Rhizospheric Strains Research Articles

Degradation of Cinnamic Acid by the Rhizospheric Strain Achromobacter insolitus LCu2

Degradation of Cinnamic Acid by the Rhizospheric Strain Achromobacter insolitus LCu2

Growth Behaviours of Two Rhizospheric Bacterial Strains in the Presence of Different Cadmium Concentrations and Temperatures

Understanding the interaction of Cd with plants, as well as the search for alternatives to minimize its effects, has caught the interest of the scientific community, due to the accelerated growth of contamination with this metal and its high toxicity. The aim of the present study was to evaluate the ability of two rhizospheric bacterial strains LC7504001.1 Burkholderia cepacia (C65RLIM) and FJ972527.1 Pseudomonas aeruginosa (C85RLIM) to three concentrations of cadmium (100, 300 and 500 mg/L) and to compare the growth behaviour with increasing temperature from 32 to 45°C. The results show different growth patterns for each strain tested against exposure to the three cadmium concentrations and the four temperatures tested. The Pseudomonas aeruginosa strain (C85RLIM) had the best adaptive behaviour to the three cadmium concentrations tested, and also showed stability when subjected to 500 mg/L CdCl2 and temperatures between 40 and 45°C. The results predict the possible behaviour of rhizospheric bacteria in the face of global warming and heavy metal remediation processes.

Genomics and taxonomy of the glyphosate-degrading, copper-tolerant rhizospheric bacterium Achromobacter insolitus LCu2.

A rhizosphere strain, Achromobacter insolitus LCu2, was isolated from alfalfa (Medicago sativa L.) roots. It was able to degrade of 50% glyphosate as the sole phosphorus source, and was found resistant to 10mM copper (II) chloride, and 5mM glyphosate-copper complexes. Inoculation of alfalfa seedlings and potato microplants with strain LCu2 promoted plant growth by 30-50%. In inoculated plants, the toxicity of the glyphosate-copper complexes to alfalfa seedlings was decreased, as compared with the noninoculated controls. The genome of A. insolitus LCu2 consisted of one circular chromosome (6,428,890bp) and encoded 5843 protein genes and 76 RNA genes. Polyphasic taxonomic analysis showed that A. insolitus LCu2 was closely related to A. insolitus DSM23807T on the basis of the average nucleotide identity of the genomes of 22 type strains and the multilocus sequence analysis. Genome analysis revealed genes putatively responsible for (1) plant growth promotion (osmolyte, siderophore, and 1-aminocyclopropane-1-carboxylate deaminase biosynthesis and auxin metabolism); (2) degradation of organophosphonates (glyphosate oxidoreductase and multiple phn clusters responsible for the transport, regulation and C-P lyase cleavage of phosphonates); and (3) tolerance to copper and other heavy metals, effected by the CopAB-CueO system, responsible for the oxidation of copper (I) in the periplasm, and by the efflux Cus system. The putative catabolic pathways involved in the breakdown of phosphonates are predicted. A. insolitus LCu2 is promising in the production of crops and the remediation of soils contaminated with organophosphonates and heavy metals.

Microbial detoxification of chlorpyrifos, profenofos, monocrotophos, and dimethoate by a multifaceted rhizospheric Bacillus cereus strain PM38 and its potential for the growth promotion in cotton.

