Plant Growth-promoting Microbes Research Articles

Selected Beneficial Microbes Alleviate Salinity Stress in Hydroponic Lettuce and Pak Choi

Hydroponics is widely used in greenhouse and vertical farming production because these facilities can precisely control environmental conditions such as lighting, temperature, and vapor pressure deficit. However, the fertilizer solutions have a short life span, and they often do not have adequate microbial populations to enhance plant growth. Previous studies have shown the potential of beneficial microbes to promote plant production and alleviate abiotic and biotic stressors in the field, and studies on their use in controlled environments such as greenhouses and vertical farms are limited in the literature. In this study, we selected several plant growth promoting microbes (PGPMs) and tested their effects on alleviating salinity stress in ‘Rex’ lettuce (Lactuca sativa) and ‘Red Pac’ pak choi (Brassica chinensis) grown in deep water culture hydroponics. Our goal was to use one stressor, salinity, that induces profound symptoms in plant morphology. A three-cycle study was conducted using five PGPMs [Bacillus, Glomus, Lactobacillus, Trichoderma, and Bacillus/Pseudomonas/Trichoderma (B/P/T) mix] and two salinity levels [no salinity and salinity treatment, with 120 mM, 40 mM, and 80 mM sodium chloride (NaCl) solution used for the first, second, and third cycles, respectively]. We measured the effects of PGPMs and salinity on plant growth and quality and the solution pH and electrical conductivity (EC). Salinity stress decreased lettuce and pak choi leaf area and shoot fresh weight and increased plant leaf chlorophyll and anthocyanin contents with increased solution EC. Under high-salinity stress (120 mM NaCl), the addition of Trichoderma reduced pak choi leaf area and fresh weight but increased solution pH, whereas under low salinity stress (40 mM NaCl), Trichoderma increased pak choi leaf chlorophyll content. Under moderate-salinity stress (80 mM NaCl) condition, the addition of Glomus sp. increased lettuce fresh weight and leaf area, and B/P/T mix increased pak choi leaf area. In conclusion, using the selected PGPMs in low to moderate-salinity stress could increase lettuce and pak choi growth and quality parameters. These results have some practical applications in the future when more saline water is used for production.

Linnemannia elongata: A Key Species in Chitin-Based Plant Growth Promotion

Chitin has proven to be a valuable alternative to mineral fertilizers in growing media. We recently hypothesized that chitin might work as a biostimulant, attracting plant growth-promoting microbes to the rhizosphere. In particular, Mortierellales species increase in abundance massively with chitin application and might have a profound role in chitin-mediated plant growth promotion. We isolated four strains of this order classified as Linnemannia elongata from chitin-enriched growing medium and the lettuce rhizosphere. The isolates induced a consistent increase in shoot and root fresh weight and increased chlorophyll content of Arabidopsis thaliana in vitro, as measured by multispectral imaging. By studying the isolate's genomes, we postulated that this growth promotion was induced through auxin production, translocation of calcium to the plant, or both. The synergy between chitin and L. elongata was demonstrated by (i) the chitinase activity and chitin degradation potential of all isolates and (ii) the positive effect of chitin and L. elongata seed coating on germination of A. thaliana seeds compared with L. elongata seed coating without chitin. We conclude that chitin-related growth promotion is dependent on activation of the microbial community, with L. elongata as a key species. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Evolution and adaptation of terrestrial plant-associated Plantibacter species into remote marine environments.

Microbes are thought to be distributed and circulated around the world, but the connection between marine and terrestrial microbiomes remains largely unknown. We use Plantibacter, a representative genus associated with plants, as our research model to investigate the global distribution and adaptation of plant-related bacteria in plant-free environments, particularly in the remote Southern Ocean and the deep Atlantic Ocean. The marine isolates and their plant-associated relatives shared over 98% whole-genome average nucleotide identity (ANI), indicating recent divergence and ongoing speciation from plant-related niches to marine environments. Comparative genomics revealed that the marine strains acquired new genes via horizontal gene transfer from non-Plantibacter species and refined existing genes through positive selection to improve adaptation to new habitats. Meanwhile, marine strains retained the ability to interact with plants, such as modifying root system architecture and promoting germination. Furthermore, Plantibacter species were found to be widely distributed in marine environments, revealing an unrecognized phenomenon that plant-associated microbiomes have colonized the ocean, which could serve as a reservoir for plant growth-promoting microbes. This study demonstrates the presence of an active reservoir of terrestrial plant growth-promoting bacteria in remote marine systems and advances our understanding of the microbial connections between plant-associated and plant-free environments at the genome level.

