic bacterial community structure varied among Sphagnum moss species and Sphagnum capillifolium had the highest endophytic bacterial alpha diversity. Moreover, chlorophyll, phenol oxidase, carbon contents, and water retention capacity strongly shaped the communities of endophytic bacteria. Finally, Sphagnum palustre in Hani (SP) had a higher methane oxidation rate than S. palustre in Taishanmiao. This result is associated with the higher average relative abundance of Methyloferula an obligate methanotroph in SP. In summary, this work highlights the effects of Sphagnum moss characteristics on the endophytic bacteriome. The endophytic bacteriome is important for Sphagnum moss productivity, as well as for carbon and nitrogen cycles in Sphagnum moss peatlands.

Molecular mechanism of endophytic bacteria DX120E regulating polyamine metabolism and promoting plant growth in sugarcane.

Sugarcane endophytic nitrogen-fixing bacterium Klebsiella variícola DX120E displayed broad impact on growth, but the exact biological mechanism, especially polyamines (PAs) role, is still meager. To reveal this relationship, the content of polyamine oxidase (PAO), PAs, reactive oxygen species (ROS)-scavenging antioxidative enzymes, phytohormones, 1-aminocyclopropane-1-carboxylic synthase (ACS), chlorophyll content, and biomass were determined in sugarcane incubated with the DX120E strain. In addition, expression levels of the genes associated with polyamine metabolism were measured by transcriptomic analysis. Genomic analysis of Klebsiella variícola DX120E revealed that 39 genes were involved in polyamine metabolism, transport, and the strain secrete PAs in vitro. Following a 7-day inoculation period, DX120E stimulated an increase in the polyamine oxidase (PAO) enzyme in sugarcane leaves, however, the overall PAs content was reduced. At 15 days, the levels of PAs, ROS-scavenging antioxidative enzymes, and phytohormones showed an upward trend, especially spermidine (Spd), putrescine (Put), catalase (CAT), auxin (IAA), gibberellin (GA), and ACS showed a significant up-regulation. The GO and KEGG enrichment analysis found a total of 73 differentially expressed genes, involving in the cell wall (9), stimulus response (13), peroxidase activity (33), hormone (14) and polyamine metabolism (4). This study demonstrated that endophytic nitrogen-fixing bacteria stimulated polyamine metabolism and phytohormones production in sugarcane plant tissues, resulting in enhanced growth. Dual RNA-seq analyses provided insight into the early-stage interaction between sugarcane seedlings and endophytic bacteria at the transcriptional level. It showed how diverse metabolic processes selectively use distinct molecules to complete the cell functions under present circumstances.

Regulation of an endophytic nitrogen-fixing bacteria GXS16 promoting drought tolerance in sugarcane

BackgroundDrought limits crop growth and is an important issue in commercial sugarcane (Saccharum officinarum) production. Drought tolerance in sugarcane induced by endophytic nitrogen-fixing bacteria is a complex biological process that ranges from altered gene expression and cellular metabolism to changes in growth and productivity.ResultsIn this study, changes in physiological features and transcriptome related to drought tolerance in sugarcane conferred by the Burkholderia endophytic nitrogen-fixing bacterial strain GXS16 were investigated. Sugarcane samples inoculated with GXS16 exhibited significantly higher leaf relative water content than those without GXS16 inoculation during the drought stages. Sugarcane treated with GXS16 had lower levels of H2O2 and higher levels of abscisic acid than sugarcane not treated with GXS16 in the non-watering groups. Transcriptomic analysis of sugarcane roots identified multiple differentially expressed genes between adjacent stages under different treatments. Moreover, both trend and weighted correlation network analyses revealed that carotenoid biosynthesis, terpenoid backbone biosynthesis, starch and sucrose metabolism, and plant hormone signal transduction strongly contributed to the drought-tolerant phenotype of sugarcane induced by GXS16 treatment. Accordingly, a gene regulatory network including four differentially regulated genes from carotenoid biosynthesis (crtB, crtZ, ZEP and CYP707A) and three genes from terpenoid backbone biosynthesis (dxs, dxr, and PCME) was constructed.ConclusionsThis study provides insights into the molecular mechanisms underlying the application of GXS16 treatment to enhance drought tolerance in sugarcane, which will lay the foundation for crop development and improve productivity.

