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Frontiers in Bioengineering and... 2020Poly-(3-hydroxyalkanoates) (PHAs) are bacterial carbon and energy storage compounds. These polymers are synthesized under conditions of nutritional imbalance, where a... (Review)
Review
Poly-(3-hydroxyalkanoates) (PHAs) are bacterial carbon and energy storage compounds. These polymers are synthesized under conditions of nutritional imbalance, where a nutrient is growth-limiting while there is still enough carbon source in the medium. On the other side, the accumulated polymer is mobilized under conditions of nutrient accessibility or by limitation of the carbon source. Thus, it is well known that the accumulation of PHAs is affected by the availability of nutritional resources and this knowledge has been used to establish culture conditions favoring high productivities. In addition to this effect of the metabolic status on PHAs accumulation, several genetic regulatory networks have been shown to drive PHAs metabolism, so the expression of the PHAs genes is under the influence of global or specific regulators. These regulators are thought to coordinate PHAs synthesis and mobilization with the rest of bacterial physiology. While the metabolic and biochemical knowledge related to the biosynthesis of these polymers has led to the development of processes in bioreactors for high-level production and also to the establishment of strategies for metabolic engineering for the synthesis of modified biopolymers, the use of knowledge related to the regulatory circuits controlling PHAs metabolism for strain improvement is scarce. A better understanding of the genetic control systems involved could serve as the foundation for new strategies for strain modification in order to increase PHAs production or to adjust the chemical structure of these biopolymers. In this review, the regulatory systems involved in the control of PHAs metabolism are examined, with emphasis on those acting at the level of expression of the enzymes involved and their potential modification for strain improvement, both for higher titers, or manipulation of polymer properties. The case of the PHAs producer is taken as an example of the complexity and variety of systems controlling the accumulation of these interesting polymers in response to diverse situations, many of which could be engineered to improve PHAs production.
PubMed: 32426348
DOI: 10.3389/fbioe.2020.00386 -
Ecotoxicology and Environmental Safety Dec 2022Elevated atmospheric carbon dioxide (eCO) concentrations can alter the carbon:nitrogen ratio and palatability of host plants for herbivorous insects, but rhizobacteria...
Elevated atmospheric carbon dioxide (eCO) concentrations can alter the carbon:nitrogen ratio and palatability of host plants for herbivorous insects, but rhizobacteria likely mitigate the alteration and influence physiological adaptation of insects. In this study, we conducted transcriptomic analysis of maize (Zea mays) response to Azotobacter chroococcum (AC) inoculation under eCO conditions in contrast to ambient CO (aCO), and studied the effects of plant-defense change of maize under eCO on the oriental armyworm, Mythimna separata. Results showed that there were 16, 14, 16 and 135 differentially expressed genes that were associated with plant-defense response in maize leaves between aCO-CK and aCO-AC, eCO-CK and eCO-AC, aCO-CK and eCO-CK, aCO-AC and eCO-AC, respectively. Moreover, A. chroococcum inoculation and eCO influenced plant hormone signal transduction of maize. Interestingly, A. chroococcum inoculation significantly decreased the contents of JA (jasmonic acid) and JA-Ile (isoleucine conjugate of JA) in leaves, but eCO markedly increased contents of JA-Ile, JA and SA (salicylic acid). Compared to aCO, eCO significantly decreased activity of protective enzyme (catalase), and increased activities of digestive (lipase and protease), protective (peroxidase) and detoxifying enzymes (carboxylesterase, Mixed-functional oxidase and glutathione s-transferase), prolonged developmental time, and decreased survival rate and body weight of larvae (P < 0.05). A. chroococcum inoculation significantly increased the activity of protective enzyme (catalase), and decreased the activities of detoxifying enzymes (carboxylesterase, glutathione s-transferase and mixed-functional oxidase), thus increased the growth rate and body weight of larvae in comparison with no-inoculation of A. chroococcum (P < 0.05). The indices of M. separata were significantly correlated with the foliar contents of JA, JA-Ile and SA (|r| = 0.44-0.85, P < 0.05), indicating that A. chroococcum inoculation altered the physiological adaptation of M. separata under eCO by disturbing defense substances in maize. Our results in understanding effects of A. chroococcum inoculation on maize resistance to herbivorous insects will be valuable for agricultural pest control in the future at eCO conditions.
Topics: Animals; Zea mays; Catalase; Carbon Dioxide; Spodoptera; Glutathione Transferase; Carboxylic Ester Hydrolases
PubMed: 36399994
DOI: 10.1016/j.ecoenv.2022.114296 -
Nature Microbiology Feb 2020Legumes obtain nitrogen from air through rhizobia residing in root nodules. Some species of rhizobia can colonize cereals but do not fix nitrogen on them. Disabling...
