Azospirillum Brasilense Research Articles

Plant Growth Promoting Rhizobacteria (PGPR) Isolated from an Arid Soil in Saudi Arabia Improve Maize Growth

The rhizosphere represents the main source of bacteria commonly referred to as rhizobacteria. Such beneficial rhizobacteria with plant-beneficial activities are generally defined as plant growth promoting rhizobacteria (PGPR). The aim of this study was to investigate the ability of native rhizobacteria (PGPR) isolated from an arid soil of date palm in Al-Qassim region, Saudi Arabia, to enhance plants growth. Maize (Zea mays L.) was used as model crop for this research. Maize seedlings roots were inoculated with Bacillus and Enterobacter bacteria. The seedlings showed significant increases in stem, leaf, and root growth. The maximal shoot lengths were obtained with strain (I2: Bacillus cereus) (95.41 cm) with an increase of 33.45 % compared to uninoculated control seedlings. The three isolates I2: Bacillus cereus, AZS2: Bacillus subtilis and commercial strain AZB: Azospirillum brasilense) caused a highly significant increase in the total number of leaves ranging from 10.9% to 12.7% compared to the uninoculated controls. Seedlings inoculated with AZS2: Bacillus subtilis strain exhibited the highest aerial dry biomasses with an improvement of more than 85 % (30.76 g) compared with uninoculated control plants and more than 62 % compared to uninoculated NaCl control plants. The inoculation treatment with I2: Bacillus cereus strain induced an improvement of more than 65 % (27.44 g) over uninoculated control and more than 45 % over uninoculated NaCl control. The strain AZS2: Bacillus subtilis produced the highest root dry weights, in comparison to other isolates and induced an improvement of 30.17% (26.06 g) compared to uninoculated control plants and 24.09% compared to uninoculated plants (NaCl control).The most effective rhizobacterial treatment in the dry biomasses of whole seedling (aerial dry biomass and root dry biomass) is AZS2: Bacillus subtilis strain which induced an improvement of 55% (56.83 g) compared to uninoculated plants and 42% compared to uninoculated plants (NaCl-control)...

Combined application of humic substances and PGPR inoculated and co-inoculated in plants of Phaseolus lunatus (L.) and Leucaena leucocephala (Lam.) de Wit

The objective of this research was to evaluate the effect of inoculation and co-inoculation of rhizobia and Azospirillum brasilense combined with humic substances (HS) in growth promotion of Phaseolus lunatus (lima bean) and Leucaena leucocephala (leucaena). For this, experiments in a greenhouse with the cultivation of each plant species were carried out. A randomized complete block experimental design with five repetitions was followed. Plant seeds were sown and then inoculated with rhizobia and co-inoculated with A. brasilense. Subsequently, HS were added at the dose recommended by the manufacturer. In the experiments with both plants, control treatments with the addition of nitrogen (N) with or without HS were used. After 45 days, the shoot dry mass (SDM), root dry mass (RDM), shoot-accumulated N (Nac) and relative efficiency index (REI) were determined. In addition, the mass of dry nodules (MDN) in the lima bean plants and the number of nodules (NN) in leucaena plants were determined. The results showed that in the lima bean and leucaena plants there was a greater increase in SDM, RDM and Nac in treatments that received HS and co-inoculation with rhizobia and A. brasilense than in treatments that were inoculated only with rhizobia and HS and in treatments that received N and HS compared to addition of N and isolated inoculation of rhizobia. The combined application of HS and rhizobia in co-inoculation with A. brasilense had a greater effect on the increase of MDN in lima bean and NN in leucaena, than in treatments where only rhizobia with HS were added. These results indicate the existence of potential interaction of the use of HS with the co-inoculation of rhizobia and A. brasilense, showing promise for the production of sustainable agricultural crops.

