Growth-promoting Metabolites Research Articles

Toxic effects and mechanisms of chronic cadmium exposure on Litopenaeus vannamei growth performance based on combined microbiome and metabolome analysis

Cadmium (Cd) pollution seriously affects marine organisms' health and poses a threat to food safety. Although Cd pollution has attracted widespread attention in aquaculture, little is known about the toxic mechanisms of chronic Cd exposure on shrimp growth performance. The study investigated the combined effects of chronic exposure to Cd of different concentrations including 0, 75, 150, and 300 μg/L for 30 days on the growth performance, tissue bioaccumulation, intestinal microbiology, and metabolic responses of Litopenaeus vannamei. The results revealed that the growth was significantly inhibited under exposure to 150 and 300 μg/L Cd2+. The bioaccumulation in gills and intestines respectively showed an increasing and inverted "U" shaped trend with increasing Cd2+ concentration. Chronic Cd altered the intestinal microflora with a significant decrease in microbial richness and increasing trends in the abundances of the potentially pathogenic bacteria Vibrio and Maribacter at exposure to 75 and 150 μg/L Cd2+, and Maribacter at 300 μg/L. In addition, chronic Cd interfered with intestinal metabolic processes. The expressions of certain metabolites associated with growth promotion and enhanced antioxidant power, including N-methyl-D-aspartic acid, L-malic acid, guanidoacetic acid, betaine, and gluconic acid were significantly down-regulated, especially at exposure to 150 and 300 μg/L Cd2+, and were negatively correlated with Vibrio and Maribacter abundance levels. In summary, chronic Cd exposure resulted in severe growth inhibition and increased Cd accumulation in shrimp tissues. Increased levels of intestinal pathogenic bacteria and decreased levels of growth-promoting metabolites may be the key causes of growth inhibition. Harmful bacteria Vibrio and Maribacter may be associated with the inhibition of growth-promoting metabolite expression and may be involved in disrupting intestinal metabolic functions, ultimately impairing shrimp growth potential. This study sheds light on the potential toxicological mechanisms of chronic Cd inhibition on shrimp growth performance, offering new insights into Cd toxicity studies in aquaculture.

Dictyophora indusiata and Bacillus aryabhattai improve sugarcane yield by endogenously associating with the root and regulating flavonoid metabolism.

Endophytes play a significant role in regulating plant root development and facilitating nutrient solubilization and transportation. This association could improve plant growth. The present study has uncovered a distinct phenotype, which we refer to as "white root", arising from the intricate interactions between endophytic fungi and bacteria with the roots in a sugarcane and bamboo fungus (Dictyophora indusiata) intercropping system. We investigated the mechanisms underlying the formation of this "white root" phenotype and its impact on sugarcane yield and metabolism by metabarcoding and metabolome analysis. Initial analysis revealed that intercropping with D. indusiata increased sugarcane yield by enhancing the number of viable tillers compared with bagasse and no input control. Metabarcoding based on second-generation and third-generation sequencing indicated that D. indusiate and Bacillus aryabhattai dominates the fungal and bacterial composition in the "white root" phenotype of sugarcane root. The coexistence of D. indusiata and B. aryabhattai as endophytes induced plant growth-promoting metabolites in the sugarcane root system, such as lysoPC 18:1 and dihydrobenzofuran, probably contributing to increased sugarcane yield. Furthermore, the association also enhanced the metabolism of compounds, such as naringenin-7-O-glucoside (Prunin), naringenin-7-O-neohesperidoside (Naringin)*, hesperetin-7-O-neohesperidoside (Neohesperidin), epicatechin, and aromadendrin (Dihydrokaempferol), involved in flavonoid metabolism during the formation of the endophytic phenotype in the sugarcane root system. These observations suggest that the "white root" phenotype promotes sugarcane growth by activating flavonoid metabolism. This study reports an interesting phenomenon where D. indusiata, coordinate with the specific bacteria invade, forms a "white root" phenotype with sugarcane root. The study also provides new insights into using D. indusiata as a soil inoculant for promoting sugarcane growth and proposes a new approach for improve sugarcane cultivation.

