Valorization of treated swine wastewater and generated biomass by microalgae: Their effects and salt tolerance mechanisms on wheat seedling growth.

The extensive use of mineral fertilizers has a negative impact on the environment, whereas wastewater and microalgal biomass can provide crops with nutrients such as nitrogen, phosphorus, and potassium, and have the potential to be used as a source of fertilizers in circular agriculture. In this study, a step-by-step resource utilization study of algae-containing wastewater generated from microalgae treatment of swine wastewater was carried out. When wheat seedlings were cultivated in the effluent after microalgae separation, the root fresh weight, seedling fresh weight, and total seedling length were increased by 3.44%, 14.45%, and 13.64%, respectively, compared with that of the algae-containing wastewater, and there was no significant difference in seedling fresh weight, total seedling length, maximum quantum yields of PSII photochemistry (Fv/Fm), and performance index (PIABS) from that of the Hogland solution group, which has the potential to be an alternative liquid fertilizer. Under salt stress, microalgae extract increased the contents of GA3, IAA, ABA, and SA in wheat seedlings, antioxidant enzymes maintained high activity, and the PIABS value increased. Low-dose microalgae extract (1 mL/L) increased the root fresh weight, seedling fresh weight, longest seedling length, and total seedling length by 30.73%, 31.28%, 16.43%, and 28.85%, respectively. Algae extract can act as a plant biostimulant to regulate phytohormone levels to attenuate the damage of salt stress and promote growth.

A scientific version of understanding "Why did the chickens cross the road"? - A guided journey through Bacillus spp. towards sustainable agriculture, circular economy and biofortification.

The world, a famished planet with an overgrowing population, requires enormous food crops. This scenario compelled the farmers to use a high quantity of synthetic fertilizers for high food crop productivity. However, prolonged usage of chemical fertilizers results in severe adverse effects on soil and water quality. On the other hand, the growing population significantly consumes large quantities of poultry meats. Eventually, this produces a mammoth amount of poultry waste, chicken feathers. Owing to the protein value of the chicken feathers, these wastes are converted into protein hydrolysate and further extend their application as biostimulants for sustained agriculture. The protein profile of chicken feather protein hydrolysate (CFPH) produced through Bacillus spp. was the maximum compared to physical and chemical protein extraction methods. Several studies proved that the application of CFPH and active Bacillus spp. culture to soil and plants results in enhanced plant growth, phytochemical constituents, crop yield, soil nutrients, fertility, microbiome and resistance against diverse abiotic and biotic stresses. Overall, "CFPH - Jack of all trades" and "Bacillus spp. - an active camouflage to the surroundings where they applied showed profound and significant benefits to the plant growth under the most adverse conditions. In addition, Bacillus spp. coheres the biofortification process in plants through the breakdown of metals into metal ions that eventually increase the nutrient value of the food crops. However, detailed information on them is missing. This can be overcome by further real-world studies on rhizoengineering through a multi-omics approach and their interaction with plants. This review has explored the best possible and efficient strategy for managing chicken feather wastes into protein-rich CFPH through Bacillus spp. bioconversion and utilizing the CFPH and Bacillus spp. as biostimulants, biofertilizers, biopesticides and biofortificants. This paper is an excellent report on organic waste management, circular economy and sustainable agriculture research frontier.

A review on fungal-based biopesticides and biofertilizers production.

The escalating use of inorganic fertilizers and pesticides to boost crop production has led to the depletion of natural resources, contamination of water sources, and environmental crises. In response, the scientific community is exploring eco-friendly alternatives, such as fungal-based biofertilizers and biopesticides, which have proven effectiveness in enhancing plant health and growth while sustainably managing plant diseases and pests. This review article examines the production methodologies of these bioproducts, highlighting their role in sustainable agriculture and advancing our understanding of soil microorganisms. Despite their increasing demand, their global market presence remains limited compared to traditional chemical counterparts. The article addresses: 1) the production of biofertilizers and biopesticides, 2) their contribution to crop productivity, 3) their environmental impact and regulations, and 4) current production technologies. This comprehensive approach aims to promote the transition towards more sustainable agricultural practices.

Microbeads as carriers for Bacillus pumilus: a biofertilizer focus on auxin production.