Physiological and photochemical profiling of soybean plant using biological and chemical methods of treatment against biotic stress management

Phyto-pathogenic fungal species is a leading biotic stress factor to agri-food production and ecosystem of globe. Chemical (Systemic fungicides) and biological treatment (micro-organism) are globally accepted methods that are being used against biotic stress (disease) management. Plant Growth-Promoting Microbes are being used as an alternative to ease chemical dependency as their overdoses have generated injurious effects on plants and environment. Therefore, present study performs to evaluate the photochemical and physiological profiling of plants exposed to chemical and biological treatment in biotic stress (disease) environment. Two concentrations of each chemical treatment i.e. Topsin-M 70 (Dimethyl 4,4′-o-phenylene bis 3-thioallaphanate, MF1 = 3 g kg−1 and MF2 = 6 g kg−1 seeds) and biological treatment i.e. Trichoderma harzianum strain Th-6 (MT1 = 106 spores mL−1and MT2 = 107 spores mL−1) were used in this experiment. Macrophomina phaseolina (MP) were used as biotic stress factor causing root rot disease in soybean plants. Morpho-physiological assessments and light harvesting efficiency of photosystem II were conducted after 52 days of treatment. Maximum quantum yield (Fv/Fm), number and size of active reaction center (Fv/Fo), photochemical quenching (qP), efficiency of photosystem II (ΦPSII), electron transport rate (ETR), chlorophyll content index (CCI), relative water content (RWC) and stomatal conductance (SC) were increased in MT2 and MF1 treatments as compared to stress plants (MP). Biological (MT2) and chemical (MF1) treatment lessen the production of stress markers showing −48.0 to −54.3% decline in malondialdehyde (MDA) and −42.0 to −53.7% in hydrogen peroxide (H2O2) as compared to stress plant (MP). Biological treatment in both concentration (MF1 & MF2) while chemical treatment at low dose effectively mitigates biotic stress and eases the magnitude of disease. Increasing doses of chemical treatment persuaded deleterious effects on the physiology and light harvesting efficiency of stressed plant suggesting the role of biological treatment (T. harzianum) against biotic stress management in future of crop protection.

Lactic acid bacteria as an eco-friendly approach in plant production: Current state and prospects.

Since the late nineteenth century, the agricultural sector has experienced a tremendous increase in chemical use in response to the growing population. Consequently, the intensive and indiscriminate use of these substances caused serious damage on several levels, including threatening human health, disrupting soil microbiota, affecting wildlife ecosystems, and causing groundwater pollution. As a solution, the application of microbial-based products presents an interesting and ecological restoration tool. The use of Plant Growth-Promoting Microbes (PGPM) affected positive production, by increasing its efficiency, reducing production costs, environmental pollution, and chemical use. Among these microbial communities, lactic acid bacteria (LAB) are considered an interesting candidate to be formulated and applied as effective microbes. Indeed, these bacteria are approved by the European Food Safety Authority (EFSA) and Food and Drug Administration (FDA) as Qualified Presumption of Safety statute and Generally Recognized as Safe for various applications. To do so, this review comes as a road map for future research, which addresses the different steps included in LAB formulation as biocontrol, bioremediation, or plant growth promoting agents from the isolation process to their field application passing by the different identification methods and their various uses. The plant application methods as well as challenges limiting their use in agriculture are also discussed.