Multifarious Characterization and Efficacy of Three Phosphate-Solubilizing Aspergillus Species as Biostimulants in Improving Root Induction of Cassava and Sugarcane Stem Cuttings.

Several soil fungi significantly contribute to the enhancement of plant development by improving nutrient uptake and producing growth-promoting metabolites. In the present study, three strains of phosphate-solubilizing fungi, namely, Aspergillus chiangmaiensis SDBR-CMUI4, A. pseudopiperis SDBR-CMUI1, and A. pseudotubingensis SDBR-CMUO2, were examined for their plant-growth-promoting capabilities. The findings demonstrated that all fungi showed positive siderophore production, but only A. pseudopiperis can produce indole-3-acetic acid. All fungi were able to solubilize insoluble phosphate minerals [Ca3(PO4)2 and FePO4] by producing phosphatase enzymes and organic acids (oxalic, tartaric, and succinic acids). These three fungal species were grown at a water activity ranging from 0.837 to 0.998, pH values ranging from 4 to 9, temperatures between 4 and 40 °C, and 16-17% NaCl in order to evaluate their drought, pH, temperature, and salt tolerances, respectively. Moreover, the results indicated that A. pseudopiperis and A. pseudotubingensis were able to tolerate commercial insecticides (methomyl and propargite) at the recommended dosages for field application. The viability of each fungal strain in the inoculum was higher than 50% at 4 and 20 °C after 3 months of storage. Subsequently, all fungi were characterized as plant-growth-promoting strains by improving the root inductions of cassava (Manihot esculenta Crantz) and sugarcane (Saccharum officinarum L.) stem cuttings in greenhouse experiments. No symptoms of plant disease were observed with any of the treatments involving fungal inoculation and control. The cassava and sugarcane stem cuttings inoculated with fungal strains and supplemented with Ca3(PO4)2 exhibited significantly increased root lengths, shoot and root dry biomasses, chlorophyll concentrations, and cellular inorganic phosphate contents. Therefore, the application of these phosphate-solubilizing fungi is regarded as a new frontier in the induction of roots and the promotion of growth in plants.

Identification and characterization of siderophilic biocontrol strain SL-44 combined with whole genome

Using rhizobacteria as biological fertilizer is gradually expanding in agriculture as excellent substitutes for chemical fertilizers. Bacillus subtilis SL-44 is a plant growth-promoting rhizobacteria screened from the severely salinized cotton rhizosphere soil in Xinjiang. Study showed that indole-3-acetic acid, organic acid production, nitrogen fixation, and other beneficial secondary metabolite secretion can be synthesized by stain SL-44. At the same time, fencyclin, lipopeptide, chitinase, and other antifungal substances were also detected from the secretion of Bacillus subtilis SL-44, which can effectively control plant diseases. Siderophore separated from SL-44 was verified by HPLC, and results showed it was likely bacillibactin. This study also verified that SL-44 has high antifungal activity against Rhizoctonia solani through in vitro antifungal experiments. The B. subtilis SL-44 whole genome was sequenced and annotated to further explore the biotechnological potential of SL-44. Anda large number of genes involved in the synthesis of anti-oxidative stress, antibiotic, and toxins were found. Genome-wide analysis provides clear evidence to support the great potential of B. subtilis SL-44 strain to produce multiple bioantagonistic natural products and growth-promoting metabolites, which may facilitate further research into effective therapies for harmful diseases.

Cytokinin biosynthesis in cyanobacteria: Insights for crop improvement.