Legumes obtain nitrogen from air through rhizobia residing in root nodules. Some species of rhizobia can colonize cereals but do not fix nitrogen on them. Disabling native regulation can turn on nitrogenase expression, even in the presence of nitrogenous fertilizer and low oxygen, but continuous nitrogenase production confers an energy burden. Here, we engineer inducible nitrogenase activity in two cereal endophytes (Azorhizobium caulinodans ORS571 and Rhizobium sp. IRBG74) and the well-characterized plant epiphyte Pseudomonas protegens Pf-5, a maize seed inoculant. For each organism, different strategies were taken to eliminate ammonium repression and place nitrogenase expression under the control of agriculturally relevant signals, including root exudates, biocontrol agents and phytohormones. We demonstrate that R. sp. IRBG74 can be engineered to result in nitrogenase activity under free-living conditions by transferring a nif cluster from either Rhodobacter sphaeroides or Klebsiella oxytoca. For P. protegens Pf-5, the transfer of an inducible cluster from Pseudomonas stutzeri and Azotobacter vinelandii yields ammonium tolerance and higher oxygen tolerance of nitrogenase activity than that from K. oxytoca. Collectively, the data from the transfer of 12 nif gene clusters between 15 diverse species (including Escherichia coli and 12 rhizobia) help identify the barriers that must be overcome to engineer a bacterium to deliver a high nitrogen flux to a cereal crop.
Topics: Azorhizobium caulinodans; Bacterial Proteins; Edible Grain; Escherichia coli; Genes, Bacterial; Metabolic Engineering; Multigene Family; Nitrogen Fixation; Nitrogenase; Plant Root Nodulation; Pseudomonas; Rhizobium; Symbiosis
PubMed: 31844298
DOI: 10.1038/s41564-019-0631-2 -
PeerJ 2021Organic and biological fertilizers are considered as a very important source of plant nutrients. A field experiment was conducted during 2017-2018 in paddy soil to...
Organic and biological fertilizers are considered as a very important source of plant nutrients. A field experiment was conducted during 2017-2018 in paddy soil to investigate the effect of vermicomposting of cattle manure mixture with and rice straw on soil microbial activity, nutrient uptake, and grain yield under inoculation of N-fixing bacteria. Experimental factors consisted of organic amendments at six levels (vermicomposts prepared from manure (VM); manure + rice straw (VRM); manure + mixture (VAM); manure + rice straw + mixture (VRAM); raw manure without vermicomposting (M), and a control) and N-fixing bacteria at three levels (, , and non-inoculation). The results showed that, vermicompost treatments compared to control and raw manure significantly increased the number and biomass-C of soil microorganisms, urease activity, number of tillers hill, phosphorus (P) and potassium (K) uptake, and grain and protein yield. Inoculation of plants with N-fixing bacteria, especially increased the efficiency of organic amendments, so that the maximum urease activity, soil microbial activity, P and N uptake, and grain yield (4,667 (2017) and 5,081 (2018) kg/h) were observed in vermicompost treatments containing (VAM and VRAM) under inoculation with . The results of the study suggested that, using an organic source along with inoculation with appropriate N-fixing bacteria for vermicompost has a great effect on enzyme activity, soil biology, nutrient uptake and grain yield has a synergistic interaction on agronomic traits under flooded conditions. Therefore, this nutrient method can be used as one of the nutrient management strategies in the sustainable rice production.
PubMed: 34557340
DOI: 10.7717/peerj.10833 -
Plants (Basel, Switzerland) Aug 2023The problem of phosphorus and nitrogen deficiency in agricultural soils has been solved by adding chemical fertilizers. However, their excessive use and their...
The problem of phosphorus and nitrogen deficiency in agricultural soils has been solved by adding chemical fertilizers. However, their excessive use and their accumulation have only contributed to environmental contamination. Given the high content of nutrients in biosolids collected from a food industry waste treatment plant, their use as fertilizers was investigated in plants grown in sandy loam soil collected from a semi-desert area. These biosolids contained insoluble phosphorus sources; therefore, given the ability of to solubilize phosphates, this strain was incorporated into the study. In vitro, the suitable conditions for the growth of plants were determined by using biosolids as a fertilizer and as a plant-growth-promoting microorganism; in vitro, the ability of to solubilize phosphates, fix nitrogen, and produce indole acetic acid, a phytohormone that promotes root formation, was also evaluated. At the greenhouse stage, the plants fertilized with biosolids at concentrations of 15 and 20% (/) and inoculated with favored the development of bending strength plants, which was observed on the increased stem diameter (>13.5% compared with the negative control and >7.4% compared with the positive control), as well as a better absorption of phosphorus and nitrogen, the concentration of which increased up to 62.8% when compared with that in the control treatments. The interactions between plants and were observed via scanning electron microscopy. The application of biosolids and in plants grown in greenhouses presented better development than when plants were treated with a chemical fertilizer. The enhanced plant growth was attributed to the increase in root surface area.
