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Pea, Pisum sativum L. is a popular legume crop, the advantage of which is that nitrogen accumulates in the soil after its cultivation. It requires less nitrogen fertilizers, since nodule nitrogen-fixing bacteria are found on the roots of the crop. The study aimed to evaluate the effect of biological and chemical preparations on the yield and content of heavy metals in peas. The Aksaisky Usatyi 55 pea variety was selected, characterized by the drought and heat resistance. In total, two experiments were conducted. Experiment 1 included sowing peas with the introduction of organic manure at a calculated dose of 10 ton ha-1. Biometric indicators of pea plants corresponding to the characteristics of the variety were recorded. On average the vegetation period took 94 days, and the height of the plants by the ripening phase was 50.9 cm. Boraginaceae, Asteraceae, Convolvulaceae, Poaceae, Amaranthaceae, Euphorbiaceae, and Plantaginaceae represented the weed families. According to the weed estimation scale, the weed infestation was slight or negligible. The yield of peas ranged from 12.5 to 17.0 c ha-1, the maximum yield was obtained in the variant using the Baikal EM-1 biological preparation (17.0 c ha-1), compared to the control variant (12.5 c ha-1). The pea quality ranged from 16.4 to 18.5%; the carbohydrate content from 67.7 to 69.5%; fiber from 3.8 to 4.9%; fat from 0.7 to 1.6%; and ash from 1.9 to 2.8%. The heavy metal content was within the maximum permissible concentration. The heavy metal content in peas ranged from 0.79 to 46.0 mg kg-1, in the control variant from 0.60 to 40.64 mg kg-1, with the use of chemicals from 1.20 to 46.0 mg kg-1, and with the use of biological preparations from 0.92 to 40.72 mg kg-1. [ABSTRACT FROM AUTHOR]

The article discusses the challenges faced by alternative food networks as they grow in size and attract potential buyers. It highlights the success story of Timeless Seeds, a group of renegade farmers in Montana who chose to grow legumes and employ agroecological farming practices. Timeless Seeds developed an underground marketing network that bypassed conventional food chains and built a multi-million dollar business. Recently, Timeless Seeds was acquired by Mad Agriculture, a nonprofit aiming to improve the ecosystem for farmers transitioning to regenerative organic farming. The article emphasizes the importance of safeguarding the interests of farmers and maintaining the integrity and values of alternative food businesses. [Extracted from the article]

The health of soil is paramount for sustaining life, as it hosts diverse communities of microorganisms that interact with plants, influencing their growth, health, and resilience. Beneficial microorganisms, including fungi and bacteria, form symbiotic relationships with plants, providing essential nutrients, promoting growth, and enhancing stress tolerance. These microorganisms, such as mycorrhizal fungi and plant growth-promoting bacteria, play crucial roles in nutrient cycling, soil health, and plant productivity. Additionally, they help lessen reliance on chemical fertilizers, thereby mitigating the environmental risks associated with their use. Advances in agricultural practices harness the potential of these beneficial microorganisms to improve crop yields while minimizing the environmental impact. However, challenges such as competition with indigenous microbial strains and environmental factors limit the universal utilization of microbial inoculants. Despite these challenges, understanding and leveraging the interactions between plants and beneficial microorganisms hold promise for sustainable agriculture and enhanced food security.

This study investigated the interaction between extracellular polymeric substances (EPS) and Pb2+, and the toxic effects of Pb2+ on Klebsiella trevisan. According to the experimental data, Pb2+ mainly inhibited the division and reproduction of Klebsiella trevisan during the logarithmic growth period. In addition, the activity of superoxide dismutase (SOD) and the content of malondialdehyde (MDA) were affected, which indicated that Pb2+ had a strong toxic effect on Klebsiella trevisan and could inhibit cell survival. When the concentration of Pb2+ reached 250 mg/L, the cell membrane damage rate reached as high as 95.7%. Three-dimensional excitation-emission matrix (3D-EEM), synchronous fluorescence and two-dimensional correlation spectroscopy (2D-COS) were selected to analyze the interaction between EPS and Pb2+. The results of 3D-EEM showed that the most important component of EPS was protein-like substance. Further linear fitting of the Stern-Volmer model indicated that the quenching process of Pb2+ and EPS was mainly static quenching. Besides, 2D-COS demonstrated that aromatic proteins in EPS were preferred to tryptophan proteins in binding to Pb2+. The findings of this study are of great significance for revealing the binding interaction between EPS and Pb2+, and proving the toxic effect of Pb2+ on nitrogen-fixing bacteria. It also provides a basis for studying the interaction between EPS and heavy metals by using spectral response.

Summary: Symbiotic nitrogen fixation carried out by the interaction between legumes and rhizobia is the main source of nitrogen in natural ecosystems and in sustainable agriculture. For the symbiosis to be viable, nutrient exchange between the partners is essential. Transition metals are among the nutrients delivered to the nitrogen‐fixing bacteria within the legume root nodule cells. These elements are used as cofactors for many of the enzymes controlling nodule development and function, including nitrogenase, the only known enzyme able to convert N2 into NH3. In this review, we discuss the current knowledge on how iron, zinc, copper, and molybdenum reach the nodules, how they are delivered to nodule cells, and how they are transferred to nitrogen‐fixing bacteria within. [ABSTRACT FROM AUTHOR]

The black locust (Robinia pseudoacacia L.) is the second-most abundant deciduous tree in forest plantations, and one of the most important invasive woody species worldwide. The species has a strong transformer capacity, especially expressed by its nitrogen enrichment effect caused by nitrogen-fixing bacteria living in its root-nodules. The aim of this study was to explore the mutually interacting factors of nitrogen-fixing root-nodules, site characteristics, and herb-layer composition of 28 North Hungarian black locust stands. In the herb-layers of the study sites, a total of 121 plant species were identified, representing a relatively low species richness. The studied black locust stands showed high variability both in their herb-layer compositions and root-nodule formation, but no clear relationship could be demonstrated between these characteristics. The PCA component with which the species richness and Shannon–Wiener diversity index were strongly correlated was negatively associated with all root-nodule parameters (number, surface area, and weight), supporting the biodiversity-reducing effect of black locust by its nitrogen-fixing bacteria. All of the root-nodule parameters were negatively correlated with the PCA factor predominantly determined by stand age, confirming that the root-nodule biomass decreases as time progresses. [ABSTRACT FROM AUTHOR]

We report a rationally designed membrane‐intercalating conjugated oligoelectrolyte (COE), namely COE‐IC, which endows aerobic N2‐fixing bacteria Azotobacter vinelandii with a light‐harvesting ability that enables photosynthetic ammonia production. COE‐IC possesses an acceptor‐donor‐acceptor (A‐D‐A) type conjugated core, which promotes visible light absorption with a high molar extinction coefficient. Furthermore, COE‐IC spontaneously associates with A. vinelandii to form a biohybrid in which the COE is intercalated within the lipid bilayer membrane. In the presence of L‐ascorbate as a sacrificial electron donor, the resulting COE‐IC/A. vinelandii biohybrid showed a 2.4‐fold increase in light‐driven ammonia production, as compared to the control. Photoinduced enhancement of bacterial biomass and production of L‐amino acids is also observed. Introduction of isotopically enriched 15N2 atmosphere led to the enrichment of 15N‐containing intracellular metabolites, consistent with the products being generated from atmospheric N2. [ABSTRACT FROM AUTHOR]

