Organic Acid Synthesis Research Articles

Carboxylate anion generation in aqueous solution from carbonate radiolysis, a potential route for abiotic organic acid synthesis on Earth and beyond

Low molecular weight carboxylate anions such as formate (HCOO−), acetate (CH3COO−) and oxalate (C2O42−) have been shown to play an important role in supporting deep subsurface microbial ecosystems. Their origin whether biological or abiotic is currently highly debated, but surprisingly radiolytic production has rarely been considered, as it is the case for H2. Here, we address this question through dedicated irradiation experiments. Aqueous solutions containing carbonate, formate, acetate or oxalate have been irradiated using both the 60.7 MeV α-beam of the ARRONAX cyclotron (Nantes, France) and 661.7 keV γ-Ray in order to reveal the mechanism and chemical yield of radiation-induced dissolved carbonate degradation.The yields (G-values) of carboxylate anions production/degradation in low-concentration carbonate solution (0.01 to 1 mmolL−1) are measured. Carbonate degradation occurs through three consecutive steps (Carbonate →I Formate →II Acetate →III Oxalate) involving formate radical (CO2−•), dihydrogen (H2), and carbon dioxide (CO2) generation. Dissolved carbonate radiolysis provides a consistent pathway for both enhancing two-fold the radiolytic H2 production compared to pure water and generating carboxylic species, chiefly oxalate, readily available for microbes. Radiation-induced carbonate degradation may produce substantial amount (millimolar concentration) of carboxylate anions in ancient groundwaters from deep crystalline bedrocks. Subsurface lithoautotrophic microbial ecosystems may not only be supported by radiolytic H2 but also by carboxylate species from carbonate radiolysis. Carbonate radiolysis can be also an endogenous source of carboxylate species on Mars and other planetary bodies.

In Vitro Modulatory Effect of Stevioside, as a Partial Sugar Replacer in Sweeteners, on Human Child Microbiota.

The effect of stevioside on human health is still insufficiently highlighted by recent research. The total or partial replacement of sugar with sweeteners influences the general state of health, especially the human microbiota’s response as a determining factor in the onset of type 2 diabetes. The present study aimed to present the long-term (one-year) in vitro effect that regular stevioside consumption had on children’s pattern microbiota. A metabolomic response was established by determining the synthesis of organic acids and a correlation with antioxidant status. An increase in the number of bacterial strains and the variation of amount of butyrate and propionate to the detriment of lactic acid was observed. The effect was evidenced by the progressive pH increasing, the reduction of acetic acid, and the proliferation of Escherichia coli strains during the simulations. Synthesis of the main short-chain fatty acids (SCFAs) was interpreted as a response (adaptation) of the microbiota to the stevioside, without a corresponding increase in antioxidant status. This study demonstrated the modulatory role of stevioside on the human microbiota and on the fermentation processes that determine the essential SCFA synthesis in maintaining homeostasis. The protection of the microbiota against oxidative stress was also an essential aspect of reducing microbial diversity.

Laser Light Treatment of Seeds for Improving the Biomass Photosynthesis, Chemical Composition and Biological Activities of Lemongrass Sprouts