Germination and Initial Development of Calendula Officinallis as a Function of Seed Treatment with Promoter Bacteria

Objective: The study aims to evaluate the agronomic efficiency of different dosages and modes of application of inoculants based on Bacillus subtilis, Azospirillum brasilense, and Pseudomonas fluorescens in marigold plants, focusing on seed germination aspects and initial plant development. Method: The research was conducted in two stages, including seed germination tests in the laboratory and evaluation of plant development in the field. Treatments were applied at different dosages and modes of application, with appropriate experimental design and statistical analysis of the data. Research results and discussions: The results demonstrate that inoculation with growth-promoting microorganisms positively influenced the shoot length, root length, number of flowers, and fresh flower mass of marigold plants. Application of Bacillus subtilis yielded the best results in various variables, while the combination of seed treatment and foliar application provided the best results in fresh and dry root mass. The interaction between growth promoters and application modes also influenced the chlorophyll content of the plant leaves. Research implications: The results indicate that inoculation with the studied microorganisms may be a viable alternative to enhance the agronomic performance of marigold, providing benefits such as increased fresh flower mass, flower quantity, and root length. This suggests the potential of these microorganisms as biological agents for plant growth promotion. Originality/Value: This study contributes to the understanding of the agronomic effectiveness of different growth-promoting microorganisms in marigold plants, highlighting the importance of bacterial inoculation in plant development and providing insights for more sustainable agricultural practices.

The Contribution of Azospirillum brasilense and Vermicompost to Improving Plant Growth Characteristics, Yield Variables, Physical Characteristics and Maintaining Sustainable Agriculture in Custard Apple cv. “Balanagar”

The Contribution of Azospirillum brasilense and Vermicompost to Improving Plant Growth Characteristics, Yield Variables, Physical Characteristics and Maintaining Sustainable Agriculture in Custard Apple cv. “Balanagar”

Investigating the synergistic effects of biochar, trans-zeatin riboside, and Azospirillum brasilense on soil improvement and enzymatic activity in water-stressed wheat

BackgroundWater stress is a major danger to crop yield, hence new approaches to strengthen plant resilience must be developed. To lessen the negative effects of water stress on wheat plants, present study was arranged to investigate the role of synergistic effects of biochar, trans-zeatin riboside (t-ZR), and Azospirillum brasilense on soil improvement and enzymatic activity in water-stressed wheat.ResultsIn a three-replication experiment comprising of four treatments (T0: Control, T1: Drought stress (DS), T2: DS + t-ZR with biochar, T3: DS + A. brasilense with biochar), we observed notable improvements in soil quality and enzymatic activities in water-stressed wheat plants with the application of t-ZR and A. brasilense with biochar. In drought stress, Treatment having the application of A. brasilense with biochar performs best as compared to the other and significant increased the enzymatic activities such as peroxidase (7.36%), catalase (8.53%), superoxide dismutase (6.01%), polyphenol oxidase (14.14%), and amylase (16.36%) in wheat plants. Different enzymatic activities showed different trends of results. Soil organic C, dissolved organic C, dissolved organic N also enhanced 29.46%, 8.59%, 22.70% respectively with the application of A. brasilense with biochar under drought stress condition.ConclusionsThe synergistic action of A. brasilense and biochar creates an effective microbiological environment that supports essential plant physiological processes during drought stress. This enhancement is attributed to improved soil fertility and increased organic matter content, highlighting the potential of these novel strategies in mitigating water stress effects and enhancing crop resilience.