Bacillus genera, especially among rhizobacteria, are known for their ability to promote plant growth and their effectiveness in alleviating several stress conditions. This study aimed to utilize indigenous Bacillus cereus PM38 to degrade four organophosphate pesticides (OPs) such as chlorpyrifos (CP), profenofos (PF), monocrotophos (MCP), and dimethoate (DMT) to mitigate the adverse effects of these pesticides on cotton crop growth. Strain PM38 exhibited distinct characteristics that set it apart from other Bacillus species. These include the production of extracellular enzymes, hydrogen cyanide, exopolysaccharides, Indol-3-acetic acid (166.8μg/mL), siderophores (47.3μg/mL), 1-aminocyclopropane-1-carboxylate deaminase activity (32.4μg/mL), and phosphorus solubilization (162.9μg/mL), all observed at higher concentrations. This strain has also shown tolerance to salinity (1200mM), drought (20% PEG-6000), and copper and cadmium (1200mg/L). The amplification of multi-stress-responsive genes, such as acdS, ituC, czcD, nifH, sfp, and pqqE, further confirmed the plant growth regulation and abiotic stress tolerance capability in strain PM38. Following the high-performance liquid chromatography (HPLC) analysis, the results showed striking compatibility with the first kinetic model. Strain PM38 efficiently degraded CP (98.4%), PF (99.7%), MCP (100%), and DMT (95.5%) at a concentration of 300ppm over 48h at 35°C under optimum pH conditions, showing high coefficients of determination (R2) of 0.974, 0.967, 0.992, and 0.972, respectively. The Fourier transform infrared spectroscopy (FTIR) analysis and the presence of opd, mpd, and opdA genes in the strain PM38 further supported the potential to degrade OPs. In addition, inoculating cotton seedlings with PM38 improved root length under stressful conditions. Inoculation of strain PM38 reduces stress by minimizing proline, thiobarbituric acid-reactive compounds, and electrolyte leakage. The strain PM38 has the potential to be a good multi-stress-tolerant option for a biological pest control agent capable of improving global food security and managing contaminated sites.

Phytochemical and biological assessment of secondary metabolites isolated from a rhizosphere strain, Sphingomonas sanguinis DM of Datura metel

BackgroundThe plant roots excrete a large number of organic compounds into the soil. The rhizosphere, a thin soil zone around the roots, is a hotspot for microbial activity, making it a crucial component of the soil ecosystem. Secondary metabolites produced by rhizospheric Sphingomonas sanguinis DM have sparked significant curiosity in investigating their possible biological impacts.MethodsA bacterial strain has been isolated from the rhizosphere of Datura metel. The bacterium’s identification, fermentation, and working up have been outlined. The ethyl acetate fraction of the propagated culture media of Sphingomonas sanguinis DM was fractioned and purified using various chromatographic techniques. The characterization of the isolated compounds was accomplished through the utilization of various spectroscopic techniques, such as UV, MS, 1D, and 2D-NMR. Furthermore, the evaluation of their antimicrobial activity was conducted using the agar well diffusion method, while cytotoxicity was assessed using the MTT test.ResultsThe extract from Sphingomonas sanguinis DM provided two distinct compounds: n-dibutyl phthalic acid (1) and Bis (2-methyl heptyl) phthalate (2) within its ethyl acetate fraction. Furthermore, the 16S rRNA gene sequence of Sphingomonas sanguinis DM has been registered under the NCBI GenBank database with the accession number PP422198. The bacterial extract exhibited its effect against gram-positive bacteria, inhibiting Streptococcus mutans (12.6 ± 0.6 mm) and Staphylococcus aureus (10.6 ± 0.6 mm) compared to standard antibiotics. Conversely, compound 1 showed a considerable effect against phytopathogenic fungi such as Alternaria alternate (56.3 ± 10.6 mm) and Fusarium oxysporum (21.3 ± 1.5 mm) with a MIC value of 17.5 µg/mL. However, it was slightly active against Klebsiella pneumonia (11.0 ± 1.0 mm). Furthermore, compound 2 was the most active metabolite, having a significant antimicrobial efficacy against Rhizoctonia solani (63.6 ± 1.1 mm), Pseudomonas aeruginosa (16.7 ± 0.6 mm), and Alternaria alternate (20.3 ± 0.6 mm) with MIC value at 15 µg/mL. In addition, compound 2 exhibited the most potency against hepatocellular (HepG-2) and skin (A-431) carcinoma cell lines with IC50 values of 107.16 µg/mL and 111.36 µg/mL, respectively.ConclusionSphingomonas sanguinis DM, a rhizosphere bacterium of Datura metel, was studied for its phytochemical and biological characteristics, resulting in the identification of two compounds with moderate antimicrobial and cytotoxic activities.

