Applications of the Microalgae Chlamydomonas and Its Bacterial Consortia in Detoxification and Bioproduction.

The wide metabolic diversity of microalgae, their fast growth rates, and low-cost production make these organisms highly promising resources for a variety of biotechnological applications, addressing critical needs in industry, agriculture, and medicine. The use of microalgae in consortia with bacteria is proving valuable in several areas of biotechnology, including the treatment of various types of wastewater, the production of biofertilizers, and the extraction of various products from their biomass. The monoculture of the microalga Chlamydomonas has been a prominent research model for many years and has been extensively used in the study of photosynthesis, sulphur and phosphorus metabolism, nitrogen metabolism, respiration, and flagellar synthesis, among others. Recent research has increasingly recognised the potential of Chlamydomonas-bacteria consortia as a biotechnological tool for various applications. The detoxification of wastewater using Chlamydomonas and its bacterial consortia offers significant potential for sustainable reduction of contaminants, while facilitating resource recovery and the valorisation of microalgal biomass. The use of Chlamydomonas and its bacterial consortia as biofertilizers can offer several benefits, such as increasing crop yields, protecting crops, maintaining soil fertility and stability, contributing to CO2 mitigation, and contributing to sustainable agricultural practises. Chlamydomonas-bacterial consortia play an important role in the production of high-value products, particularly in the production of biofuels and the enhancement of H2 production. This review aims to provide a comprehensive understanding of the potential of Chlamydomonas monoculture and its bacterial consortia to identify current applications and to propose new research and development directions to maximise their potential.

Plant-Growth-Promoting Rhizobacteria Improve Seeds Germination and Growth of Argania spinosa.

Argania spinosa is among the most important species of the Moroccan forest in terms of ecological, environmental, and socio-economic aspects. However, it faces a delicate balance between regeneration and degradation in its natural habitat. Hence, the efforts to preserve and regenerate argan forests are crucial for biodiversity, soil quality, and local livelihoods, yet they face challenges like overgrazing and climate change. Sustainable management practices, including reforestation and community engagement, are vital for mitigating degradation. Similarly, exploiting the argan tree's rhizosphere can enhance soil quality by leveraging its rich microbial diversity. This approach not only improves crop growth but also maintains ecosystem balance, ultimately benefiting both agriculture and the environment. This enrichment can be achieved by different factors: mycorrhizae, plant extracts, algae extracts, and plant growth-promoting rhizobacteria (PGPR). The benefits provided by PGPR may include increased nutrient availability, phytohormone production, shoot, root development, protection against several plant pathogens, and disease reduction. In this study, the effect of rhizobacteria isolated from the Agran rhizosphere was evaluated on germination percentage and radicle length for Argania spinosa in vitro tests, growth, collar diameter, and branching number under greenhouse conditions. One hundred and twenty (120) bacteria were isolated from the argan rhizosphere and evaluated for their capacity for phosphate solubilization and indole acetic acid production. The results showed that 52 isolates could solubilize phosphorus, with the diameters of the solubilization halos varying from 0.56 ± 0.14 to 2.9 ± 0.08 cm. Among 52 isolates, 25 were found to be positive for indole acetic acid production. These 25 isolates were first tested on maize growth to select the most performant ones. The results showed that 14 isolates from 25 tested stimulated maize growth significantly, and 3 of them by 28% (CN005, CN006, and CN009) compared to the control. Eight isolates (CN005, CN006, CN004, CN007, CN008, CN009, CN010, and CN011) that showed plant growth of more than 19% were selected to evaluate their effect on argan germination rate and radicle length and were subjected to DNA extraction and conventional Sanger sequencing. The 8 selected isolates were identified as: Brevundimonas naejangsanensis sp2, Alcaligenes faecalis, Brevundimonas naejangsanensis sp3, Brevundimonas naejangsanensis sp4, Leucobacter aridicollis sp1, Leucobacter aridicollis sp2, Brevundimonas naejangsanensis sp1, and Staphylococcus saprophyticus. The results showed that Leucobacter aridicollis sp2 significantly increased the germination rate by 95.83%, and the radicle length with a value of 2.71 cm compared to the control (1.60 cm), followed by Brevundimonas naejangsanensis sp3 and Leucobacter aridicollis sp1 (2.42 cm and 2.11 cm, respectively). Under greenhouse conditions, the results showed that the height growth increased significantly for Leucobacter aridicollis sp1 (42.07%) and Leucobacter aridicollis sp2 (39.99%). The isolates Brevundimonas naejangsanensis sp3 and Leucobacter aridicollis sp1 increased the gain of collar diameter by 41.56 and 41.21%, respectively, followed by Leucobacter aridicollis sp2 and Staphyloccocus saprophyticus (38.68 and 22.79%). Leucobacter aridicollis sp1 increased the ramification number per plant to 12 compared to the control, which had 6 ramifications per plant. The use of these isolates represents a viable alternative in sustainable agriculture by improving the germination rate and root development of the argan tree, as well as its development, while increasing the availability of nutrients in the soil and consequently improving fertilization.