Effect of endophytic diazotroph Enterobacter roggenkampii ED5 on nitrogen-metabolism-related microecology in the sugarcane rhizosphere at different nitrogen levels.

Sugarcane is an important sugar and energy crop worldwide, requiring a large amount of nitrogen (N). However, excessive application of synthetic N fertilizer causes environmental pollution in farmland. Endophytic nitrogen-fixing bacteria (ENFB) provide N nutrition for plants through biological N fixation, thus reducing the need for chemical fertilizers. The present study investigated the effect of the N-fixing endophytic strain Enterobacter roggenkampii ED5 on phytohormone indole-3-acetic acid (IAA), N-metabolism enzyme activities, microbial community compositions, and N cycle genes in sugarcane rhizosphere soil at different N levels. Three levels of 15N-urea, such as low N (0 kg/ha), medium N (150 kg/ha), and high N (300 kg/ha), were applied. The results showed that, after inoculating strain ED5, the IAA content in sugarcane leaves was significantly increased by 68.82% under low N condition at the seedling stage (60 days). The nitrate reductase (NR) activity showed a downward trend. However, the glutamine synthase (GS) and NADH-glutamate dehydrogenase (NADH-GDH) activities were significantly enhanced compared to the control under the high N condition, and the GS and NR genes had the highest expression at 180 and 120 days, respectively, at the low N level. The total N content in the roots, stems, and leaves of sugarcane was higher than the control. The 15N atom % excess of sugarcane decreased significantly under medium N condition, indicating that the medium N level was conducive to N fixation in strain ED5. Metagenome analysis of sugarcane rhizosphere soil exhibited that the abundance of N-metabolizing microbial richness was increased under low and high N conditions after inoculation of strain ED5 at the genus level, while it was increased at the phylum level only under the low N condition. The LefSe (LDA > 2, p < 0.05) found that the N-metabolism-related differential microorganisms under the high N condition were higher than those under medium and low N conditions. It was also shown that the abundance of nifDHK genes was significantly increased after inoculation of ED5 at the medium N level, and other N cycle genes had high abundance at the high N level after inoculation of strain ED5. The results of this study provided a scientific reference for N fertilization in actual sugarcane production.

Cloning, Prokaryotic Expression and Functional Characterization of NifH Gene from the Associative Nitrogen-Fixing Bacteria Klebsiella Variicola DX120E.

Biological nitrogen fixation (BNF) is a unique mechanism in which microorganisms utilize the nitrogenase enzyme to catalyze the conversion of atmospheric nitrogen (N2) to ammonia (NH3). Fe protein, encoded by the nifH gene, is an essential component of the nitrogenase in Klebsiella variicola DX120E. However, the function of this gene in regulating nitrogen fixing activity is still unclear. The objective of this study was to reveal the function of nifH gene in associative nitrogen-fixing bacteria Klebsiella variicola DX120E and micro-sugarcane system by immunoassay and gene editing. In the current investigation, the nifH gene was cloned in a pET-30a (+) vector and expressed in Escherichia coli. The NifH protein was purified and used to immunize rabbit, and then the serum was collected and purified to obtain rabbit anti-NifH polyclonal antibodies. The CRISPR-Cas9 system was applied to produce nifH mutant strains, and the nitrogen-fixing enzyme activity, gene, and protein expression were analyzed. Both in vitro and in vivo NifH proteins were detected by Western blotting, which were 43 and 32 kDa respectively. The expression of nifD and nifK genes was decreased, and nitrogenase activity was reduced in the nifH mutant strain. The nifH gene mutant weakened the nitrogenase activity by regulating the expression of Fe protein, which suggests a potential strategy to study the nitrogen fixation-related genes and the interactions between endophytic nitrogen-fixing bacteria and sugarcane.

Whole-genome assembly of A02 bacteria involved in nitrogen fixation within cassava leaves.