Characterisation of the Endophytic and Rhizospheric Bacillus licheniformis Strains Isolated from Sweet Potato with Plant Growth-Promoting and Yield Enhancing Potential

The primary aim of the present study was to identify bacterial isolates with yield-enhancing potential for application as biofertilisers in the cultivation of sweet potato. Therefore, endophytic and rhizospheric strains were isolated from sweet potato plantations in Hungary to identify bacterial strains with plant growth-promoting and antifungal potential. In total, seven Bacillus licheniformis strains were identified and subjected to detailed ecophysiological investigations. Experiments have been conducted to investigate the tolerance of selected strains to different limiting factors such as pH, temperature, and water activity, which affect survivability in various agricultural environments. The majority of tested B. licheniformis strains exhibited plant growth-promoting potential (e.g., production of indole-3-acetic acid up to 40.42 μg mL−1, production of ammonia up to 0.87 mg mL−1, phosphorus solubilising activity, siderophore production), with two strains (SZMC 27713 and SZMC 27715) demonstrating inhibitory activity (ranging between 7% and 38%) against plant pathogenic fungi prevalent in sweet potato cultivation. Furthermore, strain SZMC 27715 induced accelerated germination and a significantly higher germination rate in tomato seeds compared to the control. In a field study, it was observed that strain SZMC 27715 had a potent yield enhancing effect in sweet potato, where a significant yield per plant increase was observed in all treatments (1.13, 1.09 and 1.40 kg) compared to the control plants (0.92 kg). The highest yield per plant was observed when the cuttings were soaked combined with two additional foliar treatments. To the best of our knowledge, this is the first report of the successful utilisation of the B. licheniformis strain as a biofertiliser for yield enhancement in sweet potato cultivation. Based on our results, strain SZMC 27715 has potential for application as a biofertiliser in sweet potato cultivation either as a standalone option or in a microbial consortium.

Nutritional enhancement in black seed (Nigella sativa L.) using bacteria‐based biofertilizers

AbstractNigella sativa L. is an aromatic spice, utilized as an original and peculiar flavoring ingredient in a variety of culinary applications and pharmaceuticals. Black seed (Nigella sativa L.) belongs to the family Ranunculaceae. It is an undercultivated crop in Pakistan. The present study was planned keeping in mind sustainable development goals SDG 3 (good health and well‐being) and SDG 15 (life on land). The effects of several rhizospheric bacterial strains and synthetic fertilizers on the development of N. sativa and nutrition were studied using a completely randomized experimental design. For this purpose, plant growth‐promoting effects of different strains (Azospirillum brasilense, Azospirillum lipoferum, and Pantoea agglomerans) and synthetic fertilizers (nitrogen and phosphorus) were assembled to check their effects individually and in combination form. Azospirillum lipoferum and Pantoea agglomerans inoculation significantly enhanced the morphological characteristics of N. sativa, whether applied individually or in combination, with positive effects on seedlings, plant height, number of branches, number of leaves, number of flowers, stamens numbers, follicles number, number of tentacles and seed production. N. sativa plants that were simultaneously inoculated with Azospirillum lipoferum and Pantoea agglomerans showed the highest potential for antioxidant activity, particularly in petroleum ether extracts. In the methanolic extract, a higher amount of radical scavenging was observed as compared to positive and negative control. There was also increase in fat, moisture and carbohydrate contents of the combination inoculated plant. So, from the present study, in Pakistan, the technique is recommended to enhance the yield and nutritional value of N. sativa.

RsaL is a self-regulatory switch that controls alternative biosynthesis of two AHL-type quorum sensing signals in Pseudomonas aeruginosa PA1201.