The study aimed to develop a solid biofertilizer using Bacillus pumilus, focusing on auxin production to enhance plant drought tolerance. Methods involved immobilising B. pumilus in alginate-starch beads, focusing on microbial concentration, biopolymer types, and environmental conditions. The optimal formulation showed a diameter of 3.58 mm ± 0.18, a uniform size distribution after 15 h of drying at 30 °C, a stable bacterial concentration (1.99 × 109 CFU g-1 ± 1.03 × 109 over 180 days at room temperature), a high auxin production (748.8 µg g-1 ± 10.3 of IAA in 7 days), and a water retention capacity of 37% ± 4.07. In conclusion, this new formulation of alginate + starch + L-tryptophan + B. pumilus has the potential for use in crops due to its compelling water retention, high viability in storage at room temperature, and high auxin production, which provides commercial advantages.

Recent advances in Bacillus-mediated plant growth enhancement: a paradigm shift in redefining crop resilience.

The Bacillus genus has emerged as an important player in modern agriculture, revolutionizing plant growth promotion through recent advances. This review provides a comprehensive overview of the critical role Bacillus species play in boosting plant growth and agricultural sustainability. Bacillus genus bacteria benefit plants in a variety of ways, according to new research. Nitrogen fixation, phosphate solubilization, siderophore production, and the production of growth hormones are examples of these. Bacillus species are also well-known for their ability to act as biocontrol agents, reducing phytopathogens and protecting plants from disease. Molecular biology advances have increased our understanding of the complex interplay between Bacillus species and plants, shedding light on the genetic and metabolic underpinnings of these interactions. Furthermore, novel biotechnology techniques have enabled the development of Bacillus-based biofertilizers and biopesticides, providing sustainable alternatives to conventional chemical inputs. Apart from this, the combination of biochar and Bacillus species in current biotechnology is critical for improving soil fertility and encouraging sustainable agriculture through enhanced nutrient retention and plant growth. This review also emphasizes the Bacillus genus bacteria's ability to alleviate environmental abiotic stresses such as drought and salinity, hence contributing to climate-resilient agriculture. Moreover, the authors discuss the challenges and prospects associated with the practical application of Bacillus-based solutions in the field. Finally, recent advances in Bacillus-mediated plant growth promotion highlight their critical significance in sustainable agriculture. Understanding these improvements is critical for realizing the full potential of Bacillus genus microorganisms to address current global food production concerns.

Effect of Sargassum on the Behavior and Survival of the Earthworm Eisenia Fetida.

The massive influx of Sargassum natans and S. fluitans to the shores of the Mexican Caribbean has raised concerns regarding their potential impact on soil quality and health in coastal and agroecosystems. The effects of Sargassum accumulation remain largely unexplored. This study aimed to assess the impact of Sargassum on soil ecosystems by examining the behavior and survival of the epigean earthworm Eisenia fetida. The earthworm was exposed to varying concentrations of Sargassum (0, 25, 50, 75, and 100%) in two toxicological tests. Results from the avoidance test demonstrated that E. fetida exhibited strong aversion (> 80%) to a diet containing 100% Sargassum. Conversely, the acute test revealed minimal mortality, but growth decreased with increasing Sargassum concentrations. These findings can serve as early warning bioindicators for assessing the environmental risk posed by Sargassum in soil ecosystems.

Mitigating climate change and pandemic impacts on global food security: dual sustainable agriculture approach (2S approach).

MAIN CONCLUSION: Simultaneous application of two sustainability approaches such as the application of biofertilizers to GM plants and microbe bioengineering to enhance physiological response and beneficial interaction with GM plants may have a significant impact on strengthening global food security amid climate change and the pandemic. The second sustainable development goal (SDG 02, Zero Hunger) aims global agricultural sustainability and food security challenges. The agriculture sector has been an integral part of developing countries for millions of farmers and their families. Their contribution provides stability of raw matter related to food availability. But climate change, higher population growth and worldwide pandemics are the main obstacles to food quality, higher crop productivity and global food security. Scientists are concerned with the manifestation of agriculture sustainability in the modern crop management approach to resolving the issues. It is the only way to higher yield productivity by protecting the environment, conserving natural resources, and slowing climate change. Several strategies can be an option to implement, yet the proposed two sustainability approach or 2S approach will be the significant way toward the goal of zero hunger. The first sustainability approach is an application of genetically modified (S1: GMO) Plants and the other is an application of beneficiary plant growth-promoting microbes (S2: Biofertilizers) to the plants for both higher crops and maintenance of the environment. This study summarizes the essential points of S1 and S2 for the widespread utilization of the 2S approach in agriculture and recommends the potential alternatives to be implemented to produce food for all. Simultaneous application of the 2S approach can defeat all threats to gain sustainability in agriculture.