PubMed: 37687299
DOI: 10.3390/plants12173052 -
Journal of Fungi (Basel, Switzerland) Apr 2022Antifungal efficacy of against trichothecene-producing spp. was investigated in maize, sorghum, and wheat. The three cereals were subjected to four treatments as...
Antifungal efficacy of against trichothecene-producing spp. was investigated in maize, sorghum, and wheat. The three cereals were subjected to four treatments as control (T1), alone (T2), combination of and treatment (T3), and only (T4). All the treatments were evaluated for total mass of seedlings, root and shoot length, seed germination, and vigor index (VI), and extent of rhizoplane colonization by was investigated. Further, greenhouse studies were conducted to learn the efficacy of in vivo conditions. Antifungal efficacy was tested by the dual-culture method which resulted in significant reduction in growth. Infection by was reduced up to 50% in treated cereals such as maize, sorghum, and wheat, and there was also significant increase in seedling mass in the three hosts. Maize showed the highest VI (1859.715), followed by sorghum (1470.84), and wheat (2804.123) with treatment. In addition, seed germination was enhanced to 76% in maize, 69% in sorghum, and 68% in wheat, respectively. Efficacy of rhizoplane colonization showed successful isolation of with high CFU rate, and furthermore, significant colonization inhibition by spp. was observed. In the greenhouse conditions, on the 45th day of the experimental set-up, the highest shoot length/root length recorded in maize was 155.70/70.0 cm, in sorghum 165.90/48.0 cm, and in wheat 77.85/56.0 cm, and the maximum root mass recorded was 17.53 g in maize, 4.52 g in sorghum, and 1.90 g in wheat. Our present study showed that seed treatment by may be used as an alternate biocontrol method against infection in maize, sorghum, and wheat.
PubMed: 35628729
DOI: 10.3390/jof8050473 -
Foods (Basel, Switzerland) Sep 2022The use of microbial biostimulants such as plant growth-promoting rhizobacteria (PGPB) and arbuscular mycorrhizal fungi (AMF) has gained popularity in recent years as a... (Review)
Review
The use of microbial biostimulants such as plant growth-promoting rhizobacteria (PGPB) and arbuscular mycorrhizal fungi (AMF) has gained popularity in recent years as a sustainable approach to boost yield as well as the quality of produce. The beneficial effects of microbial biostimulants have been reported numerous times. However, information is missing concerning quantitative assessment of the overall impact of microbial biostimulants on the yield and quality of vegetable crops. Here we provide for the first time a comprehensive, semi-systematic review of the effects of microbial biostimulants allowed by Regulation (EU) 2019/1009, including microorganisms belonging to the AMF (phylum Glomeromycota), or to , and genera, on vegetable crops' quality and yield, with rigorous inclusion and exclusion criteria based on the PRISMA method. We identified, selected and critically evaluated all the relevant research studies from 2010 onward in order to provide a critical appraisal of the most recent findings related to these EU-allowed microbial biostimulants and their effects on vegetable crops' quality and yield. Moreover, we highlighted which vegetable crops received more beneficial effects from specific microbial biostimulants and the protocols employed for plant inoculation. Our study is intended to draw more attention from the scientific community to this important instrument to produce nutrient-dense vegetables in a sustainable manner. Finally, our semi-systematic review provides important microbial biostimulant application guidelines and gives extension specialists and vegetable growers insights into achieving an additional benefit from microbial biostimulant application.
PubMed: 36076841
DOI: 10.3390/foods11172656 -
PloS One 2018Safflower is an important industrial oil seed and bioenergy crop in semi-arid subtropical regions due to its potential to grow on marginal land and having good...