Compared to seeds and mature plants, sprouts are well characterized based on their nutritive values and biological properties. Moreover, laser light application is known to be a promising approach to improving plant growth, photosynthesis, and nutraceutical values. However, no studies have investigated the phytochemicals and biological activity of lemongrass (Cymbopogon proximus (Hochst. ex A.Rich.) Chiov.) sprouts or the further improvement of their quality by applying laser light treatment. We carried out a preliminary experiment for the optimization of laser treatment conditions, finding that a helium neon (He–Ne) laser at 632 nm and 5 mW for 5 min provided the most favorable conditions. We then investigated fresh weight, photosynthetic reactions, and primary and secondary metabolites, including sugars, amino acids, organic acids, essential oils, and phenolic compounds. Moreover, we studied the effect of laser light-induced changes in chemical compositions on the antioxidant, anti-diabetic, and anti-cholesterol activities of Cymbopogon proximus sprouts grown from laser-treated seeds. Laser light treatment increased the photosynthesis and respiration and hence the fresh weight of Cymbopogon proximus sprouts. Overall, sprouting increased most bioactive primary and secondary metabolites as compared to seeds. Increased photosynthesis by laser light improved carbon allocation and raised non-structural carbohydrates, which in turn led to improved synthesis of amino acids, organic acids, and essential oils, as well as phenolic and flavonoid compounds. As a result, laser light significantly improved the antioxidant capacity in terms of increasing the levels of ferric reducing antioxidant power (FRAP) (from 9.5 to 21 µmole trolox/g fresh weight (FW)), oxygen radical absorbance (ORAC) (from 400 to 1100 µmole trolox/100 g FW), and DPPH (from 5% to 25% of inhibation) and enhanced the hypocholesterolemic and antidiabetic activity through increasing the percentage of cholesterol micellar solubility (CMS) inhibition (from 42% to 62%) and glycemic index (from 33 to 17 µmole/g) over sprouts and seeds. In conclusion, the synergism of seed laser treatment and sprouting induced the health-promoting bioactive compounds in Cymbopogon proximus as compared to seeds, which can be applied at a large scale to improve the biochemical, physiological, and nutraceutical values of medicinal and crop sprouts.

Nitrogen and Phosphorus Interplay in Lupin Root Nodules and Cluster Roots.

Nitrogen (N) and phosphorus (P) are two major plant nutrients, and their deficiencies often limit plant growth and crop yield. The uptakes of N or P affect each other, and consequently, understanding N–P interactions is fundamental. Their signaling mechanisms have been studied mostly separately, and integrating N–P interactive regulation is becoming the aim of some recent works. Lupins are singular plants, as, under N and P deficiencies, they are capable to develop new organs, the N2-fixing symbiotic nodules, and some species can also transform their root architecture to form cluster roots, hundreds of short rootlets that alter their metabolism to induce a high-affinity P transport system and enhance synthesis and secretion of organic acids, flavonoids, proteases, acid phosphatases, and proton efflux. These modifications lead to mobilization in the soil of, otherwise unavailable, P. White lupin (Lupinus albus) represents a model plant to study cluster roots and for understanding plant acclimation to nutrient deficiency. It tolerates simultaneous P and N deficiencies and also enhances uptake of additional nutrients. Here, we present the structural and functional modifications that occur in conditions of P and N deficiencies and lead to the organogenesis and altered metabolism of nodules and cluster roots. Some known N and P signaling mechanisms include different factors, including phytohormones and miRNAs. The combination of the individual N and P mechanisms uncovers interactive regulation pathways that concur in nodules and cluster roots. L. albus interlinks N and P recycling processes both in the plant itself and in nature.

The molecular regulatory mechanisms of the bacteria involved in serpentine weathering coupled with carbonation

Development of an effective biotechnological method of reducing the continuous emission of CO2 has caused wide public concern. Research on serpentine bio-weathering coupled with carbonation is a current focus of interest. To investigate the molecular mechanisms, Bacillus subtilis was cultured in the Mg2+-free medium with the addition of serpentine. Based on the composition of organic matter and the characterization of the weathered serpentine, quantitative proteomics technology was adopted to elucidate the roles of proteins played in the coupled process. Electrochemical analysis and vapor diffusion crystallization experiments were also performed to reveal the molecular mechanisms. The results demonstrated that more oxidoreductases were secreted to facilitate the transformation of serpentine, and drive the synthesis of organic acids to accelerate the weathering of serpentine. In the late stage of serpentine weathering, that is, the serpentine carbonation stage, the characterization of the secondary minerals showed that struvite and amorphous carbonate had been formed with some organic matter. In serpentine carbonation stage, excessive Ni in the microenvironment drove N metabolism to facilitate the elevation of pH, resulting in the serpentine carbonation. This study enriched our understanding of the molecular mechanisms at protein-level in serpentine bio-weathering coupled with carbonation.

Genomic and Phenotypic Insights Into the Potential of Rock Phosphate Solubilizing Bacteria to Promote Millet Growth in vivo.