'A plant's major strength in rhizosphere': the plant growth promoting rhizobacteria.

Human activities, industrialization and civilization have deteriorated the environment which eventually has led to alarming effects on plants and animals by heightened amounts of chemical pollutants and heavy metals in the environment, which create abiotic stress. Environmental conditions like drought, salinity, diminished macro-and micro-nutrients also contribute in abiotic stress, resulting in decrement of survival and growth of plants. Presence of pathogenic and competitive microorganisms, as well as pests lead to biotic stress and a plant alone can not defend itself. Thankfully, nature has rendered plant's rhizosphere with plant growth promoting rhizobacteria which maintain an allelopathic relationship with host plant to defend the plant and let it flourish in abiotic as well as biotic stress situations. This review discusses the mechanisms behind increase in plant growth via various direct and indirect traits expressed by associated microorganisms in the rhizosphere, along with their current scenario and promising future for sustainable agriculture. It also gives details of ten such bacterial species, viz. Acetobacter, Agrobacterium, Alcaligenes, Arthrobacter, Azospirillum, Azotobacter, Bacillus, Burkholderia, Enterobacter and Frankia, whose association with the host plants is famed for enhancing plant's growth and survival.

Analysis of Bacterial Microbiota of Aerated Compost Teas and Effect on Tomato Growth.

Mature composts and their water-based extracts, known as aerated compost teas (ACTs), are biofertilizers that share bioactive effects like soil restoration and plant health promotion, widely used for sustainable agriculture. Bioactive effects of compost and ACTs could be associated with their physicochemical and biological characteristics, like carbon/nitrogen (C/N) ratio and microbiota structure respectively. In our study, we elaborated ACTs using mature homemade compost, wheat bran, and grass clippings, following the C/N ratio criteria. Irrigation of tomato plantlets with ACT whose C/N ratio was close to the expected C/N ratio for mature compost evidenced plant growth promotion. Exploring the bacterial microbiota of elaborated ACTs and origin compost revealed significant structural differences, including phyla involved in N mineralization and free-living N-fixing bacteria. Therefore, ACTs harbor diverse bacterial microbiota involved in the N cycle, which would enrich plant and soil bacterial communities at the taxonomic and functional levels. Furthermore, ACTs are considered a part of agroecological and circular economy approaches.

Biostimulants and environmental stress mitigation in crops: A novel and emerging approach for agricultural sustainability under climate change.

Pesticide and fertilizer usage is at the center of agricultural production to meet the demands of an ever-increasing global population. However, rising levels of chemicals impose a serious threat to the health of humans, animals, plants, and even the entire biosphere because of their toxic effects. Biostimulants offer the opportunity to reduce the agricultural chemical footprint owing their multilevel, beneficial properties helping to make agriculture more sustainable and resilient. When applied to plants or to the soil an increased absorption and distribution of nutrients, tolerance to environmental stress, and improved quality of plant products explain the mechanisms by which these probiotics are useful. In recent years, the use of plant biostimulants has received widespread attention across the globe as an ecologically acceptable alternative to sustainable agricultural production. As a result, their worldwide market continues to grow, and further research will be conducted to broaden the range of the products now available. Through this review, we present a current understanding of biostimulants, their mode of action and their involvement in modulating abiotic stress responses, including omics research, which may provide a comprehensive assessment of the crop's response by correlating molecular changes to physiological pathways activated under stress conditions aggravated by climate change.

Unravelling the potential plant growth activity of halotolerant Bacillus licheniformis NJ04 isolated from soil and its possible use as a green bioinoculant on Solanum lycopersicum L.