The endophytic nitrogen (N)-fixing bacterium A02 belongs to the genus Curtobacterium (Curtobacterium sp.) and is crucial for the N metabolism of cassava ( Manihot esculenta Crantz). We isolated the A02 strain from cassava cultivar SC205 and used the 15N isotope dilution method to study the impacts of A02 on growth and accumulation of N in cassava seedlings. Furthermore, the whole genome was sequenced to determine the N-fixation mechanism of A02. Compared with low N control (T1), inoculation with the A02 strain (T2) showed the highest increase in leaf and root dry weight of cassava seedlings, and 120.3 nmol/(mL·h) was the highest nitrogenase activity recorded in leaves, which were considered the main site for colonization and N-fixation. The genome of A02 was 3,555,568 bp in size and contained a circular chromosome and a plasmid. Comparison with the genomes of other short bacilli revealed that strain A02 showed evolutionary proximity to the endophytic bacterium NS330 (Curtobacterium citreum) isolated from rice (Oryza sativa) in India. The genome of A02 contained 13 nitrogen fixation (nif) genes, including 4 nifB, 1 nifR3, 2 nifH, 1 nifU, 1 nifD, 1 nifK, 1 nifE, 1 nifN, and 1 nifC, and formed a relatively complete N fixation gene cluster 8-kb long that accounted for 0.22% of the whole genome length. The nifHDK of strain A02 (Curtobacterium sp.) is identical to the Frankia alignment. Function prediction showed high copy number of the nifB gene was related to the oxygen protection mechanism. Our findings provide exciting information about the bacterial genome in relation to N support for transcriptomic and functional studies for increasing N use efficiency in cassava.

Metagenomic Profile of Endophytic Bacteria in Acacia mearnsii.

Acacia mearnsii is one of the invasive plants belonging to the Mimosaceae family. The family is known to be able to symbiosis with some endophytic nitrogen-fixing soil bacteria. Such ability will significantly contribute to plant growth and development by influencing nutrient uptake and stress tolerance and thus to improve soil conditions for a better and more fertile. Comprehensive identification of bacterial population dynamic in that zone should elucidate symbiosis mechanism that in turn can be used for soil improvement. Metagenomic-based profiling are now commonly used in studying whole total microbial communities in nature. Sampling of the root was collected from A. mearnsii young trees grown in Alahan Panjang at 60 and 120 days after transplanting, sterilized and stored at -80°C in a falcon tube before being subjected to metagenome analysis. The dynamics of growth and diversity of endophytic microbes were checked through amplicon sequence of the 16S rRNA gene in the V3-V4 region using Next Generation Sequencing (NGS) platform. Data analysis was performed using the QIIME2 application. The metagenomics analysis of endophytic bacteria on root A. mearnsii elucidates that the Proteobacteria is a dominant phyla in A. mearnsii root and analysis at the genera level shows that most of the Proteobacteria is dominated by the Bradyrhizobium which increase significantly during early growth phase.

Presence and activity of nitrogen-fixing bacteria in Scots pine needles in a boreal forest: a nitrogen-addition experiment.

Endophytic nitrogen-fixing bacteria have been detected and isolated from the needles of conifer trees growing in North American boreal forests. Because boreal forests are nutrient-limited, these bacteria could provide an important source of nitrogen for tree species. This study aimed to determine their presence and activity in a Scandinavian boreal forest, using immunodetection of nitrogenase enzyme subunits and acetylene-reduction assays of native Scots pine (Pinus sylvestris L.) needles. The presence and rate of nitrogen fixation by endophytic bacteria were compared between control plots and fertilized plots in a nitrogen-addition experiment. In contrast to the expectation that nitrogen-fixation rates would decline in fertilized plots, as seen, for instance, with nitrogen-fixing bacteria associated with bryophytes, there was no difference in the presence or activity of nitrogen-fixing bacteria between the two treatments. The extrapolated calculated rate of nitrogen fixation relevant for the forest stand was 20gNha-1year-1, which is rather low compared with Scots pine annual nitrogen use but could be important for the nitrogen-poor forest in the long term. In addition, of 13 colonies of potential nitrogen-fixing bacteria isolated from the needles on nitrogen-free media, 10 showed in vitro nitrogen fixation. In summary, 16S rRNA sequencing identified the species as belonging to the genera Bacillus, Variovorax, Novosphingobium, Sphingomonas, Microbacterium and Priestia, which was confirmed by Illumina whole-genome sequencing. Our results confirm the presence of endophytic nitrogen-fixing bacteria in Scots pine needles and suggest that they could be important for the long-term nitrogen budget of the Scandinavian boreal forest.