Pseudomonas aeruginosa is a ubiquitous and metabolically versatile microorganism naturally found in soil and water. It is also an opportunistic pathogen in plants, insects, animals, and humans. In response to increasing cell density, P. aeruginosa uses two acyl-homoserine lactone (AHL) quorum-sensing (QS) signals (i.e.,N-3-oxo-dodecanoyl homoserine lactone [3-oxo-C12-HSL] and N-butanoyl-homoserine lactone [C4-HSL]), which regulate the expression of hundreds of genes. However, how the biosynthesis of these two QS signals is coordinated remains unknown. We studied the regulation of these two QS signals in the rhizosphere strain PA1201. PA1201 sequentially produced 3-oxo-C12-HSL and C4-HSL at the early and late growth stages, respectively. The highest 3-oxo-C12-HSL-dependent elastase activity was observed at the early stage, while the highest C4-HSL-dependent rhamnolipid production was observed at the late stage. The atypical regulator RsaL played a pivotal role in coordinating 3-oxo-C12-HSL and C4-HSL biosynthesis and QS-associated virulence. RsaL repressed lasI transcription by binding the -10 and -35 boxes of the lasI promoter. In contrast, RsaL activated rhlI transcription by binding the region encoding the 5'-untranslated region of the rhlI mRNA. Further, RsaL repressed its own expression by binding a nucleotide motif located in the -35 box of the rsaL promoter. Thus, RsaL acts as a molecular switch that coordinates the sequential biosynthesis of AHL QS signals and differential virulence in PA1201. Finally, C4-HSL activation by RsaL was independent of the Las and Pseudomonas quinolone signal (PQS) QS signaling systems. Therefore, we propose a new model of the QS regulatory network in PA1201, in which RsaL represents a superior player acting at the top of the hierarchy.

Sustainable agriculture through rhizosphere bacteria for plant growth promotion, nutrient acquisition, and stress alleviation

Rhizosphere bacteria are attracting a lot of interest in sustainable agriculture because of their capacity to stimulate plant growth, improve nutrient uptake, and reduce stress in plants. A review of recent discoveries in the field of using rhizosphere bacteria for these advantageous agricultural techniques is given in this article. Rhizosphere bacteria facilitate plant growth by solubilizing inaccessible elements like phosphorus, potassium, zinc, and manganese by producing a variety of enzymes and organic acids. Furthermore, these bacteria support plant nutrition by fixing atmospheric nitrogen, a necessary component for plant growth and development. Moreover, some rhizosphere bacterial strains can inhibit plant diseases, which lessen the need for artificial chemical pesticides. Rhizosphere bacteria have improved plant stress tolerance by producing stress-related substances, including phytohormones and osmoprotectants. These bacteria also give rise to systemic resistance in plants, successfully allowing them to survive various biotic and abiotic challenges. Concerning climate change and environmental variations, this rhizosphere bacteria-mediated stress reduction component holds a tremendous potential for sustainable agriculture. But for rhizosphere bacteria-based agricultural techniques to be successfully utilized, a thorough grasp of their variety, ecological relationships, and mode of action are necessary. Optimizing application techniques, formulating bioinoculants, and considering environmental aspects are crucial for consistent and dependable outcomes through rhizosphere bacteria.

N- acyl homoserine lactones (AHLs) type signal molecules produced by rhizobacteria associated with plants that growing in a metal(oids) contaminated soil: A catalyst for plant growth