Cytokinins, a type of phytohormones that induce division of cytoplasm, have considerable value in agriculture due to their influences on several physiological processes of plants such as morphogenesis, development of chloroplast, seed dormancy, leaf senescence, etc. Previously, it was assumed that plants obtain cytokinin from the soil produced by microbes as these hormones were first discovered in soil-inhabiting bacteria i.e., Agrobacterium tumefaciens. Later, the cytokinin biosynthesis gene, i.e., ipt gene, has been reported in plants too. Though plants synthesize cytokinins, several studies have reported that the exogenous application of cytokinins has numerous beneficial effects including the acceleration of plant growth and boosting economic yield. Cyanobacteria may be employed in the soil not only as the source of cytokinins but also as the source of other plant growth-promoting metabolites. These organisms biosynthesize the cytokinins using the enzyme isopentenyl transferases (IPTs) in a fashion similar to the plants; however, there are few differences in the biosynthesis mechanism of cytokinins in cyanobacteria and plants. Cytokinins are important for the establishment of interaction between plants and cyanobacteria as evidenced by gene knockout experiments. These hormones are also helpful in alleviating the adverse effects of abiotic stresses on plant development. Cyanobacterial supplements in the field result in the induction of adventitious roots and shoots on petiolar as well as internodal segments. The leaf, root, and stem explants of certain plants exhibited successful regeneration when treated with cyanobacterial extract/cell suspension. These successful regeneration practices mark the way of cyanobacterial deployment in the field as a great move toward the goal of sustainable agriculture.

Impact of Phyllosphere Methylobacterium on Host Rice Landraces.

ABSTRACTThe genus Methylobacterium includes widespread plant-associated bacteria that are abundant in the plant phyllosphere (leaf surfaces), consume plant-secreted methanol, and can produce plant growth-promoting metabolites. However, despite the potential to increase agricultural productivity, their impact on host fitness in the natural environment is relatively poorly understood. Here, we conducted field experiments with three traditionally cultivated rice landraces from northeastern India. We inoculated seedlings with native versus nonnative phyllosphere Methylobacterium strains and found significant impacts on plant growth and grain yield. However, these effects were variable. Whereas some Methylobacterium isolates were beneficial for their host, others had no impact or were no more beneficial than the bacterial growth medium on its own. Host plant benefits were not consistently associated with Methylobacterium colonization and did not have altered phyllosphere microbiome composition, changes in the early expression of plant stress response pathways, or bacterial auxin production. We provide the first demonstration of the benefits of phyllosphere Methylobacterium for rice yield under field conditions and highlight the need for further analysis to understand the mechanisms underlying these benefits. Given that the host landrace-Methylobacterium relationship was not generalizable, future agricultural applications will require careful testing to identify coevolved host-bacterium pairs that may enhance the productivity of high-value rice varieties.IMPORTANCE Plants are associated with diverse microbes in nature. Do the microbes increase host plant health, and can they be used for agricultural applications? This is an important question that must be answered in the field rather than in the laboratory or greenhouse. We tested the effects of native, leaf-inhabiting bacteria (genus Methylobacterium) on traditionally cultivated rice varieties in a crop field. We found that inoculation with some bacteria increased rice grain production substantially while a nonnative bacterium reduced plant health. Overall, the effect of bacterial inoculation varied across pairs of rice varieties and their native bacteria. Thus, knowledge of evolved associations between specific bacteria hosted by specific rice varieties is necessary to develop ways to increase the yield of traditional rice landraces and preserve these important sources of cultural and genetic diversity.

Sargassum wightii Aqueous Extract Improved Salt Stress Tolerance in Abelmoschus esculentus by Mediating Metabolic and Ionic Rebalance