Potassium Solubilizers, Aspergillus sp. and Trichoderma sp. Promote Growth in Tomato


 
 
 Potassium (K) is the third most significant plant macronutrient that plays a crucial role in growth and development of plants. K is abundant in soil, but 90-98% of K exists as insoluble minerals and only 1-2% becomes available to the plants. Certain microbes, K solubilizing microbes (KSMs), can solubilize unavailable forms of K and making it available to plants. The objective of the current study was to evaluate the growth promotion ability of two previously (2019) isolated KSMs, Aspergillus sp. and Trichoderma sp in-vitro and under greenhouse conditions using feldspar as the K source. Khandeparkar‘s selection ratio calculated based on K solubilizing assay on Alexandrov medium showed that Aspergillus (1.72+0.16) has a higher and faster K solubilization ability than Trichoderma (1.0+0.16). Effect of KSMs was assayed in a Tomato seed germination assay carried out in Petri plates with KSMs treated and non-treated soils. Both Aspergillus (58%) and Trichoderma (72%) showed enhanced percentage germination of tomato seeds under in vitro conditions compared to that of controls (Aspergillus sp.: 24%, 14%, 22.7%, 51.3%, 39.3%, Trichoderma sp.: 22%, 12%, 13%, 59%, 51%) which was statistically significant (Aspergillus, P=0.026; Trichoderma, P=0.003) at 0.05 confidence level. Seedling length (P=0.102, P=0.028) and root length (P=0.453, P=0.002) of tomato were enhanced when raised in non-autoclaved natural soil than autoclaved natural soil inoculated with Aspergillus and Trichoderma respectively. The greenhouse experiment was carried out with same experimental set up as an in vitro assay. No significant difference was observed in shoot length, number of leaves and length of leaves of tomato plants planted in soil treated with Aspergillus (P=0.093, P=0.906, P=0.260) and Trichoderma (P=0.334, P=0.239, P=0.243) respectively in comparison to controls during the vegetative stage (2 months after sawing). However, flowering was started four days early in plants planted in non-autoclaved soil treated with Aspergillus sp. suggesting that the impact of Aspergillus sp. starts to become visible in the reproductive stage. The results suggest that K solubilizing ability of Aspergillus sp. and Trichoderma sp. seem to show a positive effect on germination ability of tomato, however, only Aspergillus sp. seems to have a positive effect on the later stages of plant growth where K is mainly needed for flower and fruit development. Therefore, Aspergillus sp. can be a potential candidate to be used in up scaling the natural K fertilizers such as feldspar after intensive future experimentation.
 Keywords: Plant Growth Promoting Microbes (PGPMs), Growth promotion, K deficiency
 
 

Combined Effect of Biochar and Plant Growth-Promoting Rhizbacteria on Physiological Responses of Canola (Brassica napus L.) Subjected to Drought Stress

AbstractBiochar (BC) and plant growth-promoting microbes (PGPR) could represent a suitable agronomical strategy to mitigate the impacts of drought in arid agro-environmental conditions. However, there is currently little understanding of the synergistic benefit of combining BC and PGPR to increase drought tolerance in oilseeds. In this study, the physiological response of two water-stressed canola (Brassica napus L.) plants subjected to the application of BC obtained from waste wood of Morus alba applied solely or in combination with PGPR strains (Pseudomonas sp.) was evaluated. The experiment consists of two genotypes and nine treatments [(C-Control, T1-15 days drought (15DD), T2-30 days drought (30DD), T3-15 days of drought + PG (15DD + PG), T4-30 days of drought + PG (30DD + PG), T5-15 days drought + biochar (15DD + BC), T6-30 days drought + biochar (30DD + BC), T7-15 days drought + biochar + PG (15DD + BC + PG), T8-30 days drought + biochar + PG (30DD + BC + PG)]. Drought stress decreased emergence energy (EE), leaf area index (LAI), leaf area ratio (LAR), root shoot ratio (RSR), moisture content of leaves (MCL), percent moisture content (%MC), moisture content of shoot (MCS) and moisture content of root (MCR), and relative water content (RWC) in both varieties of Brassica napus L., which in contrast, it is increased by the collective application of both biochar and PGPR. In both varieties, N, P, K, Mg, and Ca concentrations were highest in all the biochar and PGPRs separate and combined treatments, while lowest in 15 and 30 days drought treatments. Osmolyte contents like Glycine betaine (GB) and sugar remarkably increased in the stress condition and then reduced due to the synergistic application of biochar and PGPR. Drought stress has a repressive effect on the antioxidant enzymatic system like Peroxidase (POD), Superoxide dismutase (SOD), and glutathione reductase (GR) as well as total flavonoids, phenolics, and protein content. The antioxidant enzymes and phenolic compounds were dramatically increased by the combined action of biochar and PGPRs. A significant increase in EE, LAR, RSR, and RWC under 15 and 30 days drought conditions, evidently highlighting the synergistic effect of BC and PGPR. The results conclude a substantial and positive effect of the combined use of BC and PGPR strains on canola's response to induced drought stress, by regulating the physiological, biochemical, and agronomic traits of the plants. Graphical Abstract