The present study explores the potential of rhizobacteria isolated from Baccharis linearis and Solidago chilensis in metal(loid)-contaminated soil for producing N-acyl-homoserine lactones (AHLs)-type signal molecules and promoting plant growth. A total of 42 strains were isolated, four demonstrating the production of AHL-type signal molecules. Based on 16S rRNA gene sequencing analyses and MALDI-TOF analyses, these four isolates were identified as belonging to the Pseudomonas genus, specifically P. brassicacearum, P. frederickberguensis, P. koreensis, and P. orientalis. The four AHL-producing strains were evaluated for metal(loid)s tolerance, their plant growth promotion traits, AHL quantification, and their impact on in vitro Lactuca sativa plant growth.The study found that four strains exhibited high tolerance to metal(loid)s, particularly As, Cu, and Zn. Additionally, plant growth-promoting traits were detected in AHL-producing bacteria, such as siderophore production, ammonia production, ACC deaminase activity, and P solubilization. Notably, AHL production varied among strains isolated from B. linearis, where C7-HSL and C9-HSL signal molecules were detected, and S. chilensis, where only C7-HSL signal molecules were observed. In the presence of copper, the production of C7-HSL and C9-HSL significantly decreased in B. linearis isolates, while in S. chilensis isolates, C7-HSL production was inhibited. Further, when these strains were inoculated on lettuce seeds and in vitro plants, a significant increase in germination and plant growth was observed. Mainly, the inoculation of P. brassicacearum and P. frederickberguensis led to extensive root hair development, significantly increasing length and root dry weight.Our results demonstrate that rhizospheric strains produce AHL molecules and stimulate plant growth, primarily through root development. However, the presence of copper reduces the production of these molecules, potentially affecting the root development of non-metalloid tolerant plants such as S. chilensis, which would explain its low population in this hostile environment.

Root-associated Streptomyces produce galbonolides to modulate plant immunity and promote rhizosphere colonization.

The rhizosphere, which serves as the primary interface between plant roots and the soil, constitutes an ecological niche for a huge diversity of microbial communities. Currently, there is little knowledge on the nature and the function of the different metabolites released by rhizospheric microbes to facilitate colonization of this highly competitive environment. Here, we demonstrate how the production of galbonolides, a group of polyene macrolides that inhibit plant and fungal inositol phosphorylceramide synthase (IPCS), empowers the rhizospheric Streptomyces strain AgN23, to thrive in the rhizosphere by triggering the plant's defence mechanisms. Metabolomic analysis of AgN23-inoculated Arabidopsis roots revealed a strong induction in the production of an indole alkaloid, camalexin, which is a major phytoalexin in Arabidopsis. By using a plant mutant compromised in camalexin synthesis, we show that camalexin production is necessary for the successful colonization of the rhizosphere by AgN23. Conversely, hindering galbonolides biosynthesis in AgN23 knock-out mutant resulted in loss of inhibition of IPCS, a deficiency in plant defence activation, notably the production of camalexin, and a strongly reduced development of the mutant bacteria in the rhizosphere. Together, our results identified galbonolides as important metabolites mediating rhizosphere colonization by Streptomyces.

Use of plant growth-promoting bacteria to facilitate phytoremediation.

Here, phytoremediation studies of toxic metal and organic compounds using plants augmented with plant growth-promoting bacteria, published in the past few years, were summarized and reviewed. These studies complemented and extended the many earlier studies in this area of research. The studies summarized here employed a wide range of non-agricultural plants including various grasses indigenous to regions of the world. The plant growth-promoting bacteria used a range of different known mechanisms to promote plant growth in the presence of metallic and/or organic toxicants and thereby improve the phytoremediation ability of most plants. Both rhizosphere and endophyte PGPB strains have been found to be effective within various phytoremediation schemes. Consortia consisting of several PGPB were often more effective than individual PGPB in assisting phytoremediation in the presence of metallic and/or organic environmental contaminants.

Inoculation with plant growth-promoting rhizobacteria improves seagrass Thalassia hemprichii photosynthesis performance and shifts rhizosphere microbiome