Simple Summary: Acacia longifolia is an invasive plant highly dispersed in the Mediterranean region. Being a legume, the association with nitrogen-fixing bacteria (i.e., rhizobia) allows access to readily fixed nitrogen, facilitating its growth, development, and dispersal. The extent to which this relation is restricted to bacteria was investigated in this study. We aimed to (i) characterize the microbial community inside root nodules, i.e., structures where nitrogen fixation occurs, and (ii) understand how these partners change following a fire event. In fact, fire potentiates A. longifolia invasion, so it is of remarkable interest to understand the role of nodulation in dispersal. We found that root nodules are a guesthouse for microorganisms and, while some are common between unburnt and burnt sites, others shift, particularly considering fungal community. Acacia longifolia is one of the most aggressive invaders worldwide whose invasion is potentiated after a fire, a common perturbation in Mediterranean climates. As a legume, this species establishes symbioses with nitrogen-fixing bacteria inside root nodules; however, the overall microbial diversity is still unclear. In this study, we addressed root nodules' structure and biodiversity through histology and Next-Generation Sequencing, targeting 16S and 25S-28S rDNA genes for bacteria and fungi, respectively. We wanted to evaluate the effect of fire in root nodules from 1-year-old saplings, by comparing unburnt and burnt sites. We found that although having the same general structure, after a fire event, nodules had a higher number of infected cells and greater starch accumulation. Starch accumulated in uninfected cells can be a possible carbon source for the microbiota. Regarding diversity, Bradyrhizobium was dominant in both sites (ca. 77%), suggesting it is the preferential partner, followed by Tardiphaga (ca. 9%), a non-rhizobial Alphaproteobacteria, and Synechococcus, a cyanobacteria (ca. 5%). However, at the burnt site, additional N-fixing bacteria were included in the top 10 genera, highlighting the importance of this process. Major differences were found in the mycobiome, which was diverse in both sites and included genera mostly described as plant endophytes. Coniochaeta was dominant in nodules from the burnt site (69%), suggesting its role as a facilitator of symbiotic associations. We highlight the presence of a large bacterial and fungal community in nodules, suggesting nodulation is not restricted to nitrogen fixation. Thus, this microbiome can be involved in facilitating A. longifolia invasive success. [ABSTRACT FROM AUTHOR]

• Peptides from P. tetraphylla colleter extract have a molecular weight of around six kDa. • Peptides from P. tetraphylla colleter extract act on the plasma membrane permeability of the tested microorganisms. • Bacteria isolated from P. tetraphylla could grow in a selective medium for nitrogen-fixing bacteria. • Bacteria form an aerotaxic film showing its potential to benefit plants. • Antifungal activity and an environment for the proliferation of beneficial organisms were described for colleters. Colleters are secretory structures producing exudates that provide physical and/or chemical protection for plant organs in development. Furthermore, these structures harbor complex microbial communities with scarce explored potential roles in plant-microbial interactions. Therefore, this study aimed to analyze the potential function of the colleter s' secretion of Palicourea tetraphylla driven by the antifungal activity and the associated culturable beneficial bacteria diversity. For this purpose, colleter secretion of P. tetraphylla was collected and processed to obtain the total protein extract and access its antifungal properties. Moreover, bacteria associated with colleters and exudates were accessed, and taxonomic position was defined by 16S-rDNA sequencing. The bacterial isolates were characterized by their N 2 -fixing capacity and solubilization of macro and micronutrients. The consistency of the secreted material was mucilaginous with an alkaline nature and contained proteins and microorganisms. The protein extract from P. tetraphylla secretion revealed the presence of proteins up to 6 kDa and antifungal properties based on fungal growth inhibition and membrane permeabilization revealed by fluorescent probe SYTOX Green. In addition, several secretion-associated bacteria showed the diazotrophic ability and combined with phosphorus and/or zinc and/or manganese solubilization. The results obtained through the fungal growth inhibition assay, associated with the membrane permeabilization of the microorganisms by the SYTOX Green test, confirmed the presence of antifungal proteins and defense activities of the colleter secretion. In addition, several bacteria isolated from the stipular colleters secretion demonstrate that these colleters are possibly responsible for maintaining a community of beneficial potentially bacteria for the plant. [ABSTRACT FROM AUTHOR]

All nitrogen-fixing bacteria and archaea (diazotrophs) use molybdenum (Mo) nitrogenase to reduce dinitrogen (N2) to ammonia, with some also containing vanadium (V) and iron-only (Fe) nitrogenases that lack Mo. Among diazotrophs, the regulation and usage of the alternative V-nitrogenase and Fe-nitrogenase in methanogens are largely unknown. Methanosarcina acetivorans contains nif, vnf, and anf gene clusters encoding putative Mo-nitrogenase, V-nitrogenase, and Fe-nitrogenase, respectively. This study investigated nitrogenase expression and growth by M. acetivorans in response to fixed nitrogen, Mo/V availability, and CRISPRi repression of the nif, vnf, and/or anf gene clusters. The availability of Mo and V significantly affected growth of M. acetivorans with N2 but not with NH4Cl. M. acetivorans exhibited the fastest growth rate and highest cell yield during growth with N2 in medium containing Mo, and the slowest growth in medium lacking Mo and V. qPCR analysis revealed the transcription of the nif operon is only moderately affected by depletion of fixed nitrogen and Mo, whereas vnf and anf transcription increased significantly when fixed nitrogen and Mo were depleted, with removal of Mo being key. Immunoblot analysis revealed Mo-nitrogenase is detected when fixed nitrogen is depleted regardless of Mo availability, while V-nitrogenase and Fe-nitrogenase are detected only in the absence of fixed nitrogen and Mo. CRISPRi repression studies revealed that V-nitrogenase and/or Fe-nitrogenase are required for Mo-independent diazotrophy, and unexpectedly that the expression of Mo-nitrogenase is also required. These results reveal that alternative nitrogenase production in M. acetivorans is tightly controlled and dependent on Mo-nitrogenase expression. Methanogens and closely related methanotrophs are the only archaea known or predicted to possess nitrogenase. Methanogens play critical roles in both the global biological nitrogen and carbon cycles. Moreover, methanogens are an ancient microbial lineage and nitrogenase likely originated in methanogens. An understanding of the usage and properties of nitrogenases in methanogens can provide new insight into the evolution of nitrogen fixation and aid in the development nitrogenase-based biotechnology. This study provides the first evidence that a methanogen can produce all three forms of nitrogenases, including simultaneously. The results reveal components of Mo-nitrogenase regulate or are needed to produce V-nitrogenase and Fe-nitrogenase in methanogens, a result not seen in bacteria. Overall, this study provides a foundation to understand the assembly, regulation, and activity of the alternative nitrogenases in methanogens. [ABSTRACT FROM AUTHOR]