Microbial consortia and biochar as sustainable biofertilisers: Analysis of their impact on wheat growth and production

The European Union is among the top wheat producers in the world, but its productivity relies on adequate soil fertilisation. Biofertilisers, either alone or in combination with biochar, can be a preferable alternative to chemical fertilisers. However, the addition of biofertilisers, specifically plant growth promoting microbes (PGPM), could modify grain composition, and/or deteriorate the soil composition. In this study, the two wheat cultivars Triticum aestivum (Bramante) and T. durum (Svevo) were cultivated in open fields for two consecutive years in the presence of a commercial PGPM mix supplied alone or in combination with biochar. An in-depth analysis was conducted by collecting physiological and agronomic data throughout the growth period. The effects of PGPM and biochar were investigated in detail; specifically, soil chemistry and rhizosphere microbial composition were characterized, along with the treatment effects on seed storage proteins. The results demonstrated that the addition of commercial microbial consortia and biochar, alone or in combination, did not modify the rhizospheric microbial community; however, it increased grain yield, especially in the cultivar Svevo (increase of 6.8 %–13.6 %), even though the factors driving the most variations were associated with both climate and cultivar. The total gluten content of the flours was not affected, whereas the main effect of the treatments was a variation in gliadins and low-molecular-weight-glutenin subunits in both cultivars when treated with PGPM and biochar. This suggested improved grain quality, especially regarding the viscoelastic properties of the dough, when the filling period occurred in a dry climate. The results indicate that the application of biofertilisers and biochar may aid the effective management of sustainable wheat cultivation, to support environmental health without altering the biodiversity of the resident microbiome.

Draft genome sequence of Enterobacter sp. from wheat grain.

Here, we report the draft genome sequence of an isolate from the Enterobacter cloacae species complex. Enterobacter spp. are plant growth-promoting microbes and biocontrol agents. Analyses of this genome will serve as a useful resource for future studies of similar microbes isolated from grain.

Enhancing Resistance to Salinity in Wheat by Using Streptomyces sp. HU2014

Salt stress affects the growth and global production of wheat (Triticum aestivum L.). Plant growth-promoting microbes can enhance plant resistance to abiotic stresses. In this study, we aimed to assess the inoculation of soil with Streptomyces sp. HU2014 to improve wheat tolerance to salt stress from multiple perspectives, including the interaction of the strain, the addition of NaCl, the condition of the wheat, and rhizosphere microbial communities. The results showed that the strain promoted wheat growth under NaCl stress by increasing biomass by 19.8%, total chlorophyll content by 72.1%, proline content by 152.0%, and malondialdehyde content by 106.9%, and by decreasing catalase by 39.0%, peroxidase by 1.4%, and soluble sugar by 61.6% when compared to the control. With HU2014 soil inoculation, total nitrogen, nitrate nitrogen, total phosphorus, and Olsen phosphorus increased, whereas ammonium nitrogen and pH decreased. HU2014 inoculation and/or the addition of NaCl affected the diversity of rhizosphere bacteria, but not fungi. The structure of the microbial community differed after HU2014 inoculation, with Proteobacteria, Acidobacteriota, Bacteroidota, and unclassified fungi being the dominant phyla, and these taxa correlated with the above-mentioned soil parameters. Thus, this study provided a promising way to enhance wheat tolerance to salt stress and improve the agricultural ecological environment by using plant growth-promoting microbes.

