Plant Probiotics Research Articles

Seed-Borne Probiotic Yeasts Foster Plant Growth and Elicit Health Protection in Black Gram (Vigna mungo L.)

Black gram is one of the most indispensable components of the world food basket and the growth and health of the crop get influenced by biotic and abiotic factors. Beneficial phyto-microbes are one among them that influence the crop growth, more particularly the seed borne microbes are comparatively beneficial, that they pass from generation to generation and are associated with the plants from establishment to development. In the present study, twenty seed-borne yeasts were characterized and tested for growth promotion of black gram and their antagonism against black gram phytopathogens. Two yeasts, Pichia kudriavzevii POY5 and Issatchenkia terricola GRY4, produced indole acetic acid (IAA), siderophore, 1-amino cyclopropane-1-carboxylic acid deaminase (ACCD), and plant defense enzymes. They solubilized phosphate and zinc and fixed atmospheric nitrogen. Inoculation of these two yeast isolates and Rhizobium BMBS1 improved the seed germination, physiological parameters and yield of black gram. Inoculation of Rhizoctonia solani-challenged plants with plant growth-promoting yeasts, resulted in the synthesis of defense-related enzymes such as peroxidases (POD), chitinases, catalase (CAT), and polyphenol oxidases (PPO). Thus, the seed-borne yeasts, Pichia kudriavzevii POY5 and Issatchenkia terricola GRY4, could be used as plant probiotics for black gram.

Advanced Development of Bio-fertilizer Formulations Using Microorganisms as Inoculant for Sustainable Agriculture and Environment – A Review

Conventional types of fertilizer such as chemical and synthetic fertilizers have demonstrated various adverse effects on the environment, crops, and humans. The utilization of plant probiotics as a bio-fertilizer in agriculture has been recognized to benefit the growth of the plant and inhibit the activity of plant pathogens. Traditional formulations of bio-fertilizer have provided insight into the beneficial use of microorganisms in crops. Despite its advantage to the environment, the effectiveness of traditional bio-fertilizer is common as compared to chemical fertilizer. Thus, a variety of bio-fertilizer formulations have been developed to improve the success rate of bio-fertilizer in increasing plant productivity. This review was focused on the development of bio-fertilizer formulation and the potential of bio-fertilizer to substitute chemical fertilizer application. In addition, this research review was also undertaken with a great demand on producing low cost and highly effective fertilizer without harming the environment and humans. Thus, the advantages and disadvantages of each formulation type have also been reviewed, emphasizing the perspective of bio-fertilizer and their suitability as bio-fertilizer as a substitute for chemical fertilizers in sustainable agriculture.

Effects Induced by the Agricultural Application of Probiotics on Antioxidant Potential of Strawberries.

With the recent rapid development of the functional food sector, agriculture is looking for alternatives to improve the quality of food grown by limiting chemical fertilizers. This study evaluated the effects of two commercial plant probiotics, ProbioHumus and NaturGel, on the growth and quality of strawberry fruits. Strawberry plants were sprayed with microbial probiotics twice a year: after harvesting at the beginning of dormancy and at the stage of leaf development. Spray applications of ProbioHumus, NaturGel, and NaturGel + ProbioHumus in the organic farm fields significantly increased the fresh fruit weight up to 42%, 35%, and 37%, respectively, compared to the non-treated control. An increase in the weight of fresh strawberry fruits may be associated with an increase in dry matter accumulation. The probiotics had a positive effect on the total content of phenols, anthocyanins, and especially ascorbic acid in strawberry fruits. The increase in ascorbic acid in strawberry fruits was up to 97% compared to the non-treated control. The fruits from plants inoculated with probiotics showed significantly higher antioxidant activity. In summary, ProbioHumus and NaturGel are effective tools for improving the quality of strawberries and can be exploited in sustainable agriculture as a tool for adding value to functional food.