Promoting black oat and ryegrass growth via Azospirillum brasilense inoculation after corn and soybean crop rotation

Promoting black oat and ryegrass growth via Azospirillum brasilense inoculation after corn and soybean crop rotation

Impact of nitrogen fertilizer sustainability on corn crop yield: the role of beneficial microbial inoculation interactions

BackgroundConsidering the challenges posed by nitrogen (N) pollution and its impact on food security and sustainability, it is crucial to develop management techniques that optimize N fertilization in croplands. Our research intended to explore the potential benefits of co-inoculation with Azospirillum brasilense and Bacillus subtilis combined with N application rates on corn plants. The study focused on evaluating corn photosynthesis-related parameters, oxidative stress assay, and physiological nutrient use parameters. Focus was placed on the eventual improved capacity of plants to recover N from applied fertilizers (AFR) and enhance N use efficiency (NUE) during photosynthesis. The two-year field trial involved four seed inoculation treatments (control, A. brasilense, B. subtilis, and A. brasilense + B. subtilis) and five N application rates (0 to 240 kg N ha−1, applied as side-dress).ResultsOur results suggested that the combined effects of microbial consortia and adequate N-application rates played a crucial role in N-recovery; enhanced NUE; increased N accumulation, leaf chlorophyll index (LCI), and shoot and root growth; consequently improving corn grain yield. The integration of inoculation and adequate N rates upregulated CO2 uptake and assimilation, transpiration, and water use efficiency, while downregulated oxidative stress.ConclusionsThe results indicated that the optimum N application rate could be reduced from 240 to 175 kg N ha−1 while increasing corn yield by 5.2%. Furthermore, our findings suggest that replacing 240 by 175 kg N ha−1 of N fertilizer (-65 kg N ha−1) with microbial consortia would reduce CO2 emission by 682.5 kg CO2 −e ha−1. Excessive N application, mainly with the presence of beneficial bacteria, can disrupt N-balance in the plant, alter soil and bacteria levels, and ultimately affect plant growth and yield. Hence, highlighting the importance of adequate N management to maximize the benefits of inoculation in agriculture and to counteract N loss from agricultural systems intensification.

Potencial bioestimulante de Azospirillum brasilense e nicotinamida para cultivo hidropônico de abóbora

ABSTRACT The application of biostimulants in agriculture has been studied to increase production while using smaller physical spaces and agricultural inputs to increase sustainability in production systems. Despite the promising results, there is a need to study the effects of joint applications of these products, identifying possible interactions during crop development. Thus, this study aimed to verify the biostimulant potential of the isolated and combined use of nicotinamide and Azospirillum brasilense during the initial growth of pumpkin plants in hydroponic cultivation. A completely randomized design with six treatments and four replicates was performed. The treatments were composed by the combination of the application of nicotinamide (foliar) and A. brasilense (foliar or applied in the hydroponic solution). Treatments increased the gas exchanges, particularly the assimilation rate and carboxylation efficiency, being superior to the control treatment. However, for growth characteristics, the isolated application of nicotinamide favored the development of the shoot and, when combined with A. brasilense via foliar, increased root growth. Thus, the application of nicotinamide and A. brasilense alone or together enhances the growth and gas exchanges of pumpkin plants grown in a hydroponic system, especially when using foliar application of A. brasilense. Whereby its action can be referred to as a biostimulant effect. Furthermore, the application method affects the efficiency and compatibility of the products applied. Therefore, foliar application is recommended.

Impacts of the tillage systems on the production of green corn (Zea mays L.) in long‐term plots in Northeastern Brazil

AbstractIn the current global context of climate change and the increasing demand for sustainability, optimizing agricultural production is very important in order to meet the demands for food and to mitigate environmental impact. To achieve sustainable agricultural production, particularly in regions with tropical soil and climate conditions, is necessary to adopt conservation‐oriented techniques. This includes no‐tillage system, the use of soil‐cover crops, and the application of inoculants. The objective of this research was, at the end of the 22nd cropping season, to assess the influence of soil compaction in the production of green corn (Zea mays L.) in a long‐term field experiment. This study was conducted under different soil tillage systems in a Red‐Yellow Ultisol from the Coastal Tablelands of northeastern Brazil. Three soil tillage systems were applied: Conventional Tillage (CT), Minimum Tillage (MT), and No‐tillage (NT). These were combined with four previous crops: cowpea (Vigna unguiculata), crotalaria (Crotalaria juncacea), pigeon pea (Cajanus cajan), and millet (Pennisetum glaucum), as well as two levels of nitrogen fertilizer application: (1) 100% of the recommended N dose, and (2) 50% of the recommended N dose plus Azospirillum brasilense inoculant. The experimental design consisted of strip plots with subplots divided and randomized within each strip, with three replications. Soil compaction was assessed using parameters of soil density (SD) and soil mechanical resistance to penetration (MRP) in conjunction with moisture content (MC). The principal component analysis (PCA) highlighted that conservation‐oriented systems exhibited greater soil organic carbon (SOC) levels, leading to increased productivity of commercial green corn cobs. The synergistic effect of diversifying previous crops and adopting conservation tillage systems, especially in soils under long‐term tillage, resulted in heightened productivity of commercial green corn ears.