Differential influence of Bacillus subtilis strains on Arabidopsis root architecture through common and distinct plant hormonal pathways

Plant growth-promoting microbes (PGPM) can enhance crop yield and health, but knowledge of their mode-of-action is limited. We studied the influence of two Bacillus subtilis strains, the natural isolate ALC_02 and the domesticated 168 Gö, on Arabidopsis and hypothesized that they modify the root architecture by modulating hormone transport or signaling. Both bacteria promoted increase of shoot and root surface area in vitro, but through different root anatomical traits. Mutant plants deficient in auxin transport or signaling responded less to the bacterial strains than the wild-type, and application of the auxin transport inhibitor NPA strongly reduced the influence of the strains. Both bacteria produced auxin and enhanced shoot auxin levels in DR5::GUS reporter plants. Accordingly, most of the beneficial effects of the strains were dependent on functional auxin transport and signaling, while only 168 Gö depended on functional ethylene signaling. As expected, only ALC_02 stimulated plant growth in soil, unlike 168 Gö that was previously reported to have reduced biofilms. Collectively, the results highlight that B. subtilis strains can have strikingly different plant growth-promoting properties, dependent on what experimental setup they are tested in, and the importance of choosing the right PGPM for a desired root phenotype.

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

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

Hormesis of glyphosate on ferulic acid metabolism and antifungal volatile production in rice root biocontrol endophyte Burkholderia cepacia LS-044

Glyphosate (GP, N-phosphonomethyl glycine) is one of the most popular organophosphate herbicides widely used in agricultural practices worldwide. There have been extensive reports on the biohazard attributes and hormetic impacts of GP on plant and animal systems. However, the effects of GP on plant growth-promoting microbes and its ecological relevance remain unknown. Here, we show that GP does exert a hormetic impact on Burkholderia cepacia LS-044, a rice (Oryza sativa ssp. japonica cv. Tainung 71) root endophytic isolate. We used increasing doses of ferulic acid (FA, 1–25 mM) and GP (0.5–5 mM) to test the growth and antifungal volatile production in LS-044 by electrochemical, liquid chromatographic, gas chromatographic and spectrophotometric means. GP treatment at a low dose (0.5 mM) increased FA utilization and significantly (P < 0.0001) enhanced antifungal volatile activity in LS-044. Although FA (1 mM) was rapidly utilized by LS-044, no chromatographically detectable utilization of GP was observed at tested doses (0.5–5 mM). LS-044 emitted predominant amounts of tropone in addition to moderate-to-minor amounts of diverse ketones and/or their derivatives (acetone, acetophenone, 2-butanone, 1-propanone, 1-(2-furanyl-ethanone, 1-phenyl-1-propanone and 1-(3-pyridinyl)-1-propanone), d-menthol, 2-methoxy-3-(1-methylethyl)-pyrazine, dimethyl disulfide, pyridine and ammonium carbamate when grown under GP supplement. GP hormesis on LS-044 induced phenotypic variations in O. sativa ssp. japonica cv. Tainan 11 as evident through seed germination assay. Genes involved in the transformation of FA, and a key gene encoding 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) with Gly-94 and Tyr-95 residues localized at active site most likely rendering EPSPS sensitivity to GP, were detected in LS-044. This is the first report on the GP hormesis influencing morphological and metabolic aspects including volatile emission in a biocontrol bacterium that could modulate rice plant phenotype.

Potential roles of plant growth-promoting microbes in wheat adaptation and tolerance to herbicide and drought stress combination

Potential roles of plant growth-promoting microbes in wheat adaptation and tolerance to herbicide and drought stress combination

Isolation and Characterisation of Culturable Thermophilic Cyanobacteria from Perak Hot Springs and their Plant Growth Promoting Properties Effects on Rice Seedlings (Oryza sativa L.).

Malaysia is home to a number of hot springs that are rich in microbial diversity including the photosynthetic cyanobacteria. Although this microbial community has been characterised based on metagenomics approach, the culturable thermophilic isolates have not been isolated and characterised extensively. Compared to the mesophiles, information on plant growth promoting (PGP) properties of these thermophiles remain largely untapped. As the amount of arable land for microbial bioprospecting is decreasing due to extensive human activities, the search for alternative source for microbial strains with PGP properties is important for the development of potential biofertilisers. This study sought to isolate and characterise culturable cyanobacteria strains from two local hot springs - Sungai Klah (SK) and Lubuk Timah (LT) located in Perak using morphological and molecular methods. The IAA production from the axenic cultures were measured. The PGP properties were also measured by priming the rice seeds with cyanobacterial water extracts. A total of six strains were isolated from both hot springs. Strains LTM and LTW from LT were identified as Leptolyngbya sp. whereas strains SEM, SEH, STH and STM were identified as Thermosynechococcus elongatus. All six strains produced IAA ranged from 670.10 pg/μL to 2010 pg/μL. The water extracts were found to increase the seed amylase activity of the rice seeds from 5th day of germination (DAG) to 10th DAG. In general, the IAA production and increased seed amylase activity might have contributed in enhancing the longest root length, shoot length and root-to-shoot (RS) ratio. To conclude, the thermophilic cyanobacteria from hot springs can be further exploited as a novel source of PGP microbes for the development of biofertilsers.