Extremophiles as Plant Probiotics to Promote Germination and Alleviate Salt Stress in Soybean

Extremophiles as Plant Probiotics to Promote Germination and Alleviate Salt Stress in Soybean

Cross Talk Between Zinc-Solubilizing Bacteria and Plants: A Short Tale of Bacterial-Assisted Zinc Biofortification

A contemporary approach to bacterially mediated zinc (Zn) biofortification offers a new dimension in the crop improvement program with better Zn uptake in plants to curb Zn malnutrition. The implication of Zn solubilizing bacteria (ZSB) represents an inexpensive and optional strategy for Zn biofortification, with an ultimate green solution to enlivening sustainable agriculture. ZSB dwelling in the rhizospheric hub or internal plant tissues shows their competence to solubilize Zn via a variety of strategies. The admirable method is the deposition of organic acids (OAs), which acidify the surrounding soil environment. The secretion of siderophores as a metal chelating molecule, chelating ligands, and the manifestation of an oxidative–reductive system on the bacterial cell membrane are further tactics of bacterially mediated Zn solubilization. The inoculation of plants with ZSB is probably a more effective tactic for enhanced Zn translocation in various comestible plant parts. ZSB with plant growth-enhancing properties can be used as bioelicitors for sustainable plant growth via the different approaches that are crucial for plant health and its productivity. This article provides an overview of the functional properties of ZSB-mediated Zn localization in the edible portions of food crops and provides an impetus to explore such plant probiotics as natural biofortification agents.

Insight into how fertilization strategies increase quality of grape (Kyoho) and shift microbial community.

Organic and bioorganic fertilizers were increasingly used for agricultural soil. However, little is known on what kind of organic fertilizer application strategies can promote grape production well and how appropriate fertilization strategies improve soil properties and shift microbial community. This study investigated the improvement in soil physicochemical properties as well as their relations with microbial community structure and grape quality under different fertilization strategies. Our results found that (bio)organic fertilizer (CF1, CF2, and BF) especially combined application of organic and bioorganic fertilization (CBF) had smaller effects on electrical conductivity (EC) and pH, while it improved soil nutrients including N, P, K, and organic matter (OM) well, thereby promoting the grape quality comparing to the group without any fertilizer (CK) and with chemical fertilizer (NPK). Especially, the concentrations of Cr, Hg, Zn, and Cu were reduced by 13.63%, 12.50%, 12.52%, and 11.75% in CBF, respectively. Additionally, CF1, CF2, and BF, especially CBF, optimized the communities' composition and increased the abundance of some plant probiotics such as Solirubrobacter and Lysobacter. Nevertheless, excessive application of organic fertilizer derived from livestock manure could cause the accumulation of heavy metals such as Zn and Cu in soil and leaves, which could further influence the grape quality. Additionally, the structure of microbial communities was also changed possibly because some bacterial genera showed distinct adaptability to the stress of heavy metals or the utilization capacity of N, P, K, and OM. Our results demonstrated that combined application of organic and bioorganic fertilization showed a great influence on soil physicochemical properties, whose positive changes could further optimize microbial communities and facilitate the promotion of grape quality.

Application of Commercial Plant Probiotics Improves the Berry Yield and Quality of Field-Grown Blackcurrant

The berries of blackcurrants are commercially important and rich in antioxidants and have a high free radical scavenging capacity. Four controlled fields 1 ha in size were set up in an organic farm to test two commercial plant probiotic products, ProbioHumus and NaturGel, and their combined impact on blackcurrant berry yield and quality. Spray applications of ProbioHumus, NaturGel, and their combination significantly increased fruit yields 38, 25, and 16%, respectively, versus the nontreated control. The berries from plants inoculated with probiotics had significantly higher contents of anthocyanins versus the nontreated control and tended to exhibit increased levels of ascorbic acid. The blackcurrant berries treated with both probiotics exhibited a fair ability to scavenge DPPH free radicals. This is the first study of the improvement of both the yield and the quality of blackcurrant berries by the application of commercial plant probiotics under field conditions.

Plant Microbial Biostimulants as a Promising Tool to Enhance the Productivity and Quality of Carrot Root Crops.

The interest in studies focused on applying probiotic microorganisms is increasing due to sustainable agriculture development. In this research, we aimed to evaluate the impact of two commercial plant probiotics—ProbioHumus and NaturGel on carrot growth, yield, and quality in organic and nonorganic production systems. The research was carried out under laboratory and field conditions. Plants were treated with probiotics (2 L/ha) at the nine leaves stage. Biometrical measurements and chemical analyses were performed at a maturation stage. The average weight of carrot roots increased by 17 and 20 g in the test variant with ProbioHumus as compared to the control in the organic and nonorganic farms, respectively. Plant microbial biostimulants ProbioHumus and NaturGel had a positive effect on the quality of carrots from organic and nonorganic farms: applied in couple they promoted the accumulation of monosaccharides, ascorbic acid, carotenoids, phenols, and increased antioxidant activity. Quantitative nitrate analysis regardless of the biostimulant used revealed about twofold lower nitrate content of carrots from organic than nonorganic farms, and probiotics did not show a significant effect on nitrate accumulation. Finally, ProbioHumus and NaturGel were effective at low doses. The use of microbial biostimulants can be recommended as an element of cultivation for creating ecologically friendly technologies.

Elucidating Adhesion Behaviors and the Interfacial Interaction Mechanism between Plant Probiotics and Modified Bentonite Carriers

Elucidating Adhesion Behaviors and the Interfacial Interaction Mechanism between Plant Probiotics and Modified Bentonite Carriers

New Insights into the Virulence Traits and Antibiotic Resistance of Enterococci Isolated from Diverse Probiotic Products.

The GRAS (generally recognized as safe) status of Enterococcus has not yet been authenticated, but enterococci, as probiotics, have been increasingly applied in human healthcare and animal husbandry, for instance as a dietary supplement, feed additive, or growth promotor. The food chain is the important route for introducing enterococci into the human gut. The pathogenicity of Enterococcus from probiotic products requires investigation. In the study, 110 commercial probiotic products used for human, animal, aquaculture, and plants were examined, among which 36 enterococci were identified, including 31 from Enterococcus faecium, 2 from E. faecalis, 2 from E. casseliflavus, and 1 from E. gallinarum. Strikingly, 28 of the 36 enterococci isolated from probiotics here did not mention the presence of Enterococcus in the labeled ingredients, and no Enterococcus isolates were found from 5 animal probiotics that were labeled with the genus. In total, 35 of the 110 products exhibited hemolysis, including 5 (10.6%) human probiotics, 14 (41.2%) animal probiotics, 8 (57.1%) aquaculture probiotics, and 8 (53.3%) plant probiotics. The detection rates of virulence factors associated with adhesion, antiphagocytosis, exoenzyme, biofilm, and other putative virulence markers (PVM) in 36 enterococci were 94.4%, 91.7%, 5.6%, 94.4% and 8.3%. Twenty-six of the 36 isolated strains exhibited biofilm formation ability, where 25 strains (69.4%) and one (2.8%) were strong and weak biofilm producers, respectively. We analyzed the resistance rates against erythromycin (97%), vancomycin and ciprofloxacin (8%), tetracycline (3%), and high-level aminoglycosides (0%), respectively. High detection rates of msrC/lsaA (86%) and aac(6′)-Ii (86%) were observed, followed by vanC (8%), tetM (3%). The Tn5801-tetM-like integrative conjugative element (ICE) was identified in E. gallinarum, exhibiting resistance to tetracycline (64 μg/mL). Seven probiotic E. faecalis and E. faecium, as active ingredients in human probiotics, shared the same STs (sequence types) and were distinct from the STs of other contaminated or mislabeled enterococci, indicating that two particular STs belonged to native probiotic isolates. These findings advocate appropriate assessments of enterococci when used in probiotics.

Laponite® nanoclay gel based microenvironment for plant probiotic rhizobacterial delivery

The current study reports the development of nanoclay based delivery system for the encapsulation of for plant growth promoting rhizobacteria. Five strains of Pseudomonas spp. were selected for the study. They were encapsulated in laponite gel beads and used to treat Vigna unguiculata seedlings. The growth parameters of the treated plants were studied. The treated plants showed significant improvement in leaf length, leaf number, and shoot length than the control plants. The viability studies ascertained the stable condition of the rhizobacteria within the laponite beads up to 60 days after entrapment. Soil analysis of laponite-consortium treated samples showed enhancement in organic carbon levels (2.83%) when compared to the untreated plants (1.55%). In addition, enhanced photosynthetic and nutrient solubilising potential was observed in the treated seedlings. The promising results of the study indicate the potential of laponite mediated system for efficient delivery of plant probiotics by enhancing its stability when compared to other available methods.

Overall assessment of antibiotic substitutes for pigs: a set of meta-analyses

BackgroundAntibiotic growth promoters are widely used to improve weight gain. However, the abuse of antibiotics can have many negative effects on people. Developing alternatives to antibiotics is an urgent need in livestock production. We aimed to perform a meta-analysis and network meta-analysis (NMA) to investigate the effects of feed additives as potential antibiotic substitutes (ASs) on bacteriostasis, growth performance, intestinal morphology and immunity. Furthermore, the primary, secondary, and tertiary ASs were defined by comparing their results with the results of antibiotics.ResultsAmong 16,309 identified studies, 37 were summarized to study the bacteriostasis effects of feed additives, and 89 were included in the meta-analysis and NMA (10,228 pigs). We summarized 268 associations of 57 interventions with 32 bacteria. The order of bacteriostasis effects was as follows: antimicrobial peptides (AMPs) ≈ antibiotics>organic acids>plant extracts>oligosaccharides. We detected associations of 11 feed additives and 11 outcomes. Compared with a basal diet, plant extract, AMPs, probiotics, microelements, organic acids, bacteriophages, lysozyme, zymin, and oligosaccharides significantly improved growth performance (P < 0.05); organic acids, probiotics, microelements, lysozyme, and AMPs remarkably increased the villus height:crypt depth ratio (V/C) (P < 0.05); and plant extracts, zymin, microelements, probiotics, and organic acids notably improved immunity (P < 0.05). The optimal AMP, bacteriophage, lysozyme, microelements, oligosaccharides, organic acids, plants, plant extracts, probiotics, and zymin doses were 0.100%, 0.150%, 0.012%, 0.010%, 0.050%, 0.750%, 0.20%, 0.040%, 0.180%, and 0.100%, respectively. Compared with antibiotics, all investigated feed additives exhibited no significant difference in effects on growth performance, IgG, and diarrhoea index/rate (P > 0.05); AMPs and microelements significantly increased V/C (P < 0.05); and zymin significantly improved lymphocyte levels (P < 0.05). Furthermore, linear weighting sum models were used to comprehensively estimate the overall impact of each feed additive on pig growth and health.ConclusionsOur findings suggest that AMPs and plant extracts can be used as primary ASs for weaned piglets and growing pigs, respectively. Bacteriophages, zymin, plants, probiotics, oligosaccharides, lysozyme, and microelements can be regarded as secondary ASs. Nucleotides and organic acids can be considered as tertiary ASs. Future studies should further assess the alternative effects of combinational feed additives.

NEW APPROACH TO AGRICULTURAL PRODUCTION: PLANT PROBIOTICS

With the increase in the world population every year, the need for plant and animal foods has increased. In order to meet these needs, the amount of fertilizers (with chemical content) used to increase productivity in agriculture has increased and has become a threat to the soil and the environment. In order to minimize the harms of chemical fertilizers and to preserve the fertility of the soil, new environmentally friendly applications have been researched. In this context, studies on "Plant Probiotics", which are one of the effective applications both in protecting the quality of the soil and increasing the yield in plant production, especially on local isolates and formulations to be prepared from them, have gained momentum. Plant probiotics are a group of microorganisms or microorganisms that can improve soil health, plant growth, and plant tolerance or immunity to various abiotic and biotic stresses, thanks to their potential role in enhanced nutrient acquisition and/or biocontrol activities by colonizing the root zone of plants, called the rhizosphere. As a result of inoculation of plants with strains of these bacteria, which have very different properties (nitrogen binding, phosphate solubilizing, biocontrol agent, stress resistance, phytohormone synthesis), it directly affects the growth and development of the roots and shoots of the plant, increasing the biomass, as well as contributing to the increase of the yield and quality of the product. In this context, the preparation and use of biofertilizer formulations of local plant probiotic bacteria, which will be obtained from their natural areas, has become very important in rational agricultural practices in recent years and intensive researches are carried out. With the use of the aforementioned plant probiotic formulations, environmentally friendly green production will be made by contributing to the production of both foodstuffs and feed raw materials in order to ensure the continuity of the world population. As a result, the protection of the ecosystem will be ensured by preventing environmental pollution, which is the problem of the whole world.

Актиномицеты как основа пробиотиков для растений

The present review describes the concept of probiotics for plants and analyzes the prospects for using actinomycetes as producers of these drugs. The minimum requirements for plant probiotic microorganisms are proposed, similar to those for human probiotic microorganisms. These are utility, efficiency and safety for plants, as well as mandatory isolation from plant samples. It is noted that these requirements are usually met by endophytic and rhizosphere microorganisms that stimulate plant growth and provide them with protection from phytopathogens. Evidence is given for the possibility of attributing actinomycetes to probiotic plant bacteria, due to the close relationship of these microorganisms with plants, their wide distribution in populations of endophytic and rhizosphere microorganisms, and the presence of phytoregulatory activity. The review provides examples of genera and species of actinomycetes that are promising producers of probiotics for agronomically important crops. The most studied and commercialized of them are representatives of the Streptomyces genus. The current state, prospects and problems in commercialization of probiotics based on actinomycetes are discussed. probiotic microorganisms of plants, associative actinomycetes, endophytes, rhizosphere, biological preparations

Antimicrobial resistance, virulence characteristics and genotypes of Bacillus spp. from probiotic products of diverse origins

Spore-forming probiotic Bacillus spp. have received extensively increasing scientific and commercial interest, but raised the concerns in the potential risks and pathogenesis. In this study, 50 commercial probiotic products were collected from all over the country and Bacillus spp. isolated from products were evaluated for the safety on the aspects of hemolytic activity, contamination profiles, toxin genes, cytotoxicity, antimicrobial resistance, and genotyping. 34 probiotic products (68%) exhibited hemolysis, including 19 human probiotics, 9 animal probiotics, and 6 plant probiotics. 28 products (56%) contained other bacteria not labeled in the ingredients. 48 strains in Bacillus spp. including 17 B. subtilis group isolates, 28 B. cereus, and 3 other Bacillus spp. were isolated from human, food animal, and plant probiotic products. Detection rates of enterotoxin genes, nheABC and hblCDA, and cytotoxin cytK2 in 48 Bacillus spp. isolates were 58%, 31%, and 46%, respectively. Also, one isolate B. cereus 34b from an animal probiotic product was positive for ces, encoding cereulide. 28 of 48 Bacillus spp. isolates were cytotoxic. 19 of 28 B. cereus isolates maintained to exhibit hemolysis after heat treatment. All 48 Bacillus spp. isolates exhibited resistance to lincomycin, and 5 were resistant to tetracycline. The genotyping of commercial probiotic Bacillus spp. reported in this study showed that ces existed in B. cereus 34b with the specific sequence type (ST1066). These findings support the hypothesis that probiotic products were frequently contaminated and that some commercial probiotics consisted of Bacillus spp. may possess toxicity and antimicrobial resistance genes. Thus, the further efforts are needed in regarding the surveillance of virulence factors, toxins, and antibiotic resistance determinants in probiotic Bacillus spp.

Draft Genome Sequences of Six Strains of Lactococcus lactis (Phylum Firmicutes), Spanning the Seeds of Cucumis sativus L. (Cucumber), Cucumis melo L. (Cantaloupe), and Cucurbita pepo var. turbinate (Acorn Squash).

We announce the draft genome sequences of six strains of Lactococcus lactis (EKM101L, EKM102L, EKM201L, EKM203L, EKM501L, and EKM502L). These candidate plant probiotics were isolated from surface-sterilized seeds of Cucumis sativus L. (cucumber), Cucumis melo L. (cantaloupe), and Cucurbita pepo var. turbinate (acorn squash). They display beneficial activities, including biocontrol.

Draft Genome Sequences of Seven Strains of Paenibacillus spp. (Phylum Firmicutes) Inhabiting the Seeds of Cucumis melo L. (Cantaloupe) and Exhibiting Plant Probiotic Traits.

Here, we report the draft genome sequences of seven Paenibacillus sp. strains (EKM202P, EKM205P, EKM206P, EKM207P, EKM208P, EKM211P, and EKM212P) that were previously isolated from cultivated surface-sterilized seeds of Cucumis melo L. (cantaloupe). These candidate Paenibacillus plant probiotics displayed in vitro growth-promoting traits and suppressive activity against root-associated fungal/oomycete pathogens.

Identification and characterization of promising endophytic bacteria for growth promotion in chickpea (Cicer arietinum)

The present study was carried out for the isolation and characterization of endophytic bacteria from chickpea nodules. A total of 107 endophytes were isolated from five districts of Haryana using three media, viz. YEMA for rhizobia, Pikovskaya and TSA for non-rhizobial isolates. The endophytes were then screened for various growth promoting traits like IAA production, Phosphate solubilization, Siderophore production, ACC utilization, Potassium solubilization and tolerance to NaCl concentrations. Total six endophytes, one rhizobium (HM2) and five non-rhizobial endophytes (RE6, BE13, ME3, HE5, HE7) were selected based on of plant growth promoting traits. Furthermore, the most promising non-rhizobial endophytes RE6 and BE13, compatible with Rhizobial isolate HM2 were Pseudomonas protegens and Bacillus boroniphilus using 16s rDNA sequencing. Both the isolates are non-pathogenic to humans and thus, are potential plant probiotics that can be used as biofertilizers.

Microbiome-Mediated Stress Resistance in Plants.

Plants are subjected to diverse biotic and abiotic stresses in life. These can induce changes in transcriptomics and metabolomics, resulting in changes to root and leaf exudates and, in turn, altering the plant-associated microbial community. Emerging evidence demonstrates that changes, especially the increased abundance of commensal microbes following stresses, can be beneficial for plant survival and act as a legacy, enhancing offspring fitness. However, outstanding questions remain regarding the microbial role in plant defense, many of which may now be answered utilizing a novel synthetic community approach. In this article, building on our current understanding on stress-induced changes in plant microbiomes, we propose a 'DefenseBiome' concept that informs the design and construction of beneficial microbial synthetic communities for improving fundamental understanding of plant-microbial interactions and the development of plant probiotics.

Current perspectives and applications in plant probiotics

As agriculture and food security face unprecedented challenges, emerging agricultural innovations and existing practices require ongoing examination in the context of sustainability. In this review, we focus on the use of probiotic microorganisms for improved plant production. As plants are enormously diverse, emphasis is placed on the fundamental sites of plant-microbe interactions regarding benefits and challenges encountered when altering the microbiome of these locations. The soil, the external plant epidermis, and internal plant tissue are considered in discussion regarding the type of plant probiotic application. Plant probiotics range from broader soil beneficial microorganisms (such as Trichoderma spp.) through to specialised epiphytes and endophytes (such as root nodule bacteria). As each site of interaction affects plant growth differently, potential outcomes from the introduction of these exogenous microorganisms are discussed with regard to plant productivity. Finally, recommendations regarding regulation and future use of plant probiotics are points of consideration throughout this review.