Nitrogen-fixing bacteria such as cyanobacteria have the capability to fix atmospheric nitrogen at ambient temperature and pressure, and intensive cultivation of cyanobacteria for fertilizer could lead to its use as an "environmentally friendly" replacement or supplement for nitrogen (N) fertilizer derived from the Haber–Bosch process. Prior research has focused on the use of N-fixing bacteria as a soil inoculum, and while this can improve crop yields, yield improvements are generally attributed to plant-growth-promoting substances produced by the bacteria, rather than to biological N fixation. The intensive cultivation of cyanobacteria in raceways or bioreactors can result in a fertilizer that provides N and organic carbon, as well as potentially similar growth-promoting substances observed in prior research work. On-farm or local production of cyanobacterial fertilizer could also circumvent infrastructure limitations, economic and geopolitical issues, and challenges in distribution and transport related to Haber–Bosch-derived N fertilizers. The use of cyanobacterial N fertilizer could have many agronomic and environmental advantages over N fertilizer derived from the Haber–Bosch process, but study of cyanobacteria as a replacement for other N fertilizers remains very limited. Scientific and practical challenges remain for this promising but as-yet unproven approach to maintaining or improving soil N fertility. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effect of biological control agents (BCA) and two biological formulations (Bio-Terra and Bio-CNPR) against the phytopathogens found in the soil of huacle chili (Capsicum annuum) plantations, in order to obtain healthy seedlings. Design/Methodology/Approach: The following design variables were evaluated: germination (%), disease incidence (%), and survival (%). Stem height and root length were also evaluated. The experimental unit was a tray with n=30 seedlings per each treatments (T0, T1, T2, T3, and T4) and four repetitions. An analysis of variance (ANOVA) was used. Tukey's mean test was applied (using the Minitab Statistical program version 20.0) in units that presented differences (p ≤ 0.05). Results: The phytopathogenic microorganism Fusarium spp. was isolated from the soil of the plots cultivated with huacle chili. The T1 treatment recorded the best inhibitory effect against Fusarium spp.: it had 92.2% germination, 18.3% incidence of Fusarium spp., and 82% surviving seedlings (with an average height of 16 cm and a root length of 7.9 cm). The sterilization of the soil lead to T4 having the best results in germination, incidence, and survival, since Fusarium spp. did not damage huacle chili seedlings. In contrast, T0 did not prosper neither with BCA nor with biological products, since all the seedlings in non-sterile soil died. Study Limitations/Implications: A plastic barrier was placed between the trays with the chili seedlings to avoid cross-contamination between treatments. Findings/Conclusions: T1 (the BCA with nitrogen-fixing bacteria and B. subtilis) recorded the best counteracting results against the damage generated by Fusarium spp. Their antagonism allowed a high percentage of survival of huacle chili seedlings and encouraged plant development through the best root growth and height of the seedlings. [ABSTRACT FROM AUTHOR]

The family Rhizobiaceae contains 19 validly described genera including the rhizobia groups, many of which are important nitrogen-fixing bacteria. Early classification of Rhizobiaceae relied heavily on the poorly resolved 16S rRNA genes and resulted in several taxonomic conflicts. Although several recent studies illustrated the taxonomic status of many members in the family Rhizobiaceae, several para- and polyphyletic genera still needed to be elucidated. The rapidly increasing number of genomes in Rhizobiaceae has allowed for a revision of the taxonomic identities of members in Rhizobiaceae. In this study, we performed analyses of genome-based phylogeny and phylogenomic metrics to review the relationships of 155-type strains within the family Rhizobiaceae. The UBCG and concatenated protein phylogenetic trees, constructed based on 92 core genes and concatenated alignment of 170 single-copy orthologous proteins, demonstrated that the taxonomic inconsistencies should be assigned to eight novel genera, and 22 species should be recombined. All these reclassifications were also confirmed by pairwise cpAAI values, which separated genera within the family Rhizobiaceae with a demarcation threshold of ~86%. In addition, along with the phenotypic and chemotaxonomic analyses, a novel strain BDR2-2T belonging to a novel genus of the family Rhizobiaceae was also confirmed, for which the name Ectorhizobium quercum gen. nov., sp. nov. was proposed. The type strain is BDR2-2T (=CFCC 16492T = LMG 31717T). [ABSTRACT FROM AUTHOR]

Agave lechuguilla is a widely distributed plant in arid ecosystems. It has been suggested that its microbiome is partially responsible for its great adaptability to the oligotrophic environments of the Chihuahuan Desert. To lead the recruitment of beneficial rhizobacteria, the root exudates are essential; however, the amino acids contained within these compounds had been largely overlooked. Thus, we investigated how the variations of amino acids in the rhizosphere at different growth stages of A. lechuguilla affect the rhizobacterial community composition, its functions, and activity of the beneficial bacteria. In this regard, it was found that arginine and tyrosine were related to the composition of the rhizobacterial community associated to A. lechuguilla, where the most abundant genera were from the phylum Proteobacteria and Bacteroidetes. Moreover, Firmicutes was largely represented by Bacillus in the phosphorus-mineralizing bacteria community, which may indicate its great distribution and versatility in the harsh environments of the Chihuahuan Desert. In contrast, we found a high proportion of Unknown taxa of nitrogen-fixing bacteria, reflecting the enormous diversity in the rhizosphere of these types of plants that remains to be explored. This work also reports the influence of micronutrients and the amino acids methionine and arginine over the increased activity of the nitrogen-fixing and phosphorus-mineralizing bacteria in the rhizosphere of lechuguillas. In addition, the results highlight the multiple beneficial functions present in the microbiome that could help the host to tolerate arid conditions and improve nutrient availability. [ABSTRACT FROM AUTHOR]

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 20 g N ha−1 year−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. [ABSTRACT FROM AUTHOR]

Aims: To understand the species composition, abundance and diversity of nitrogen-fixing bacteria in the Cenchrus fungigraminus rhizosphere and to screen nitrogen-fixing bacteria to study their potential role in plant growth promotion. Methods: Soil were collected from 4 depths (G1, G2, G3 and G4) of the C. fungigraminus rhizosphere, and their physical and chemical properties were determined. The diversity and abundance of nitrogen-fixing bacteria and the nifH gene was analysed. Nitrogen-fixing bacteria were screened and selected to promote growth of C. fungigraminus seedlings. Results: The highest diversity and abundance of nitrogen-fixing bacteria was observed in the G2 samples collected from the C. fungigraminus rhizosphere. These bacteria mainly included Proteobacteria (93.91%), Actinobacteria (0.42%), and Firmicutes (0.18%) and were significantly affected by total nitrogen, available nitrogen and soil depth. The nifH gene copy number was highest (1.56 ± 0.17 × 107copies/g) in G2. Rhizobium pusense No. 8 and No. 28 were isolated from G1 and G2, with nitrogenase activities of 145.06 ± 4.10 and 199.78 ± 7.50 U/L. The promotion experiment revealed that the plant height, root length, and leaf length of C. fungigraminus seedlings treated with both strains significantly increased by 56.79%, 76.99% and 55.71%, and the soil moisture and total nitrogen were significantly increased compared to the control (P < 0.05). The available nitrogen, organic matter and organic carbon in soil with strain No. 28 significantly increased compared to CK. Conclusion: Rhizobacteria in the C. fungigraminus rhizosphere play an important role as plant growth promoting rhizobacteria (PGPR). Two strains showed potential for the development of biological fertilizers. [ABSTRACT FROM AUTHOR]