Exploring the Role of Debaryomyces hansenii as Biofertilizer in Iron-Deficient Environments to Enhance Plant Nutrition and Crop Production Sustainability.

The European "Green Deal" policies are shifting toward more sustainable and environmentally conscious agricultural practices, reducing the use of chemical fertilizer and pesticides. This implies exploring alternative strategies. One promising alternative to improve plant nutrition and reinforce plant defenses is the use of beneficial microorganisms in the rhizosphere, such as "Plant-growth-promoting rhizobacteria and fungi". Despite the great abundance of iron (Fe) in the Earth's crust, its poor solubility in calcareous soil makes Fe deficiency a major agricultural issue worldwide. Among plant promoting microorganisms, the yeast Debaryomyces hansenii has been very recently incorporated, for its ability to induce morphological and physiological key responses to Fe deficiency in plants, under hydroponic culture conditions. The present work takes it a step further and explores the potential of D. hansenii to improve plant nutrition and stimulate growth in cucumber plants grown in calcareous soil, where ferric chlorosis is common. Additionally, the study examines D. hansenii's ability to induce systemic resistance (ISR) through a comparative relative expression study by qRT-PCR of ethylene (ET) biosynthesis (ACO1), or ET signaling (EIN2 and EIN3), and salicylic acid (SA) biosynthesis (PAL)-related genes. The results mark a significant milestone since D. hansenii not only enhances nutrient uptake and stimulates plant growth and flower development but could also amplify induced systemic resistance (ISR). Although there is still much work ahead, these findings make D. hansenii a promising candidate to be used for sustainable and environmentally friendly integrated crop management.

Phosphate solubilizing Pseudomonas and Bacillus combined with rock phosphates promoting tomato growth and reducing bacterial canker disease.

Nowadays, sustainable agriculture approaches are based on the use of biofertilizers and biopesticides. Tomato (Solanum lycopersicum L.) rhizosphere could provide rhizobacteria with biofertilizing and biopesticide properties. In this study, bacteria from the rhizosphere of tomato were evaluated in vitro for plant growth promotion (PGP) properties. Five Pseudomonas isolates (PsT-04c, PsT-94s, PsT-116, PsT-124, and PsT-130) and one Bacillus isolate (BaT-68s), with the highest ability to solubilize tricalcium phosphate (TCP) were selected for further molecular identification and characterization. Isolates showed phosphate solubilization up to 195.42 µg mL-1. All isolates showed phosphate solubilization by organic acid production. The six isolates improved seed germination and showed effective root colonization when tomato seeds were coated with isolates at 106 cfu g-1 in axenic soil conditions. Furthermore, the selected isolates were tested for beneficial effects on tomato growth and nutrient status in greenhouse experiments with natural rock phosphate (RP). The results showed that inoculated tomato plants in the presence of RP have a higher shoot and root lengths and weights compared with the control. After 60 days, significant increases in plant Ca, Na, P, protein, and sugar contents were also observed in inoculated seedlings. In addition, inoculated tomato seedlings showed an increase in foliar chlorophyll a and b and total chlorophyll, while no significant changes were observed in chlorophyll fluorescence. In greenhouse, two Pseudomonas isolates, PsT-04c and PsT-130, showed ability to trigger induced systemic resistance in inoculated tomato seedlings when subsequently challenged by Clavibacter michiganensis subsp. michiganensis, the causal agent of tomato bacterial canker. High protection rate (75%) was concomitant to an increase in the resistance indicators: total soluble phenolic compounds, phenylalanine-ammonia lyase, and H2O2. The results strongly demonstrated the effectiveness of phosphate-solubilizing bacteria adapted to rhizosphere as biofertilizers for tomato crops and biopesticides by inducing systemic resistance to the causal agent of tomato bacterial canker disease.

Endophytic Bacillus vallismortis and Bacillus tequilensis bacteria isolated from medicinal plants enhance phosphorus acquisition and fortify Brassica napus L. vegetative growth and metabolic content.

Phosphorus fertilization imposes critical limitations on crop productivity and soil health. The aim of the present work is to explore the potential of two phosphate solubilizing bacteria (PSB) species in phosphorus supplementation of canola (Brassica napus L.). Out of 38 bacterial isolates obtained from nine medicinal plants, two bacterial strains (20P and 28P) were proved as the most potent for the in-vitro tricalcium phosphate solubilization test. These isolates verified their activity toward different enzymes as nitrogenase and alkaline phosphatase. Also, 20P and 28P gave a high amount of indole-3-acetic acid, 34.16 µg/ml and 35.20 µg/ml, respectively, and were positive for siderophores production as they detected moderate affinity for iron chelation. Molecular identification confirmed that strain 20P was Bacillus vallismortis and strain 28P was Bacillus tequilensis. A pot experiment was conducted to study the effect of four different phosphorus concentrations (0%, 50%, 75%, and 100% P) each alone and/or in combination with B. vallismortis, B. tequilensis, or both bacterial isolates on the vegetative growth and some physiological parameters of canola. The combined treatment of 50% phosphorus + (B. vallismortis + B. tequilensis) was generally the most effective with respect to shoot height, shoot dry mass, leaf area, photosynthetic pigment fractions, total sugar content, and accumulated NPK content. In contrast, the rhizosphere pH reached the minimum value under the same treatment. These findings highlighted the potential use of PSB (B. vallismortis and B. tequilensis) along with phosphorus fertilization as a safe sustainable tactic.

Co-inoculation of the endophytes Bacillus thuringiensis CAPE95 and Paenibacillus polymyxa CAPE238 promotes Tropaeolum majus L. growth and enhances its root bacterial diversity.

Tropaeolum majus L. is a versatile edible plant that is widely explored due to its medicinal properties and as a key element in intercropping systems. Its growth could be improved by the use of biofertilizers that can enhance nutrient uptake by the plant or provide tolerance to different abiotic and biotic stresses. In a previous study, 101 endophytes isolated from T. majus roots showed more than three plant growth-promoting (PGP) features in vitro, such as phosphate mineralization/solubilization, production of siderophores, antimicrobial substances and indole-related compounds, and presence of the nifH gene. To provide sustainable alternatives for biofertilization, the genomes of two promising endophytes-CAPE95 and CAPE238-were sequenced to uncover metabolic pathways related to biofertilization. Greenhouse experiments were conducted with 216 seeds and 60 seedlings, half co-inoculated with the endophytes (treatment) and half inoculated with 1X PBS (control), and the impact of the co-inoculation on the plant's bacteriome was accessed through 16S rRNA gene metabarcoding. The strains CAPE95 and CAPE238 were taxonomically assigned as Bacillus thuringiensis and Paenibacillus polymyxa, respectively. Metabolic pathways related to the enhancement of nutrient availability (nitrogen fixation, sulfate-sulfur assimilation), biosynthesis of phytohormones (indole-3-acetic acid precursors) and antimicrobial substances (bacilysin, paenibacillin) were found in their genomes. The in vivo experiments showed that treated seeds exhibited faster germination, with a 20.3% higher germination index than the control on the eleventh day of the experiment. Additionally, treated seedlings showed significantly higher plant height and leaf diameters (p < 0.05). The bacterial community of the treated plants was significantly different from that of the control plants (p < 0.001) and showed a higher richness and diversity of species (Chao and Shannon indexes, p < 0.001). A higher relative abundance of potential synergistic PGP bacteria was also shown in the bacteriome of the treated plants, such as Lysinibacillus and Geobacter. For the first time, co-inoculation of B. thuringiensis and P. polymyxa was shown to have great potential for application as a biofertilizer to T. majus plants. The bacterial consortium used here could also be explored in other plant species in the future.

In silico biotechnological potential of Bacillus sp. strain MHSD_37 bacterial endophyte.

BACKGROUND: Endophytic bacteria possess a range of unique characteristics that enable them to successfully interact with their host and survive in adverse environments. This study employed in silico analysis to identify genes, from Bacillus sp. strain MHSD_37, with potential biotechnological applications. RESULTS: The strain presented several endophytic lifestyle genes which encode for motility, quorum sensing, stress response, desiccation tolerance and root colonisation. The presence of plant growth promoting genes such as those involved in nitrogen fixation, nitrate assimilation, siderophores synthesis, seed germination and promotion of root nodule symbionts, was detected. Strain MHSD_37 also possessed genes involved in insect virulence and evasion of defence system. The genome analysis also identified the presence of genes involved in heavy metal tolerance, xenobiotic resistance, and the synthesis of siderophores involved in heavy metal tolerance. Furthermore, LC-MS analysis of the excretome identified secondary metabolites with biological activities such as anti-cancer, antimicrobial and applications as surfactants. CONCLUSIONS: Strain MHSD_37 thereby demonstrated potential biotechnological application in bioremediation, biofertilisation and biocontrol. Moreover, the strain presented genes encoding products with potential novel application in bio-nanotechnology and pharmaceuticals.