Immensely expanding world population and narrowing arable land for agriculture is a mighty concern faced by the planet at present. One of the major reasons for decline in arable lands is the increased soil salinity, making it unfavourable for crop cultivation. Utilisation of these saline land for agriculture is possible with suitable invention for improving the soil quality. Biofertizers manufactured out of Plant Growth Promoting Rhizobacteria is one such innovation. In the present study, Bacillus licheniformis NJ04 strain was isolated and studied for its halotolerance and other effective plant growth promoting traits. The NJ04 strain was able to tolerate salt up to 10% and highlighted remarkable antifungal activity against common fungal phytopathogens. The preliminary seed germination test in Solanum lycopersicum seeds revealed a significant increase in root length (16.29 ± 0.91 cm) and shoot length (9.66 ± 0.11 cm) of treated plants as compared with the control plants and thereby shows its possible use as a green bioinoculant in agriculture and an ideal candidate to compete with salt stress.

Development of Bacteria biofertilizers using locally isolated rhizosphere populations and agricultural refuse and their impacts on growth of local test crops.

Biofertilizers are the preparations of live microorganisms added to the root, seed or soil to promote plant growth. In this study, Plant Growth Promoting Bacteria able to solubilize insoluble phosphate (P) and potassium (K) forms were isolated, characterized and identified. Two isolates that demonstrated excellent solubilization of potassium or phosphate from abundant and bio-available waste biomass (rice husk and cattle bone) were used to produce biofertilizers by solid-state fermentation. The biofertilizers were applied to grow three food security crops, Zea mays, Solanum lycopersicum, and Arachis hypogea, in a screenhouse, and monitored for growth impacts. Treatments A, B, and A + B biofertilizers caused a significant (p < 0.05) increase in plant dry weights. The highest microbial colonization was obtained from treatment A + B (for S. lycopersicum) with a microbial count (log 2.89 (108) cfu/g), whereas treatment with B (for A. hypogea) had the least microbial count (log 2.73 (108) cfu/g). Maximum values of experimental parameters: shoot height, leaf number, plant dry weight and leaf width were obtained with the combined application of both biofertilizers. P and K solubilizing PGPB have shown potential for use as biofertilizers in growing these key crops under the soil conditions and in the environment studied.

This work demonstrates a first, sensitive and reliable method for low-cost, sustainable, eco-friendly production and utilization of biofertilizers for improved growth of major tropical food security crops using native bacterial strains in a defined tropical agronomic environment. Its novelty is the choice of Bacillus cereus and Pseudomonas aeruginosa singly and in combination (synergy/additive) as biofertilizers for growing tropical test crops. It also demonstrated the use of a novel and cheap delivery method/carrier that ensured the establishment and persistence of PGPB in the rhizosphere. Native B. cereus and P. aeruginosa were able to solubilize and make available to plants phosphate and potassium, thereby improving soil quality and plant growth while the process achieved the reuse of waste biomass.

A Culturomics-Based Bacterial Synthetic Community for Improving Resilience towards Arsenic and Heavy Metals in the Nutraceutical Plant Mesembryanthemum crystallinum.

Plant-growth-promoting bacteria (PGPB) help plants thrive in polluted environments and increase crops yield using fewer inputs. Therefore, the design of tailored biofertilizers is of the utmost importance. The purpose of this work was to test two different bacterial synthetic communities (SynComs) from the microbiome of Mesembryanthemum crystallinum, a moderate halophyte with cosmetic, pharmaceutical, and nutraceutical applications. The SynComs were composed of specific metal-resistant plant-growth-promoting rhizobacteria and endophytes. In addition, the possibility of modulating the accumulation of nutraceutical substances by the synergetic effect of metal stress and inoculation with selected bacteria was tested. One of the SynComs was isolated on standard tryptone soy agar (TSA), whereas the other was isolated following a culturomics approach. For that, a culture medium based on M. crystallinum biomass, called Mesem Agar (MA), was elaborated. Bacteria of three compartments (rhizosphere soil, root endophytes, and shoot endophytes) were isolated on standard TSA and MA media, stablishing two independent collections. All bacteria were tested for PGP properties, secreted enzymatic activities, and resistance towards As, Cd, Cu, and Zn. The three best bacteria from each collection were selected in order to produce two different consortiums (denominated TSA- and MA-SynComs, respectively), whose effect on plant growth and physiology, metal accumulation, and metabolomics was evaluated. Both SynComs, particularly MA, improved plant growth and physiological parameters under stress by a mixture of As, Cd, Cu, and Zn. Regarding metal accumulation, the concentrations of all metals/metalloids in plant tissues were below the threshold for plant metal toxicity, indicating that this plant is able to thrive in polluted soils when assisted by metal/metalloid-resistant SynComs and could be safely used for pharmaceutical purposes. Initial metabolomics analyses depict changes in plant metabolome upon exposure to metal stress and inoculation, suggesting the possibility of modulating the concentration of high-value metabolites. In addition, the usefulness of both SynComs was tested in a crop plant, namely Medicago sativa (alfalfa). The results demonstrate the effectiveness of these biofertilizers in alfalfa, improving plant growth, physiology, and metal accumulation.