The excessive use of chemical substances such as pesticides, herbicides, and fungicides, along with other harmful practices, has disrupted the beneficial microflora in the soil. These harmful effects extend beyond the soil and can lead to the spread of dangerous diseases in both humans and animals. Pesticides are frequently applied in modern agriculture to boost crop production and meet the demands of a growing population. However, the accumulation of pesticides in the soil poses a threat to both the soil itself and the overall ecosystem. As pesticides enter the food chain, groundwater, and marine water, they have direct or indirect impacts on human health and negatively affect terrestrial and aquatic life. These chemical compounds contribute to various biological and microscopic contaminants, resulting in detrimental environmental consequences. Fortunately, certain microorganisms possess natural tolerance to pesticides and can survive under adverse conditions. Diazotrophs, which are nitrogen-fixing bacteria, have also been found to play a role in the biodegradation of toxic compounds released from pesticides, thereby contributing to a healthier environment. This review focuses on the essential microbial community involved in pesticide degradation, with particular emphasis on Diazotrophs. It explores their classification, mechanisms of pesticide degradation, and regulation under stress conditions. Understanding the characteristics of these essential microbes (Diazotrophs) operating in stressful environments is crucial for pesticide degradation. The study highlights the significant role of microbial diversity in the breakdown of xenobiotic pesticide compounds in the soil, emphasising the importance of an eco-friendly approach to improve agricultural practices, sustain soil fertility, promote crop production, and protect ecotoxicology. [ABSTRACT FROM AUTHOR]

In Mexico, agave has a significant cultural and economic impact via its use as a raw material for producing fermented drinks. The agave plant grows in arid and nitrogen-deficient soil where it associates with fungi and bacteria to meet nutrient demands, particularly under extreme conditions of fungal growth; this community of microorganisms is called the microbiome. In the microbiome, aromatic volatile synthesis activates the defense response, resistance to abiotic stress, and plant growth. These aromatic volatiles also impact the organoleptic characteristics of fermented beverages and are produced by microorganisms during agave fermentation. This research presents the behavior of K. marxianus cultivated in the presence of extreme and deficient nitrogen concentrations. In addition, a new biological relationship between K. marxianus ITD0090 from mezcal fermentation and Bacillus tequilensis ITD-UANL-01 is reported, confirmed by fluorescence microscopy and intracellular recovery. Our results also reveal that B. tequilensis ITD-UANL-01 is a nitrogen-fixing bacterium that provides assimilable nitrogen to K. marxianus under nitrogen starvation conditions. This phenomenon allows for 144 h of viability without nitrogen. Furthermore, this is the first report of an endosymbiont of K. marxianus ITD0090 in fermentation. [Display omitted] • Kluyveromyces marxianus ITD0090 remains viable under nitrogen starvation stress for 144 h. • Bacillus tequilensis ITD-UANL-01 is the endosymbiont identified in K. marxianus ITD0090. • B. tequilensis ITD-UANL-01 can fix nitrogen and gives to K. marxianus ITD0090 assimilable nitrogen in NH 4 form. [ABSTRACT FROM AUTHOR]

A conductive polymer‐based photosynthetic biohybrid is constructed to enhance biological nitrogen fixation by increasing nitrogenase activity in the non‐photosynthetic bacterium Azotobacter Chroococcum (A. Chroococcum). The light‐harvesting cationic poly(fluorene‐alt‐phenylene) (PFP) electrostatically binds to the surface of the bacteria and possesses satisfactory conductivity to facilitate electron transfer to the bacterium, promoting the nitrogen fixation pathway through redox proteins on the surface of the bacteria when under illumination. Therefore, the nitrogenase activity, hydrogen, NH4+‐N and L‐amino acids production are increased by 260 %, 37 %, 44 %, and 47 %, respectively. The expression levels of nifD and nifK encoding molybdenum‐iron (MoFe) protein and relevant nitrogen‐fixing proteins are up‐regulated. These photoactive conductive polymer‐bacteria biohybrids provide a new method for improving the biological nitrogen fixation capability of non‐photosynthetic nitrogen‐fixing bacteria. [ABSTRACT FROM AUTHOR]

In rice paddy soil, biological nitrogen fixation is important for sustaining soil nitrogen fertility and rice growth. Anaeromyxobacter and Geobacteriaceae, iron-reducing bacteria belonging to Deltaproteobacteria, are newly discovered nitrogen-fixing bacteria dominant in paddy soils. They utilize acetate, a straw-derived major carbon compound in paddy soil, as a carbon and energy source, and ferric iron compounds as electron acceptors for anaerobic respiration. In our previous paddy field experiments, a significant increase in soil nitrogen-fixing activity was observed after the application of iron powder to straw-returned paddy field soil. In addition, combining iron application with 60–80% of the conventional nitrogen fertilizer rate could maintain rice yields similar to those with the conventional nitrogen fertilization rate. It was thus suggested that iron application to paddy soil increased the amount of nitrogen fixed in the soil by enhancing nitrogen fixation by diazotrophic iron-reducing bacteria. The present study was conducted to directly verify this suggestion by 15N-IRMS analysis combined with 15N-DNA-stable isotope probing of iron-applied and no-iron-applied plot soils in an experimental paddy field. In no-iron-applied native paddy soil, atmospheric 15N2 was incorporated into the soil by biological nitrogen fixation, in which diazotrophic iron-reducing bacteria were the most active drivers of nitrogen fixation. In iron-applied paddy soil, the amount of 15N incorporated into the soil was significantly higher due to enhanced biological nitrogen fixation, especially via diazotrophic iron-reducing bacteria, the most active drivers of nitrogen fixation in the soil. Thus, our previous suggestion was verified. This study provided a novel picture of active nitrogen-fixing microorganisms dominated by diazotrophic iron-reducing bacteria in paddy soil, and directly proved the effectiveness of iron application to enhance their nitrogen fixation and increase the incorporation of atmospheric nitrogen into soil. The enhancement of biological nitrogen fixation in paddy fields by iron application may lead to novel and unique paddy soil management strategies to increase soil nitrogen fertility and ensure rice yields with reduced nitrogen fertilizer input and lower environmental nitrogen burdens. [ABSTRACT FROM AUTHOR]

Background: Magnesium deficiency has become a major nutritional disorder in lateritic soils of Kerala. Appropriate magnesium fertilization is the best strategy to combat deficiency issues. Apart from correcting nutritional deficiency, magnesium fertilization has an influence on the growth of beneficial microbes such as nitrogen fixing bacterias and arbuscular mycorrhizal fungi. The experiment aimed to investigate the effect of magnesium fertilization on crop yield and population rhizosphere micoflora of cowpea in lateritic soils of Kerala. Methods: A pot culture experiment was conducted with a gradient of magnesium additions ranging from 5 mg kg-1 to 80 mg kg-1 of soil along with recommended dose of fertilizers. Population of rhizobium, free living nitrogen fixing bacteria, spore count of arbuscular mycorrhizal fungi and per cent root colonization of arbuscular mycorrhizal fungi were studied during flowering. The available magnesium and magnesium uptake were also worked out during harvest. Yield and yield contributing characteristics of cowpea were measured during harvest stage. Result: Magnesium addition produced significant variations in population of rhizobium and free- living nitrogen fixing bacteria whereas spore count of AMF and per cent root colonization of AMF did not vary according to the added doses of magnesium. A higher population of rhizobium, free living nitrogen fixers, root nodules, magnesium uptake, plant height and yield were obtained in the treatment where magnesium was applied @ 10 mg kg-1 soil. [ABSTRACT FROM AUTHOR]

While in the atmosphere nitrogen is abundant, this element plays a limited role as nutrient for plants. Cereal crops, as an example, are uncapable to directly use freely available nitrogen gas. As a consequence, their optimal growing and, in general, the productivity of such crops relies mainly on the use of chemical fertilizers, which, under the European Green Deal and the Farm to Fork Strategy are under scrutiny with plans of reduction of their use. As increasing crop production is a vital target for agriculture and food systems, the role of nitrogen fixers could play a fundamental role to match the targets of increasing the food production by decreasing the use of chemical fertilizers. Also, such approach is very appropriate from the perspective of sustainable production and conservative agriculture. The present work has the objective to examine the role of nitrogen fixers on the maize yield, respectively the productivity in harvested maize crop treated with Azotobacter chrococcum, Azotobacter vinelandii and Bacillus megaterium, three different nitrogen-fixing bacteria. The investigations were based on field tests. Thus, there at the beginning the seeds were inoculated before seeding; and during the vegetation the crops were treated with the three bacteria species. The fields experiment was organized in four variants (one non-treated variant and three with the bacteria Azotobacter chrococcum, Azotobacter vinelandii and Bacillus megaterium) and three replicates. The examination of collected samples revealed a general increase in productivity in the variants treated with Azotobacter vinelandii. [ABSTRACT FROM AUTHOR]

It is well known that chemical inputs are the main determinant of yields, but their impact is considerable, causing significant changes in the soil. Soil microbiota is a very important component of the agricultural ecosystem and is involved in nutrient cycling. Its structure and dynamics are easily influenced by tillage, fertilizers and crops. The aim of the present study was to observe the effects of different tillage systems combined with the application of inorganic fertilizers and a phosphorus-solubilizing bacterial fertilizer in different rates and combinations on nitrogen-fixing bacteria in the soil. The study was conducted in 2023 growing season at the Ezareni Farm from Iasi. The tillage systems were represented by conventional (CT) and no-tillage (NT). Sunflower and maize crops were fertilized with: NPK (20% N, 10% P2O5, 5% K2O), phosphorus solubilizing bacteria (PSB) fertilizer containing Bacillus megaterium var. phosphaticum, applied twice, and Corona N foliar fertilizer (21% N), applied to 3 of the 5 treatment formulations. For the quantification of nitrogen-fixing bacteria populations (Azotobacter spp. and Clostridium pasteurianum), soil samples were collected four times and the method used in the laboratory was that of successive dilutions. During the growing season, an increase in colony numbers was observed in CT maize when treated with the manufacturer's recommended dose (10 l/ha) of biofertilizer in combination with foliar application of nitrogen. In contrast, in sunflower, the number of bacterial populations was higher in NT under biofertilizer treatment at the prescribed dose but without foliar fertilizer application. At the beginning of the growing season, Clostridium sp. is more numerous, but this is reversed 4 weeks after the second application of PSB, which corresponds to the flowering period of the plants, when Azotobacter spp. predominates. The results indicate increased populations of nitrogen-fixing bacteria in both the recommended and higher-dose PSB treatments, and in sunflower this is more evident in the no-tillage system. [ABSTRACT FROM AUTHOR]

Carnivorous pitcher plants are uniquely adapted to nitrogen limitation, using pitfall traps to acquire nutrients from insect prey. Pitcher plants in the genus Sarracenia may also use nitrogen fixed by bacteria inhabiting the aquatic microcosms of their pitchers. Here, we investigated whether species of a convergently evolved pitcher plant genus, Nepenthes, might also use bacterial nitrogen fixation as an alternative strategy for nitrogen capture. First, we constructed predicted metagenomes of pitcher organisms from three species of Singaporean Nepenthes using 16S rRNA sequence data and correlated predicted nifH abundances with metadata. Second, we used gene-specific primers to amplify and quantify the presence or absence of nifH directly from 102 environmental samples and identified potential diazotrophs with significant differential abundance in samples that also had positive nifH PCR tests. Third, we analyzed nifH in eight shotgun metagenomes from four additional Bornean Nepenthes species. Finally, we conducted an acetylene reduction assay using greenhouse-grown Nepenthes pitcher fluids to confirm nitrogen fixation is indeed possible within the pitcher habitat. Results show active acetylene reduction can occur in Nepenthes pitcher fluid. Variation in nifH from wild samples correlates with Nepenthes host species identity and pitcher fluid acidity. Nitrogen-fixing bacteria are associated with more neutral fluid pH, while endogenous Nepenthes digestive enzymes are most active at low fluid pH. We hypothesize Nepenthes species experience a trade-off in nitrogen acquisition; when fluids are acidic, nitrogen is primarily acquired via plant enzymatic degradation of insects, but when fluids are neutral, Nepenthes plants take up more nitrogen via bacterial nitrogen fixation. [ABSTRACT FROM AUTHOR]

The association of conventional fertilizers with fertilizers of organic origin is a well-known practice in agriculture for achieving high productivity and also with the adoption of inoculants, composed of bacteria for promoting better plant development of crops. Thus, the objective of the work was to investigate the growth and productivity of radish with organic fertilization and the influence of the use of nitrogen fixing bacteria of the genus Azospirillum spp. radish (Raphanus sativus L.) Hybrid Margaret Queen. The treatments were the use of different doses of organic fertilizer and the application of Azospirillum brasilense, besides the control. At the end of the cycle, plant height, tuber diameter, tuber fresh mass, tuber dry mass, and total tuber fresh mass were evaluated. With and without application of A. brasilense, increases of 16.5% and 6.40% in tuber diameter were obtained, respectively. Without application of A. brasilense, there was an increase of 0.37% in leaf dry mass when the maximum concentration of 8 kg m² of organic fertilizer was used. For root fresh mass and root dry mass, with foliar application of A. brasilense, there was an increase of 9.57% and 0.67%, while without A. brasilense there was an increase of 2.43% and 0.22%. There were increases of 12.83% for total fresh mass with the management of A. brasilense and 3.4% without A. brasilense, using the maximum concentration of 8 kg m² of organic fertilizer. For height, there was an increase of 5.12% without A. brasilense. It was concluded that organic fertilization alone or combined with A. brasilense is an alternative in radish production. [ABSTRACT FROM AUTHOR]

Copyright of Philosophy & History of Biology / Filosofia e História da Biologia is the property of Associacao Brasileira de Filosofia e Historia da Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Agriculturae Serbica is the property of University of Kragujevac, Faculty of Agronomy and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The efficiency of the natural symbiotic relationship between communally produced legumes and nitrogen fixing bacteria has been reported to be very poor, mainly due to poor soils in communal farming areas. With the use of synthetic fertilizers to increase soil fertility being both environment-unfriendly and unaffordable for majority of communal farmers, strategies that are cost-effective and climate smart need to be put in place to improve the productivity of communal legumes such as Bambara groundnuts. A 5 x 3 factorial arrangement experiment in a randomised complete block design with five replications was established under greenhouse conditions. Factors consisted of bacterial species: [Bradyrhizobium japonicum (Bj), Rhizobium loti (Rl), Rhizobium meliloti (Rm), Rhizobium leguminosarum biovar phaseoli (Rlt) and a negative control (untreated)], and local Bambara groundnut varieties: black, creamy white-eye, and red. Bambara groundnut seeds were inoculated with levels recommended for cowpea and soyabean. Nitrogen fixing bacteria application on Bambara groundnuts increased plant growth and nodulation variables, with the effects varying with Bambara groundnut variety and rhizobium type. Bj outperformed the other tested bacteria on nodulation variables, with the red cultivar performing better in all growth variables, making it suitable for pod and vegetative production. [ABSTRACT FROM AUTHOR]

By 2050, the global population is set to reach 9.8 billion, which means high food demands. Therefore, the necessity of using alternative protein sources for food development, instead of meat, is of great interest. Meat alternatives which are generally based on proteins that are not of animal source present chemical characteristics very similar to animal protein and they intend to present same flavour, texture and appearance. These types of proteins are gaining more attention due to their health benefits, sustainability from an environmental point of view and ethics. Their sources are of plant origin (edible seeds, cereals, pseudo-cereals, tubers, legumes), microorganisms (bacteria and fungi), unconventional alternative sources (by-products of agro-industrial processes), algae, microalgae and insects. This study aimed at presenting consumer attitudes and perceptions related to alternative protein sources, and in this respect, a questionnaire was developed and distributed to be completed on-line. The results of our study showed that consumers are not totally informed about alternative protein sources and the majority are reluctant to some of these sources, but a small percent would be willing to pay more and consume alternative protein-based products. [ABSTRACT FROM AUTHOR]

Abstract Background Root-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. Results The 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. Conclusions Results 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. Video Abstract

Abstract Background Sugarcane 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. Results During 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). Conclusions This 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.

【Objective】 Reclaimed soils are usually poor in nutrients and the aim of this paper is to investigate the efficacy of nitrogen-fixing bacteria combined with different nitrogen fertilizations in improving fertility of reclaimed soils. 【Method】 The experiments were conducted in pots filled with soil collected from a subsidized coal mining. The soil was incubated with nitrogen-fixing bacteria combined with different nitrogen fertilizers. In each treatment, we measured carbon and nitrogen in microbial biomass, enzymatic activity, total nitrogen, and ammonium and nitrate nitrogen in the soil. 【Result】 Combining nitrogen-fixing bacteria with ammonium or nitrate nitrogen fertilizer increases carbon and nitrogen in microbial biomass, total dissolved nitrogen, ammonium nitrogen in the soil. Compared with treatment with nitrate and ammonium nitrogen fertilization only, their combination with nitrogen-fixing bacteria increases the activity of catalase, sucrase, protease and urease by 4.96%, 17.85%, 12.53% and 6.12% respectively. Correlation analysis shows a close relationship between soil nutrients, enzymatic activity and carbon and nitrogen in microbial biomass; the activity of sucrase, protease and urease is positively correlated with total nitrogen, total dissolved nitrogen and ammonium nitrogen in the soil (P

Background: A 2-year field trial was conducted to test the effect of biochar addition (0, 15, 30, and 45 t hm−2) on soil properties, nutrients, diazotrophic community diversity, abundance, and structure, and soybean growth, yield, and quality. Furthermore, we aimed to explore the responses of diazotrophs, grain yield, and quality to nine soil environmental factors. Rhizosphere soil and plant samples were collected after harvest. Results: Biochar application resulted in a lower soil bulk density (γd) but higher total organic carbon (TOC), effective phosphorus (AP) and total nitrogen (TN). Compared with untreated soil, the diversity index of diazotrophic bacteria in biochar-amended soil decreased, but the abundance of diazotrophic bacteria increased. The microbial community remained stable when a small amount of biochar was applied but changed as biochar amount increased. Furthermore, biochar reduced the proportion of unique nitrogen-fixing bacteria, but did not affect that of common nitrogen-fixing bacteria between biochar-amended and untreated soils, and increased the relative abundance of Bradyrhizobium (B9 vs. B0) and Sinorhizobium (B18 or B21 vs. B0) involved in symbiotic nitrogen fixation. The main components and content of fatty acids (except for stearic acid) and the content of protein and soybean oil remained stable under biochar application. The low biochar treatment (15 t hm−2) promoted soybean growth and yield. Redundancy analysis suggested that TN greatly influenced the diazotrophic community structure at the phylum and genus levels, and that pH, TOC, and NO3−-N greatly influenced grain yield and quality. Conclusions: Soil diazotroph environment can be improved by targeted farmland implementation based on changes in soil physicochemical properties, which would benefit biological N fixation in agricultural soils and further increase economic benefit. [ABSTRACT FROM AUTHOR]

Background: Root and soil microbial communities constitute the below-ground plant microbiome, are drivers of nutrient cycling, and affect plant productivity. However, our understanding of their spatiotemporal patterns is confounded by exogenous factors that covary spatially, such as changes in host plant species, climate, and edaphic factors. These spatiotemporal patterns likely differ across microbiome domains (bacteria and fungi) and niches (root vs. soil). Results: To capture spatial patterns at a regional scale, we sampled the below-ground microbiome of switchgrass monocultures of five sites spanning > 3 degrees of latitude within the Great Lakes region. To capture temporal patterns, we sampled the below-ground microbiome across the growing season within a single site. We compared the strength of spatiotemporal factors to nitrogen addition determining the major drivers in our perennial cropping system. All microbial communities were most strongly structured by sampling site, though collection date also had strong effects; in contrast, nitrogen addition had little to no effect on communities. Though all microbial communities were found to have significant spatiotemporal patterns, sampling site and collection date better explained bacterial than fungal community structure, which appeared more defined by stochastic processes. Root communities, especially bacterial, were more temporally structured than soil communities which were more spatially structured, both across and within sampling sites. Finally, we characterized a core set of taxa in the switchgrass microbiome that persists across space and time. These core taxa represented < 6% of total species richness but > 27% of relative abundance, with potential nitrogen fixing bacteria and fungal mutualists dominating the root community and saprotrophs dominating the soil community. Conclusions: Our results highlight the dynamic variability of plant microbiome composition and assembly across space and time, even within a single variety of a plant species. Root and soil fungal community compositions appeared spatiotemporally paired, while root and soil bacterial communities showed a temporal lag in compositional similarity suggesting active recruitment of soil bacteria into the root niche throughout the growing season. A better understanding of the drivers of these differential responses to space and time may improve our ability to predict microbial community structure and function under novel conditions. [ABSTRACT FROM AUTHOR]

Plants associate with nitrogen-fixing bacteria to secure nitrogen, which is generally the most limiting nutrient for plant growth. Endosymbiotic nitrogen-fixing associations are widespread among diverse plant lineages, ranging from microalgae to angiosperms, and are primarily one of three types: cyanobacterial, actinorhizal or rhizobial. The large overlap in the signaling pathways and infection components of arbuscular mycorrhizal, actinorhizal and rhizobial symbioses reflects their evolutionary relatedness. These beneficial associations are influenced by environmental factors and other microorganisms in the rhizosphere. In this review, we summarize the diversity of nitrogen-fixing symbioses, key signal transduction pathways and colonization mechanisms relevant to such interactions, and compare and contrast these interactions with arbuscular mycorrhizal associations from an evolutionary standpoint. Additionally, we highlight recent studies on environmental factors regulating nitrogen-fixing symbioses to provide insights into the adaptation of symbiotic plants to complex environments. Xu and Wang review the symbioses between plants and nitrogen-fixing bacteria, detailing the important signalling events that lead to the establishment of these symbioses and how they are influenced by the state of the host and environmental factors. [ABSTRACT FROM AUTHOR]