Plant growth-promoting rhizobacteria (PGPR) inoculation is a crucial strategy for maintaining the sustainability of agriculture and presents a promising solution for seagrass ecological restoration in the face of disturbances. However, the possible roles and functions of PGPRs in the seagrass rhizosphere remain unclear. Here, we isolated rhizosphere bacterial strains from both reef and coastal regions and screened two PGPR isolates regarding their in vivo functional traits. Subsequently, we conducted microcosm experiments to elucidate how PGPR inoculation affected seagrass photosynthesis and shape within each rhizosphere microbiome. Both screened PGPR strains, Raoultella terrigena NXT28 and Bacillus aryabhattai XT37, excelled at expressing a specific subset of plant-beneficial functions and increased the photosynthetic rates of the seagrass host. PGPR inoculation not only decreased the abundance of sulfur-cycling bacteria, it also improved the abundance of putative iron-cycling bacteria in the seagrass rhizosphere. Strain XT37 successfully colonized the seagrass rhizosphere and displayed a leading role in microbial network structure. As a nitrogen-fixing bacteria, NXT28 showed potential to change the microbial nitrogen cycle with denitrification in the rhizosphere and alter dissimilatory and assimilatory nitrate reduction in bulk sediment. These findings have implications for the development of eco-friendly strategies aimed at exploiting microbial communities to confer sulfide tolerance in coastal seagrass ecosystem.

The Imperative Use of Bacillus Consortium and Quercetin Contributes to Suppress Fusarium Wilt Disease by Direct Antagonism and Induced Resistance.

Fusarium wilt diseases severely influence the growth and productivity of numerous crop plants. The consortium of antagonistic rhizospheric Bacillus strains and quercetin were evaluated imperatively as a possible remedy to effectively manage the Fusarium wilt disease of tomato plants. The selection of Bacillus strains was made based on in-vitro antagonistic bioassays against Fusarium oxysporum f.sp. lycoprsici (FOL). Quercetin was selected after screening a library of phytochemicals during in-silico molecular docking analysis using tomato LysM receptor kinases "SILKY12" based on its dual role in symbiosis and plant defense responses. After the selection of test materials, pot trials were conducted where tomato plants were provided consortium of Bacillus strains as soil drenching and quercetin as a foliar spray in different concentrations. The combined application of consortium (Bacillus velezensis strain BS6, Bacillus thuringiensis strain BS7, Bacillus fortis strain BS9) and quercetin (1.0 mM) reduced the Fusarium wilt disease index up to 69%, also resulting in increased plant growth attributes. Likewise, the imperative application of the Bacillus consortium and quercetin (1.0 mM) significantly increased total phenolic contents and activities of the enzymes of the phenylpropanoid pathway. Non-targeted metabolomics analysis was performed to investigate the perturbation in metabolites. FOL pathogen negatively affected a range of metabolites including carbohydrates, amino acids, phenylpropanoids, and organic acids. Thereinto, combined treatment of Bacillus consortium and quercetin (1.0 mM) ameliorated the production of different metabolites in tomato plants. These findings prove the imperative use of Bacillus consortium and quercetin as an effective and sustainable remedy to manage Fusarium wilt disease of tomato plants and to promote the growth of tomato plants under pathogen stress conditions.

Antifungal Trait and Plant Growth Promotion Potential of Bacillus Spp. from Rhizosphere Soils of Black Aromatic Rice, ‘Chakhao’

Manipuri black aromatic rice, ‘Chakhao’, is a nutrient rich unique local rice cultivar of Manipur, India. Rhizosphere bacteria may have potential as antifungal agent and seedling growth promoter. Hence, the current investigation was aimed at screening, for the above traits, using bacteria, Bacillus spp., isolated from the soil of Rhizosphere of six Chakhao rice cultivars. Altogether, 323 bacterial isolates were obtained from the rhizospheric soils of 6 different cultivars of Chakhao, namely Chakhao Amubi (CA), Chakhao Poireiton (CP), Chakhao Sempak (CS), Chakhao Angoubi (CAng), Chakhao Angangbi (CR) and Chakhao Wairi (CW). All the rhizobacterial isolates were screened for antifungal activity against 5 rice fungal pathogens viz. Rhizoctonia solani (RS), Fusarium oxysporum (FO), Curvularia oryzae (CO), Pyricularia oryzae (PO) and Aspergillus niger (AN). The isolates were also subjected to PGP (plant growth promotion) assays such as ammonia, indole acetic acid (IAA), siderophore and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production, and phosphate solubilization. Of 323 isolates obtained, 64 were found to exhibit antifungal activity while 69 showed PGP traits. Twenty-five (25) isolates were found to be positive for both antifungal and PGP traits. Of 25 bioactive isolates, 4 (CR12, CW11, CA2 and CP2) potent isolates were shortlisted for further studies. The shortlisted potent isolates were subjected to quantitative estimation of PGP activities like phosphate solubilization, IAA and siderophore production. The strains could produce significant amount of IAA and siderophore and solubilize phosphate. Molecular characterization by 16S rDNA sequence analyses revealed the identity of the isolates: CR12: Bacillus subtilis (Accn. No.OM866257), CW11: Bacillus paralicheniformis (Accn. No.OM868047), CA2: Bacillus sp. CCMB1014 (Accn. No.OM868070) and CP2: Bacillus licheniformis (Accn. No.OM892495). Seedling vigor assays of the shortlisted potent strains were carried out on Chakhao Amubi rice. The isolates exhibited higher seedling vigor indices (CR12: 668.00, CA2: 618.66, CP2: 510.92 and CW11: 478.91) over the control (164.48). These rhizospheric strains have the potential to be developed as bioinoculants or biostimulants for enhancing Chakhao rice growth.