Microorganisms in biological control strategies to manage microbial plant pathogens: a review.

Chemical fertilizers and pesticides are an integral part of modern agriculture and are often associated with numerous environmental problems. Biological agents such as microorganisms can largely replace chemical fertilizers and pesticides. The proper use of selected microorganisms such as bacteria, fungi and viruses have several benefits for agriculture. These include a healthy soil microbiota, biological production of important compounds that promote plant health, and to be used as biocontrol agents (BCAs) that provide protection from plant pathogenic microorganisms. Scientists have found that several bacterial genera including Bacillus and Pseudomonas have antimicrobial activity against numerous pathogenic bacterial and fungal plant pathogens. Trichoderma, Aspergillus, and Penicillium are among the most common fungal genera used as BCAs against both bacterial and fungal plant pathogens. Several bacteriophages and mycoviruses are also found effective as BCAs against selective plant pathogens. Fusarium oxysporum is a commonly found microbial plant pathogen causing wilts and rots in plants. Overall, it can be concluded that the use of microbial BCAs is an effective practice against microbial plant pathogens.

Perspective on the biotechnological production of bacterial siderophores and their use.

Iron (Fe) is an essential element in several fundamental cellular processes. Although present in high amounts in the Earth's crust, Fe can be a scarce element due to its low bioavailability. To mitigate Fe limitation, microorganism (bacteria and fungi) and grass plant biosynthesis and secret secondary metabolites, called siderophores, with capacity to chelate Fe(III) with high affinity and selectivity. This review focuses on the current state of knowledge concerning the production of siderophores by bacteria. The main siderophore types and corresponding siderophore-producing bacteria are summarized. A concise outline of siderophore biosynthesis, secretion and regulation is given. Important aspects to be taken into account in the selection of a siderophore-producing bacterium, such as biological safety, complexing properties of the siderophores and amount of siderophores produced are summarized and discussed. An overview containing recent scientific advances on culture medium formulation and cultural conditions that influence the production of siderophores by bacteria is critically presented. The recovery, purification and processing of siderophores are outlined. Potential applications of siderophores in different sectors including agriculture, environment, biosensors and the medical field are sketched. Finally, future trends regarding the production and use of siderophores are discussed. KEY POINTS : • An overview of siderophore production by bacteria is critically presented • Scientific advances on factors that influence siderophores production are discussed • Potential applications of siderophores, in different fields, are outlined.

Prospecting the significance of methane-utilizing bacteria in agriculture.

Microorganisms act as both the source and sink of methane, a potent greenhouse gas, thus making a significant contribution to the environment as an important driver of climate change. The rhizosphere and phyllosphere of plants growing in natural (mangroves) and artificial wetlands (flooded agricultural ecosystems) harbor methane-utilizing bacteria that oxidize methane at the source and reduce its net flux. For several decades, microorganisms have been used as biofertilizers to promote plant growth. However, now their role in reducing net methane flux, especially from flooded agricultural ecosystems is gaining momentum globally. Research in this context has mainly focused on taxonomic aspects related to methanotrophy among diverse bacterial genera, and environmental factors that govern methane utilization in natural and artificial wetland ecosystems. In the last few decades, concerted efforts have been made to develop multifunctional microbial inoculants that can oxidize methane and alleviate greenhouse gas emissions, as well as promote plant growth. In this context, combinations of taxonomic groups commonly found in rice paddies and those used as biofertilizers are being explored. This review deals with methanotrophy among diverse bacterial domains, factors influencing methane-utilizing ability, and explores the potential of novel methane-utilizing microbial consortia with plant growth-promoting traits in flooded ecosystems.