Salinity stress has hindered the growth and yield of crops globally. The demands for inducing salt stress tolerance by natural and biological sources with potent antioxidants and growth-promoting metabolites have been the main focus of the recent era. Therefore, the current research was conducted to extract salt stress tolerance-ameliorating metabolites and growth-promoting hormones from the marine brown macroalgaeSargassum wightiiGreville ex J. Agardh with maximum antioxidant potential used as a liquid fertilizer for okra (Abelmoschus esculentusL.). In the current study, the biochemical analysis showed thatSargassumaqueous extract (SAE) was rich in growth-promoting metabolites, antioxidants, and hormones. Meanwhile, overaccumulation of glycine betaine attracted the focus of the current research dealing with salt stress tolerance amelioration inA. esculentus. The plants supplemented with SAE (2% and 4%) and 0.04% ascorbic acid (AsA) alone and in combinations were subjected to sodium salt stress (NaCl; 75 mM). Results revealed that SAE efficiently promoted the vegetative and reproductive growth of plants by elevating the growth-promoting metabolites and hormones in comparison to control plants. Ionic contents (Na+, K+, Ca2+, and Mg2+) and ratios (K+/Na+, Mg2+/Na+, and Ca2+/Na+) were modulated in SAE-treated plants. SAE also increased the level of carbohydrates, proteins, lipids, carotenoids, and proline and decreased the level of hydrogen peroxide and abscisic acid in salt-treated plants compared with the control groups. Enzymatic activities of catalase, ascorbate peroxidase, and guaiacol peroxidase were also enhanced by SAE treatment upon salt stress. The SAE-mediated stress tolerance amelioration and the positive growth response ofA. esculentuswere further accelerated by AsA (0.04%) supplementation used in combination with SAE (2% and 4%). The current study revealed a novel report of the antioxidant and metabolite-rich algal extract (S. wightii) formulation along with AsA that induced salt stress tolerance and promoted the overall growth performance ofA. esculentusby rebalancing the ionic and metabolic status.

Biodegradation of 4-nitroaniline by novel isolate Bacillus sp. strain AVPP64 in the presence of pesticides

In this study, Bacillus sp. strain AVPP64 was isolated from diuron-contaminated soil. It showed 4-nitroaniline (4-NA) degradation, pesticide tolerance, and self-nutrient integration via nitrogen (N)-fixation and phosphate (P)-solubilization. The rate constant (k) and half-life period (t1/2) of 4-NA degradation in the aqueous medium inoculated with strain AVPP64 were observed to be 0.445 d−1 and 1.55 d, respectively. Nevertheless, in the presence of chlorpyrifos, profenofos, atrazine and diuron pesticides, strain AVPP64 degraded 4-NA with t1/2 values of 2.55 d, 2.26 d, 2.31 d and 3.54 d, respectively. The strain AVPP64 fixed 140 μg mL−1 of N and solubilized 103 μg mL−1 of P during the presence of 4-NA. In addition, strain AVPP64 produced significant amounts of plant growth-promoting metabolites like indole 3-acetic acid, siderophores, exo-polysaccharides and ammonia. In the presence of 4-NA and various pesticides, strain AVPP64 greatly increased the growth and biomass of Vigna radiata and Crotalaria juncea plants. These results revealed that Bacillus sp. strain AVPP64 can be used as an inoculum for bioremediation of 4-NA contaminated soil and sustainable crop production even when pesticides are present.

Plant growth promoting bacteria improve growth and phytostabilization potential of Zea mays under chromium and drought stress by altering photosynthetic and antioxidant responses

Drought in heavy metal polluted arid and semiarid regions severely inhibits the plant growth and phytoremediation potential by affecting photosynthesis, antioxidant defense mechanism, and other biochemical processes. In the present study, we explored the role of plant growth-promoting bacteria (PGPB) on Zea mays growth and phytoremediation efficiency in Chromium (Cr) contaminated soils under drought stress by assessing plant stress tolerance, photosynthetic gas exchange activities, chlorophyll fluorescence, and Cr accumulation. Two efficient Cr and drought resistant PGPB with the potential to reduce Cr(VI) to Cr(III) and produce plant growth-promoting metabolites even under Cr, drought, or Cr+drought stress conditions were isolated and identified as Providencia sp. (TCR05) and Proteus mirabilis (TCR20). In pot experiments, the inoculation of TCR05 and TCR20 increased the plant growth, pigments, protein, phenolics, and relative water content and decreased the lipid peroxidation, proline, and superoxide dismutase activity under Cr, drought, or Cr+drought conditions. Irrespective of stress treatment, TCR05 and TCR20 also improved plant photosynthetic efficiency by increasing the CO 2 assimilation rate, stomatal conductance to water vapor, transpiration rate, maximum quantum efficiency of PSII, actual quantum efficiency of PSII, electron transport rate, photochemical quenching, reducing the internal CO 2 concentration and non-photochemical quenching. Besides, the PGPB decreased the translocation of Cr through immobilization of Cr in root. These results denoted that strains TCR05 and TCR20 could be a capable bio-inoculant for improving plant growth and phytostabilization practices in Cr contaminated sites even under water-limited conditions. • Potential Cr(VI) reducing MST-PGPB strains TCR05 and TCR20 were isolated. • MST-PGPB enhanced stress tolerance of Z. mays under combined stress conditions. • PGPB inoculation improved the PSII performance of Z. mays under combined stresses. • PGPB inoculation improved Cr phytostabilization under combined stress conditions.

Metabolism of Imidazole Dipeptides, Taurine, Branched-Chain Amino Acids, and Polyamines of the Breast Muscle Are Affected by Post-Hatch Development in Chickens.

To explore metabolic characteristics during the post-hatch developmental period, metabolomic analyses of breast muscle and plasma were performed in chickens. The most significant growth-related changes in metabolite levels were observed between seven and 28 days of age. Some of these metabolites are essential nutrients or reported as growth-promoting metabolites. In the muscle, two imidazole dipeptides—carnosine and its methylated metabolite, anserine—increased with the development. These dipeptide levels may be, in part, regulated transcriptionally because in the muscle mRNA levels of carnosine synthase and carnosine methylation enzyme increased. In contrast, taurine levels in the muscle decreased. This would be substrate availability-dependent because some upstream metabolites decreased in the muscle or plasma. In branched-chain amino acid metabolism, valine, leucine, and isoleucine decreased in the muscle, while some of their downstream metabolites decreased in the plasma. The polyamines, putrescine and spermidine, decreased in the muscle. Furthermore, mRNA levels associated with insulin/insulin-like growth factor 1 signaling, which play important roles in muscle growth, increased in the muscle. These results indicate that some metabolic pathways would be important to clarify metabolic characteristics and/or growth of breast muscle during the post-hatch developmental period in chickens.

Lantana charcoal as potent carrier material for Azotobacter chroococcum

Abstract Azotobacter chroococcum is a universally accepted plant growth-promoting rhizospheric bacterium, which, as a biofertilizer, helps to increase the nitrogen level, solubilize the unavailable form of phosphorus, ensure growth-promoting metabolites, and control pathogenic microbes in the soil. A good strain of plant growth-promoting rhizobacteria (PGPR) needs to be produced, formulated, transported, stored, and distributed to the agriculture field. During all these operations, bacterial inoculants are transferred via a carrier material. One of the important challenges in biofertilizer technology is to ensure stability of the bacteria in the carrier. The study aimed to assess a novel carrier Lantana charcoal (LC; obtained from Lantana camara biomass), as compared to some currently available carriers. LC exhibited higher carbon content, low N2 content, neutral pH, and, above all, higher water-holding capacity, making it a suitable carrier material for A. chroococcum and possibly other PGPR. As a carrier, it showed no contamination during storage, exhibited the highest moisture content and moderate culture holding coefficient, and supported the highest colony-forming units per gram at the end of the storage period. Thus, LC cannot only serve as a better carrier, but its large-scale application would also ensure a reasonable use of this weed.

Profiling of Plant Growth-Promoting Metabolites by Phosphate-Solubilizing Bacteria in Maize Rhizosphere.

Microbial treatment has recently been attracting attention as a sustainable agricultural strategy addressing the current problems caused by unreasonable agricultural practices. However, the mechanism through which microbial inoculants promote plant growth is not well understood. In this study, two phosphate-solubilizing bacteria (PSB) were screened, and their growth-promoting abilities were explored. At day 7 (D7), the lengths of the root and sprout with three microbial treatments, M16, M44, and the combination of M16 and M44 (Com), were significantly greater than those with the non-microbial control, with mean values of 9.08 and 4.73, 7.15 and 4.83, and 13.98 and 5.68 cm, respectively. At day 14 (D14), M16, M44, and Com significantly increased not only the length of the root and sprout but also the underground and aboveground biomass. Differential metabolites were identified, and various amino acids, amino acid derivatives, and other plant growth-regulating molecules were significantly enhanced by the three microbial treatments. The profiling of key metabolites associated with plant growth in different microbial treatments showed consistent results with their performances in the germination experiment, which revealed the metabolic mechanism of plant growth-promoting processes mediated by screened PSB. This study provides a theoretical basis for the application of PSB in sustainable agriculture.

1H Nuclear Magnetic Resonance and Liquid Chromatography Coupled with Mass Spectrometry-Based Metabolomics Reveal Enhancement of Growth-Promoting Metabolites in Onion Seedlings Treated with Green-Synthesized Nanomaterials.

Seed priming is a promising approach to improve germination, emergence, and seedling growth by triggering pre-germinative metabolism and enhancing seedling vigor. Recently, nanopriming gained importance in seed improvement as a result of the small size and unique physicochemical characteristics of nanomaterials. In the present study, silver and gold nanoparticles were synthesized using onion extracts as the reducing agent. Similarly, the agro-food industrial byproducts citrus seed oil and curcumin-removed turmeric oleoresin were used for the preparation of nanoemulsions. For seed priming, these green-synthesized nanomaterials were incubated with seeds of two onion (Allium cepa L.) cultivars (Legend and 50147) for 72 h, and then the plants were grown in a greenhouse for 3 weeks. Seed priming with these nanomaterials increased seed germination and seedling emergence. One-dimensional 1H nuclear magnetic resonance and liquid chromatography coupled with mass spectrometry metabolomics studies showed that different nanopriming treatments distinctly altered the metabolome of onion seedlings. Seed priming treatments significantly inhibited plant hormones and growth regulators, such as abscisic acid and cis-(+)-12-oxo-phytodienoic acid, and enhanced germination stimulators, such as γ-aminobutyric acid and zeatin, in onion seeds and seedlings. Therefore, these priming treatments have positive impact on improving seed performance and plant growth.

Metabolomics and traditional indicators unveil stress of a seagrass (Cymodocea nodosa) meadow at intermediate distance from a fish farm

Abstract Seasonal variation of structural, physiological and growth indicators and the metabolome of the seagrass Cymodocea nodosa, as well as biogeochemical conditions of underlying sediment were studied in two meadows growing at increasing distance downstream from a fish farm in the Aegean Sea in order to assess seagrass performance under stress. Horizontal rhizome production decreased significantly with proximity to the fish farm (0.67 and 1.57 g DW m−2 d−1 close and far from the fish-farm, respectively). This coincided with observed effects on ecophyiological indicators, such as rhizome nitrogen, leaf carbon and leaf δ13C, which were elevated with proximity to the fish-farm. Seasonality was shown by some indicators being elevated in either in the warm (C of all tissues and leaf δ34S) or the cold period (N of all tissues). Growth promoting metabolites (sucrose, fructose, myo-inositol, heptacosane, tetracosane, stigmasterol, catechin and alpha-tocopherol) were lower close to the zone, whereas metabolites involved with stress-response (alanine, serine, proline, putrescine, ornithine, 3,4-dihydroxybenzoic acid and cinnamic acid) were higher. We found that growth-promoting metabolites were positively correlated with horizontal rhizome production, whereas the metabolites related to stress were negatively correlated. Metabolomic fingerprinting of seagrass provides opportunities for early detection of environmental degradation in marine ecological studies.

Jasmonates-Mediated Rewiring of Central Metabolism Regulates Adaptive Responses.

The lipid-derived hormones jasmonates (JAs) play key functions in a wide range of physiological and developmental processes that regulate growth, secondary metabolism and defense against biotic and abiotic stresses. In this connection, biosynthesis, tissue-specific distribution, metabolism, perception, signaling of JAs have been the target of extensive studies. In recent years, the involvement of JAs signaling pathway in the regulation of growth and adaptive responses to environmental challenges has been further examined. However, JAs-mediated mechanisms underlying the transition from 'growth mode' to 'adaptive mode' remain ambiguous. Combined analysis of transgenic lines deficient in JAs signaling in conjunction with the data from JAs-treated plants revealed the function of these hormones in rewiring of central metabolism. The collective data illustrate JAs-mediated decrease in the levels of metabolites associated with active growth such as sucrose, raffinose, orotate, citrate, malate, and an increase in phosphorylated hexoses, responsible for the suppression of growth and photosynthesis, concurrent with the induction of protective metabolites, such as aromatic and branched-chain amino acids, and aspartate family of metabolites. This finding provides an insight into the function of JAs in shifting the central metabolism from the production of growth-promoting metabolites to protective compounds and expands our understanding of the role of JAs in resource allocation in response to environmental challenges.

Ameliorating effects of chicken feathers in plant growth promotion activity by a keratinolytic strain of Bacillus subtilis PF1

Feathers are the major byproducts of poultry industry and considered as waste. Feathers (composed of protein keratin) are metabolized by a number of microorganisms as a source of carbon and nitrogen. Degradation of feathers results in production of amino acids and peptides, which can be employed as precursors for plant growth-promoting metabolites such as indole acetic acid, ammonia and HCN. The aim of the present investigation was to assess the influence of these metabolites (termed as feather protein hydrolysate) on plant growth promotion activity of keratinolytic bacterial strain Bacillus subtilis PF1. Strain PF1 exhibits potent keratinolytic activity and can efficiently degrade 10 g/l chicken feathers under submerged cultivation with 81.4 ± 4.40 U/ml keratinase activity. Different concentrations of feathers supported the production of indole acetic acid by strain PF1. Strain PF1 produces maximum indole acetic acid (46.2 ± 0.21 µg/ml) in the presence of 2.0 % feathers at 120 h of incubation. The indole acetic acid production was confirmed by thin-layer chromatography and Fourier transform infrared spectroscopic analysis. However, increased concentration of feathers exhibited negative effect on phosphate solubilization due to increased alkalinity. HCN production also exhibited positive correlation with concentration of feathers. Finally, plant growth of Vigna radiata in the presence of strain PF1 with chicken feathers in soil was investigated, which showed good plant growth promotion activity. Increased ratio of C/N in soil also supported the plant growth promotion activity of feathers. Feather degradation property of B. subtilis PF1 could be efficiently utilized for feather waste management. The metabolites released by feather degradation along with strain PF1 could be successfully employed as an economic source of nitrogen fertilizers for plants.

It’s in the Milk: Feeding the Microbiome to Promote Infant Growth

Malnutrition is a global health burden affecting the development of millions of children worldwide, but the effects of current treatment strategies are modest. Charbonneau et al. (2016) identify sialylated oligosaccharides in breast milk as microbiota-dependent growth-promoting metabolites, paving the way for a new rational treatment of severe infant stunting.

In-vitro antagonism of Trichoderma spp. against Sclerotium rolfsii and Rhizoctonia solani and their response towards growth of cucumber, bottle gourd and bitter gourd

In the current study we evaluated the production of potential growth-promoting metabolites (IAA, phosphate, siderophore) for 20 isolates of Trichoderma collected from different geographical locations of Chhattisgarh and assessed their growth response on cucumber, bottle gourd and bitter gourd. All the Trichoderma isolates were able to release inorganic phosphorus from tri-calcium phosphate and showed consistent ability to produce siderophores and indole-3-acetic acid (IAA). The production of these metabolites varied greatly within species. Using the same set of isolates we evaluated the production of potential cell wall degrading enzymes. Confrontation assays of Trichoderma isolates against two soilborne plant pathogens (Scelrotium rolfsii and Rhizoctonia solani) expressed varying degrees of antagonistic responses, in-vitro antagonism being more effective against R. solani than S. rolfsii. The production of metabolites in all the Trichoderma isolates did not correlate with enhanced growth on cucumber, bottle gourd and bitter gourd, and bio control efficacy. However, one of the Trichoderma viride isolate (T14) was identified as highest producer of inorganic phosphate, IAA and siderophore exhibited high antagonistic and plant growth promoting ability. A characteristic aromatic odour resembling coconut in T14 isolate was observed which we speculate is due to 6-Pentyl pyrone (one of the best studied secondary metabolites having both antifungal and plant growth-promoting activities).

Growth stimulation in bean (Phaseolus vulgaris L.) by Trichoderma

Trichoderma species are commonly used as biological control agents against phytopathogenic fungi and some strains are able to produce metabolites that enhance plant growth. In the current study we evaluated the production of potential growth-promoting metabolites, rhizosphere competence and endophytism for 101 isolates of Trichoderma from Colombia, and assessed the relationship of these factors to the enhancement of early stages of growth on bean seedlings. Twenty percent of these Trichoderma strains were able to produce soluble forms of phosphate from phosphoric rock. Only 8% of the assessed strains showed consistent ability to produce siderophores to convert ferric iron to soluble forms by chelation. Sixty percent of isolates produced indole-3-acetic acid (IAA) or auxin analogues. The production of any of these metabolites was a characteristic of specific strains, as the ability to produce these metabolites varied greatly within species. Moreover, the production of these substances did not correlate with enhanced growth on bean seedlings, measured as the combined increase in length of roots and aerial parts in the V3 stage of growth. Seven Trichoderma isolates significantly improved the growth of bean seedlings. However, metabolite production varied widely in these seven strains, and some isolates did not produce any of the assessed growth-promoting metabolites. Results indicated that growth was enhanced in the presence of rhizosphere competent and endophytic strains of Trichoderma, and these characteristics were strain-specific and not characteristic for species.

Plant growth promotion and Penicillium citrinum.

BackgroundEndophytic fungi are known plant symbionts. They produce a variety of beneficial metabolites for plant growth and survival, as well as defend their hosts from attack of certain pathogens. Coastal dunes are nutrient deficient and offer harsh, saline environment for the existing flora and fauna. Endophytic fungi may play an important role in plant survival by enhancing nutrient uptake and producing growth-promoting metabolites such as gibberellins and auxins. We screened roots of Ixeris repenes (L.) A. Gray, a common dune plant, for the isolation of gibberellin secreting endophytic fungi.ResultsWe isolated 15 endophytic fungi from the roots of Ixeris repenes and screened them for growth promoting secondary metabolites. The fungal isolate IR-3-3 gave maximum plant growth when applied to waito-c rice and Atriplex gemelinii seedlings. Analysis of the culture filtrate of IR-3-3 showed the presence of physiologically active gibberellins, GA1, GA3, GA4 and GA7 (1.95 ng/ml, 3.83 ng/ml, 6.03 ng/ml and 2.35 ng/ml, respectively) along with other physiologically inactive GA5, GA9, GA12, GA15, GA19, GA20 and, GA24. The plant growth promotion and gibberellin producing capacity of IR-3-3 was much higher than the wild type Gibberella fujikuroi, which was taken as control during present study. GA5, a precursor of bioactive GA3 was reported for the first time in fungi. The fungal isolate IR-3-3 was identified as a new strain of Penicillium citrinum (named as P. citrinum KACC43900) through phylogenetic analysis of 18S rDNA sequence.ConclusionIsolation of new strain of Penicillium citrinum from the sand dune flora is interesting as information on the presence of Pencillium species in coastal sand dunes is limited. The plant growth promoting ability of this fungal strain may help in conservation and revegetation of the rapidly eroding sand dune flora. Penicillium citrinum is already known for producing mycotoxin citrinin and cellulose digesting enzymes like cellulase and endoglucanase, as well as xylulase. Gibberellins producing ability of this fungus and the discovery about the presence of GA5 will open new aspects of research and investigations.