Optimizing tomato seedling growth with indigenous mangrove bacterial inoculants and reduced NPK fertilization.

The search for ecofriendly products to reduce crop dependence on synthetic chemical fertilizers presents a new challenge. The present study aims to isolate and select efficient native PGPB that can reduce reliance on synthetic NPK fertilizers. A total of 41 bacteria were isolated from the sediment and roots of mangrove trees (Avicennia marina) and assessed for their PGP traits under in vitro conditions. Of them, only two compatible strains of Bacillus species were selected to be used individually and in a mix to promote tomato seedling growth. The efficiency of three inoculants applied to the soil was assessed in a pot experiment at varying rates of synthetic NPK fertilization (0, 50, and 100% NPK). The experiment was set up in a completely randomized design with three replications. Results showed that the different inoculants significantly increased almost all the studied parameters. However, their effectiveness is strongly linked to the applied rate of synthetic fertilization. Applying bacterial inoculant with only 50% NPK significantly increased the plant height (44-51%), digital biomass (60-86%), leaf area (77-87%), greenness average (29-36%), normalized difference vegetation index (29%), shoot dry weight (82-92%) and root dry weight (160-205%) compared to control plants. Concerning the photosynthetic activity, this treatment showed a positive impact on the concentrations of chlorophyll a (25-31%), chlorophyll b (34-39%), and carotenoid (45-49%). Interestingly, these increases ensured the highest values significantly similar to or higher than those of control plants given 100% NPK. Furthermore, the highest accumulation of N, P, K, Cu, Fe, Zn, and Ca in tomato shoots was recorded in plants inoculated with the bacterial mix at 50% NPK. It was proven for the first time that the native PGP bacteria derived from mangrove plant species A. marina positively affects the quality of tomato seedlings while reducing 50% NPK.

Improving soil fertility through dual inoculation with arbuscular mycorrhizal fungi and Rhizobium on a eutric cambisol cultivated with forage legumes in a semi-arid region.

The Sub-Saharan region of southern Africa is characterized by high temperatures, low rainfall, and poor land-use management practices such as continuous cropping without replenishment of soil nutrients. The combination of these factors has resulted in nutrient depletion and land degradation. The current study aimed at investigating the effect of arbuscular mycorrhizal fungi (AMF) and Rhizobium bacteria inoculation on soil chemical properties in field-grown forage legumes, namely, Mucuna pruriens (mucuna), Lablab purpureus (lablab) and Vigna unguiculata (cowpea), in the semi-arid region of the Eastern Cape Province (South Africa). Forage legumes were inoculated with the AMF species Paraglomus occulum and the Rhizobia bacteria species Bradyrhizobium strain and grown for 120 days. Soil samples were collected in the following sequence: prior to planting, before flowering and after harvesting the forage legumes in each of the two seasons (2017/2018 and 2018/2019) and soil chemical properties were determined using standard procedures. The results showed that the addition of dual inoculation over time greatly improved soil chemical properties when compared to the control treatment. This was advocated by the significant (P ≤ 0.05) increase in soil pH, soil organic carbon, soil organic matter, total nitrogen, phosphorus, calcium, potassium, magnesium, sodium, sulfur and iron in soils. The concentration of cation exchange capacity was significantly (P ≤ 0.05) higher in cowpea treated with Rhizobium as compared to other treatment combinations. The control treatment of mucuna forage greatly improved the concentrations of manganese, boron, copper, molybdenum, and zinc over other treatment combinations only before the flowering stage. However, the concentrations of micronutrients were significantly higher on the treatment combination of lablab and single inoculation of AMF after harvesting. Generally, dual inoculation with AMF and Rhizobia enhanced soil properties when compared to a single inoculation or untreated control.

Understanding the sugar beet holobiont for sustainable agriculture.

The importance of crop-associated microbiomes for the health and field performance of plants has been demonstrated in the last decades. Sugar beet is the most important source of sucrose in temperate climates, and-as a root crop-yield heavily depends on genetics as well as on the soil and rhizosphere microbiomes. Bacteria, fungi, and archaea are found in all organs and life stages of the plant, and research on sugar beet microbiomes contributed to our understanding of the plant microbiome in general, especially of microbiome-based control strategies against phytopathogens. Attempts to make sugar beet cultivation more sustainable are increasing, raising the interest in biocontrol of plant pathogens and pests, biofertilization and -stimulation as well as microbiome-assisted breeding. This review first summarizes already achieved results on sugar beet-associated microbiomes and their unique traits, correlating to their physical, chemical, and biological peculiarities. Temporal and spatial microbiome dynamics during sugar beet ontogenesis are discussed, emphasizing the rhizosphere formation and highlighting knowledge gaps. Secondly, potential or already tested biocontrol agents and application strategies are discussed, providing an overview of how microbiome-based sugar beet farming could be performed in the future. Thus, this review is intended as a reference and baseline for further sugar beet-microbiome research, aiming to promote investigations in rhizosphere modulation-based biocontrol options.