Safflower is an important industrial oil seed and bioenergy crop in semi-arid subtropical regions due to its potential to grow on marginal land and having good percentage of seed oil contents which is an important parameter for biofuel production. However, it is an ignored crop in Pakistan. In order to improve the crop productivity and reduce the use of agrochemicals for sustainable biodiesel feedstock production, an experiment was conducted for two years to improve the fatty acid composition and oil quality of Carthamus tinctorius L. (safflower) by the inoculation of Azospirillum and Azotobacter alone as well as in combined application with nitrogen and phosphate (NP) fertilizers on cultivars Thori and Saif-32 under field conditions. Separation and quantification of fatty acids were done on precise comprehensive two-dimensional gas chromatography (GC×GC). The results showed that fatty acid profile specifically monounsaturated fatty acids i-e oleic acid (C18:1) was significantly improved by Azospirillum supplemented with the quarter dose of NP fertilizers (SPQ) with concomitant decrease in polyunsaturated fatty acids by the respective treatment. Oil quality attributes such as acid value, saponification number, iodine value, refractive index and free fatty acid contents were reduced by the application of Azotobacter and Azospirillum in combination with half and quarter doses of NP fertilizers treatments (BTH, SPH, BTQ and SPQ). The reduction in these variables is positively linked with improved biodiesel yield and quality. It can be concluded that application of Azospirillum and Azotobacter not only reduced the use of NP fertilizers up to 50%-75% but also improved the oil quality in order to obtain environment friendly, sustainable and green fuel.
Topics: Agriculture; Azospirillum; Azotobacter; Biofuels; Carthamus tinctorius; Fatty Acids; Fertilizers; Nitrogen; Phosphates; Safflower Oil; Soil Microbiology; Species Specificity
PubMed: 30096207
DOI: 10.1371/journal.pone.0201738 -
Proceedings of the National Academy of... Mar 2021Nitrogenases utilize Fe-S clusters to reduce N to NH The large number of Fe sites in their catalytic cofactors has hampered spectroscopic investigations into their...
Nitrogenases utilize Fe-S clusters to reduce N to NH The large number of Fe sites in their catalytic cofactors has hampered spectroscopic investigations into their electronic structures, mechanisms, and biosyntheses. To facilitate their spectroscopic analysis, we are developing methods for incorporating Fe into specific sites of nitrogenase cofactors, and we report herein site-selective Fe labeling of the L-cluster-a carbide-containing, [FeSC] precursor to the Mo nitrogenase catalytic cofactor. Treatment of the isolated L-cluster with the chelator ethylenediaminetetraacetate followed by reconstitution with Fe results in Fe labeling of the terminal Fe sites in high yield and with high selectivity. This protocol enables the generation of L-cluster samples in which either the two terminal or the six belt Fe sites are selectively labeled with Fe. Mössbauer spectroscopic analysis of these samples bound to the nitrogenase maturase NifX reveals differences in the primary coordination sphere of the terminal Fe sites and that one of the terminal sites of the L-cluster binds to H35 of NifX. This work provides molecular-level insights into the electronic structure and biosynthesis of the L-cluster and introduces postbiosynthetic modification as a promising strategy for studies of nitrogenase cofactors.
Topics: Azotobacter vinelandii; Electron Spin Resonance Spectroscopy; Molybdoferredoxin; Nitrogenase; Protein Precursors; Spectroscopy, Mossbauer
PubMed: 33836573
DOI: 10.1073/pnas.2015361118 -
PloS One 2017The effects of adding the biosurfactant rhamnolipid, the lignolytic and cellulolytic fungus Phanerochete chrysosporium, and the free-living nitrogen-fixing bacterium...
The effects of adding the biosurfactant rhamnolipid, the lignolytic and cellulolytic fungus Phanerochete chrysosporium, and the free-living nitrogen-fixing bacterium Azotobacter chrococcum on vermicomposting of green waste with Eisenia fetida was investigated. The addition of rhamnolipid and/or either microorganism alone or in all combinations significantly increased E. fetida growth rate, the number of E. fetida juveniles and cocoons, the population densities of cellulolytic fungi and Azotobacter bacteria, and cellulase and urease activities in the vermicomposts. The quality of the final vermicompost (in terms of electrical conductivity, nutrient content, C/N ratio, humic acid content, lignin and cellulose contents, and phytotoxicity to germinating seeds) was enhanced by addition of rhamnolipid and/or microorganisms. The physical characteristics of vermicomposts produced with rhamnolipid and/or microorganisms were acceptable for agricultural application. The best quality vermicompost was obtained with the combined addition of P. chrysosporium, A. chrococcum, and rhamnolipid.
Topics: Agricultural Inoculants; Animals; Biodegradation, Environmental; Glycolipids; Manure; Oligochaeta; Soil
PubMed: 28122059
DOI: 10.1371/journal.pone.0170820