Microbiota and functional analyses of nitrogen-fixing bacteria in root-knot nematode parasitism of plants

BackgroundRoot-knot nematodes (RKN) are among the most important root-damaging plant-parasitic nematodes, causing severe crop losses worldwide. The plant rhizosphere and root endosphere contain rich and diverse bacterial communities. However, little is known about how RKN and root bacteria interact to impact parasitism and plant health. Determining the keystone microbial taxa and their functional contributions to plant health and RKN development is important for understanding RKN parasitism and developing efficient biological control strategies in agriculture.ResultsThe analyses of rhizosphere and root endosphere microbiota of plants with and without RKN showed that host species, developmental stage, ecological niche, and nematode parasitism, as well as most of their interactions, contributed significantly to variations in root-associated microbiota. Compared with healthy tomato plants at different developmental stages, significant enrichments of bacteria belonging to Rhizobiales, Betaproteobacteriales, and Rhodobacterales were observed in the endophytic microbiota of nematode-parasitized root samples. Functional pathways related to bacterial pathogenesis and biological nitrogen fixation were significantly enriched in nematode-parasitized plants. In addition, we observed significant enrichments of the nifH gene and NifH protein, the key gene/enzyme involved in biological nitrogen fixation, within nematode-parasitized roots, consistent with a potential functional contribution of nitrogen-fixing bacteria to nematode parasitism. Data from a further assay showed that soil nitrogen amendment could reduce both endophytic nitrogen-fixing bacteria and RKN prevalence and galling in tomato plants.ConclusionsResults demonstrated that (1) community variation and assembly of root endophytic microbiota were significantly affected by RKN parasitism; (2) a taxonomic and functional association was found for endophytic nitrogen-fixing bacteria and nematode parasitism; and (3) the change of nitrogen-fixing bacterial communities through the addition of nitrogen fertilizers could affect the occurrence of RKN. Our results provide new insights into interactions among endophytic microbiota, RKN, and plants, contributing to the potential development of novel management strategies against RKN.-jDL8N_U_j-q41CTzHNcARVideo

Integrated metabolomic and transcriptomic study unveils the gene regulatory mechanisms of sugarcane growth promotion during interaction with an endophytic nitrogen-fixing bacteria

BackgroundSugarcane growth and yield are complex biological processes influenced by endophytic nitrogen-fixing bacteria, for which the molecular mechanisms involved are largely unknown. In this study, integrated metabolomic and RNA-seq were conducted to investigate the interaction between an endophytic bacterial strain, Burkholderia GXS16, and sugarcane tissue culture seedlings.ResultsDuring treatment, the colonization of GXS16 in sugarcane roots were determined, along with the enhanced activities of various antioxidant enzymes. Accordingly, 161, 113, and 37 differentially accumulated metabolites (DAMs) were found in the pairwise comparisons of adjacent stages. In addition, transcriptomic analyses obtained 1,371 (IN-vs-CN), 1,457 (KN-vs-IN), and 365 (LN-vs-KN) differentially expressed genes (DEGs), which were mainly involved in the pathways of glutathione metabolism and carbon metabolism. We then assessed the pattern of metabolite accumulation and gene expression in sugarcane during GXS16 colonization. The results showed that both DAMs and DGEs in the upregulated expression profiles were involved in the flavonoid biosynthesis pathway. Overall, p-coumaroyl-CoA in sugarcane roots transferred into homoeriodictyol chalcone and 5-deoxyleucopelargonidin due to the upregulation of the expression of genes shikimate O-hydroxycinnamoyltransferase (HCT), chalcone synthase (CHS), and phlorizin synthase (PGT1).ConclusionsThis study provides insights into the gene regulatory mechanisms involved in the interaction between GXS16 and sugarcane roots, which will facilitate future applications of endophytic nitrogen-fixing bacteria to promote crop growth.

