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AbstractUsing an engineered Escherichia coli to produce lipase and can easily achieve high-level expression. The investigation of biochemical processes during lipase fermentation, approached from a metabolomics perspective, will yield novel insights into the efficient secretion of recombinant proteins. In this study, the lipase batch fermentation was carried out first with enzyme activity of 36.83 U/mg cells. Then, differential metabolites and metabolic pathways were identified using an untargeted metabolomics approach through comparative analysis of various fermentation periods. In total, 574 metabolites were identified: 545 were up-regulated and 29 were down-regulated, mainly in 153 organic acids and derivatives, 160 organoheterocyclic compounds, 64 lipids and lipid-like molecules, and 58 organic oxygen compounds. Through metabolic pathways and network analysis, it could be found that tryptophan metabolism was of great significance to lipase production, which could affect the secretion and synthesis of recombinant protein. In addition, the promotion effects of cell growth by varying concentrations of indole acetic acid serve to validate the results obtained from tryptophan metabolism. This study offers valuable insights into metabolic regulation of engineered E. coli, indicating that its fermentation bioprocess can be systematically designed according to metabolomics findings to enhance recombinant protein production. [ABSTRACT FROM AUTHOR]

Owing to ineffective biological nitrogen (N) fixation, and imbalanced doses of N and potassium (K) fertilization, soybean productivity is declining under intensive cropping practices. This study aimed to find out the effectiveness of Trichoderma viride priming on soybean root growth promotion, and enhancement of soil-N and K uptakes under graded fertilization. Soybean seeds were treated with freshly prepared T. viride BHU-2953 talc. Root lignification, indole acetic acid (IAA) production, and activity of 1-aminocyclopropane-1-carboxylate deaminase (ACCD) were determined to observe root growth-promoting activities. A pot experiment was conducted to evaluate root volume, and soil exploration by roots, i.e., the potential volume of influence (PVI), uptakes of N and K, and different physiological attributes at different growth periods of soybean. Results revealed that biopriming enhanced the root lignification, IAA, and ACCD, assisting more soil volume exploration (PVI) for better N and K acquisitions. Biopriming increased the plant biomasses which ultimately, led to more seed yield than untreated soybeans, receiving even higher N-K doses. The PVI correlated well with root volume (r2 = 0.95; P < 0.01), explaining good soil-nutrient foraging by bioprimed soybeans. Hence, we conclude that T. viride priming can enhance the N and K uptakes in soybeans under graded soil fertilization. [ABSTRACT FROM AUTHOR]

• Lessertia frutescens is a medicinal plant that harbours many bacteria endophytes. • Endophytes of Lessertia frutescens have potential plant growth promoting attributes. • Two native Bacillus species are ideal candidates for bio-fertilization. Many endophytic bacteria have plant growth promoting attributes that could improve agricultural yield as well as resistance to various types of stress and disease. Detection of such attributes usually involves in vitro screening and the subsequent testing of the isolates on the plants for specific or combined effects on germination, seedling growth and yield. Despite many studies in this field, there is a knowledge gap on the influence of endophytes on early growth of certain economically important plants such as medicinal plants. In the present study, we evaluated the in vitro capabilities of bacterial endophytes isolated from Lessertia frutescens (L.) Goldblatt & J.C.Manning (syn. Sutherlandia frutescens (L.) W.T.Aiton) for plant growth promotion and their effect on initial seedling growth. Using a culture-dependent approach, plant samples of Lessertia frutes cens were screened for bacterial endophytes. The isolated bacterial endophytes were subsequently evaluated for their plant growth-promoting attributes along with their ability to produce hydrolytic enzymes. Molecular identification of selected endophytic bacteria based on the 16S rRNA genes of strains that tested negative in the hemolysis test was conducted. The two most promising isolates were evaluated for their ability to promote Lessertia frutescens seedling growth in a two-month pot trial study. The obtained results revealed that many of the bacterial endophytes had potential to promote plant growth. Specifically, 86 % of the endophytes possessed nitrogen-fixing, phosphate solubilizing, and IAA-producing abilities, while approximately 71 % were able to exhibit siderophore-producing capabilities. The endophytes exhibited significant production of essential hydrolytic enzymes, including amylase (86 %), gelatinase (86 %), protease (29 %), lipase (43 %), and D-nase (57 %). The two best isolates were identified as relatives of Bacillus spp. (Bacillus licheniformis BaDB06 and Bacillus velezensis strain SM-95). Their plant growth-promoting properties such as their ability to enhance plant height and their ability to be used as bio-agent were further confirmed in the pot trial study as they enhanced the growth of Lessertia frutescens seedlings compared to the control. This study provides insights into the functional roles of endophytic bacteria of Lessertia frutescens in seedling growth and their potential plant growth enhancement, highlighting their potential for sustainable agriculture and ecosystem management. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen deficiency in low organic matter soils significantly reduces crop yield and plant health. The effects of foliar applications of indole acetic acid (IAA), trehalose (TA), and nanoparticles-coated urea (NPCU) on the growth and physiological attributes of tomatoes in nitrogen-deficient soil are not well documented in the literature. This study aims to explore the influence of IAA, TA, and NPCU on tomato plants in nitrogen-deficient soil. Treatments included control, 2mM IAA, 0.1% TA, and 2mM IAA + 0.1% TA, applied with and without NPCU. Results showed that 2mM IAA + 0.1% TA with NPCU significantly improved shoot length (~ 30%), root length (~ 63%), plant fresh (~ 48%) and dry weight (~ 48%), number of leaves (~ 38%), and leaf area (~ 58%) compared to control (NPCU only). Additionally, significant improvements in chlorophyll content, total protein, and total soluble sugar, along with a decrease in antioxidant activity (POD, SOD, CAT, and APX), validated the effectiveness of 2mM IAA + 0.1% TA with NPCU. The combined application of 2mM IAA + 0.1% TA with NPCU can be recommended as an effective strategy to enhance tomato growth and yield in nitrogen-deficient soils. This approach can be integrated into current agricultural practices to improve crop resilience and productivity, especially in regions with poor soil fertility. To confirm the efficacy of 2mM IAA + 0.1% TA with NPCU in various crops and climatic conditions, additional field studies are required.

Abstract Background Microbial growth during plant tissue culture is a common problem that causes significant losses in the plant micro-propagation system. Most of these endophytic microbes have the ability to propagate through horizontal and vertical transmission. On the one hand, these microbes provide a rich source of several beneficial metabolites. Results The present study reports on the isolation of fungal species from different in vitro medicinal plants (i.e., Breynia disticha major, Breynia disticha, Duranta plumieri, Thymus vulgaris, Salvia officinalis, Rosmarinus officinalis, and Ocimum basilicum l) cultures. These species were tested for their indole acetic acid (IAA) production capability. The most effective species for IAA production was that isolated from Thymus vulgaris plant (11.16 µg/mL) followed by that isolated from sweet basil plant (8.78 µg/mL). On screening for maximum IAA productivity, medium, “MOS + tryptophan” was chosen that gave 18.02 μg/mL. The macroscopic, microscopic examination and the 18S rRNA sequence analysis indicated that the isolate that given code T4 was identified as Neopestalotiopsis aotearoa (T4). The production of IAA by N. aotearoa was statistically modeled using the Box-Behnken design and optimized for maximum level, reaching 63.13 µg/mL. Also, IAA extract was administered to sweet basil seeds in vitro to determine its effect on plant growth traits. All concentrations of IAA extract boosted germination parameters as compared to controls, and 100 ppm of IAA extract exhibited a significant growth promotion effect for all seed germination measurements. Conclusions The IAA produced from N. aotearoa (T4) demonstrated an essential role in the enhancement of sweet basil (Ocimum basilicum) growth, suggesting that it can be employed to promote the plant development while lowering the deleterious effect of using synthetic compounds in the environment.