Characterization of three new plant growth-promoting microbes and effects of the interkingdom interactions on plant growth and disease prevention.

The novel interkingdom PGPM consortia enhanced the ability of plant growth promotion and disease resistance, which would be beneficial to improve plant growth in sustainable agriculture through engineering microbiome. Plant growth-promoting microbes (PGPMs) play important roles in promoting plant growth and bio-controlling of pathogens. Much information reveals that the plant growth-promoting ability of individual PGPM affects plant growth. However, the effects of the PGPM consortia properties on plant growth remain largely unexplored. Here, we characterized three new PGPM strains including Rhodotorula graminis JJ10.1 (termed as J), Pseudomonas psychrotolerans YY7 (termed as Y) and P. chlororaphis T8 (termed as T), and assessed their effects in combination with Bacillus amyloliquefaciens FZB42 (termed as F) on plant growth promotion and disease prevention in Arabidopsis thaliana and tomato (Solanum lycopersicum) plants by investigating morphological changes, whole-genome sequencing and plant growth promoting (PGP) characterization. Results revealed that the three new strains R. graminis JJ10.1, P. psychrotolerans YY7 and P. chlororaphis T8 had the potential for being combined with B. amyloliquefaciens FZB42 to form interkingdom PGPM consortia. The combinations of R. graminis JJ10.1, B. amyloliquefaciens FZB42, and P. psychrotolerans YY7, i. e. JF and JYF, exhibited the strongest ability of synergetic biofilm production. Furthermore, the growth-promotion abilities of the consortia were significantly enhanced compared with those of individual strains under both inoculation and volatile organic compounds (VOCs) treatment. Importantly, the consortia showed stronger abilities of in planta disease prevention than individual strains. Findings of our study may provide future guidance for engineering the minimal microbiome communities to improve plant growth and/or disease resistance in sustainable agriculture.

Conservation of beneficial microbes between the rhizosphere and the cyanosphere.

Biocrusts are phototroph-driven communities inhabiting arid soil surfaces. Like plants, most photoautotrophs (largely cyanobacteria) in biocrusts are thought to exchange fixed carbon for essential nutrients like nitrogen with cyanosphere bacteria. Here, we aim to compare beneficial interactions in rhizosphere and cyanosphere environments, including finding growth-promoting strains for hosts from both environments. To examine this, we performed a retrospective analysis of 16S rRNA gene sequencing datasets, host-microbe co-culture experiments between biocrust communities/biocrust isolates and a model grass (Brachypodium distachyon) or a dominant biocrust cyanobacterium (Microcoleus vaginatus), and metabolomic analysis. All 18 microbial phyla in the cyanosphere were also present in the rhizosphere, with additional 17 phyla uniquely found in the rhizosphere. The biocrust microbes promoted the growth of the model grass, and three biocrust isolates (Bosea sp._L1B56, Pseudarthrobacter sp._L1D14 and Pseudarthrobacter picheli_L1D33) significantly promoted the growth of both hosts. Moreover, pantothenic acid was produced by Pseudarthrobacter sp._L1D14 when grown on B. distachyon exudates, and supplementation of plant growth medium with this metabolite increased B. distachyon biomass by over 60%. These findings suggest that cyanobacteria and other diverse photoautotrophic hosts can be a source for new plant growth-promoting microbes and metabolites.