Responses in Nodulated Bean (Phaseolus vulgaris L.) Plants Grown at Elevated Atmospheric CO2.

The increase in the concentration of CO2 in the atmosphere is currently causing metabolomic and physiological changes in living beings and especially in plants. Future climate change may affect crop productivity by limiting the uptake of soil resources such as nitrogen (N) and water. The contribution of legume-rhizobia symbioses to N2 fixation increases the available biological N reserve. Elevated CO2 (eCO2) has been shown to enhance the amount of fixed N2 primarily by increasing biomass. Greater leaf biomass under eCO2 levels increases N demand, which can stimulate and increase N2 fixation. For this reason, bean plants (Phaseolus vulgaris L.) were used in this work to investigate how, in a CO2-enriched atmosphere, inoculation with rhizobia (Rhizobium leguminosarum) affects different growth parameters and metabolites of carbon and nitrogen metabolism, as well as enzymatic activities of nitrogen metabolism and the oxidative state of the plant, with a view to future scenarios, where the concentration of CO2 in the atmosphere will increase. The results showed that bean symbiosis with R. leguminosarum improved N2 fixation, while also decreasing the plant's oxidative stress, and provided the plant with a greater defense system against eCO2 conditions. In conclusion, the nodulation with rhizobia potentially replaced the chemical fertilization of bean plants (P. vulgaris L.), resulting in more environmentally friendly agricultural practices. However, further optimization of symbiotic activities is needed to improve the efficiency and to also develop strategies to improve the response of legume yields to eCO2, particularly due to the climate change scenario in which there is predicted to be a large increase in the atmospheric CO2 concentration.

Utility of Plant Growth-Promoting Rhizobacteria for Sustainable Production of Bermudagrass Forage.

A two-year study was conducted in bermudagrass hay fields in central Alabama to estimate the potential of plant growth-promoting rhizobacteria (PGPR) as a tool for sustainable agriculture in forage management. This study compared the effects of two treatments of PGPR, applied with and without lowered rates of nitrogen, to a full rate of nitrogen fertilizer in a hay production system. The PGPR treatments included a single-strain treatment of Paenibacillus riograndensis (DH44), and a blend including two Bacillus pumilus strains (AP7 and AP18) and a strain of Bacillus sphaericus (AP282). Data collection included estimates of forage biomass, forage quality, insect populations, soil mesofauna populations, and soil microbial respiration. Applications of PGPR with a half rate of fertilizer yielded similar forage biomass and quality results as that of a full rate of nitrogen. All PGPR treatments increased soil microbial respiration over time. Additionally, treatments containing Paenibacillus riograndensis positively influenced soil mesofauna populations. The results of this study indicated promising potential for PGPR applied with lowered nitrogen rates to reduce chemical inputs while maintaining yield and quality of forage.

Nuclear Genome Sequence and Gene Expression of an Intracellular Fungal Endophyte Stimulating the Growth of Cranberry Plants.

Ericaceae thrive in poor soil, which we postulate is facilitated by microbes living inside those plants. Here, we investigate the growth stimulation of the American cranberry (Vaccinium macrocarpon) by one of its fungal endosymbionts, EC4. We show that the symbiont resides inside the epidermal root cells of the host but extends into the rhizosphere via its hyphae. Morphological classification of this fungus is ambiguous, but phylogenetic inference based on 28S rRNA identifies EC4 as a Codinaeella species (Chaetosphaeriaceae, Sordariomycetes, Ascomycetes). We sequenced the genome and transcriptome of EC4, providing the first 'Omics' information of a Chaetosphaeriaceae fungus. The 55.3-Mbp nuclear genome contains 17,582 potential protein-coding genes, of which nearly 500 have the capacity to promote plant growth. For comparing gene sets involved in biofertilization, we annotated the published genome assembly of the plant-growth-promoting Trichoderma hamatum. The number of proteins involved in phosphate transport and solubilization is similar in the two fungi. In contrast, EC4 has ~50% more genes associated with ammonium, nitrate/nitrite transport, and phytohormone synthesis. The expression of 36 presumed plant-growth-promoting EC4 genes is stimulated when the fungus is in contact with the plant. Thus, Omics and in-plantae tests make EC4 a promising candidate for cranberry biofertilization on nutrient-poor soils.