Nitrogen fixation of Cyndon dactylon: A possible strategy coping with long-term flooding in the Three Gorges Reservoir

The Three Gorges Reservoir (TGR) is one of the largest hydropower projects around the world which greatly alters the ecological function of the original ecosystem. The riparian zone of TGR is subject to a frequent fluctuation of water level, leading to severe nitrogen loss by leaching. Cyndon dactylon, a perennial stress tolerant plant, is one of the dominant plant species in the riparian zone of TGR. The underlying mechanism that C. dactylon can survive the nitrogen limitation has been under debate. In this study, we sampled the plant tissues of C. dactylon and the surrounding soils across different water levels and seasons in the riparian zone of TGR to explore the possible strategy for them to mining nitrogen. Our study found that the C. dactylon in the TGR riparian zone had endophytic nitrogen-fixing bacteria, particularly enriched in the plant foliage. The abundance of endophytic nitrogen-fixing bacteria was significantly negatively correlated with soil ammonia, nitrate, and organic matter, and significantly positively correlated with total phosphorous and moisture content. The endophytic nitrogen-fixing bacteria in C. dactylon were highly diverse, with Proteobacteria as the main dominant genera. The mutual cooperation mode among bacterial species made the endophytic nitrogen-fixing bacteria community of C. dactylon more resilient to environmental pressure, thus more readily adapting to conditions of repeated long-term flooding in the riparian zone of the TGR.

Assessment of nitrogen-fixing endophytic and mineral solubilizing rhizospheric bacteria as multifunctional microbial consortium for growth promotion of wheat and wild wheat relative Aegilops kotschyi

Microbes play crucial functions in maintaining the health and growth of the plants directly or indirectly by supplying nutrients. These microbes could be used as biofertilizers for the enhancement of soil health and growth of crops. In preset investigation, potential microbes from endophytic and rhizospheric region of Aegilops kotschyi growing in green slopes of Shivaliks, Himachal Pradesh were sorted out and screened for plant growth promoting attributes including phosphorus and potassium solubilization. The potential bacterial strains were identified through 16S rRNA gene sequencing and developed as microbial consortium for the plant growth of wheat and wild wheat relative Aegilops kotschyi. A total 125 isolates of bacteria were sorted out and among them 36 were found as P-solubilizers and 19 showed K-solubilization attribute and two highly potential bacterial strain were identified as Bacillus tropicus EU-ARP-44 (P-solubilizer; 270.5 ± 0.00 mg L−1) and B. megaterium EU-ARK-23 (K-Solubilizer; 51.3 ± 1.7 mg mL−1). The microbial consortium of Rahnella sp. strain EU-A3SNfb (N-fixer; MN294545), B. tropicus EU-ARP-44 (P-solubilizer) and B. megaterium EU-ARK-23 (K-solubilizer) evaluation in Aegilops kotschyi and wheat crop resulted in the enhancement of growth as well as physiological parameter including shoot/root length, fresh/dry weight and chlorophyll, carotenoid, total soluble sugar content, phenolic and flavonoid content as compared to un-inoculated control. Microbial consortium consisting of potential plant growth promoting (PGP) bacterial strains could be used as biofertilizer and bioinoculants in cereals crop growing in hilly region.

Endophytic nitrogen-fixing bacteria DX120E inoculation altered the carbon and nitrogen metabolism in sugarcane.