Structurally Diverse Metabolites from the Marine-Derived Streptomyces sp. DS-27 Based on Two Different Culture Conditions.

Nine new compounds, including streptothiomycin A-E (1-5), two cyclopentenones (6, 7), one α-pyrone (8), wailupemycin Q (20), along with sixteen known compounds were identified from a rhizosphere strain Streptomyces sp. DS-27 derived from the marine cordgrass Spartina alterniflora under two different culture conditions. All of the structures were elucidated by extensive analysis of 1D/2D NMR and HR-ESI-MS data. The absolute configurations were determined by NOESY analysis, ECD, specific rotation and GIAO NMR calculations, and DP4+ probability analysis. Bioactivity investigation showed that compounds 5 and 7 exhibited significant inhibitory effects on LPS-induced NO production in a dose-dependent manner, which indicates their anti-inflammatory potential.

Characterization and Antioxidant Activity of Exopolysaccharides Produced by Lysobacter soyae sp. nov Isolated from the Root of Glycine max L.

Microbial exopolysaccharides (EPSs) have attracted attention from several fields due to their high industrial applicability. In the present study, rhizosphere strain CJ11T was isolated from the root of Glycine max L. in Goyang-si, Republic of Korea, and a novel exopolysaccharide was purified from the Lysobacter sp. CJ11T fermentation broth. The exopolysaccharide's average molecular weight was 0.93 × 105 Da. Its monosaccharide composition included 72.2% mannose, 17.2% glucose, 7.8% galactose, and 2.8% arabinose. Fourier-transform infrared spectroscopy identified the exopolysaccharide carbohydrate polymer functional groups, and the structural properties were investigated using nuclear magnetic resonance. In addition, a microstructure of lyophilized EPS was determined by scanning electron microscopy. Using thermogravimetric analysis, the degradation of the exopolysaccharide produced by strain CJ11T was determined to be 210 °C. The exopolysaccharide at a concentration of 4 mg/mL exhibited 2,2-diphenyl-1-picrylhydrazyl free-radical-scavenging activity of 73.47%. Phylogenetic analysis based on the 16S rRNA gene sequencing results revealed that strain CJ11T was a novel isolate for which the name Lysobacter soyae sp. nov is proposed.

Trichoderma viride establishes biodefense against clubroot (Plasmodiophora brassicae) and fosters plant growth via colonizing root hairs in pak choi (Brassica campestrisspp.chinesnsis)