Acinetobacter schindleri SR-5-1 decipher morpho-physio-biochemical and nutritional improvements to Pisum sativum L. and Linum usitatissimum L. maintained under wastewater/cadmium stress.

Metal retention in wastewater fertigated crops poses a potential hazard to food chain. Current work demonstrates the bioremediation and growth-promoting potential of Acinetobacter schindleri SR-5-1 by using nitrogen-fixing (pea) and non-nitrogen fixing (linseed) plants under cadmium (Cd) and wastewater irrigation regimes. Both plants were grown at 250 or 500 CdCl2 and 75 or 100% wastewater, each separately with and without A. schindleri SR-5-1 inoculation. The results revealed that Cd and wastewater significantly decreased growth, biomass, antioxidants, and nutrient acquisition through increased malondialdehyde, H2O2, and Cd accumulation. However, application of A. schindleri SR-5-1 significantly promoted morpho-physio-biochemical attributes while diminishing MDA and H2O2 under applied Cd and wastewater stress levels in both pea and linseed. Further, PGPR inoculation positively influenced pea and linseed seedlings through a substantial decline in Cd accumulation in roots/shoots and retained the optimal level of essential nutrients. It was inferred that both pea and linseed, with A. schindleri SR-5-1 application, exhibited higher growth and metabolism under Cd and wastewater stress but substantial tolerance was acquired under wastewater stress. Studied plants exhibited tolerance in order of 75% WW ≥ 250 µM Cd ≥ 100%WW ≥ 500 µM Cd treatment under A. schindleri inoculation. Current findings revealed the potential of A. schindleri to be exploited both for bioremediation and bio-fertilization under Cd, and wastewater-polluted regimes to reduce metal contamination of edible plants. It was suggested that with inoculation of A. schindleri SR-5-1, 75% WW dilution can be applied for irrigation of both nitrogen-fixing and non-nitrogen-fixing crops.

Fighting Obesity-Related Micronutrient Deficiencies through Biofortification of Agri-Food Crops with Sustainable Fertilization Practices.

Obesity is a critical medical condition worldwide that is increasingly involved with nutritional derangements associated with micronutrient deficiencies, including iron, zinc, calcium, magnesium, selenium, and vitamins A, C, D, and E. Nutritional deficiencies in obesity are mainly caused by poor-quality diets, higher nutrient requirements, alterations in micronutrient metabolism, and invasive obesity treatments. The current conventional agricultural system is designed for intensive food production, focusing on food quantity rather than food quality, consuming excessive agricultural inputs, and producing nutrient-deficient foods, thus generating severe health and environmental problems; agricultural food products may worsen obesity-related malnutrition. Therefore, modern agriculture is adopting new biofortification technologies to combat micronutrient deficiencies and improve agricultural productivity and sustainability. Biofertilization and nanofertilization practices are increasingly used due to their efficiency, safety, and reduced environmental impact. Biofertilizers are preparations of PGP-microorganisms that promote plant growth by influencing plant metabolism and improving the nutrient uptake, and nanofertilizers consist of synthesized nanoparticles with unique physicochemical properties that are capable of increasing plant nutrition and enriching agricultural products. This review presents the current micronutrient deficiencies associated with obesity, the modern unsustainable agri-food system contributing to obesity progression, and the development of bio- and nanofertilizers capable of biofortifying agri-food crops with micronutrients commonly deficient in patients with obesity.

Cyanobacteria as Candidates to Support Mars Colonization: Growth and Biofertilization Potential Using Mars Regolith as a Resource.

Cyanobacteria are indicated as organisms that can possibly support Mars colonization, contributing to the production of oxygen and other commodities therein. In this general context, the aim of this work was to evaluate the ability of three species of cyanobacteria (Anabaena cylindrica, Nostoc muscorum, and Arthrospira platensis) and a green microalga (Chlorella vulgaris) to grow using only the resources existing in Mars, i.e., water and Martian regolith stimulant (MGS-1), under an Earth-like atmosphere. A Martian regolith extract was produced and used as a culture medium to grow these species. Their growth was assessed during a period of 25 days, using optical density and fluorometric parameters. After this period, the possible contribution of end-of-life cyanobacteria/microalga as biofertilizing agents was also assessed, using the macrophyte Lemna minor as a vegetable model. Among the three species, N. muscorum showed the best growth performance when compared to the other species, while A. platensis and C. vulgaris were not able to thrive on Mars regolith extract. Therefore, N. muscorum should be the target of future studies not only due to their role in oxygen production but also due to their possible use as a food source, as many members of the Nostoc genus. Cyanobacteria and microalgae (A. platensis and C. vulgaris) showed good abilities as biofertilizing agents, i.e., they stimulated biomass (i.e., dry weight) production at levels comparable to the plants that grew on standard synthetic medium. The highest yield was reached with A. platensis, while the lowest was achieved using the media with N. muscorum. FTIR-ATR (Fourier transform infrared with attenuated total reflectance) spectroscopy showed that the differences between the plants grown on media with or without Martian regolith seem to be related mainly to polysaccharides.

Potential role of rhizobia to enhance chickpea-growth and yield in low fertility-soils of Tunisia.

Plant growth-promoting rhizobacteria are bacteria that improve plant growth and reduce plant pathogen damages. In this study, 100 nodule bacteria were isolated from chickpea, screened for their plant growth-promoting (PGP) traits and then characterised by PCR-RFLP of 16 S rDNA. Results showed that most of the slow-growing isolates fixed nitrogen but those exhibiting fast-growth did not. Fourteen isolates solubilized inorganic phosphorus, 16 strains produced siderophores, and 17 strains produced indole acetic acid. Co-culture experiments identified three strains having an inhibitory effect against Fusarium oxysporum, the primary pathogenic fungus for chickpea in Tunisia. Rhizobia with PGP traits were assigned to Mesorhizobium ciceri, Mesorhizobium mediterraneum, Sinorhizobium meliloti and Agrobacterium tumefaciens. We noted that PGP activities were differentially distributed between M. ciceri and M. mediterraneum. The region of Mateur in northern Tunisia, with clay-silty soil, was the origin of 53% of PGP isolates. Interestingly, we found that S. meliloti and A. tumefaciens strains did not behave as parasitic nodule-bacteria but as PGP rhizobacteria useful for chickpea nutrition and health. In fact, S. meliloti strains could solubilize phosphorus, produce siderophore and auxin. The A. tumefaciens strains could perform the previous PGP traits and inhibit pathogen growth also. Finally, one candidate strain of M. ciceri (LL10)-selected for its highest symbiotic nitrogen fixation and phosphorus solubilization-was used for field experiment. The LL10 inoculation increased grain yield more than three-fold. These finding showed the potential role of rhizobia to be used as biofertilizers and biopesticides, representing low-cost and environment-friendly inputs for sustainable agriculture.

Heavy Metal-Resistant Plant Growth-Promoting Citrobacter werkmanii Strain WWN1 and Enterobacter cloacae Strain JWM6 Enhance Wheat (Triticum aestivum L.) Growth by Modulating Physiological Attributes and Some Key Antioxidants Under Multi-Metal Stress.

Due to wastewater irrigation, heavy metal (HM) exposure of agricultural soils is a major limiting factor for crop productivity. Plant growth-promoting bacteria (PGPB) may lower the risk of HM toxicity and increase crop yield. In this context, we evaluated two HM-resistant PGPB strains, i.e., Citrobacter werkmanii strain WWN1 and Enterobacter cloacae strain JWM6 isolated from wastewater-irrigated agricultural soils, for their efficacy to mitigate HM (Cd, Ni, and Pb) stress in a pot experiment. Increasing concentrations (0, 50, 100, and 200 ppm) of each HM were used to challenge wheat plants. Heavy metal stress negatively affected wheat growth, biomass, and physiology. The plants under elevated HM concentration accumulated significantly higher amounts of heavy metals (HMs) in shoots and roots, resulting in increased oxidative stress, which was evident from increased malondialdehyde (MDA) content in roots and shoots. Moreover, alterations in antioxidants like superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), and catalase (CAT) were observed in plants under HM stress. The severity of damage was more pronounced with rising HM concentration. However, inoculating wheat with Citrobacter werkmanii strain WWN1 and Enterobacter cloacae strain JWM6 (107 CFU ml-1) improved plant shoot length (11-42%), root length (19-125%), fresh weight (41-143%), dry weight (65-179%), and chlorophyll a (14%-24%) and chlorophyll b content (2-24%) under HM stress. Citrobacter werkmanii strain WWN1 and Enterobacter cloacae strain JWM6 either alone or in co-inoculation enhanced the antioxidant enzyme activity, which may lower oxidative stress in plants. However, seeds treated with the bacterial consortium showed an overall better outcome in altering oxidative stress and decreasing HM accumulation in wheat shoot and root tissues. Fourier transform infrared spectroscopy indicated the changes induced by HMs in functional groups on the biomass surface that display effective removal of HMs from aqueous medium using PGPB. Thus, the studied bacterial strains may have adequate fertilization and remediation potential for wheat cultivated in wastewater-irrigated soils. However, molecular investigation of mechanisms adopted by these bacteria to alleviate HM stress in wheat is required to be conducted.

Multiple Arbuscular Mycorrhizal Fungal Consortia Enhance Yield and Fatty Acids of Medicago sativa: A Two-Year Field Study on Agronomic Traits and Tracing of Fungal Persistence.

Arbuscular mycorrhizal fungi are promoted as biofertilizers due to potential benefits in crop productivity, and macro- and microelement uptake. However, crop response to arbuscular mycorrhizal fungi (AMF) inoculation is context-dependent, and AMF diversity and field establishment and persistence of inoculants can greatly contribute to variation in outcomes. This study was designed to test the hypotheses that multiple and local AMF inoculants could enhance alfalfa yield and fatty acids (FA) compared to exotic isolates either single or in the mixture. We aimed also to verify the persistence of inoculated AMF, and which component of the AMF communities was the major driver of plant traits. Therefore, a field experiment of AMF inoculation of alfalfa (Medicago sativa L.) with three single foreign isolates, a mixture of the foreign isolates (FMix), and a highly diverse mixture of local AMF (LMix) was set up. We showed that AMF improved alfalfa yield (+ 68%), nutrient (+ 147% N content and + 182% P content in forage), and FA content (+ 105%). These positive effects persisted for at least 2 years post-inoculation and were associated with enhanced AMF abundance in roots. Consortia of AMF strains acted in synergy, and the mixture of foreign AMF isolates provided greater benefits compared to local consortia (+ 20% forage yield, + 36% forage N content, + 18% forage P content, + 20% total FA in forage). Foreign strains of Funneliformis mosseae and Rhizophagus irregularis persisted in the roots of alfalfa 2 years following inoculation, either as single inoculum or as a component of the mixture. Among inoculants, F. mosseae BEG12 and AZ225C and the FMix exerted a higher impact on the local AMF community compared with LMix and R. irregularis BEG141. Finally, the stimulation of the proliferation of a single-taxa (R. irregularis cluster1) induced by all inoculants was the main determinant of the host benefits. Crop productivity and quality as well as field persistence of inoculated AMF support the use of mixtures of foreign AMF. On the other hand, local mixtures showed a lower impact on native AMF. These results pave the way for extending the study on the effect of AMF mixtures for the production of high-quality forage for the animal diet.

Zinc-biochemical co-fertilization improves rice performance and reduces nutrient surplus under semi-arid environmental conditions.

Biofertilizers are a promising approach to substantially improve nutrient recovery and crop production. Moreover, zinc (Zn) deficiency is one of the key abiotic factors limiting global rice production. However, the effect of Zn-biochemical co-fertilization on rice production and nutrients recovery and surplus under semi-arid environmental conditions is not fully obvious. Two years field experiment was conducted to evaluate the effect of Zn-biochemical (nitrogen "N", phosphorus "P", and potassium "K") co-fertilization on yield and yield components, physico-chemical characteristics, and nutrient recovery and surplus as well as farm profitability of four rice (Oryza sativa L.) cultivars treated with two Zn levels (no Zn application, and 600 mg chelated Zn L-1 as a foliar application) and six fertilization regimes (no fertilizers application, biofertilizers, 25% NPK plus biofertilizers, 50% NPK plus biofertilizers, 75% NPK plus biofertilizers, and 100% NPK). Biofertilizers mixture (cerealin, phosphorine, and potassiomage) were used. The results revealed that chemical constituents, growth attributes, yield, yield components, nutrients uptake (N, P, K, and Zn), and nutrients recovery (N, P, and K) significantly increased due to Zn foliar application. Biofertilizers replacement for 25% of inorganic NPK combined with Zn provides the highest nutrients uptake through increasing N, P, and K recovery by 57-94%, 61-128%, and 45-69%, respectively in the four rice cultivars compared with 100% NPK treatment. This improvement in nutrients uptake and recovery was attributed to decrease nutrients surplus by 64-78%, 46-53%, and 50-59%, respectively. Additionally, Zn-biochemical co-fertilization improves growth attributes, yield, and yield components of rice cultivars through producing more contents of chlorophyll a and b, carotenoids, total carbohydrates, and total amino acids than using 100% NPK alone. All previous characteristics significantly affected by the cultivated rice variety. The net return under the treatment of 75% NPK plus biofertilizers plus Zn foliar application was 21.5-27.5% higher than the treatment of 100% NPK. Therefore, our findings suggest that biofertilizers replacement for 25% of inorganic NPK combined with Zn foliar application supplies a financially attractive choice to substantially enhance nutrient recovery and production of rice, while effectively reducing nutrients loss.