Endophytic nitrogen-fixing bacteria are versatile and widely distributed in plants. Numerous strains of endophytic nitrogen-fixing bacteria are used as biofertilizers to minimize the utilization of chemical fertilizers, improve nutrient use efficiency, increase crop productivity, and reduce environmental pollution. However, the mechanism underlying the interaction between nitrogen-fixing bacteria and plants is still unclear. So, the present study was planned to assess the effects of endophytic nitrogen-fixing bacteria on sugarcane by analyzing the changes in physiological and biochemical activities. In the current study, Klebsiella variicola DX120E, an endophytic nitrogen-fixing bacterium, was inoculated on sugarcane varieties B8 and ROC22 to evaluate the effects on nitrogen and carbon metabolism-related enzymatic activity and biomass. Results showed that DX120E inoculation improved the enzymatic activities related to gluconeogenesis and nitrogen metabolism increased the sugarcane plant's height, cane juice Brix, biomass, chlorophyll, and soluble sugar content in sugarcane. Metabolomics analysis revealed that the metabolome modules were highly enriched in carbon and nitrogen metabolic pathways of strain-affected sugarcane than uninoculated control. The identified carbohydrates were associated with the glycolysis or gluconeogenesis and tricarboxylic acid (TCA) cycle in plants. Metabolomic profiling in the present investigation showed that carbohydrate metabolism is coordinated with nitrogen metabolism to provide carbon skeletons and energy to amino acid synthesis, and amino acid degradation results in several metabolites used by the citric acid cycle as an energy source. Moreover, differentially expressed metabolites of non-proteinogenic amino acids have a further complementary role to the action of endophytic nitrogen-fixing bacteria. Meanwhile, a significant difference in metabolites and metabolic pathways present in stems and leaves of B8 and ROC22 varieties was found. This study discovered the potential benefits of DX120E in sugarcane and suggested candidate regulatory elements to enhance interactions between nitrogen-fixing microbes and sugarcane.

Aplikasi Pupuk Hayati Bakteri Endofitik Penambat N2 dan Pupuk N untuk Meningkatkan Pertumbuhan Tanaman Jagung (zea mays l.) Pada Ultisols Kentrong

Corn cultivation on Ultisols is limited due to low nitrogen content of the soil. Efforts to increase the N content in the soil include the use of biofertilizers by symbiotic nitrogen-fixing endophytic bacteria. This study assesed various combination of nitrogen fertilizer doses and N2-fixing endophytic biofertilizer to increase the growth of maize in Ultisols Kentrong. The experiment was conducted at the Ciparanje Experimental Greenhouse, Faculty of Agriculture, Universitas Padjadjaran, Jatinangor. A randomized block design was used which consisted of 16 treatments with 3 replications, with a combination of doses of urea fertilizer and endophytic biofertilizer applied to seeds or planting holes. The experimental results showed that the combination of urea fertilizer and biofertilizer doses had a significant effect on the population of endophytic bacteria in the roots and leaves of corn plants, plant wet weight, root dry weight and shoot dry weight, plant height, stem diameter, plant nitrogen uptake and content of plants but was not significantly affected on the number of corn leaves. Combination of 80 kg ha-1 urea fertilizer and 3.6 kg ha-1 of biofertilizer was the best combination which increased the dry weight of the corn plant and reduced the dose of urea fertilizer

Effects of Nitrogen Fertilization and Nitrogen Fixing Endophytic Bacteria Supplementation on Soil Fertility, N Uptake, Growth, and Yield of Sesame (Sesamum indicum L.) Cultivated on Alluvial Soil in Dykes

The aim of this study was to determine the proper combination of nitrogen (N) fertilizer level and nitrogen fixing endophytic bacteria (NFEB) supplementation for the maximum grain yield of sesame cultivated in alluvial soil in dykes. The experiment followed a completely randomized block design with two factors. The first one was the levels of N fertilizer used, including 0, 50, 75, and 100% N of recommended fertilizer formula (RFF), and the other consisted of no bacteria applied, an individual strain of Enterobacter cloacae ASD-48 or E. cloacae ASD-21 applied, and their mixture, with 5 replicates. The results revealed that fertilizing with 100% N of RFF led to an enhancement of the plant height (16.8 cm), the chlorophyll a and b and their total content (6.45, 1.86, and 8.30 μg mL−1), the number of capsules per plant (7.22 capsules plant−1), the total N uptake (126.5 mg N pot−1), and the grain yield (9.08 g pot−1), in comparison to no N fertilizer applied. Supplementation of two NFRB strains enhanced the soilconcentrations of NH4+ and NO3−, the total N uptake, and the grain yield. The treatment fertilized with 75% N of RFF plus an individual NFEB strain or their bacterial mixture had equivalent total N uptake to that the treatment fertilized with 100% N of RFF had, 120.8–125.5 mg N pot−1 compared to 124.4 mg N pot−1. Regarding the sesame yield, with a reduction by 25–50% N of RFF plus ASD-48 and ASD-21, either individually or in mixture, it increased by 2.39–8.56%, compared to that in the treatment fertilized with 100% N of RFF.