In Earth's regions accessible for living organisms (Earth's crust, crude oil, water sanctuaries and lower atmosphere), vanadium is present in the oxidation states +III and—essentially—+IV (cationic) and +V (cationic and anionic), with the redox interchange and biochemical recycling often monitored by bacteria. Organisms having available vanadium-containing (bio)molecules with essential functions for life include marine brown algae (haloperoxidases), ascidians and fan worms, as well as terrestrial organisms, viz., nitrogen-fixing bacteria (associated with the roots of legumes), and the fly agaric mushroom. The hypohalite generated by the algal haloperoxidases in turn is involved in the emission of bromoform into the atmosphere. Nitrogen fixation (N2 ε NH4+) is a process of immanent importance for life on our planet. Other bacterial issues include the reduction of vanadate to VO2+. Medicinal applications of vanadium coordination compounds are directed towards the treatment of diabetes mellitus (vanadium complexes with hypoglycemic activity) and cancer—although boundaries are set due to side effects such as oxidative damage elicited by vanadium-induced hyperoxide formation. Physiological actions of vanadium are often invoked due to the structural and physiological similarity between vanadate and phosphate. An additional field of medicinal applications addresses the treatment of cancer, such as leukaemia, malignant melanoma and bone cancer. [ABSTRACT FROM AUTHOR]

Bauhinia purpurea (belonging to Family Fabaceae-Leguminosae) is a small to medium-sized deciduous fast-growing tree that is very important in reforestation and agroforestry, and also used as fodder for livestock. This study investigated the influence of mycorrhizal inoculant with varying nitrogen-fixing bacteria (NFB) amendment levels on the growth performance of B. purpurea, the buildup of microbial communities in its rhizosphere soil, and root colonization in screenhouse conditions with UV plastic roofing, following a two-factor randomized complete block design. Factor 1 was the type of mycorrhizal inoculants applied on containerized seedlings grown in garden soil: AMF1 (MYKOCAP® or MCAP) and AMF2 (MYKORICH® or MRICH). Factor 2 was the rate of NFB (BioNTM) amendment (0 g, 5 g per seedling). At 90 d, MCAP + BioN treated plants were 37% taller than the MRICH + BioN treated ones (34 ± 0.50 cm). Seedlings with MCAP + BioN or MRICH + BioN had higher diameter increment; partitioned biomass from stems, lateral roots, and primary roots; root-shoot ratio; and root colonization than those without BioN and the control. Likewise, the NFB population was 276 and 126%, respectively higher with MCAP + BioN and MRICH + BioN than their counterparts without BioN. Contrarily, partitioned biomass from leaves, roots, and shoots, and the arbuscular mycorrhizal fungi (AMF) spore density were higher with AMF inoculants alone. Spore count was strongly positively correlated with primary root biomass (p = 0.013, r = 0.573), NFB buildup with height increment (p = 0.001, r = 0.708), and root colonization with diameter increment (p = 0.001, r = 0.805), total biomass (p = 0.023, r = 0.532), stem biomass (p = 0.001, r = 0.692), shoot biomass (p = 0.001, r = 0.698), primary root biomass (p = 0.029, r = 0.514), and root biomass (p = 0.005, r = 0.628). AMF and NFB symbiosis was inferred to have been developed, thereby promoting overall plant growth with an increased mycorrhizal root infection and NFB buildup, while the increased spore density contributed to enhanced primary root growth. Field verification trials must be conducted to determine the microbial fertilizer's efficacy under abiotic and biotic stresses. [ABSTRACT FROM AUTHOR]

Organic fertilizers" usage enhances crop productivity and improves soil fertility and the surrounding environment in livestock complexes. The presented study assessed the effect of biofertilizers and poultry-based organic fertilizers on rhizospheric microbial diversity, yield attributes, and productivity of spring barley (Hordeum vulgare L.). Conducting field experiments started in 2021 in Northern Kazakhstan's Southern carbonated chernozem of the steppe zone. Poultry manure application had three doses (5, 10, and 15 t ha-1), while four types of biofertilizer of microbial origin consisted of Compo-MIX, Agro-MIX, Agrarka, and Trichodermin-KZ. The poultry-based organic manure resulted in the highest number of nitrogen-fixing bacteria. By treating seeds with biofertilizers, Agrarka and Trichodermin-KZ, the organotrophic bacteria dominated the barley rhizosphere. The seed treatment with Agro-MIX, Trichodermin-KZ, and organic fertilizer (at the rate of 5 and 10 t ha-1) resulted in a predominance of nonsymbiotic nitrogen-fixing bacteria. Combined analysis of variance revealed that, on average, the organic and biofertilizers significantly increased plant viability, 1000-grain weight, and grain productivity. Combined application of poultry manure (10 t ha-1) and biofertilizer Trichodermin-KZ gave the highest average values of grain productivity, i.e., 1,550 and 1,490 kg ha-1 (15.5 and 14.9 quintal ha-1), respectively. [ABSTRACT FROM AUTHOR]

Potato cultivation in the middle land is an alternative solution to avoid pathogens. Although it reduces potato quantity and requires more chemical fertilizers to increase production that potentially damages the environment. Therefore, this study aims to characterize contaminations and indigenous microbes from semi-organic potato cultivation centers in Central Java. Soil samples from the semi-organic potato cultivation center of Kledung, Central, were analyzed for metal contamination using the atomic absorption spectrophotometry method and metagenomic soil bacterial diversity profiles. Specifically targeted genes of distinct regions 16SV3-V5. OTUs were identified using Uparse v7.0.1001, while Beta diversity analysis used UniFrac. All these indices in our samples were calculated with QIIME (Version 1.7.0) and displayed with R software (Version 2.15.3). The results showed that semi-organic cultivations had been polluted with Pb > Cd > Cr > As, and carbamate residue was detected in the rhizosphere and surface soil. Manure and compost application alongside NPK fertilizer increases N input, decreasing surface soil bacteria. The surface soil (with a depth of = 5 cm) has a lower index of species richness, diversity, and relative abundance than the rhizosphere layer (depth > 5 cm). Firmicutes, Proteobacteria, and Actinobacterium dominate soillevel bacteria. In comparison, the rhizosphere soil has a higher bacteria diversity dominated by N-tethering rhizobia from the phylum Proteobacteria. The potato root attracts rhizobacteria consortium that support plant growth. A further study should be conducted to describe how the bacterial consortium formed, rhizobia migration from surface to rhizosphere soil, and its interaction with the potato plants. [ABSTRACT FROM AUTHOR]

The potential nitrogen-fixing bacterial diversity in the rhizospheric soil of the native switchgrass (Panicum virgatum L.) from Tall Grass Prairies of Northern Oklahoma was studied using a partial region of nitrogenase structural gene—nifH. Eleven clone libraries constructed from nifH amplicons gave 407 good-quality sequences. More than 70% of sequences showed similarity of nifH with uncultured bacteria (< 98%). The dominance of sequences affiliated with Deltaproteobacterial nifH was observed, followed by Betaproteobacterial nifH sequences. The nifH gene library was dominated by the genera Geobacter, Rhizobacter, Paenibacillus, and Azoarcus. Sequences affiliated with rhizobia, such as Bradyrhizobium, Methylocystis, Ensifer, etc., were also in the rhizosphere in small numbers. From Deltaproteobacteria, five genera, namely Geobacter, Pelobacter, Geomonas, Desulfovibrio, and Anaeromyxobacter, contributed to 48% of the total sequences suggesting the dominance of group Deltaproteobacteria in the rhizosphere of native switchgrass. Considering the percent similarity of the nifH sequences with cultivated bacteria, this study demonstrated the presence of novel bacterial species in switchgrass rhizospheric soil from Tall Grass Prairie. [ABSTRACT FROM AUTHOR]

A new study reports synergistic inhibitory effects of ocean acidification and phosphate limitation on the nitrogen-fixing capacity of a globally important cyanobacterium species. Inspired by the report, this Comment presents the complexity of how ocean acidification and phosphate limitation affect phytoplankton physiologies and species beyond nitrogen fixation and cyanobacteria, and what future research is needed to address the remaining crucial questions. This Comment discusses the complexity of how ocean acidification and phosphate limitation affect phytoplankton physiologies, as well as what future research is needed to address remaining crucial questions. [ABSTRACT FROM AUTHOR]

Endophyte play an important role in plant growth and development. We deployed the clone library approach to study the community composition of endophytic bacteria and nitrogen fixing bacteria in the Thalassia hemprichii of Xincun Bay. The total DNA was extracted from different surface-sterilized Thalassia hemprichii tissues, and clone libraries of 16S rRNA gene and nitrogen fixing gene nifH were constructed. A total of 162 different OTUs (Operational Taxonomic Units) of endophytic bacteria were obtained from 16S rRNA libraries. The OTUs obtained from root, rhizome and leaf were 72, 45 and 52 respectively, classified to 9 phyla, 17 classes, 36 orders, 62 families, 108 genera. The dominant groups were Alphaproteobacteria (48.34%-62.72%), followed by Gammaproteobacteria (8.41%-33.21%). Besides, 90 OTUs of endophytic nitrogen fixing bacteria were recovered from the established libraries. The OTUs of the root, rhizome and leaf were 59, 19 and 27 respectively, belonging to 3 phyla, 7 classes, 13 orders, 17 families, 19 genera. Alphaproteobacteria dominated the community composition with an average relative abundance of 47.73%, 48.99% and 67.65% in the root, rhizome and leaf, respectively. The results demonstrated a good diversity of endophytic bacteria and endophytic nitrogen fixing bacteria in the different tissues of Thalassia hemprichii. Moreover, the results also showed a different pattern of dominant bacterial groups in the various tissues. The endophytic bacterial community was highly abundant in root and the most diverse in leaf. Root had the highest abundance and diversity of endophytic nitrogen-fixing bacteria. In addition, cluster analysis and non-metric multidimensional scaling analysis showed that there were significant differences in the community structure of endophytic bacteria and nitrogen-fixing bacteria among root, rhizome and leaf (R = 1, P ≤ 0.01). These provided a theoretical reference for the application of endophytic bacteria in the ecological restoration of seagrass beds. [ABSTRACT FROM AUTHOR]

Simple Summary: Nitrogen is a vital element that all living organisms require for growth and development. Although the atmosphere has an abundant supply of gaseous nitrogen, unfortunately, most organisms are unable to utilize it. Some microorganisms are capable of converting nitrogen gas to ammonia, which serves as a nitrogen source available to most organisms. Ammonia is subsequently utilized by organisms to synthesize a range of nitrogen-containing compounds that are necessary for life activities. For example, nitrogen-fixing microorganisms aid leguminous plants in obtaining the required nitrogen. Herbivorous insects face significant growth and development restrictions due to low total nitrogen content in their food. In this study, we isolated a nitrogen-fixing bacterium, Raoultella electrica, from the digestive tract of the leafhopper, Recilia dorsalis. R. electrica has all the nitrogen fixation genes and colonizes the gut lumen of leafhoppers. We further evaluated the growth rate of R. electrica in nitrogen-containing and nitrogen-free media and measured its nitrogenase activity through an acetylene reduction assay. These findings may be useful in studying the biological nitrogen fixation by gut microbes in host insects. Nitrogen is a crucial element for the growth and development of insects, but herbivorous insects often suffer from nitrogen nutrition deficiencies in their diets. Some symbiotic microorganisms can provide insect hosts with nitrogen nutrition through nitrogen fixation. Extensive research has clearly demonstrated the process of nitrogen fixation by symbiotic microorganisms in termites, while evidence supporting the occurrence and significance of nitrogen fixation in the diets of the Hemiptera is less conclusive. In this study, we isolated a strain of R. electrica from the digestive tract of a leafhopper, R. dorsalis, and found that it had nitrogen-fixing capabilities. Fluorescence in situ hybridization results showed that it was located in the gut of the leafhopper. Genome sequencing revealed that R. electrica possessed all the genes required for nitrogen fixation. We further evaluated the growth rate of R. electrica in nitrogen-containing and nitrogen-free media and measured its nitrogenase activity through an acetylene reduction assay. The findings of these studies could shed light on how gut microbes contribute to our understanding of nitrogen fixation. [ABSTRACT FROM AUTHOR]

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This review evaluates oilseed crop soybean endophytic bacteria, their prospects, and challenges for sustainable agriculture. Soybean is one of the most important oilseed crops with about 20–25% protein content and 20% edible oil production. The ability of soybean root-associated microbes to restore soil nutrients enhances crop yield. Naturally, the soybean root endosphere harbors root nodule bacteria, and endophytic bacteria, which help increase the nitrogen pool and reclamation of another nutrient loss in the soil for plant nutrition. Endophytic bacteria can sustain plant growth and health by exhibiting antibiosis against phytopathogens, production of enzymes, phytohormone biosynthesis, organic acids, and secondary metabolite secretions. Considerable effort in the agricultural industry is focused on multifunctional concepts and bioprospecting on the use of bioinput from endophytic microbes to ensure a stable ecosystem. Bioprospecting in the case of this review is a systemic overview of the biorational approach to harness beneficial plant-associated microbes to ensure food security in the future. Progress in this endeavor is limited by available techniques. The use of molecular techniques in unraveling the functions of soybean endophytic bacteria can explore their use in integrated organic farming. Our review brings to light the endophytic microbial dynamics of soybeans and current status of plant microbiome research for sustainable agriculture. [ABSTRACT FROM AUTHOR]

It has been established that maize/soybean intercropping can improve nitrogen use efficiency. However, few studies have addressed how maize/soybean intercropping affects nitrogen-fixing bacterial diversity and N fixation efficiency of intercropped soybean. In this study, nitrogen-fixing bacterial communities, N fixation efficiency, and their relationships with soil properties under three nitrogen fertilization application rates (N0 0 kg/ha, N1 40 kg/ha, N2 80 kg/ha) were explored through field experiments. Nitrogen fixation and nitrogen-fixing bacteria diversity were assessed using 15N natural abundance, Illumina high-throughput sequencing, and nifH (nitrogen fixation) gene copies quantification in the rhizosphere soil of intercropped soybean. The results showed that nitrogen application rates significantly decreased the nitrogen-fixing bacteria diversity, nitrogen fixation efficiency, and nifH gene copies in the rhizosphere soil. Nitrogen fixation efficiency, nodule number, and dry weight of intercropped soybean were highest in the N0 treatment, and nitrogen fixation was the highest in the N1 treatment. The nitrogen-fixing efficiency in N0, N1, and N2 treatments increased by 69%, 59%, and 42% and the nodule number of soybean was 10%, 22%, and 21%, respectively, compared with monocultures. The soybean nitrogen-fixing bacteria diversity in intercropping under N0 and N1 treatments significantly increased compared with monocultures. There was a significant positive correlation between soil nifH gene copies and N fixation efficiency and a negative correlation with soil available nitrogen. Bradyrhizobium abundance in soybean rhizosphere soil decreased significantly with the increase in nitrogen application rates and was significantly correlated with soil AN (available nitrogen) and pH content in the soybean rhizosphere. These results help us to understand the mechanisms by which nitrogen use efficiency was improved, and nitrogen fertilizer could be reduced in legume/Gramineae intercropping, which is important to improve the sustainability of agricultural production. [ABSTRACT FROM AUTHOR]