The significant economic importance of the pak choi crop leads farmers to take numerous measures to combat the club root disease, which is harmful to Brassicaceae plants. The mechanical understanding of clubroot biocontrol, on the other part, is still largely unknown. The fundamental criterion for choosing rhizospheric strains obtained from tomato was the germination inhibitory activity of Plasmodiophora brassicae resting spores. The resting spores of the clubroot causing pathogen were inhibited by 10 fungal isolates. TR-7 had the strongest inhibitory impact, reducing spore germination to 25.3 %. The plant growth promoting and extracellular enzyme activities of the fungal strain TR-7 were investigated. TR-7 produced indole acetic acid (IAA), as well as siderophore and extracellular enzymatic activities. Inoculation with strain TR-7 improved pak choi plant growth in greenhouse settings when compared to plants grown without TR-7 and P. brassicae infected plants. During fungal association, the activity of lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), and malate dehydrogenase (MDH) was dramatically enhanced in clubroot infected plants. Co-inoculation including both P. brassicae and TR-7 showed 56.7 % decline in gall growth when compared to plants only infected with P. brassicae. Multiple treatments of TR-7 were more efficient than one treatment at repressing root hair infestation in clubroot infected plants at 7, 14, and 21 days after inoculation (DAI). TR-7 was identified as Trichoderma viride based on the internal transcribed spacer (ITS) sequence analysis. The findings show that the application of T. viride as bio-fungicides provides another potential promising strategy for suppressing clubroot disease in pak choi.

Biocontrol Potential of Some Rhizospheric Soil Bacterial Strains against Fusarium culmorum and Subsequent Effect on Growth of Two Tunisian Wheat Cultivars

PGPR (Plant Growth Promoting Rhizobacteria) are used as biofertilizers and biological control agents against fungi. The objective of this work was to evaluate the antagonistic activities of some bacterial strains isolated from soil against four phytopathogenic fungal strains (Fusarium graminearum, F. culmorum, Phytophthora sp. and Verticillium dahlia). Two strains having an antagonist effect on fungi and displaying the maximum of plant growth promoting (PGP) traits were selected for further study and identified as Bacillus subtilis and B. amyloliquefaciens respectively. In planta assays demonstrated that the two Bacillus strains are able to enhance plant growth of two wheat cultivars in absence of nitrogen and protect them against F. culmorum. Pot experiments performed in a greenhouse showed that wheat plants inoculation with two bacterial strains reduce F. culmorum disease severity correlated with the accumulation of phenolic compounds and chlorophyll content. These could partly explain the effectiveness of these bacteria in protecting Tunisian durum wheat cultivars against F. culmorum. Application B. amyloliquefaciens, showed better protection than B. subtilis although the last one enhanced more the plant growth of two wheat cultivars in absence of fungus. Hence, combination of two bacterial strains could be a strategic approach to enhance plant growth and control plant diseases.

Genome Sequence of the Streptomyces Strain AgN23 Revealed Expansion and Acquisition of Gene Repertoires Potentially Involved in Biocontrol Activity and Rhizosphere Colonization

Streptomycetes are gram-positive actinobacteria largely represented in the plant root microbiota. The genetic determinants involved in the adaption of Streptomyces in the rhizosphere environment are mostly unknown but can rely on the ability to release phytohormones, degrade plant cell-wall polysaccharides, and produce specialized metabolites notably involved in microbial competition. Here, we sequenced the genome of the rhizospheric and plant defense-stimulating strain Streptomyces sp. AgN23. We found that it belongs to the soil- and plant root-dwelling S. violaceusniger clade. The genome annotation of AgN23 revealed the genetic potential of the bacterium to degrade the plant cell wall with a large repertoire of carbohydrate degrading enzymes, to synthesize auxin, a major regulator of plant development, and to produce antimicrobials (rustmicin, mediomycin, niphimycin, nigericin) and plant bioactive compounds (nigericin, echosides, elaiophylin) through a set of biosynthetic gene clusters. We also found that these genomic features are well conserved among members of the S. violaceusniger clade. In addition, AgN23 displays original events of biosynthetic gene cluster acquisitions and losses, which may account for its interaction with plants. Taken together, our work supports the hypothesis that evolution of a large set of conserved hydrolytic enzymes directed against plant polymers and specialized metabolite repertoires can mediate the adaptation of S. violaceusniger strains to the rhizospheric ecological niches. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .