Bacterial endophytes modulates the withanolide biosynthetic pathway and physiological performance in Withania somnifera under biotic stress

Withanolides production by the endophytic fungus Penicillium oxalicum associated with Withania somnifera (L.) Dunal

Withanolides are steroidal lactones with diverse bioactive potential and their production from plant sources varies with genotype, age, culture conditions, and geographical region. Endophytic fungi serve as an alternative source to produce withanolides, like their host plant, Withania somnifera (L.) Dunal. The present study aimed to isolate endophytic fungi capable of producing withanolides, characterization and investigation of biological activities of these molecules. The methanolic fungal crude extract of one of the fungal isolates WSE16 showed maximum withanolide production (219 mg/L). The fungal isolate WSE16 was identified as Penicillium oxalicum based on its morphological and internal transcribed spacer (ITS) sequence analysis and submitted in NCBI (accession number OR888725). The methanolic crude extract of P. oxalicum was further purified by column chromatography, and collected fractions were assessed for the presence of withanolides. Fractions F3 and F4 showed a higher content of withanolides (51.8 and 59.1 mg/L, respectively) than other fractions. Fractions F3 and F4 exhibited antibacterial activity against Staphylococcus aureus with an IC50 of 23.52 and 17.39 µg/ml, respectively. These fractions also showed antioxidant activity (DPPH assay with IC50 of 39.42 and 38.71 µg/ml, superoxide anion scavenging assay with IC50 of 41.10 and 38.84 µg/ml, and reducing power assay with IC50 of 42.61 and 41.40 µg/ml, respectively) and acetylcholinesterase inhibitory activity (IC50 of 30.34 and 22.05 µg/ml, respectively). The withanolides present in fraction 3 and fraction 4 were identified as (20S, 22R)-1a-Acetoxy-27-hydroxywitha-5, 24-dienolide-3b-(O-b-D-glucopyranoside) and withanamide A, respectively, using UV, FTIR, HRMS, and NMR analysis. These results suggest that P. oxalicum, an endophytic fungus isolated from W. somnifera, is a potential source for producing bioactive withanolides.

Plant-Entomopathogenic Fungi Interaction: Recent Progress and Future Prospects on Endophytism-Mediated Growth Promotion and Biocontrol

Entomopathogenic fungi, often acknowledged primarily for their insecticidal properties, fulfill diverse roles within ecosystems. These roles encompass endophytism, antagonism against plant diseases, promotion of the growth of plants, and inhabitation of the rhizosphere, occurring both naturally and upon artificial inoculation, as substantiated by a growing body of contemporary research. Numerous studies have highlighted the beneficial aspects of endophytic colonization. This review aims to systematically organize information concerning the direct (nutrient acquisition and production of phytohormones) and indirect (resistance induction, antibiotic and secondary metabolite production, siderophore production, and mitigation of abiotic and biotic stresses) implications of endophytic colonization. Furthermore, a thorough discussion of these mechanisms is provided. Several challenges, including isolation complexities, classification of novel strains, and the impact of terrestrial location, vegetation type, and anthropogenic reluctance to use fungal entomopathogens, have been recognized as hurdles. However, recent advancements in biotechnology within microbial research hold promising solutions to many of these challenges. Ultimately, the current constraints delineate potential future avenues for leveraging endophytic fungal entomopathogens as dual microbial control agents.

Current Status and Future Perspectives on Distribution of Fungal Endophytes and Their Utilization for Plant Growth Promotion and Management of Grapevine Diseases

Grapevine is one of the economically most important fruit crops cultivated worldwide. Grape production is significantly affected by biotic constraints leading to heavy crop losses. Changing climatic conditions leading to widespread occurrence of different foliar diseases in grapevine. Chemical products are used for managing these diseases through preventive and curative application in the vineyard. High disease pressure and indiscriminate use of chemicals leading to residue in the final harvest and resistance development in phytopathogens. To mitigate these challenges, the adoption of potential biocontrol control agents is necessary. Moreover, multifaceted benefits of endophytes made them eco-friendly, and environmentally safe approach. The genetic composition, physiological conditions, and ecology of their host plant have an impact on their dispersion patterns and population diversity. Worldwide, a total of more than 164 fungal endophytes (FEs) have been characterized originating from different tissues, varieties, crop growth stages, and geographical regions of grapevine. These diverse FEs have been used extensively for management of different phytopathogens globally. The FEs produce secondary metabolites, lytic enzymes, and organic compounds which are known to possess antimicrobial and antifungal properties. The aim of this review was to understand diversity, distribution, host-pathogen-endophyte interaction, role of endophytes in disease management and for enhanced, and quality production.

Bacillus subtilis NBRI-W9 simultaneously activates SAR and ISR against Fusarium chlamydosporum NBRI-FOL7 to increase wilt resistance in tomato

AIMS

The study aimed to determine the pathogenicity of Fusarium species currently prevalent in tomato fields having history of chemical fungicide applications and determine the bio-efficacy of Bacillus subtilis NBRI-W9 as a potent biological control agent.

METHODS AND RESULTS

Fusarium was isolated from surface-sterilized infected tomato plants collected from fields. Pathogenicity of 30 Fusarium isolates was determined by in vitro and in vivo assays. Following Koch's postulates, F. chlamydosporum (FOL7) was identified as a virulent pathogen. The biological control of FOL 7 by B. subtilis NBRI-W9 (W9) and the colonization potential of W9 were established using spontaneous rifampicin-resistant mutants. W9 showed 82% inhibition of FOL7 on a dual-culture plate and colonization levels in tomato plants of ∼5.5, ∼3.3, and ∼2.2 log10 CFU/g in root, stem, and leaf tissue, respectively. Antagonistic activity was shown by scanning electron microscopy (SEM) and cell-wall-degradative enzymes. W9 reduced FOL7 infection in net-house and field experiments by 60% and 41%, respectively. Biochemical investigation, defence enzymes, defence gene expression analysis, SEM, and field studies provide evidence of hyperparasitism and induced resistance as the mode of biological control. The study also demonstrates that the potent biocontrol agent W9, isolated from Piper, can colonize tomato plants, control fungal disease by inducing induced systemic resistance (ISR) and systemic acquired resistance (SAR) simultaneously, and increase crop yield by 21.58% under field conditions.

CONCLUSIONS

This study concludes that F. chlamydosporum (NBRI-FOL7) is a potent, fungicide-resistant pathogen causing wilt in tomatoes. NBRI-W9 controlled FOL7 through mycoparasitism and simultaneously activated ISR and SAR in plants, providing an attractive tool for disease control that acts at multiple levels.

Deciphering the mechanisms, hormonal signaling, and potential applications of endophytic microbes to mediate stress tolerance in medicinal plants

The global healthcare market in the post-pandemic era emphasizes a constant pursuit of therapeutic, adaptogenic, and immune booster drugs. Medicinal plants are the only natural resource to meet this by supplying an array of bioactive secondary metabolites in an economic, greener and sustainable manner. Driven by the thrust in demand for natural immunity imparting nutraceutical and life-saving plant-derived drugs, the acreage for commercial cultivation of medicinal plants has dramatically increased in recent years. Limited resources of land and water, low productivity, poor soil fertility coupled with climate change, and biotic (bacteria, fungi, insects, viruses, nematodes) and abiotic (temperature, drought, salinity, waterlogging, and metal toxicity) stress necessitate medicinal plant productivity enhancement through sustainable strategies. Plants evolved intricate physiological (membrane integrity, organelle structural changes, osmotic adjustments, cell and tissue survival, reclamation, increased root-shoot ratio, antibiosis, hypersensitivity, etc.), biochemical (phytohormones synthesis, proline, protein levels, antioxidant enzymes accumulation, ion exclusion, generation of heat-shock proteins, synthesis of allelochemicals. etc.), and cellular (sensing of stress signals, signaling pathways, modulating expression of stress-responsive genes and proteins, etc.) mechanisms to combat stresses. Endophytes, colonizing in different plant tissues, synthesize novel bioactive compounds that medicinal plants can harness to mitigate environmental cues, thus making the agroecosystems self-sufficient toward green and sustainable approaches. Medicinal plants with a host set of metabolites and endophytes with another set of secondary metabolites interact in a highly complex manner involving adaptive mechanisms, including appropriate cellular responses triggered by stimuli received from the sensors situated on the cytoplasm and transmitting signals to the transcriptional machinery in the nucleus to withstand a stressful environment effectively. Signaling pathways serve as a crucial nexus for sensing stress and establishing plants' proper molecular and cellular responses. However, the underlying mechanisms and critical signaling pathways triggered by endophytic microbes are meager. This review comprehends the diversity of endophytes in medicinal plants and endophyte-mediated plant-microbe interactions for biotic and abiotic stress tolerance in medicinal plants by understanding complex adaptive physiological mechanisms and signaling cascades involving defined molecular and cellular responses. Leveraging this knowledge, researchers can design specific microbial formulations that optimize plant health, increase nutrient uptake, boost crop yields, and support a resilient, sustainable agricultural system.

Plants and endophytes interaction: a "secret wedlock" for sustainable biosynthesis of pharmaceutically important secondary metabolites

Many plants possess immense pharmacological properties because of the presence of various therapeutic bioactive secondary metabolites that are of great importance in many pharmaceutical industries. Therefore, to strike a balance between meeting industry demands and conserving natural habitats, medicinal plants are being cultivated on a large scale. However, to enhance the yield and simultaneously manage the various pest infestations, agrochemicals are being routinely used that have a detrimental impact on the whole ecosystem, ranging from biodiversity loss to water pollution, soil degradation, nutrient imbalance and enormous health hazards to both consumers and agricultural workers. To address the challenges, biological eco-friendly alternatives are being looked upon with high hopes where endophytes pitch in as key players due to their tight association with the host plants. The intricate interplay between plants and endophytic microorganisms has emerged as a captivating subject of scientific investigation, with profound implications for the sustainable biosynthesis of pharmaceutically important secondary metabolites. This review delves into the hidden world of the "secret wedlock" between plants and endophytes, elucidating their multifaceted interactions that underpin the synthesis of bioactive compounds with medicinal significance in their plant hosts. Here, we briefly review endophytic diversity association with medicinal plants and highlight the potential role of core endomicrobiome. We also propose that successful implementation of in situ microbiome manipulation through high-end techniques can pave the way towards a more sustainable and pharmaceutically enriched future.

Decrypting the multi-functional biological activators and inducers of defense responses against biotic stresses in plants

Plant diseases are still the main problem for the reduction in crop yield and a threat to global food security. Additionally, excessive usage of chemical inputs such as pesticides and fungicides to control plant diseases have created another serious problem for human and environmental health. In view of this, the application of plant growth-promoting rhizobacteria (PGPR) for controlling plant disease incidences has been identified as an eco-friendly approach for coping with the food security issue. In this review, we have identified different ways by which PGPRs are capable of reducing phytopathogenic infestations and enhancing crop yield. PGPR suppresses plant diseases, both directly and indirectly, mediated by microbial metabolites and signaling components. Microbial synthesized anti-pathogenic metabolites such as siderophores, antibiotics, lytic enzymes, hydrogen cyanide, and several others act directly on phytopathogens. The indirect mechanisms of reducing plant disease infestation are caused by the stimulation of plant immune responses known as initiation of systemic resistance (ISR) which is mediated by triggering plant immune responses elicited through pathogen-associated molecular patterns (PAMPs). The ISR triggered in the infected region of the plant leads to the development of systemic acquired resistance (SAR) throughout the plant making the plant resistant to a wide range of pathogens. A number of PGPRs including Pseudomonas and Bacillus genera have proven their ability to stimulate ISR. However, there are still some challenges in the large-scale application and acceptance of PGPR for pest and disease management. Further, we discuss the newly formulated PGPR inoculants possessing both plant growth-promoting activities and plant disease suppression ability for a holistic approach to sustaining plant health and enhancing crop productivity.

Endophytes and their potential in biotic stress management and crop production

Biotic stress is caused by harmful microbes that prevent plants from growing normally and also having numerous negative effects on agriculture crops globally. Many biotic factors such as bacteria, fungi, virus, weeds, insects, and nematodes are the major constrains of stress that tends to increase the reactive oxygen species that affect the physiological and molecular functioning of plants and also led to the decrease in crop productivity. Bacterial and fungal endophytes are the solution to overcome the tasks faced with conventional farming, and these are environment friendly microbial commodities that colonize in plant tissues without causing any damage. Endophytes play an important role in host fitness, uptake of nutrients, synthesis of phytohormone and diminish the injury triggered by pathogens via antibiosis, production of lytic enzymes, secondary metabolites, and hormone activation. They are also reported to help plants in coping with biotic stress, improving crops and soil health, respectively. Therefore, usage of endophytes as biofertilizers and biocontrol agent have developed an eco-friendly substitute to destructive chemicals for plant development and also in mitigation of biotic stress. Thus, this review highlighted the potential role of endophytes as biofertilizers, biocontrol agent, and in mitigation of biotic stress for maintenance of plant development and soil health for sustainable agriculture.

Biosynthetic Mechanisms of Secondary Metabolites Promoted by the Interaction Between Endophytes and Plant Hosts

Endophytes is a kind of microorganism resource with great potential medicinal value. The interactions between endophytes and host not only promote the growth and development of each other but also drive the biosynthesis of many new medicinal active substances. In this review, we summarized recent reports related to the interactions between endophytes and hosts, mainly regarding the research progress of endophytes affecting the growth and development of host plants, physiological stress and the synthesis of new compounds. Then, we also discussed the positive effects of multiomics analysis on the interactions between endophytes and their hosts, as well as the application and development prospects of metabolites synthesized by symbiotic interactions. This review may provide a reference for the further development and utilization of endophytes and the study of their interactions with their hosts.

Biocontrol competence of Beauveria bassiana, Metarhizium anisopliae and Bacillus thuringiensis against tomato leaf miner, Tuta absoluta Meyrick 1917 under greenhouse and field conditions

Tomato is one of the most important crops grown under both greenhouse and field conditions throughout the world. Its production is highly challenged by infestation of leaf miner insect, Tuta absoluta Meyrick regardless of excessive insecticide application. The chemical insecticides results insect resistance, environmental pollution, and health problems and there is urgent need for management options such as integrated pest management (IPM) to obviate these problems. Thus, the present study aims to evaluate the effectiveness of single and combination treatments of entomopathogens; Beauveria bassiana, Metarhizium anisopliae, Bacillus thuringeinsis, and an insecticide against T. absoluta under greenhouse and field conditions. Two varieties (Awash and Venes) of tomato for greenhouse experiment and one (Gellila) variety for field experiment were used with Tutan36%SC (insecticide with active ingredient of Chlorphenapyr 36%SC) and untreated plots as positive and negative controls, respectively. The results showed significant leaf and fruit damage reduction in all the treatments. B. bassiana-AAUB03, M. anisopliae-AAUM78, and B. thuringiensis-AAUF6 showed the highest (93.4%, 89.7% and 90.1%) leaf and (93.5%, 94.4% and 95%) fruit protection under greenhouse condition. The combined treatments improved leaf protection efficacy up to 95.3% under field condition. When the entomopathogens were combined with half or quarter reduced concentrations of Tutan36% SC, it showed 94.4% of pest protection. In all the treatments, 72–96% of marketable fruit was obtained as par insecticide treatment scored 85–93%. All the entomopathogens did not cause any adverse effect on the growth of tomato rather improved shoot length, shoot branching, leaf and fruit numbers. Therefore, application of entomopathogens in single, consortium or in combination reduced the recommended concentration of Tutan36%SC to control T. absoluta.

Prospecting potential of endophytes for modulation of biosynthesis of therapeutic bioactive secondary metabolites and plant growth promotion of medicinal and aromatic plants

Medicinal and aromatic plants possess pharmacological properties (antidiabetes, anticancer, antihypertension, anticardiovascular, antileprosy, etc.) because of their potential to synthesize a wide range of therapeutic bioactive secondary metabolites. The concentration of bioactive secondry metabolites depends on plant species, local environment, soil type and internal microbiome. The internal microbiome of medicinal plants plays the crucial role in the production of bioactive secondary metabolites, namely alkaloids, steroids, terpenoids, peptides, polyketones, flavonoids, quinols and phenols. In this review, the host specific secondry metabolites produced by endophytes, their therapeutic properties and host-endophytes interaction in relation to production of bioactive secondry metaboloites and the role of endophytes in enhancing the production of bioactive secondry metabolites is discussed. How biological nitrogen fixation, phosphorus solubilization, micronutrient uptake, phytohormone production, disease suppression, etc. can play a vital role in enhacing the plant growth and development.The role of endophytes in enhancing the plant growth and content of bioactive secondary metabolites in medicinal and aromatic plants in a sustainable mode is highlighted.

Bacillus subtilis suppresses the charcoal rot disease by inducing defence responses and physiological attributes in soybean

Endophytes can induce the defence responses and modulates physiological attributes in host plants during pathogen attacks. In the present study, 127 bacterial endophytes (BEs) were isolated from different parts of healthy soybean plant. Among them, two BEs (M-2 and M-4) resulted a significant antagonistic property against Macrophomina phaseolina, causes charcoal rot disease in soybean. The antagonistic potential was evaluated through dual culture plate assay, where M-4 expressed higher antifungal activity than M-2 against M. phaseolina. The M-4 produces cell wall degrading enzymes viz. cellulase (145.71 ± 1.34 μgmL-1), chitinase (0.168 ± 0.0009 unitmL-1) and β,1-3 endoglucanase (162.14 ± 2.5 μgmL-1), which helps in cell wall disintegration of pathogens. Additionally, M-4 also can produce siderophores, indole-3-acetic acid (IAA) (17.03 ± 1.10 μgmL-1) and had a phosphate solubilization potential (19.89 ± 0.26 μgmL-1). Further, GC-MS profiling of M-4 has been carried out to demonstrate the production of lipophilic secondary metabolites which efficiently suppress the M. phaseolina defensive compounds under co-culture conditions. Bio-efficacy study of M-4 strain shown a significant reduction in disease incidence around 60 and 80% in resistant and susceptible varieties of soybean, respectively. The inoculation of M-4 potentially enhances the physiological attributes and triggers various defence responsive enzymes viz. superoxide dismutase (SOD), phenol peroxidase (PPO), peroxidase (PO) and catalase (CAT). The histopathological study also confirmed that M-4 can reduce the persistence of microsclerotia in root and shoot tissue. Conclusively, M-4 revealed as an efficient biocontrol agent that can uses multifaceted measures for charcoal rot disease management, by suppress the M. phaseolina infection and enhance the physiological attributes of soybean.

Isolation and characterization of endophytic fungi having plant growth promotion traits that biosynthesizes bacosides and withanolides under in vitro conditions

Endophytes are regarded with immense potentials in terms of plant growth promoting (PGP) elicitors and mimicking secondary metabolites of medicinal importance. Here in the present study, we explored Bacopa monnieri plants to isolate, identify fungal endophytes with PGP elicitation potentials, and investigate secretion of secondary metabolites such as bacoside and withanolide content under in vitro conditions. Three fungal endophytes isolated (out of 40 saponin producing isolates) from leaves of B. monnieri were examined for in vitro biosynthesis of bacosides. On morphological, biochemical, and molecular identification (ITS gene sequencing), the isolated strains SUBL33, SUBL51, and SUBL206 were identified as Nigrospora oryzae (MH071153), Alternaria alternata (MH071155), and Aspergillus terreus (MH071154) respectively. Among these strains, SUBL33 produced highest quantity of Bacoside A3 (4093 μg mL-1), Jujubogenin isomer of Bacopasaponin C (65,339 μg mL-1), and Bacopasaponin C (1325 μg mL-1) while Bacopaside II (13,030 μg mL-1) was produced by SUBL51 maximally. Moreover, these aforementioned strains also produced detectable concentration of withanolides-Withaferrin A, Withanolide A (480 μg mL-1), and Withanolide B (1024 μg mL-1) respectively. However, Withanolide A was not detected in the secondary metabolites of strain SUBL51. To best of our knowledge, the present study is first reports of Nigrospora oryzae as an endophyte in B. monnieri with potentials of biosynthesis of economically important phytomolecules under in vitro conditions.

Bioprospecting of endophytes in medicinal plants of Thar Desert: An attractive resource for biopharmaceuticals

•

Endophytes act as chemical synthesizers of the secondary metabolites of the host plant.

•

Endophytic microflora has been isolated from a wide array of plants.

•

It can serve as a good alternative source for pharmaceutically important compounds.

•

The arid ecosystem of Thar Desert is a rich repository of ethnomedicinal plants.

•

Role of endophytes in the synthesis of bioactive molecules used to enhance production.

Endophytes live asymptomatically within the healthy tissues of plant parts of the host, has grabbed the attention of ecologists, chemists, and researchers to have a broad spectral of biotechnological potential. It has been proven that almost all plants harbor endophytes within themselves. Numerous studies indicated that endophytes act as chemical synthesizers of the secondary metabolites of their host plant. Various medicinal plants of the Thar Desert have been used by the local folks of the Rajasthan to treat several diseases ailments for time immemorial. On the basis of their prior knowledge of ethnopharmacological usage of medicinally important plants of Thar Desert, several researchers directed their studies in search of endophytic microflora of such medicinally important plants for the discovery of novel bioactive molecules of pharmaceutical importance, for instance, taxol producing endophytic fungus Phoma sp. isolated from Calotropis gigantea as well as Aspergillus fumigatus, an endophytic fungus reported from Moringa oleifera demonstrated an effective antibiofilm, antimicrobial and antiproliferative activity. This review sheds light on the endophytic microflora of the ethnomedicinal plants of the Thar Desert and their biopotential as a promising source of pharmaceutically important naturally derived compounds.

Beauveria bassiana Endophytic Strain as Plant Growth Promoter: The Case of the Grape Vine Vitis vinifera

The common grape vine, Vitis vinifera, is a widely known plant with commercial and pharmacological value. The plant hosts a variety of microorganisms known as endophytes that can live within the tissues of the plant for a considerable time period, or even their whole life cycle. The fungus Beauveria bassiana is a well-studied endophyte which can colonize a variety of plants in many ways and in different parts of the plant. In this study, we examined the effect of the endophytic fungus B. bassiana on the growth of V. vinifera. The results demonstrated not only a successful colonization of the endophyte, but also a noteworthy impact on the growth of the V. vinifera root without harming the plant in any way. The fungus was also re-isolated from the parts of the plant using inst bait method. Overall, the study demonstrates the capability of B. bassiana to colonize V. vinifera plants, adding to the already existing knowledge of its endophytic activity, and highlighting its beneficial impact on the root growth.

Medicinal Plants and Their Bacterial Microbiota: A Review on Antimicrobial Compounds Production for Plant and Human Health

Medicinal plants (MPs) have been used since antiquity in traditional and popular medicine, and they represent a very important source of bioactive molecules, including antibiotic, antiviral, and antifungal molecules. Such compounds are often of plant origin, but in some cases, an origin or a modification from plant microbiota has been shown. Actually, the research continues to report the production of bioactive molecules by plants, but the role of plant–endophytic interaction is emerging. Classic examples are mainly concerned with fungal endophytes; however, it has been recently shown that bacterial endophytes can also play an important role in influencing the plant metabolism related to the synthesis of bioactive compounds. In spite of this, a deep investigation on the power of MP bacterial endophytes is lacking. Here, an overview of the studies on MP bacterial microbiota and its role in the production of plant antimicrobial compounds contributing to prime host defense system and representing a huge resource for biotech and therapeutic applications is provided.

Biodegradation of slop oil by endophytic Bacillus cereus EN18 coupled with lipase from Rhizomucor miehei (Palatase®)

Removal of slop oil, a by-product of oil refining, also obtained in cleaning up of oil tanks and filters is a difficult issue. High content of hydrocarbons (C3-C40) and other organic compounds makes this waste difficult to eliminate from the environment. The purpose of this investigation was to combine bacterial degradation by endophytic Bacillus cereus EN18 with biotransformation performed using lipase enzyme preparation (Palatase®) to remove recalcitrant compounds present in slop oil from the environment. Endophytic B. cereus EN18 was able to biodegrade up to 40% of slop oil while supplementation with lipase improved the efficiency of contamination removal in about one third. Also the use of lipase enzyme preparation resulted in higher microbial activity of B. cereus EN18 bacterial strain, as well as higher concentration of fatty acids in the culture medium, which indicates higher degradation efficiency. Obtained results suggest that lipase preparation from Rhizomucor miehei (Palatase®) may be a useful agent to improve microbial degradation of recalcitrant pollutants, like slop oil in water environments. GC and spectrometric analysis revealed that hydrocarbons from slop oil were effectively degraded while using both microbial degradation and lipase catalysis.

Supplementation of Trichoderma improves the alteration of nutrient allocation and transporter genes expression in rice under nutrient deficiencies

Nutrients are the finite natural resources that are essential for productivity and development of rice and its deficiency causes compromised yield along with reduced immunity against several biotic and abiotic stresses. In this study, the potential of Trichoderma reesei has been investigated as a biofertilizer (BF) to ameliorate nutrient stress in different rice cultivars at physiological, biochemical and molecular levels. The results indicated that cultivar Heena is much more compatible with BF as compared to cultivar Kiran at 50% nutrient limiting condition. Enhancement in physiological attributes and photosynthetic pigments were observed in BF treated Heena seedlings. The localization of biofertilizer in treated roots was further validated by scanning electron micrographs. This result correlated well with the higher levels of Indole acetic acid and Gibberellic acid in biofertilizer treated rice. Similarly, the uptake of micro-nutrients such as Fe, Co, Cu and Mo was found to be 1.4-1.9 fold higher respectively in BF treated Heena seedlings under 50% nutrient deficient condition. Furthermore, different stress ameliorating enzymes Guaiacol peroxidase, Super oxide dismutase, Total Phenolic Content, Phenol Peroxidase, Phenylalanine ammonia lyase and Ascorbate peroxidase in Heena seedlings were also increased by 1.8, 1.4, 1.2, 2.4, 1.2, and 8.3-fold respectively, at 50% nutrient deficient condition. The up-regulation of different micro and macro-nutrients allocation and accumulation; metal tolerance related; auxin synthesis genes in BF treated Heena as compared to 50% nutrient deficient condition was further supported by our findings that the application of biofertilizer efficiently ameliorated the deficiency of nutrients in rice.

Biosurfactant production and hydrocarbon degradation activity of endophytic bacteria isolated from Chelidonium majus L

Background

The process of plant growth in the contaminated environment is often inhibited and entails the neutralization of harmful compounds. To reduce the negative impact of harmful compounds microorganisms produce unique compounds called biosurfactants. This paper describes the potential of culturable endophytic microorganisms from synanthropic plant-Chelidonium majus L. for the production of biosurfactants, as indirect plant promoting factors as well as their degradation activity. Emulsifying activity and degradation potential of tested strains were assessed by cultivation of isolates in the presence of diesel oil and waste engine oil.

Results

Ten bacterial strain were isolated. Analysis of emulsifying activity revealed that all isolates possessed the ability for biosurfactant production. However, one of the isolated endophytes—2A, identified as Bacillus pumilus, exhibited the highest emulsifying activity (OD₅₀₀ 1.96). The same strain has shown very high degradation potential, both for diesel oil and waste engine oil hydrocarbons. Results obtained with the Phytotoxkit tests revealed that the addition of biosurfactant isolated from B. pumilus 2A strain resulted in stimulation of seed germination in soil contaminated with diesel oil (137%) and waste engine oil (120%). Positive impact of the biosurfactant produced by B. pumilus 2A on the growth of Sinapis alba in hydrocarbons contaminated soil was demonstrated.

Conclusions

The endophytic strain identified as Bacillus pumilus 2A produce biosurfactant that is able to act as plant-growth promoting agent. Endophytic bacteria isolated from Chelidonium majus L. exhibit potential for hydrocarbons degradation and biosurfactant production. These properties provide promising perspectives for application of biosurfactants as potential agents for bioremediation of environment contaminated with hydrocarbons.