Evaluating Organic Fertilizers and Microbial Inoculation for Soilless and Hydroponic Crop Production

Because hydroponic operations in the United States can be certified as organic, and because the price of chemical fertilizers has increased, there is an increasing interest in using organic fertilizers and beneficial microorganisms for controlled-environment agriculture. However, there is a scarcity of information regarding their effectiveness and application methodologies. We investigated the effects of inoculating Azospirillum brasilense and Rhizophagus intraradices and using organic fertilizers on growing lettuce (Lactuca sativa ‘Cherokee’) and tomato (Solanum lycopersicum ‘Red Robin’) young plants in an indoor vertical farm. Seeds were sown in rockwool substrate, with A. brasilense (1.05 × 108 colony-forming units⋅L−1) or R. intraradices (580 propagules⋅L−1) applied weekly via subirrigation. Seedlings received chemical fertilizer, organic fertilizer derived from corn steep liquor and fermented fish by-products, and food waste-derived organic fertilizer at 100 ppm total nitrogen every 2 or 3 days. They were grown indoors at 23 °C under light-emitting diode lighting at a photosynthetic photon flux density of 200 μmol⋅m−2⋅s−1 with an 18-hour photoperiod. Lettuce under organic fertilizers had 75% lower shoot fresh mass and 64% less shoot dry mass compared with lettuce under chemical fertilizer. Similarly, tomato seedlings with organic fertilizers had fewer leaves, 75% less shoot fresh mass, and 67% less shoot dry mass. In both lettuce and tomato, the macronutrient and micronutrient concentrations in plant tissues were generally similar regardless of fertilizer treatments, but nitrogen use efficiency and nitrogen uptake efficiency were lower under organic fertilizers compared with those under chemical fertilizer. The inoculation of A. brasilense or R. intraradices showed limited effects on plant nutrient uptake, nutrient concentrations, and seedling growth in both lettuce and tomato. Further research is necessary to optimize application methods for organic fertilizers and beneficial microorganisms to fully harness the benefits of sustainable alternative fertilizers in soilless and hydroponic crop production.

Effect of microbial fertilizers and growth media on the rooting of passion fruit (cv. Possum Purple) cuttings

Propagation by cuttings is widely used in the commercial propagation of passion fruits. In propagation with cuttings, hormones are generally applied to promote rooting. However, there is limited research on the use of microbial fertilizer for the rooting purpose of passion fruit cuttings. In the present study, perlite and vermiculite were used as rooting media, along with different doses of indole-3-butyric acid (IBA) (750 and 1500 ppm) and microbial fertilizer (Best-doll), which contains seven different bacteria species, including Penicillium bilaii, Bacillus megaterium, Azospirillum brasilense, and Arthrobacter viscosus, Azotobacter vinelandii, Azotobacter chroococcum, and Pseudomonas spp. (5000 and 10000 ppm). These were tested for rooting in semi-woody cuttings of the cultivar passion fruit var. ‘Possum Purple’. The Passiflora cuttings of the ‘Possum Purple’ cultivar successfully rooted four and a half months after planting. The results indicated that the lowest rooting rate was observed in indole-3-butyric acid (IBA) treatments. Conversely, perlite emerged as the most effective rooting medium for ‘Possum Purple’ cuttings. The application of 5000 ppm microbial fertilizer led to a higher root thickness compared to other treatments. However, there were no statistical differences among treatments regarding the longest and average root length in the rooting media. Based on the findings, the concentration of 5000 ppm microbial fertilizer and the use of perlite as a rooting medium is recommended for achieving the highest rooting levels and seedling quality.