The study of plant–microbe interactions is a rapidly growing research field, with increasing attention to the role of seed-borne microbial endophytes in protecting the plant during its development from abiotic and biotic stresses. Recent evidence suggests that seed microbiota is crucial in establishing the plant microbial community, affecting its composition and structure, and influencing plant physiology and ecology. For Theobroma cacao L., the diversity and composition of vertically transmitted microbes have yet to be addressed in detail. We explored the composition and diversity of seed-borne endophytes in cacao pods of commercial genotypes (ICS95, IMC67), recently liberated genotypes from AGROSAVIA (TCS01, TCS19), and landraces from Tumaco (Colombia) (AC9, ROS1, ROS2), to evaluate microbial vertical transmission and establishment in various tissues during plant development. We observed a higher abundance of Pseudomonas and Pantoea genera in the landraces and AGROSAVIA genotypes, while the commercial genotypes presented a higher number of bacteria species but in low abundance. In addition, all the genotypes and plant tissues showed a high percentage of fungi of the genus Penicillium. These results indicate that domestication in cacao has increased bacterial endophyte diversity but has reduced their abundance. We isolated some of these seed-borne endophytes to evaluate their potential as growth promoters and found that Bacillus, Pantoea, and Pseudomonas strains presented high production of indole acetic acid and ACC deaminase activity. Our results suggest that cacao domestication could lead to the loss of essential bacteria for seedling establishment and development. This study improves our understanding of the relationship and interaction between perennial plants and seed-borne microbiota. [ABSTRACT FROM AUTHOR]

Background: Microbial growth during plant tissue culture is a common problem that causes significant losses in the plant micro-propagation system. Most of these endophytic microbes have the ability to propagate through horizontal and vertical transmission. On the one hand, these microbes provide a rich source of several beneficial metabolites. Results: The present study reports on the isolation of fungal species from different in vitro medicinal plants (i.e., Breynia disticha major, Breynia disticha, Duranta plumieri, Thymus vulgaris, Salvia officinalis, Rosmarinus officinalis, and Ocimum basilicum l) cultures. These species were tested for their indole acetic acid (IAA) production capability. The most effective species for IAA production was that isolated from Thymus vulgaris plant (11.16 µg/mL) followed by that isolated from sweet basil plant (8.78 µg/mL). On screening for maximum IAA productivity, medium, "MOS + tryptophan" was chosen that gave 18.02 μg/mL. The macroscopic, microscopic examination and the 18S rRNA sequence analysis indicated that the isolate that given code T4 was identified as Neopestalotiopsis aotearoa (T4). The production of IAA by N. aotearoa was statistically modeled using the Box-Behnken design and optimized for maximum level, reaching 63.13 µg/mL. Also, IAA extract was administered to sweet basil seeds in vitro to determine its effect on plant growth traits. All concentrations of IAA extract boosted germination parameters as compared to controls, and 100 ppm of IAA extract exhibited a significant growth promotion effect for all seed germination measurements. Conclusions: The IAA produced from N. aotearoa (T4) demonstrated an essential role in the enhancement of sweet basil (Ocimum basilicum) growth, suggesting that it can be employed to promote the plant development while lowering the deleterious effect of using synthetic compounds in the environment. [ABSTRACT FROM AUTHOR]

The recent study aimed to develop and produce bio-fertilizer as a supplement to chemical fertilizers, with the goal to reduce their application. In this study, new Streptomyces species were introduced along with nitrogen-fixing bacteria to support the growth of Mung beans in Iraq. The experiment involved the application of five strains of Rhizobium, two strains of Streptomyces, and high indole acetic acid-producing Azospirillum spp4 and Azotobacter spp7. These bio-fertilizers were tested in a field using a complete randomized design at al-Tuwaitha research station in Baghdad.The results indicated that the bio-fertilizer containing Streptomyces and Azospirillum 4 had a significantly positive impact on the growth of Mung bean crops compared to using NPK 100% (conventional chemical fertilizer). The germination percentage reached 75%, with a plant height of 73 cm and 11 branches per plant. The number of legumes per plant was 44.66, with an average legume height of 3.56 cm. The weight of 100 seeds was 142 g, and the fresh weight and dry weight were recorded as 40.33 g and 35.33 g, respectively. Moreover, the study found no statistical difference when comparing the treatment of mung bean seeds with the mono-inoculum of Rhizobium isolated from Phasoleus nodules and Streptomyces Z. This suggests that the newly developed bio-fertilizer containing Streptomyces and Azospirillum 4 is a promising and viable option to enhance the growth and yield of Mung beans without relying heavily on imported chemical fertilizers.

Considering current global climate change, drought stress is regarded as a major problem negatively impacting the growth of soybeans, particularly at the critical stages R3 (early pod) and R5 (seed development). Microbial inoculation is regarded as an ecologically friendly and low-cost-effective strategy for helping soybean plants withstand drought stress. The present study aimed to isolate newly drought-tolerant bacteria from native soil and evaluated their potential for producing growth-promoting substances as well as understanding how these isolated bacteria along with arbuscular mycorrhizal fungi (AMF) could mitigate drought stress in soybean plants at critical growth stages in a field experiment. In this study, 30 Bradyrhizobium isolates and 30 rhizobacterial isolates were isolated from the soybean nodules and rhizosphere, respectively. Polyethylene glycol (PEG) 6000 was used for evaluating their tolerance to drought, and then the production of growth promotion substances was evaluated under both without/with PEG. The most effective isolates (DTB4 and DTR30) were identified genetically using 16S rRNA gene. A field experiment was conducted to study the impact of inoculation with DTB4 and DTR30 along with AMF (Glomus clarum, Funneliformis mosseae, and Gigaspora margarita) on the growth and yield of drought-stressed soybeans. Our results showed that the bioinoculant applications improved the growth traits (shoot length, root length, leaf area, and dry weight), chlorophyll content, nutrient content (N, P, and K), nodulation, and yield components (pods number, seeds weight, and grain yield) of soybean plants under drought stress (p ≤ 0.05). Moreover, proline contents were decreased due to the bioinoculant applications under drought when compared to uninoculated treatments. As well as the count of bacteria, mycorrhizal colonization indices, and the activity of soil enzymes (dehydrogenase and phosphatase) were enhanced in the soybean rhizosphere under drought stress. This study's findings imply that using a mixture of bioinoculants may help soybean plants withstand drought stress, particularly during critical growth stages, and that soybean growth, productivity, and soil microbial activity were improved under drought stress. [ABSTRACT FROM AUTHOR]

The focus of plant health management is shifting from synthetic chemicals to bio-agents, and endophytes are beneficial for this purpose. In the present study, we isolated eleven endophytic fungi from seven wild rice species. Independent treatment of endophytic fungi in rice showed significant improvements in plant growth, higher tillering and percent fertility, panicle number/hill and filled grain number in endophyte-inoculated plants compared to control plants. Growth promotion activities of two endophytes Curvularia lunata (NRRI EF-11) and Hypocreals sp. (NRRI EF-8) were recorded with increased rice yield. These isolates also exhibited higher plant growth promoting chemicals namely, Indole acetic acid (IAA) and Inorganic phosphate (IP) which was realised into better growth promotion in rice. The biocontrol efficacy of endophytic fungi was highest in NRRI EF-11among all isolates as indicated by inhibition of radial growth of pathogens by 76.98–77.06% and in NRRI EF-8 by 74.81–76.61%, which is due to higher production of prussic acid. Defense induction was confirmed by analyzing the expression of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) defense enzymes, where expression of CAT, POD and SOD increased by 19.44–25.86, 2.70–3.16, 11.14–12.95 Units g−1 in treated NRRI EF-11 plants and 18.39–25.84, 2.16–2.94, 10.96–12.62 Units g−1 in treated NRRI EF-8 plants, respectively. These two endophytes have the potentiality to manage crop health in a sustainable way. [ABSTRACT FROM AUTHOR]

Contamination of the environment due to speedup of anthropogenic activities has become a serious threat to modern humanity. Among the contaminants, the new emerging concern is the heavy metal (HM) contamination in the environment. Because the persistence and harmfulness of heavy metals affect the ecosystem and the health of plants, animals, and humans, they are the most toxic substances in the environment. Among them, Arsenic (As) emerged as major environmental constraint leading to enormous negative effects on the plant, animal, and human health. Even in minute quantity, As is known to cause various critical diseases in humans and toxicity in plants. Research was performed to observe the capability of plant growth–promoting strains of bacteria in enhancing Zea mays (L.) growth in arsenic polluted soil. Total 30 bacterial strains were isolated from the polluted soils, screened for plant growth promotion potential and arsenic tolerance. Eighteen isolates showed resistance to different levels of sodium arsenate (ranging from 0 to 50 mM) in agar plate using LB media. Of 18 isolates, 83.3% produced IAA, methyl red, and hydrogen cyanide; 55.5% exhibited catalase activity; 61.1% showed siderophore production; 88.8% showed phosphate solubilization; and 44.4% showed oxidase, Voges proskauer activity, and KOH solubility. The most efficient isolates SR3, SD5, and MD3 with significant arsenic tolerance and plant growth–promoting (PGP) activity were examined via sequencing of amplified 16S rRNA gene. Isolates of bacteria, i.e., SR3, SD5, and MD3, showing multiple PGP-traits were identified as Bacillus pumilus (NCBI accession number: OR459628), Paenibacillus faecalis (NCBI accession number: OR461560), and Pseudochrobactrum asaccharolyticum (NCBI accession number: OR458922), respectively. Maize seeds treated with these PGPR strains were grown in pots contaminated with 50 ppm and 100 ppm sodium arsenate. Compared to untreated arsenic stressed plants, bacterial inoculation P. asaccharolyticum (MD3) resulted 20.54%, 18.55%, 33.45%, 45.08%, and 48.55% improvement of photosynthetic pigments (carotenoid content, chlorophyll content, stomatal conductance (gs), substomatal CO2, and photosynthetic rate), respectively. Principal component analysis explained that first two components were more than 96% of the variability for each tested parameter. The results indicate that in comparison to other isolates, P. asaccharolyticum isolate can be used as efficient agent for improving maize growth under arsenic polluted soil. [ABSTRACT FROM AUTHOR]

Endophytic fungi colonize the inner tissues and provide direct and indirect benefits to plants. Although Mongolia is rich in medicinal plants, due to climatic and anthropogenic reasons, the resources are being depleted, and many species are under threat of gradual extinction, while the endophytic fungi of Mongolian plants are largely unknown. In this study, a total of 24 culturable endophytic fungal strains were isolated from Cynomorium songaricum (Rupr.), a medicinal and vulnerable plant species of Mongolia. Based on the morphological characteristics and the sequences of the rDNA internal transcribed spacer (ITS) region, the isolates were identified into six genera: Fusarium (8), Clonostachys (7), Penicillium (6), Alternaria (1), Aspergillus (1), and Madurella (1). The antimicrobial activity was assessed by the agar-diffusion method, revealing that 15 strains were able to inhibit the growth of at least one of the test organisms. Among them, 1 strain showed inhibitory activity against Escherichia coli, 12 against Bacillus subtilis, 13 against Staphylococcus aureus, and 8 against Aspergillus niger, respectively. The ability to solubilize complex phosphorus and zinc minerals was observed in 3 and 21 strains, respectively, and the production of indole-3-acetic acid (IAA) was detected in nine strains in the presence of tryptophan. Our study provides the first insight into the cultivable endophytic fungal composition of C. songaricum, parasitizing the roots of Nitraria sibirica growing in the Gobi Desert of Mongolia. The resulting fungi, which have antimicrobial and plant growth-promoting properties, were preserved in the national culture collection and can be used to further exploit their biotechnological potential, as well as for the propagation of endangered and vulnerable medicinal plants. [ABSTRACT FROM AUTHOR]

Insights into plant and bacterial associations, along with their genome mining, have paved the way for the improvement of the agriculture sector. Initially, 69 morphologically different bacterial strains were isolated from 6 different extreme environment samples. For in vitro screening of plant growth-promoting bacteria, auxin, hydrogen cyanide, and antibiotic production along with phosphate solubilization potential was estimated. Only 15 strains exhibited noteworthy production of plant growth-promoting compounds. Ochrobactrum ciceri CS-10 fostered Triticum aestivum and Zea mays seedling root growth remarkably (104.12 and 159%, respectively), while Bacillus australimaris TP-10 significantly increased the number of leaves in T. aestivum (166.66%) and Z. mays (133.33%) seedlings. These strains also boosted seedling biochemical traits, like indole acetic acid, peroxidase, and soluble protein content. Particularly, O. ciceri elevated peroxidase content greatly in T. aestivum (249.7%) and Z. mays (260.5%). Scanning electron micrographs of inoculated roots revealed the aggregation of cells at the roots of Z. mays, whereas single cells/micro-colonies were observed on T. aestivum roots. For in silico analysis, AntiSMASH was used for genome mining of the environmental Ochrobactrum sp. and B. australimaris reference genome. This genome mining unveiled diverse gene clusters encoding; terpenes, beta-lactones, acyl-amino-acids, aryl polyenes, lanthipeptide, and siderophores, etc. Two common biosynthetic gene clusters (terpenes and beta-lactones) were identified in these strains, which can act as plant growth promoters. This symbiotic plant–bacteria relationship has promising ecological and economic implications, offering avenues for beneficial applications.

BackgroundTryptophan (Trp) metabolites from intestinal bacteria (indole, indole acetic acid [IAA] and indole propionic acid [IPA]), and the Trp metabolite kynurenine (Kyn) from the indoleamine 2,3-dioxygenase (IDO) pathway, are aryl hydrocarbon receptor (AhR) agonists and thus, can regulate immune activity via the AhR pathway. We hypothesized that plasma concentrations of these metabolites would be associated with markers of immune activation in a cohort of healthy adults in a manner consistent with AhR-mediated immune-regulation. We also hypothesized that the plasma Kyn/Trp ratio, a marker of IDO activity, would be associated with immune markers reflecting IDO activation in innate immune cells. Finally, we hypothesized that some intestinal bacteria would be associated with plasma indole, IPA and IAA, and that these bacteria themselves would be associated with immune markers.MethodsA novel set of 88 immune markers, and plasma Trp metabolites, were measured in 362 healthy adults. Bacterial taxa from stool were identified by 16S rRNA gene analysis. Multiple linear regression analysis was used to identify significant associations with immune markers.ResultsThe sum of indole and IAA was positively associated with natural killer T-cells levels. Kyn and Kyn/Trp were positively associated with neopterin and IP-10, markers of type 1 immunity, and TNF-α and C-reactive protein (CRP), markers of the acute phase response, and the regulatory cytokine IL-10. Three bacteria negatively associated with Trp metabolites were associated with markers of immune activation: the family Lachnospiraceae with higher lymphocyte counts but lower level of activated CD4 T-cells, the genus Dorea with higher production of IFN-γ by T-cells in PBMC cultures, and the genus Ruminococcus with higher production IL-6 in PBMC cultures stimulated with bacterial lipopolysaccharide (LPS).ConclusionsIn this cohort of healthy adults bacterial Trp metabolites were not strongly associated with immune markers. Conversely, the Kyn/Trp ratio was strongly associated with markers of systemic inflammation and the acute phase response, consistent with IDO activation in innate immune cells. Finally, commensal bacteria associated with lower plasma (and perhaps intestinal) levels of bacterial Trp metabolites were associated with greater immune activation, possibly reflecting decreased regulatory immune activity related to lower intestinal levels of bacterial indole metabolites.

This study was conducted to evaluate the role of certain abiotic and biotic inducers in inducing cucumber resistance against the root-knot nematode, Meloidogyne incognita, under greenhouse conditions. The abiotic inducers comprised acetylsalicylic acid (ASA) and Indole acetic acid (IAA) while the biotic inducer was Bacillus pumilus (B.P.). The results revealed that, among all treatments, the double combinations of IAA before B.P. by 3 days as well as ASA before B.P.by 3 days showed the best treatments to increase plant resistance against Meloidogyne incognita infection and improved plant vigor based on fresh and dry weights of shoots and roots compared to using them individually and control inoculated non-treated plants. A generalized increase was observed in the peroxidase activities and in proline amino acids and total phenols due to the application of the investigated inducer. The degree of increase differed according to treatment and biochemical aspects. The overproduction of these biochemical aspects may play a part in the induction of plant defenses against nematode infestation. In conclusion, the development of safety control measures by inducing plant resistance will protect a wide range of plant crops against nematode threats and can be used in integrated pest management programs. [ABSTRACT FROM AUTHOR]

Indole Acetic Acid (IAA), a phytohormone, has been considered as the most important native auxin. The Amla (Phyllanthus emblica Linn.) serve as an abundance of IAA-producing sources fungus and produce significant quantities of IAA in tryptophan-added medium. Different concentration of L-tryptophan between 1, 2 and 5 mg/ml were chosen for the IAA production. The study shows that the corresponding L-tryptophan concentration was associated with a progressive rise in IAA generation. The impact on IAA production was anticipated to last up to 10 days, with the maximum IAA production being shown in an incubation period of 15 days. Four isolates in total were found to be IAA-producing strains, two of these produced IAA through medium components, and physical conditions were tuned for IAA production. The Amla stem and leaf tissues have the strongest growth-promoting effect in Aspergillus ustus (72 g/20 ml) among the isolates. The positive effects on crop development and yield are attributed to the presence of such growth-promoting fungus. [ABSTRACT FROM AUTHOR]

The present study was conducted to determine the effect of osmotic stress on the plant growth hormone production by six osmotolerant plant growth promoting bacterial strains. These strains originated from the phytomicrobiome of chilli cultivated in the drought prone areas of Andhra Pradesh. They possessed multiple plant growth promotion traits including the ability to produce a variety of plant growth hormones. The effect of osmotic stress on the plant growth hormone production was determined by High Performance Liquid Chromatography (HPLC) under normal and in vitro osmotic stress conditions using 25% Poly Ethylene Glycol (PEG) 8000. In general, it was observed that osmotic stress impacted the plant growth hormone production of the isolates, but nevertheless plant hormones were detected in all the bacterial strains. An exception to this was the cytokinin molecule zeatin riboside, which was produced at higher levels by five of the six bacterial isolates under osmotic stressed conditions. [ABSTRACT FROM AUTHOR]

The aims of the presented study are to compare submerged, static, and solid-state fermentation in the production of gibberellic acid (GA3), indole acetic acid (IAA), and abscisic acid (ABA) by Inonotus hispidus, to optimize with a statistical approach, and to determine the kinetic parameters under flask and reactor conditions. The maximum concentrations of GA3, (2478.85 ± 68.53 mg/L), ABA, (273.26 ± 6.17 mg/L) and IAA (30.67 ± 0.19 mg/L) were obtained in submerged conditions. After optimization, these values reached 2998.85 ± 28.85, 339.47 ± 5.50, and 34.56 ± 0.25 mg/L, respectively. Immobilization of fungal cells on synthetic fiber, polyurethane foam, and alginate beads resulted in an increase in plant growth regulators (PGR) production by 5.53%− 5.79% under optimized conditions. At the reactor scale, a significant increase was observed for GA3 concentration, 5441.54 mg/L, which was 2.14 and 1.45 times higher than non-optimized and optimized conditions in the flask scale, respectively. The maximum values for ABA and IAA were 390.39 and 44.79 mg/L, respectively. Although the specific growth rate (µ) decreases relatively from non-optimized flask conditions to optimized reactor conditions, it was observed that the PGR amounts produced per liter medium (rp) and per gram biomass (Qp) increased significantly. This is the first report on the synthesis of PGR by Inonotus hispidus which could be crucial for sustainable agriculture. [ABSTRACT FROM AUTHOR]

Introduction: In recent years, the global demand for agricultural products has increased. One of the methods to increase crop yield, along with the decreased use of chemical fertilizers, is to apply biofertilizers. The purpose of the present study is to produce a lowcost formulation of biofertilizer synthesized from Pseudomonas putida PT. Materials and Methods: Various plant growth-promoting characteristics of P. putida PT such as P-solubilization, N- fixation, and Indole-3-acetic acid (IAA) production were assayed using Pikovskaya’s (PVK) medium, Salkowski reagent, and N-free medium, respectively. The effects of low-cost substrates to prepare inexpensive biofertilizers were analyzed by measuring the bacterial dry weight. The biofertilizer was prepared by the seed immersion method, and pot experiments were performed by using prepared biofertilizer from P. putida PT and nutritional supplements. The effect of various treatments on the growth and development of Ocimum basilicum (basil) was evaluated by measuring the root and shoot lengths, fresh weight of aerial parts, and dry weight of aerial parts. Results: P. putida PT exhibited capability of P-solubilization (OD430nm=1.1), IAA production (OD530nm=0.86), and N-fixation. The highest bacterial biomass was observed in the presence of cheese whey, followed by 2.5 °Bx molasses plus (NH4)2SO4. The prepared biofertilizer from this bacterium increased significantly plant growth, especially when it was used along with insoluble phosphate. The addition of biofertilizer and insoluble phosphate increased shoot length, fresh weight of aerial parts, and dry weight of aerial parts by 41.6%, 83.7%, and 25% compared to the untreated control plants, respectively. Discussion and Conclusion: The results of the study signify that P. putida PT can be used to prepare a cost-effective biofertilizer for the enhancement of plant growth. [ABSTRACT FROM AUTHOR]

Intestinal peristalsis is vital for gastrointestinal physiology and host homeostasis and is frequently dysregulated in intestinal disorders. Gut microbiota can regulate gut motility, especially through the tryptophan metabolism pathway. However, the role of indoles as microbial tryptophan metabolites in colonic function requires further exploration. Here, we show that the delivery of indole acetic acid (IAA) targeting the colon can improve gut motility by activating the aryl hydrocarbon receptor (AHR). To achieve colon-targeted delivery, Eudragit S-100 (ES) and chitosan (CS) were used as drug carriers. After optimisation, IAA-loaded ES-coated CS nanoparticles exhibited an encapsulation efficiency of 83% and a drug-loading capacity of 16%. These nanoparticles exhibited pH-dependent characteristics and remained stable in acidic conditions and the upper intestine. In simulated intestinal fluid (pH 7.4) and colonic lumen, considerable amounts of IAA were released after approximately 4 h. Compared with free IAA, the nanoparticles exerted enhanced therapeutic effects on gut movement disorders induced by loperamide. The efficacy of IAA treatment was attributable to the activation of the AHR signalling pathway and increased levels of AHR agonists. Furthermore, the oral administration of IAA-loaded nanoparticles promoted serotonin secretion and maintained the intestinal barrier function. The experimental outcomes demonstrate the efficiency of the proposed colon-specific delivery system and highlight the role of IAA, produced by gut microbiota metabolism, in regulating gut peristalsis through AHR activation. [ABSTRACT FROM AUTHOR]

Considering current global climate change, drought stress is regarded as a major problem negatively impacting the growth of soybeans, particularly at the critical stages R3 (early pod) and R5 (seed development). Microbial inoculation is regarded as an ecologically friendly and low-cost-effective strategy for helping soybean plants withstand drought stress. The present study aimed to isolate newly drought-tolerant bacteria from native soil and evaluated their potential for producing growth-promoting substances as well as understanding how these isolated bacteria along with arbuscular mycorrhizal fungi (AMF) could mitigate drought stress in soybean plants at critical growth stages in a field experiment. In this study, 30 Bradyrhizobium isolates and 30 rhizobacterial isolates were isolated from the soybean nodules and rhizosphere, respectively. Polyethylene glycol (PEG) 6000 was used for evaluating their tolerance to drought, and then the production of growth promotion substances was evaluated under both without/with PEG. The most effective isolates (DTB4 and DTR30) were identified genetically using 16S rRNA gene. A field experiment was conducted to study the impact of inoculation with DTB4 and DTR30 along with AMF (Glomus clarum, Funneliformis mosseae, and Gigaspora margarita) on the growth and yield of drought-stressed soybeans. Our results showed that the bioinoculant applications improved the growth traits (shoot length, root length, leaf area, and dry weight), chlorophyll content, nutrient content (N, P, and K), nodulation, and yield components (pods number, seeds weight, and grain yield) of soybean plants under drought stress (p ≤ 0.05). Moreover, proline contents were decreased due to the bioinoculant applications under drought when compared to uninoculated treatments. As well as the count of bacteria, mycorrhizal colonization indices, and the activity of soil enzymes (dehydrogenase and phosphatase) were enhanced in the soybean rhizosphere under drought stress. This study’s findings imply that using a mixture of bioinoculants may help soybean plants withstand drought stress, particularly during critical growth stages, and that soybean growth, productivity, and soil microbial activity were improved under drought stress.

A Gram-negative, aerobic, short rod-shaped, non-motile, non-spore forming bacterium, designated strain GCR5T, was isolated from soil of paddy field. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain GCR5T belongs to the genus Planobacterium and is related to Planobacterium taklimakanense NCTC 13490 T (96.1%, 16S rRNA gene sequence similarity). Colonies on R2A were white but they turn into bright yellow after exponential growth. They produce carotenoid pigment after 5–6 days of incubation, before that carotenoid pigment was not found. The major isoprenoid quinone was MK-6, and major cellular fatty acids were iso-C15:0, anteiso-C15:0 and iso-C17:0 3OH. Polar lipids include phosphatidylethanolamine, three unidentified phosphoglycolipids, three unidentified glycolipids, one unidentified aminophosphoglycolipid and five unidentified polar lipids. The strain GCR5T was found to have a 2,106,200 bp linear genome with G + C content of 43.7%. The ANI, dDDH and AAI values between the strain GCR5T and the type strains of phylogenetically related species were 60.2–71.1%, 19–24.3%, and 60.2–69.6%, respectively. The strain designated GCR5T produced indole acetic acid (IAA) in the presence of tryptophan only, and auxin responsive genes and tryptophan biosynthesis genes were found in its genome. Based on its polyphasic characteristics, strain GCR5T represents a novel species within the genus Planobacterium, for which the name Planobacterium oryzisoli sp. nov. was proposed. The type strain is GCR5T (= KCTC 82713 T = TISTR 2996 T = TBRC 15746 T). Repositories: The draft genome and 16S rRNA gene sequences of strain GCR5T have been deposited at GenBank/EMBL/DDBJ under accession numbers JADKYY000000000 and MN955408, respectively. [ABSTRACT FROM AUTHOR]

Background and Objectives: Salinity is a serious problem and one of the main factors in reducing agricultural productivity worldwide. The use of microorganisms to improve plant growth in low quality soil is a potential solution to address this problem. The salinity resistant microbiome improves the health of the salinity affected soils, maintains ecological functions and enhances plant growth. Salt tolerant plant growth promoting rhizobacteria (ST-PGPR) are able to adjust the salinity stress adverse conditions for their symbiotic plants through several mechanisms. This study aimed to isolation, identification and investigation the characteristics of salt tolerant-plant growth promoting rhizobacteria from the rhizosphere of halophyte plants. Materials and Methods: Salinity tolerant plant growth promoting bacteria were isolated from the rhizosphere of native halophyte plants collected from the north of Iran. Bacterial isolates were selected according to their ability to growth in 2 M sodium chloride and traits of the motility, inorganic phosphate solubilization ability in PKV-Agar medium using phosphate solubilization index calculation, and siderophore production capacity in CAS-agar medium by calculating of its production index. Then, the top 10 isolates were selected and the ability of nitrogen fixation in Burk's medium, potassium dissolution in Aleksandrov's medium by using potassium solubilization index, as well as, the production of intrinsic IAA and the tryptophan-dependent IAA were investigated. Finally, molecular identification of selected bacterial isolates was performed based on 16S rDNA gene sequencing. Results: Four genera of Bacillus, Klebsiella, Proteus and Halomonas were identified after 16S rDNA gene sequencing. The most of isolates belonged to the genus Bacillus. Species belonging to Klebsiella and Halomonas genera had the highest salt tolerance. Klebsiella genus showed phosphorus and potassium solubilizing ability more than other isolates. The highest amount of siderophore production was observed in the isolate belonging to Proteus genus. All isolates were able to fix nitrogen. Among the studied isolates, Bacillus isolates had the highest rate of intrinsic IAA, and the tryptophan-dependent IAA production in B. licheniformis was higher than other isolates. Conclusion: Isolation of wide range of salt-tolerant bacteria with favorable characteristics from the rhizosphere of halophyte plants indicates the microbial richness potential of this area, which provides the possibility of finding useful microorganisms that promote plant growth and reduce the adverse effects of stress in plants. [ABSTRACT FROM AUTHOR]

The aims of the this study are to select the best cultivation type for plant growth regulator (PGR) production, to optimize PGR production with statistical experimental design, and to calculate bioprocess parameters and yield factors during PGR production by P. eryngii in flask and reactor scales. Submerged fermentation was the best cultivation type with 4438.67 ± 37.14, 436.95 ± 27.31, and 54.32 ± 3.21 mg/L of GA3, ABA, and IAA production values, respectively. The Plackett–Burman and Box–Behnken designs were used to determine effective culture parameters and interactive effects of the selected culture parameters on PGR production by Pleurotus eryngii under submerged fermentation. The statistical model is valid for predicting PGR production by P. eryngii. After these studies, maximum PGR production (7926.17 ± 334.09, 634.92 ± 12.15, and 55.41 ± 4.38 mg/L for GA3, ABA, and IAA, respectively) was reached on the 18th day of fermentation under optimized conditions. The optimum formula was 50 g/L fructose, 3 g/L NaNO3, and 1.5 g/L KH2PO4, 1 mg/L thiamine, incubation temperature 25 °C, initial medium pH 7.0, and an agitation speed of 150 rpm. The kinetics of PGR production was investigated in batch cultivation under 3-L stirred tank reactor conditions. Concentrations of GA3, ABA, and IAA of 10,545.00 ± 527.25, 872.32 ± 21.81, and 60.48 ± 3.48 mg/L were obtained at the reactor scale which were 4.1, 3.4, and 2.3 times higher than the initial screening values. The specific growth rate (µ), the volumetric (rp) and specific (Qp) PGR production rates, 486.11 mg/L/day and 107.43 mg/g biomass/day for GA3, confirmed the successful transfer of optimized conditions to the reactor scale. In the presented study, PGR production of P. eryngii is reported for the first time. [ABSTRACT FROM AUTHOR]

In order to investigate the potential of Indole Acetic Acid (IAA) for affecting yield contributing factors and Nitrate Reductase Activity, an experiment was conducted on four Vigna mungo genotypes. The four mash bean genotypes, 80, 88, 97, and ES-1, were examined against Indole Acetic Acid concentrations of 25, 50, 75, 10, 12, and 150.0 mgL-1. Plants were grown in pots which were randomly placed in the Botanical garden of Bahauddin Zakariya University, Multan. Pakistan. Four replicates of each treatment were developed and evaluated. Aforementioned amounts of Indole Acetic Acid were sprayed thrice, with intervals of ten days each. Ist spray was conducted at twenty days after germination. Nitrate Reductase Activity, grains number fruit-1, legumes number plant-1, and plant total yield were the traits chosen for study. After ten days of completion of three sprays of Indole Acetic Acid, Nitrate Reductase Activity (NRA) in the leaves was evaluated, and yield plant-1 and its contributing factors were noted when the crop reached at its physiological maturity. Typically, an exponential increase in the number of grains, legume per plant, total yield, and Nitrate Reductase Activity (NRA) was seen as Indole Acetic Acid concentration increased from 75.0 to 125.0 mgL-1. By using a statistical technique, it was found that the responses of different genotypes to Indole Acetic Acid concentrations varied. MASH 97 was proved to be the most influenced in term of total yield plant-1, the number of grains plants-1, and the Nitrate Reductase Activity (NRA). While, MASH ES-1 performance lagged behind all other genotypes. [ABSTRACT FROM AUTHOR]

Quorum sensing (QS) enables bacteria to organize gene expression programs, thereby coordinating collective behaviors. It involves the production, release, and population-wide detection of extracellular signaling molecules. The cellular processes regulated by QS in bacteria are diverse and may be used in mutualistic coordination or in response to changing environmental conditions. Here, we focused on the influence of the QS-dependent genes of our model bacterial strain Serratia fonticola GS2 on potential plant growth promoting (PGP) activities including indole-3-acetic acid (IAA) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and biofilm formation. Based on genomic and phenotypic experimental data we identified and investigated the function of QS genes in the genome of the model strain. Our gene deletion study confirmed the biological functionality of the QS auto-inducer (gloI) and receptor (gloR) on potential PGP activities of GS2. A transcriptomic approach was also undertaken to understand the role of QS genes in regulation of genes primarily involved in PGP activities (IAA, ACC deaminase activity, and biofilm formation). Both transcriptomic and phenotypic data revealed that the QS-deletion mutants had considerably less PGP activities, as compared to the wild type. In addition, in vivo plant experiments showed that plants treated with GS2 had significantly higher growth rates than plants treated with the QS-deletion mutants. Overall, our results showed how QS-dependent genes regulate the potential PGP activities of GS2. This information may be helpful in understanding the relationship between QS-dependent genes and the PGP activity of bacteria, which aid in the production of practical bio-fertilizers for plant growth promotion.

Orobanche crenata parasitism on lentil ( Lens culinaris Medik) is one of the most destructive factors for this crop in Morocco. Field and pot assays were performed to study the mitigation of O. crenata stress on two lentil genotypes, Bakria (partially resistant to O. crenata) and Zaaria (susceptible), using salicylic acid (SA) and indole acetic acid (IAA). These two hormones were applied separately at concentrations of 1 mM and 0.09 mM, respectively, using seed pre-treatment and/or foliar spray methods. SA and IAA seed pre-treatment for the susceptible genotype Zaaria and foliar spray for the resistant genotype Bakria gave the best control of O. crenata under field and controlled conditions. This control reached ~91% in Zaaria and 83% in Bakria and was sometimes accompanied by an increase in plant growth and seed yield compared to the untreated plants. Biochemical assays showed that SA and IAA reduced O. crenata infestation in lentil through induction of systemic acquired resistance characterized by increasing activities of phenol metabolizing enzymes (phenylalanine ammonia-lyase, peroxidase, and polyphenol oxidase) implicated in natural defense systems of plants. Treatment of plants with SA or IAA could be an alternative strategy of crop protection with more satisfactory preservation of the environment.

Nitrogen-fixing bacteria (NFB) play a significant role in saline soil ecosystems. However, little is known about the correlation between NFB application on growth and yield components of rice plants on saline soils. Exploration and experimental methods were performed to obtain the potential of NFB from a rice field in saline soil and reinoculated in a pot experiment. The experiment was arranged as a randomised block design consisting of 8 treatments, namely inoculation application (control and seed treatments with 20 g inoculant/kg of seed) combined with soil application dosage (0, 500, 1 000 and 1 500 g/ha). The results showed that grain yield increased by 43.8-130.6% with seed treatment of 20 g inoculant/kg of seed combined with soil application 500-1 500 g inoculant/ha. Rice yield was affected by multiple variables NFB population, plant height, number of tillers, and grain straw ratio (R2 = 0.926). Path analysis findings showed that the greatest effective contribution (45.45%) yield of rice in saline soil was contributed NFB population. This finding concludes that the application of NFB inoculants as seed treatments and soil applications can serve as an effective as well as the environmentally friendly microbial-based strategy of rice cultivation on saline soil ecosystems.

Potato virus Y (PVY) is a deadly environmental constraint that damages productivity of potato (Solanum tuberosum) around the globe. One of the major challenges is to develop resistance against PVY. Emerging clustered regularly short palindromic repeat (CRISPR)/Cas systems have the potential to develop resistance against PVY. In the current research, CRISPR-Cas13 has been exploited to target multiple strains of PVYN, PVYO, and PVYNTN. Multiple genes PI, HC-Pro, P3, Cl1, Cl2, and VPg genes of PVY were targeted by CRISPR/Cas13a. Multiplex gRNA cassettes were developed on the conserved regions of the PVY-genes. Three independent CRISPR/Cas13 transgenic potato lines were developed by applying an optimized concentration of trans-ribo zeatin and indole acetic acid at callus development, rooting, and shooting growth stages. The level of resistance in transgenic plants was confirmed through double-antibody sandwich enzyme-linked immunosorbent assay and real-time quantitative PCR. Our results have shown that efficiency of PVY inhibition was positively correlated with the Cas13a/sgRNA expression. Finding provides the specific functionality of Cas13 with specific gRNA cassette and engineering the potential resistance in potato crop against multiple strains of PVY.

Abstract Background Early blight (EB), caused by Alternaria solani, is one of the alarming diseases that restrict tomato production globally. Existing cultural practices and fungicide applications are not enough to control early blight diseases. Therefore, the study aimed to isolate, identify, and characterize an endophytic Streptomyces exhibiting the potential to control early blight in tomato and also promote plant growth. Results From a Citrus jambhiri leaf, an endophytic Streptomyces sp. with antagonistic activity against Alternaria solani, Colletotrichum acutatum, Cladosporium herbarum, Alternaria brassicicola, Alternaria sp., Fusarium oxysporum and Fusarium sp. was isolated. It was identified as a Streptomyces sp. through 16S ribosomal DNA sequence analysis and designated as SP5. It also produced indole acetic acid which was confirmed by Salkowski reagent assay, TLC and HPLC analysis. Treatment of pathogen infected plants with Streptomyces sp. SP5 antagonists (culture cells/culture supernatant/solvent extract/ acetone precipitates) decreased the early blight disease incidence and significantly increased the various agronomic traits. Conclusion The present study concluded that Streptomyces sp. SP5 possessed antifungal activity against different fungal phytopathogens and had significant potential to control early blight disease and promote plant growth.

Climate changes and poor soil nutrient profiles in sub-tropics are determinant factors to estimate crop productivity. This study aims to evaluate the impact of phytohormones, e.g., indole acetic acid (IAA) and gibberellic acid (GA3), on mung bean yield, seed nutritional profile, and soil N availability in the sub-tropical region of Pakistan. The mung bean plants were treated with three levels (0, 30, and 60 mg L−1) of IAA and GA3 individually and/or in combination using a hydraulic sprayer. The amendments were applied in the flowering stage (approximately 25 days after germination) in a randomized complete block design. The results revealed that the 60 mg L−1 concentration of IAA and GA3 led to significant changes in the growth and yield traits compared to non-treated plants. For example, GA3 positively influenced the biological yield (35.0%), total carbohydrate (7.0%), protein (16.0%), and nitrogen (14.0%) contents in mung bean seeds, compared to the control (CK). Additionally, the combined foliar treatment of IAA and GA3 (IAA2 + GA2) displayed a much stronger influence on yield attributes, such as the number of pods by 66.0%, pods' weights by 142.0%, and seed yield by 106.5%, compared with the CK. Mung bean plants showed a significant improvement in leaf photosynthetic pigments under a higher level (60 mg L−1) of sole and combined treatments of IAA and GA3. Moreover, except abscisic acid, the endogenous concentration of IAA, GA3, and zeatin was enhanced by 193.0%, 67.0%, and 175.0% after the combined application of IAA and GA3 (IAA2 + GA2) compared to the CK treatment. In addition, soil N availability was increased by 72.8% under the IAA2 treatment and 61.5% under IAA2 + GA2, respectively, compared with the control plot. It was concluded that the combined treatment of IAA and GA3 (IAA2 + GA2) followed by the sole application of GA3 and IAA at a 60 mg L−1 concentration were most effective treatments to improve the morpho-physiology and nutrient profile of mung beans; however, the underlying molecular mechanisms need to be explored further. [ABSTRACT FROM AUTHOR]

Bacteria that enhance plant growth and development and are found in the vicinity of roots are referred to as plant growth-promoting rhizobacteria. Some beneficial bacteria help plant tolerance to many hazardous chemical elements. In this context, Cupriavidus basilensis , Novosphingobium humi , Bacillus zanthoxyli , Bacillus sp., Paenibacillus alvei , Ancylobacter aquaticus and Ralstonia syzygii metal-tolerant rhizospheric bacteria were isolated from rhizospheric soil associated with Bacopa monnieri. The beneficial effects of rhizospheric bacteria on B. monnieri plant physiology and biochemical responses were investigated under pot conditions at two levels (100 μM and 500 μM) of CuSO4 or FeCl3. N. humi , A. aquaticus and R. syzygii bacterial strains were associated with significantly increased height and biomass under normal and stress conditions. An assay for indole acetic acid in isolated rhizospheric bacteria found differential secretion except Bacillus zanthoxyli. Bacoside A is a major phytocompound in B. monnieri with medicinal value; maximum induction was observed in the R. syzygii treatment. High concentration of copper and iron salts negatively influenced height, biomass and photosynthetic pigments; however N. humi , A. aquaticus , Bacilllus sp. and R. syzygii beneficial bacterial helped plants under stress conditions. Moreover, a significant enhancement in chlorophyll a and b was noticed in C. basilensis , B. zanthoxyli , Bacilllus sp., P. alvei and R. syzygii treatments, without much influence on carotenoid levels. Therefore, the present study emphasises the importance of isolating plant growth-promoting rhizobacteria for use in bacopa plants exposed to metals such as copper and iron in soil. Beneficial rhizospheric bacteria are essential for plant growth and development and help under stressful conditions. Owing to industrial effluent and application of synthetic fertilisers, the concentration of heavy metal salts is increasing in soil, and this negatively influences plant growth and production. In this research, we isolated bacteria contributing to resistance to heavy metals (copper and iron) from rhizospheric soil associated with Bacopa monnieri. We studied their importance for plant growth and secondary metabolite synthesis under salt stress in pot experiments. [ABSTRACT FROM AUTHOR]

One of the most restricting macronutrients for crop yield worldwide is phosphorus, which is often less than 1% of the total amount contained in soils. To promote its bioavailability, there are microorganisms considered vital that can solubilize and mineralize their pools in soils. In the current study, we assessed the potential of phosphate-solubilizing bacteria (PSB), isolated from the olive tree rhizosphere grown on phosphate sludge, to solubilize phosphate, promote plant growth, and tolerate abiotic stresses. Based on 16S rRNA gene sequencing, twenty-four PSB strains were identified and retained for in vitro analysis. According to the results, all the strains were able to solubilize the Moroccan rock phosphate, with soluble phosphate concentrations ranged from 5.34 µg/mL to 227 µg/mL. Furthermore, the majority of the strains are thermo-tolerant and halotolerant. Nonetheless, only five strains produced indole acetic acid. Regarding biocontrol potentialities, several PSB strains were characterized by producing hydrogen cyanide and hydrolytic enzymes (cellulase, and chitinase), of which three strains identified as Pseudomonas moraviensis, Bacillus cereus, and Bacillus aryabhattai, with a remarkable multi-trait combination were selected for antagonism and co-inoculation tests. The findings revealed that these PSB strains significantly inhibited Fusarium oxysporum (17.65%–62.35%) and Verticillium dahliae (52.35%–66.87%) and promoted common bean growth. The consortium of the three strains showed the best results by significantly increasing both plant height and tap root length and dry biomass compared to individual inoculation. The PSB selected from the olive tree rhizosphere growing on phosphate sludge have the potential to be useful as biofertilizer and biocontrol agents for attaining sustainable food crop production. [ABSTRACT FROM AUTHOR]

High rates of fluorosis were reported worldwide as a result of human consumption of water with fluoride contents. Adjusting fluoride concentration in water as recommended by the World Health Organization (<1.5 mg L−1) is a concern and it needs to be conducted through inexpensive, but efficient techniques, such as phytoremediation. The application of phytohormones was investigated as a strategy to improve this process. Thus, the main goal of this research was to evaluate the effect of exogenous auxin and gibberellin on the tropical duckweed Eichhornia crassipes performance for fluoride phytoremediation. Definitive screening and central composite rotatable designs were used for experiments where fluoride concentration (5~15 mg L−1), phosphorus concentration (1~10 mg L−1), and pH (5~9) were assessed as well throughout 10 days. Fluoride contents were determined in solution and plant tissues by potentiometry. Higher concentrations of fluoride reflected on greater absorptions by plants, though in relative terms removal efficiencies were quite similar for all treatments (~60%). Auxin and acidic conditions favored fluoride removals per mass of plant. Fluoride accumulated mostly in leaves and auxin probably alleviated toxic effects on E. crassipes while gibberellin showed no effect. Therefore, E. crassipes could be employed as a fluoride accumulator plant for water treatment and exogenous auxin may be used to improve the process. [ABSTRACT FROM AUTHOR]

In the scenario of water deficit stress, use of plant growth-promoting rhizobacteria (PGPR) adapted/tolerant to osmotic stress can be of great importance in designing suitable bioinoculants for the crops grown in stressed agro-ecosystems. The present investigation was conducted to study the in vitro response of selected Azospirillumformosense strains AIM3, AIM19, AIM38, AIM57 and AIM82 to PEG 6000-induced osmotic stress. The strains were first assessed for their growth and physiological responses under osmotic stress conditions (0, 10, 20, 30% PEG 6000). The growth of the cultures was not much affected under mild stress (10% PEG 6000), however, higher stress levels (30% PEG 6000) showed significant negative effect on growth with a sharp reduction in population of the cultures. Morphologically, the bacterial cells appeared as elongated rods and highly motile under 0 and 10% PEG 6000 whereas higher stress levels (20 and 30% PEG 6000) induced non-motile spheres with thick exopolymeric layer indicating stress adaptation. The intracellular accumulation of Pro and the biofilm-forming ability enhanced with increasing stress levels indicating osmoadaptation strategy of the strains. All the five strains could express PGPR traits (indole acetic acid and siderophore production and nitrogen fixation) under all levels of PEG 6000 indicating their PGP potential even under stress conditions. However, beyond 20% PEG 6000 there was drastic reduction in the expression of PGP traits. Seed germination bioassays indicated the positive effect of inoculation of bacterial strains on seed germination, seedling vigour index under 0, 10 and 20% PEG 6000 conditions. The present in vitro studies revealed responses and survival mechanisms of the A.formosense strains under osmotic stress conditions and their potential to alleviate moisture deficit effect in pearl millet plants. [ABSTRACT FROM AUTHOR]

Introduction: Indole acetic acid (auxin) is a plant hormone that, in addition to plants, is produced by a number of bacteria. The aim of the present study was to optimize the production of indole acetic acid from whey substrate by bacteria isolated from rhizosphere and phyllosphere of plants. Materials and Methods: The desired bacteria were isolated and purified from phyllosphere and rhizosphere of green beans, cowpea, mint, and parsley plants. The ability of isolates to grow in whey substrate and production of auxin was evaluated. The effect of pH and temperature parameters on the function of isolates was investigated. Impure auxin powder was prepared from the bacterial culture in whey substrate and its function was evaluated on the seed growth rate of lentil and mung bean plants. Results: Out of 26 isolated bacterial samples, 5 isolates (19.2%) had the ability to produce indole acetic acid and grow in whey substrate simultaneously. Two isolates with the highest auxin production capacity were identified using 16S rDNA region sequencing. One isolate had 97% similarity to Enterobacter soli and the other isolate had 99% similarity to Enterobacter mori. These isolates showed the highest auxin production capacity at 30 and 35°C respectively and in pH 7. Seed irrigation of the studied plants with produced auxin solutions significantly increased the longitudinal growth of stems of these plants in comparison with control solutions. Discussion and Conclusion: Auxin-producing strains can be isolated from soil and plants, and by using inexpensive substrates such as whey, this phytohormone can be produced on an industrial scale and used as a plant growth stimulant. [ABSTRACT FROM AUTHOR]

Plants form associations with different microbes; some promote their growth and protect from biotic and abiotic stresses in different ways. However, the biological role of fungi associated with the rhizosphere of medicinal plants is not well explored. In the present study, Colletotrichum gloeosporioides, and Aspergillus fumigatus isolated from the rhizosphere of Dillenia indica were screened for their phosphate solubilization and indole-3-acetic acid (IAA) production potential. The selected fungal strains were identified by macroscopic, microscopic, and molecular characteristics. Phosphate solubilization was qualitatively and quantitatively evaluated using Pikovskaya's (PVK) agar and PVK broth medium using different substrates such as AlPO4, Ca3(PO4)2, and FePO4. Colletotrichum gloeosporioides and Aspergillus fumigatus with respect to the phosphate source showed solubilization index (SI) of 1.7 ± 0.03 and 2.1 ± 0.04, and solubilized phosphate up to 138.8 ± 0.058 µg/mL and 121.6 ± 0.062 µg/mL. These fungal strains are also good producers of IAA and significantly enhance the growth of Vigna radiata and Cicer arietinum seedlings. This is the first report on A. fumigatus and C. gloeosporioides from the rhizosphere of Dillenia indica and their phosphate solubilization and IAA production ability. [ABSTRACT FROM AUTHOR]

Fluoranthene (Flu) uptake by plants is affected by plant growth and environmental concentration. Although plant growth processes, including substance synthesis and antioxidant enzyme activities, have been reported to regulate Flu uptake, their contributions have been poorly evaluated. Moreover, the effect of Flu concentration is little known. Here, low concentrations (0, 1, 5, and 10 mg/L) and high concentrations (20, 30, and 40 mg/L) of Flu were set to compare the changes in Flu uptake by ryegrass (Lolium multiflorum Lam.). Indices of plant growth (biomass, root length, root area, root tip number, and photosynthesis and transpiration rates), substance synthesis (indole acetic acid [IAA] content), and antioxidant enzyme activities (superoxide dismutase [SOD], peroxidase [POD], and catalase [CAT]) were recorded to unravel the mechanism of Flu uptake. Findings suggested that the Langmuir model fitted Flu uptake by ryegrass well. Flu absorption capacity in the root was stronger than that that in the leaf. Flu bioconcentration and translocation factors increased then reduced with the increase in Flu concentration and reached the maximum value under 5 mg/L Flu treatment. Plant growth and IAA content had the same pattern as before bioconcentration factor (BCF). SOD and POD activities increased then decreased with Flu concentration and reached their highest levels under 30 and 20 mg/L Flu treatments, respectively, whereas CAT activity decreased continuously and reached its lowest level under 40 mg/L Flu treatment. Variance partitioning analysis indicated that IAA content had the greatest significant effect on Flu uptake under low-concentration Flu treatments, whereas antioxidant enzyme activities had the greatest significant effect on Flu uptake under high-concentration Flu treatments. Revealing the concentration-dependent mechanisms of Flu uptake could provide a basis for regulating pollutant accumulation in plants.

Endophytic fungi colonize the inner tissues and provide direct and indirect benefits to plants. Although Mongolia is rich in medicinal plants, due to climatic and anthropogenic reasons, the resources are being depleted, and many species are under threat of gradual extinction, while the endophytic fungi of Mongolian plants are largely unknown. In this study, a total of 24 culturable endophytic fungal strains were isolated from Cynomorium songaricum (Rupr.), a medicinal and vulnerable plant species of Mongolia. Based on the morphological characteristics and the sequences of the rDNA internal transcribed spacer (ITS) region, the isolates were identified into six genera: Fusarium (8), Clonostachys (7), Penicillium (6), Alternaria (1), Aspergillus (1), and Madurella (1). The antimicrobial activity was assessed by the agar-diffusion method, revealing that 15 strains were able to inhibit the growth of at least one of the test organisms. Among them, 1 strain showed inhibitory activity against Escherichia coli, 12 against Bacillus subtilis, 13 against Staphylococcus aureus, and 8 against Aspergillus niger, respectively. The ability to solubilize complex phosphorus and zinc minerals was observed in 3 and 21 strains, respectively, and the production of indole-3-acetic acid (IAA) was detected in nine strains in the presence of tryptophan. Our study provides the first insight into the cultivable endophytic fungal composition of C. songaricum, parasitizing the roots of Nitraria sibirica growing in the Gobi Desert of Mongolia. The resulting fungi, which have antimicrobial and plant growth-promoting properties, were preserved in the national culture collection and can be used to further exploit their biotechnological potential, as well as for the propagation of endangered and vulnerable medicinal plants.

Plant growth-promoting rhizobacteria (PGPR) have proved to be an effective solution for enhancing growth of various plant species. Five different bacterial isolates extracted from rhizosphere soil were extensively studied for the production of indole acetic acid (IAA) and among those Bacillus safensis YKS2 strain was found to produce substantial quantities of IAA. B. safensis YKS2 strain was characterized and submitted to National Centre for Biotechnology Information (NCBI) (Gen Bank No. MH539636). Optimization of IAA production with varying pH and temperature revealed that IAA production was maximum at pH 7 and at a temperature of 37°C. The production of IAA was confirmed and quantified by Fourier-transform infrared spectroscopy (FTIR), Thin-layer chromatography (TLC), Gas chromatography-mass spectrometry (GC-MS). The PGPR inoculum showed significant (p

Azotobacter spp. are known for their ability to fix nitrogen into the soil non-symbiotically. Their activities can be enhanced through the provision of optimum cultural conditions. Hence, this study aimed to isolate Azotobacter spp. and optimize their growth (medium and condtions) with a focus on pH, sucrose and indole acetic acid (IAA) concentrations. The counts of Azotobacter obtained from the rhizosphere of the crops ranged from 4.0 × 104 – 1.0 × 106 CFU/g. The three high IAA-producing Azotobacter spp. were identified as A. chroococcum, A. vinelandii and A. beijerinckii. They produced IAA in the absence and presence of 0.25 % tryptophan in the ranges of 0.20 – 0.36 and 604.5 – 1439.7 µg/mL respectively. However, under optimized conditions these isolates produced IAA in folds. Optimum IAA was produced by A. chroococcum, A. vinelandii and A. beijerinckii at pH, sucrose and tryptophan concentration ranging from 6.5 – 7.5, 2 – 3 % and 0.3 – 0.7 %. respectively. A. vinelandii produced a higher amount of IAA when compared with A. chroococcum and A. beijerinckii at the optimal conditions. These were 2001.1, 2541.1 and 2602.6 µg/mL at optimum pH 7.5, sucrose (2 %) and tryptophan (0.3%) respectively. It was concluded from these findings that, Azotobacter vinelandii is an excellent producer of plant growth promoting hormone, indole-3-acetic acid (IAA).

A Gram-stain-negative, halotolerant bacterium designated as PTR5T was isolated from the roots of rice plants, collected in Ilsan, South Korea. Cells were, aerobic, asporogenous, motile, rod-shaped, white in color, and grew at 5–38 °C (optimum 30 °C), at pH 5.0-0-8.0 (optimum, 7.0) and tolerates up to 10% (w/v) NaCl (optimum, 0% NaCl). According to the EZbioCloud server the most closely related Devosia species to strain PTR5T based on 16 S rRNA gene sequence comparison are Devosia crocina (97.4%), followed by D. soli (97.2%), D. lucknowensis (96.9%) and D. marina (96.5%). The respiratory quinone was identified as Q-10. The major polar lipids were phosphatidylglycerol and diphosphatidylglycerol. C16:0, C18:1ω7c 11-methyl and summed feature 8 (comprising C18:1ω7c/C18:1ω6c) constituted the main cellular fatty acids. The draft genome sequence of strain PTR5T was 3,689,283 bp in size. The average nucleotide identity (ANI), digital DNA–DNA hybridization (dDDH) and amino acid identity (AAI) values between strain PTR5T and its close relative were 72.8–76.8%, 19–20.7% and 70.3–75%, respectively. The G + C content was 63.7%. Strain PTR5T was able to produce siderophore and indole acetic acid (IAA) in the presence of l-tryptophan. Genes for siderophore production, auxin responsive and tryptophan biosynthesis were present in the genome of novel strain. Also, gene clusters involved in detoxification of various metal pollutants and antibiotics were also revealed in the genome of novel strain PTR5T, this suggest that novel strain can facilitate bioremediation of heavy metals and antibiotics in contaminated areas. This study aimed to determine the detailed taxonomic position of the strain PTR5T using the modern polyphasic approach. On the basis of evidence presented in this study, strain PTR5T is considered to represent a novel species of the genus Devosia, for which the name Devosia oryzisoli sp. nov. (type strain PTR5T (KCTC 82691T = TBRC 15163T) is proposed. [ABSTRACT FROM AUTHOR]