Improving runoff quality in vertical greenery systems: Substrate type outweighed the effect of plant growth promoting microbes

Due to limited urban green spaces and catchments, researchers are exploring the capacity of vertical greenery systems (VGSs) in stormwater management as complementary strategies. While the literature acknowledges the significant impacts of vegetated roof substrates on stormwater, comparing the stormwater management capacities of organic and non-organic substrates for VGSs remains largely unexplored. It is thus essential to gather empirical evidence to enhance the stormwater management capacity of VGSs. Here, we report on the impact of installation factors (substrate type and plant growth-promoting microbe (PGPM) inoculation) and environmental factors (simulated rainwater quantity and substrate moisture) of an innovative VGS on the concentrations and total loads of 15 elements (N, P, Al, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Se, Cd, and Pb) in the runoff. Results showed that substrate type was the most influential factor: concentrations and total loads were significantly higher from a reed-based substrate with high organic matter than from a sandy loam substrate. Substrate type also had profound interactive effects with other factors. For instance, PGPM inoculation significantly reduced the total loads of As, Cr, N, Ni, and Se, regardless of substrate type, and reduced the total loads of Cd, Co, Cu, Fe, Mn, and Pb in the reed-based substrate only. In addition, PGPM inoculation primarily reduced total loads, yet had little effect on concentrations. Substrate type also interacted with simulated rainwater quantity and substrate moisture: for example, in the reed-based substrate, a higher simulated rainwater quantity reduced concentrations but increased total loads, while concentrations and total loads remained constantly low from the sandy loam substrate under various simulated rainwater quantities. High antecedent substrate moisture increased both concentrations and total loads for most of the elements. We conclude that leaching from VGSs can be contained via substrate selection, maintenance of substrate moisture, and beneficial PGPM inoculation.

Rhizobacterial mediated interactions in Curcuma longa for plant growth and enhanced crop productivity: a systematic review.

Turmeric (Curcuma longa L.), a significant commercial crop of the Indian subcontinent is widely used as a condiment, natural dye, and as a cure for different ailments. Various bioactive compounds such as turmerones and curcuminoids have been isolated from C. longa that have shown remarkable medicinal activity against various ailments. However, reduced soil fertility, climatic variations, rapid urbanization, and enhanced food demand, pose a multifaceted challenge to the current agricultural practices of C. longa. Plant growth-promoting microbes play a vital role in plant growth and development by regulating primary and secondary metabolite production. Rhizospheric associations are complex species-specific interconnections of different microbiota with a plant that sustain soil health and promote plant growth through nutrient acquisition, nitrogen fixation, phosphate availability, phytohormone production, and antimicrobial activities. An elaborative study of microbiota associated with the roots of C. longa is essential for rhizospheric engineering as there is a huge potential to develop novel products based on microbial consortium formulations and elicitors to improve plant health, stress tolerance, and the production of secondary metabolites such as curcumin. Primarily, the purpose of this review is to implicate the rhizospheric microbial flora as probiotics influencing overall C. longa health, development, and survival for an increase in biomass, enhanced yield of secondary metabolites, and sustainable crop production.

Biochar-biofertilizer combinations enhance growth and nutrient uptake in silver maple grown in an urban soil.

Declining tree health status due to pollutant impacts and nutrient imbalance is widespread in urban forests; however, chemical fertilizer use is increasingly avoided to reduce eutrophication impacts. Biochar (pyrolyzed organic waste) has been advocated as an alternative soil amendment, but biochar alone generally reduces plant N availability. The combination of biochar and either organic forms of N or Plant Growth Promoting Microbes (PGPMs) as biofertilizers may address these challenges. We examined the effects of two wood biochar types with Bacillus velezensis and an inactivated yeast (IY) biofertilizer in a three-month factorial greenhouse experiment with Acer saccharinum L. (silver maple) saplings grown in a representative urban soil. All treatments combining biochars with biofertilizers significantly increased sapling growth, with up to a 91% increase in biomass relative to controls. Growth and physiological responses were closely related to nutrient uptake patterns, with nutrient vector analyses indicating that combined biochar and biofertilizer treatments effectively addressed nutrient limitations of both macronutrients (N, P, K, Mg, Ca), and micronutrients (B, Fe, Mn, Mo, Na, S, and Zn). Biochar-biofertilizer treatments also reduced foliar concentrations of Cu, suggesting potential to mitigate toxic metal impacts common in urban forestry. We conclude that selected combinations of biochar and biofertilizers have substantial promise to address common soil limitations to tree performance in urban settings.