Exploring the impact of titanium dioxide nanoparticles (nTiO2) at varied concentrations in combination with Azospirillum brasilense on wheat growth and physiology

BackgroundNanoparticles (NPs), as a novel source of Nano fertilizers in crop production. Titanium dioxide nanoparticles (nTiO2) also have the potential to improve plant growth, but their effect on the wheat crop is not studied enough. Nothing is known about that how nTiO2 specifically effect on wheat crops especially with soil microbes and how much its dose is effective. Azospirillum brasilense is a promising bio-fertilizer that can be applied in combination with nano-fertilizers to increase crop productivity and can enhance the efficiency of other fertilizers. MethodsThe present study was planned to investigate the role of different doses of titanium dioxide nanoparticles (nTiO2) with Azospirillum brasilense on the growth and physiology of wheat, having three replications. Eleven treatments were planned in the field condition (T0 = Control (No A. brasilense and No nTiO2), T1 = nTiO2 @20 mg/L, T2 = nTiO2 @20 mg/L + A. brasilense, T3 = nTiO2 @30 mg/L, T4 = nTiO2 @30 mg/L + A. brasilense, T5 = nTiO2 @40 mg/L, T6 = nTiO2 @40 mg/L + A. brasilense, T7 = nTiO2 @50 mg/L, T8 = nTiO2 @50 mg/L + A. brasilense, T9 = nTiO2 @60 mg/L, T10 = nTiO2 @60 mg/L + A. brasilense) having randomized complete block design (RCBD). ResultsResults revealed that the individual application of A. brasilense showed significantly higher results in all treatments, but nTiO2 application shows a positive impact on wheat growth, yield, and physiological parameters when used in a lower concentration. nTiO2 @30 mg/L with A. brasilense gives the highest results as compared to all other treatments with the production of higher antioxidant enzymes, nutrient uptake, higher leaf area index, and photosynthesis. Use of nTiO2 @40 mg/L or with the higher dose negatively affects wheat crops, but with the A. brasilense application its negative effect control up to a certain level. ConclusionThis study highlights the potential advantages of combining A. brasilense with nTiO2, for the growth of wheat crops. While A. brasilense alone consistently produced favorable results, lesser doses of nTiO2 also showed promising results but with the combination of nTiO2 and A. brasilense @ 30 mg/L producing the greatest outcomes. The detrimental effects of excessive nanoscale titanium dioxide on plant growth and development, which may result in stress and physiological abnormalities in the plants, are probably the cause of the decrease in crop output at greater nTiO2 concentrations. However, care should be used while utilizing larger nTiO2 concentrations since they could harm wheat crop growth and yield.

Co-culturing a multistrain Gram-negative inoculant useful in sustainable agriculture

Microbial-based inoculants for agricultural use consist of different strains. The consortia production process involves growing pure cultures separately and combining them in the appropriate ratio. However, the inclusion of multiple strains in the formulation increases production costs. By developing co-culture fermentations, it is possible to create consortia with the correct bacterial charge. This study aims to develop a cost-effective co-culture approach for producing an inoculum that includes the appropriate ratio of four Gram-negative bacteria, i.e., Azospirillum brasilense, Burkholderia ambifaria, Gluconacetobacter diazotrophicus, and Herbaspirillum seropedicae. The specific growth rates of strains were studied using the T4 medium, previously optimized for their culture. The co-fermentation process was optimized in 500 mL flasks to attain an equivalent density of 9.7-10 Log CFU mL-1. Then, it was successfully scaled up to a 5 L bioreactor, obtaining an equivalent density of 9.7-9.9 CFU mL-1. This first co-formulation of a four multistrain consortium formed by Gram-negative plant growth-promoting bacteria pave the road for future evaluations of other products useful for sustainable agriculture.