Potential applications of mineral solubilizing rhizospheric and nitrogen fixing endophytic bacteria as microbial consortium for the growth promotion of chilli (Capsicum annum L.)

Potential applications of mineral solubilizing rhizospheric and nitrogen fixing endophytic bacteria as microbial consortium for the growth promotion of chilli (Capsicum annum L.)

Potential of N2-fixing endophytic bacteria isolated from maize roots as biofertiliser to enhance soil fertility, N uptake, and yield of Zea mays L. cultivated in alluvial soil in dykes

This study aimed to (i) select the endophytic bacteria from maize roots for their N2-fixing ability and (ii) evaluate the efficacy of potent indigenous bacterial strains on soil fertility, nitrogen (N) uptake, and growth and yield of maize. A total of 31 maize root samples were collected from An Giang province in Vietnam to isolate the bacteria. The pot experiment was conducted in nine treatments: (i) 100% N of the recommended fertiliser formula (RFF), (ii) 85% N of RFF, (iii) 70% N of RFF, (iv) 55% N of RFF, (v) 85% N of RFF plus a mixture of two potent strains of nitrogen-fixing endophytic bacteria (NFEB), (vi) 70% N of RFF plus a mixture of two potent strains of NFEB, (vii) 25% N of RFF plus a mixture of two potent strains of NFEB, (viii) 0% N of RFF plus a mixture of two potent strains of NFEB, and (ix) 0% N of RFF. The experiment was conducted in the greenhouse to collect soil and plant samples at harvest and observe their growth and agronomic parameters. The results showed that two acid-resistant endophytic bacterial strains were selected and identified as Enterobacter cloacae ASD-21 and E. cloacae ASD-48. At 85% N level, a mixture of the two endophytic bacteria strains was applied as biofertilisers and proved their ability to significantly enhance NH4+ content and N uptake, with an increase of 14.8 mg NH4+ kg-1 and 0.26 g N pot-1, respectively. A mixture of the two potent strains of NFEB produced higher values in plant height, stem diameter, cob length, and cob diameter compared to 100% N of RFF. It replaced 15% N of RFF but still maintained the maize grain yield

Improvement of Green Soybean Growth and Yield in Alluvial Soil by Endophytic Nitrogen-Fixing Bacteria

Improvement of Green Soybean Growth and Yield in Alluvial Soil by Endophytic Nitrogen-Fixing Bacteria

Isolation, identification and characterization of nitrogen fixing endophytic bacteria and their effects on cassava production.

BackgroundCassava (Manibot esculenta Crantz) is one of the most important among tuber crops. The amount of nitrogen fertilizer used for cassava production is relatively high (400 kg ha−1), but there are few studies on biological nitrogen fixation in this crop. Therefore, it is particularly important to study whether cassava and microorganisms have the associated nitrogen-fixing and other promoting effects of endophytic bacteria.MethodsWe screened 10 endophytic bacteria using the nitrogen-free culture method from the roots of seven cassava cultivars, and the nitrogenase activity of the A02 strain was the highest 95.81 nmol mL−1 h−1. The A02 strain was confirmed as Microbacteriaceae, Curtobacterium using 16S rRNA sequence alignment. The biological and morphological characteristics of strain A02 were further analyzed.ResultsThe experimental results showed that the biomass of roots, stems, and leaves of cassava inoculated with A02 increased by 17.6%, 12.6%, and 10.3%, respectively, compared to that of the control (without A02 inoculation). These results were not only related to the secretion of auxin (IAA) and solubilization of phosphate but also in the promotion of biological nitrogen fixation of cassava leaves by strain A02. Moreover, the highest 95.81 nmol mL−1h−1 of nitrogenase activity was reported in strain A02, and thus more nitrogen fixation was observed in strain A02. In conclusion, A02 is a newly discovered endophytic nitrogen-fixing bacteria in cassava that can be further used in the research of biological bacterial fertilizers.

Endophytic nitrogen-fixing bacteria: Untapped treasurer for agricultural sustainability

Endophytic nitrogen-fixing bacteria: Untapped treasurer for agricultural sustainability