Biofertilizer microorganisms accompanying pathogenic attributes: a potential threat.

Application of biofertilizers containing living or dormant plant growth promoting bacterial cells is considered to be an ecofriendly alternative of chemical fertilizers for improved crop production. Biofertilizers opened myriad doors towards sustainable agriculture as they effectively reduce heavy use of chemical fertilizers and pesticides by keeping soils profuse in micro and macronutrients, regulating plant hormones and restraining infections caused by the pests present in soil without inflicting environmental damage. Generally, pathogenicity and biosafety testing of potential plant growth promoting bacteria (PGPB) are not performed, and the bacteria are reported to be beneficial solely on testing plant growth promoting characteristics. Unfortunately, some rhizosphere and endophytic PGPB are reported to be involved in various diseases. Such PGPB can also spread virulence and multidrug resistance genes carried by them through horizontal gene transfer to other bacteria in the environment. Therefore, deployment of such microbial populations in open fields could lead to disastrous side effects on human health and environment. Careless declaration of bacteria as PGPB is more pronounced in research publications. Here, we present a comprehensive report of declared PGPB which are reported to be pathogenic in other studies. This review also suggests the employment of some additional safety assessment protocols before reporting a bacteria as beneficial and product development.

Recent advancements for microorganisms and their natural compounds useful in agriculture.

During the past years, microorganisms have been the cause of many problems for human's health. However, today with the development of many techniques of microbiology, the researchers have studied several roles of microorganisms which may help the society. Microbial-based products are expected to play important role in agriculture-enhancing plant production and therefore increasing crop's yieldeswani et al. . Microorganisms can act by several action mechanisms including antibiosis or mechanisms in plant-microbe interactions underlining the dual function of microbial strains toward plant nutrition and protection. The market has increased with the development of microbial-based products. Currently, it is normal to think that microorganisms help us in agriculture by applying them as biological control. In this mini review, we collect the last findings about this topic including very recent literature. KEY POINTS: • Microorganisms play a beneficial role in agriculture by different mechanisms. • One of these mechanisms is the secretion of chemical compounds with different activities.

Review of patents for agricultural use of arbuscular mycorrhizal fungi.

Mycorrhizal biotechnology has emerged as a major component of sustainable agriculture and allied activities. Innovations related to its role in agriculture, land reclamation, forestry, and landscaping are well recognized. This review presents the evolution of innovations worldwide related to arbuscular mycorrhizal fungi (AMF) in the past two decades, from 2000 to April 2020, and maintains that such innovations must continue in the future. An analysis of 696 patents showed that AMF have been used consistently as a biofertilizer and bioremediator over that period, although an upsurge was noted in propagation technologies, next-generation production methods, and formulation technologies. This review will familiarize mycorrhizologists with novel and evolving trends and will convince them of the importance of applying for patents to safeguard their innovations and the use of those innovations by industry.

Compost and mycorrhizae application as a technique to alleviate Cd and Zn stress in Medicago sativa.

Soil pollution by heavy metals, in the last decades, has become a worldwide major concern for which finding a solution is becoming more important to conserve soil for future generations. This study used an ecotoxicology approach to evaluate the effectiveness of compost and arbuscular mycorrhizal fungus (AMF) and their combination on Medicago sativa performance grown under Zn and Cd stress. At 600 mg/kg of Cd and Zn, a reduction of mycorrhization frequency by 3.6- and 2-fold, respectively, was observed without applying compost. The effect of AMF-Compost combination on alfalfa biomass production was enhanced in the absence and the presence of heavy metals. An improvement of relative water content by 1.7- and 1.5-fold was recorded in case AMF-Compost plant treatments grown under 600 mg/kg of Cd and Zn, respectively. The application of AMF-compost enhanced the stomatal conductance and total chlorophyll in alfalfa plants. Sugar contents were significantly increased in mycorrhized and treated plants with compost compared to the control, regardless of the applied Cd or Zn dose. Phenol content was significantly increased in plants amended with compost alone and treated by Cd. Regarding Cd and Zn accumulation, AMF-compost combination reduced the content of heavy metals accumulated in M. sativa.