Azospirilla and Nitrogen Fertilization to Promote Maize Seed Development and Yield

Aims: This study evaluated the interaction of Azospirillum brasilense (Ab) strains and nitrogen fertilizer doses on maize.
 Study Design: Laboratory experiment evaluated Ab strains (PCR and PTF) on maize seed germination and vigor (completely randomized design). Field experiment evaluated Ab strains and nitrogen fertilization on maize yield parameters (randomized block design).
 Place and Duration of Study: The germination and vigor experiment (10 days in April 2019) was implemented in a controlled environment at the Seed Analysis Laboratory of the Universidade Federal de Uberlândia, Brazil. The field experiment (137 days in winter 2019) was implemented at the Fisioplant Research Station (Uberlândia, Brazil) under commercial maize crop management.
 Methodology: In controlled conditions (laboratory), 200 seeds of maize (K9105VIP3, Riber KWS Seeds) were incubated (25 °C) with the Ab strain solutions for germination and vigor evaluations. In the field, 60,000 plants ha-1 (0.5 m space between sowing lines) of maize were cropped under combinations of nitrogen fertilizer and volumes of Ab strains (treatments) for leaf nitrogen, SPAD index, leaf count, fresh and dry maize shoot biomass, one-thousand grains weight, grain rows per maize ear, productivity (kg ha-1).
 Results: Treatment with 100 mL ha-1 of Ab PFT strain increased maize seed germination and vigor more than Ab PCR strain and control (no-inoculation or fertilizer). The number of grain rows of the 100% N + 150 mL ha-1 of Ab PFT strain and the maize shoot dry mass of the 100% N (no-inoculation) were higher than the control. The treatments did not affect the SPAD index, weight of one thousand grains, fresh maize shoot biomass, or productivity.
 Conclusion: Using Ab with nitrogen fertilizer is a promising strategy to improve maize crop responses; however, more studies are needed to detail the ideal management of Ab strains for maize crops and yield construction.

Use of systemic biofertilizers in sugarcane results in highly reproducible increments in yield and quality of harvests

The utilization of a novel (systemic) biofertilizer containing Pseudomonas fluorescens, Azospirillum brasilense, and Bacillus subtilis and possessing the technology to facilitate the entry of bacteria through the stomata, was evaluated at three localities in Mexico (Potrero Nuevo, Veracruz; Ameca, Jalisco; and Champotón, Campeche) in two sugarcane varieties (NCO-310 and Mex 57–473) at different time scales. Inoculation of the systemic biofertilizer was imposed over the local agricultural management of the sugarcane; chemical fertilization of the experimental parcels at Potrero Nuevo was done using 70-20-20 and 120-80-80 at Ameca and Champotón. Three doses of the biofertilizer per hectare were applied during the annual productive cycle of sugarcane at each site; one year at Potrero Nuevo and Champotón; and six years at Ameca. The annual sugarcane yield was evaluated at each site. Additionally, sugar quality (°Brix or sucrose content) was evaluated at the three localities, while different variables of stalk performance were also measured at Ameca and Champotón. Our data provide evidence that this systemic biofertilizer consistently and reliably increased the sugarcane yield at all localities during the time of evaluation, ranging from 73.7 tons ha−1 at Potrero Nuevo (2.5 times increase; P < 0.05) and 77.7 tons ha−1 at Ameca (1.9 times increase; P < 0.05) to 23.8 tons ha−1 at Champotón (1.4 times increase; P < 0.05). This increase in sugarcane biomass was related to increased tillering rather than increased stalk height or diameter. This novel biological product improved the sugarcane quality in terms of °Brix (P < 0.05, 2.6° difference) and sucrose content (P < 0.5, 0.7% difference).

Growth and Phytochemistry of Cymbopogon citratus Stapf Inoculated with Plant Growth-Promoting Bacteria under Different Lead Levels.

This study aimed to investigate the phytochemistry of lemongrass (Cymbopogon citratus) inoculated with Azospirillum brasilense and grown in lead (Pb)-contaminated soil to assess its responses to inoculation under different Pb levels. The experimental design was completely randomized in a 2 × 5 factorial scheme: two levels of A. brasilense (absence or presence) and five Pb levels. After four months of treatment, the following were analyzed: total and reducing sugars, total phenolic content, flavonoids, antioxidant activity, antioxidant enzymes, proline, and essential oil (EO) content and composition. Soil Pb levels and A. brasilense inoculation affected phytochemicals in lemongrass plants. Azospirillum inoculation reduced total sugars in the roots at all soil Pb levels, while increasing Pb levels favored a rise in sugar contents. There was an increase in flavonoid content in treatments associated with Pb and inoculated with A. brasilense. Antioxidant capacity was lower at lower Pb levels, regardless of bacterial inoculation. Enzymatic response was mainly affected by Pb concentrations between 50 and 100 mg kg-1 soil. EO content was influenced by soil Pb levels, with higher EO production at 500 mg Pb kg-1 soil and without A. brasilense inoculation. Overall, lemongrass cultivation in Pb-contaminated areas can be an alternative to phytoremediation and EO production for the industry.

Chemotactic Interactions of Scenedesmus sp. and Azospirillum brasilense Investigated by Microfluidic Methods

The use of algae for industrial, biotechnological, and agricultural purposes is spreading globally. Scenedesmus species can play an essential role in the food industry and agriculture due to their favorable nutrient content and plant-stimulating properties. Previous research and the development of Scenedesmus-based foliar fertilizers raised several questions about the effectiveness of large-scale algal cultivation and the potential effects of algae on associative rhizobacteria. In the microbiological practice applied in agriculture, bacteria from the genus Azospirillum are one of the most studied plant growth-promoting, associative, nitrogen-fixing bacteria. Co-cultivation with Azospirillum species may be a new way of optimizing Scenedesmus culturing, but the functioning of the co-culture system still needs to be fully understood. It is known that Azospirillum brasilense can produce indole-3-acetic acid, which could stimulate algae growth as a plant hormone. However, the effect of microalgae on Azospirillum bacteria is unclear. In this study, we investigated the behavior of Azospirillum brasilense bacteria in the vicinity of Scenedesmus sp. or its supernatant using a microfluidic device consisting of physically separated but chemically coupled microchambers. Following the spatial distribution of bacteria within the device, we detected a positive chemotactic response toward the microalgae culture. To identify the metabolites responsible for this behavior, we tested the chemoeffector potential of citric acid and oxaloacetic acid, which, according to our HPLC analysis, were present in the algae supernatant in 0.074 mg/ml and 0.116 mg/ml concentrations, respectively. We found that oxaloacetic acid acts as a chemoattractant for Azospirillum brasilense.

Nitrogen fertilization and application of brassinosteroid in cowpea in the Amazon

Cowpea [Vigna unguiculata (L.) Walp.] is a legume of socioeconomic importance in the northern region of the country, however, its production requires high fertilizer costs, especially nitrogen fertilizers. The use of techniques with the potential to increase crop productivity, such as the application of plant regulators (brassinosteroids-BRs) and the use of nitrogen (N) are necessary. Thus, the objective of this work was to evaluate the vegetative and reproductive phases of cowpea (BR3-Tracuateua) in relation to the application of BRs, mineral nitrogen fertilization and inoculation with the bacterium Azospirillum brasilense. The research was carried out in the experimental area of ​​the Federal Rural University of the Amazon, Campus Capitão Poço. An experimental design was used in randomized blocks, with three replications, in a 3 x 4 factorial scheme: three N supply conditions (Without N, with mineral N and with biological N) and foliar application of four doses of BRs (0, 15, 30 and 45nM). The growth and production variables were not significantly influenced by the application of BRs and the forms of N supply. However, M100 and productivity were increased by the supply of N, both mineral and biological. Therefore, inoculation with Azospirillum brasilense in cowpea cultivation becomes a viable practice, with the objective of supplying N to plants, replacing mineral nitrogen fertilization.

Nutritional enhancement in black seed (Nigella sativa L.) using bacteria‐based biofertilizers

AbstractNigella sativa L. is an aromatic spice, utilized as an original and peculiar flavoring ingredient in a variety of culinary applications and pharmaceuticals. Black seed (Nigella sativa L.) belongs to the family Ranunculaceae. It is an undercultivated crop in Pakistan. The present study was planned keeping in mind sustainable development goals SDG 3 (good health and well‐being) and SDG 15 (life on land). The effects of several rhizospheric bacterial strains and synthetic fertilizers on the development of N. sativa and nutrition were studied using a completely randomized experimental design. For this purpose, plant growth‐promoting effects of different strains (Azospirillum brasilense, Azospirillum lipoferum, and Pantoea agglomerans) and synthetic fertilizers (nitrogen and phosphorus) were assembled to check their effects individually and in combination form. Azospirillum lipoferum and Pantoea agglomerans inoculation significantly enhanced the morphological characteristics of N. sativa, whether applied individually or in combination, with positive effects on seedlings, plant height, number of branches, number of leaves, number of flowers, stamens numbers, follicles number, number of tentacles and seed production. N. sativa plants that were simultaneously inoculated with Azospirillum lipoferum and Pantoea agglomerans showed the highest potential for antioxidant activity, particularly in petroleum ether extracts. In the methanolic extract, a higher amount of radical scavenging was observed as compared to positive and negative control. There was also increase in fat, moisture and carbohydrate contents of the combination inoculated plant. So, from the present study, in Pakistan, the technique is recommended to enhance the yield and nutritional value of N. sativa.

Metabolic and physiological adaptations of microalgal growth-promoting bacterium Azospirillum brasilense growing under biogas atmosphere: a microarray-based transcriptome analysis.

Using microalgal growth-promoting bacteria (MGPB) to improve the cultured microalga metabolism during biotechnological processes is one of the most promising strategies to enhance their benefits. Nonetheless, the culture condition effect used during the biotechnological process on MGPB growth and metabolism is key to ensure the expected positive bacterium growth and metabolism of microalgae. In this sense, the present research study investigated the effect of the synthetic biogas atmosphere (75% CH4-25% CO2) on metabolic and physiological adaptations of the MGPB Azospirillum brasilense by a microarray-based transcriptome approach. A total of 394 A. brasilense differentially expressed genes (DEGs) were found: 201 DEGs (34 upregulated and 167 downregulated) at 24h and 193 DEGs (140 upregulated and 53 downregulated) under the same conditions at 72h. The results showed a series of A. brasilense genes regulating processes that could be essential for its adaptation to the early stressful condition generated by biogas. Evidence of energy production is shown by nitrate/nitrite reduction and activation of the hypothetical first steps of hydrogenotrophic methanogenesis; signal molecule modulation is observed: indole-3-acetic acid (IAA), riboflavin, and vitamin B6, activation of Type VI secretion system responding to IAA exposure, as well as polyhydroxybutyrate (PHB) biosynthesis and accumulation. Moreover, an overexpression of ipdC, ribB, and phaC genes, encoding the key enzymes for the production of the signal molecule IAA, vitamin riboflavin, and PHB production of 2, 1.5 and 11 folds, respectively, was observed at the first 24h of incubation under biogas atmosphere Overall, the ability of A. brasilense to metabolically adapt to a biogas atmosphere is demonstrated, which allows its implementation for generating biogas with high calorific values and the use of renewable energies through microalga biotechnologies.