Rock phosphate (RP) is a natural source of phosphorus for agriculture, with the advantage of lower cost and less impact on the environment when compared to synthetic fertilizers. However, the release of phosphorus (P) from RP occurs slowly, which may limit its short-term availability to crops. Hence, the use of P-solubilizing microorganisms to improve the availability of P from this P source is an interesting approach, as microorganisms often perform other functions that assist plant growth, besides solubilizing P. Here, we describe the characterization of 101 bacterial isolates obtained from the rhizosphere and endosphere of maize plants for their P solubilizing activity in vitro, their growth-promoting activity on millet plants cultivated in soil amended with RP, and their gene content especially associated with phosphate solubilization. For the in vitro solubilization assays, two mineral P sources were used: rock phosphate from Araxá (Brazil) mine (AP) and iron phosphate (Fe-P). The amounts of P released from Fe–P in the solubilization assays were lower than those released from AP, and the endophytic bacteria outperformed the rhizospheric ones in the solubilization of both P sources. Six selected strains were evaluated for their ability to promote the growth of millet in soil fertilized with a commercial rock phosphate (cRP). Two of them, namely Bacillus megaterium UFMG50 and Ochrobactrum pseudogrignonense CNPMS2088, performed better than the others in the cRP assays, improving at least six physiological traits of millet or P content in the soil. Genomic analysis of these bacteria revealed the presence of genes related to P uptake and metabolism, and to organic acid synthesis. Using this approach, we identified six potential candidates as bioinoculants, which are promising for use under field conditions, as they have both the genetic potential and the experimentally demonstrated in vivo ability to improve rock phosphate solubilization and promote plant growth.

СРАВНИТЕЛЬНАЯ ОЦЕНКА ВЛИЯНИЯ ВИРДЖИНИАМИЦИНА И ПРОБИОТИКА НА СОСТАВ КИШЕЧНОГО МИКРОБИОМА И ЗООТЕХНИЧЕСКИЕ ПОКАЗАТЕЛИ ЦЫПЛЯТ-БРОЙЛЕРОВ (Gallus gallus L.)

Today, there is great interest in the development of environmentally friendly feed additives for poultry farming as a worthy alternative to antibiotics capable of positively modulating the microbiota to control pathogenic microorganisms. However, very few studies have been devoted to comparing the effects of probiotics and antibiotics on the structure of the gut microbiome in broilers. In this study, we compared the composition of the intestinal microbiota and zootechnical parameters in chickens of the Cobb 500 cross during the starter, growth and finishing periods when a probiotic (Bacillus subtilis in the composition of Cellobacterin®-T) or an antibiotic (Stafac® 110 based on virginiamycin) was added to the diet and showed that the B. subtilis strain accelerates the formation of intestinal microflora. The probiotic also reduces the number of microorganisms of the Campylobacteriaceae family which includes many types of gastroenteritis pathogens, and also increases the digestibility of fiber. T-RFLP analysis and qPCR method were used to assess changes in the intestinal microbiota of Cobb 500 broiler chickens fed a Bacillus subtilis-based dietary probiotic and virginiamycin-based dietary antibiotic Stafac® 110. On day 14, the total counts of cecal bacteria, as compared to control, were 9.1 times higher (p ≤ 0.05) in broilers fed Stafac® 110, and 54.2 times higher (p ≤ 0.001) when fed B. subtilis preparation. This indicates rapid microbial colonization of gastrointestinal tract of the chickens fed Stafac® 110 and B. subtilis. T-RFLP analysis revealed two dominant cecal phyla, Firmicutes and Proteobacteria, while phyla Actinobacteria, Bacteroidetes, and Fusobacteriawere less abundant. The taxa are detected which ferment non-starch polysaccharides to produce short-chain fatty acids, inhibit the competing pathogens due to production of bacteriocins, and acidize the chyme as synthesize organic acids. Administration of the dietary antibiotic mostly positively influences the cecal microbiota, e.g., the cellulolytic bacteria and Clostridia forms involved in the synthesis of organic acids became more abundant (p ≤ 0.05). Similar beneficial effects, e.g., an increase in Clostridia counts (p ≤ 0.05) compared to control, occurred when the probiotic strain was administered. On day 14 of rearing, the dietary antibiotic and probiotic reduced abundance of Campylobacteriaceae family comprising gastroenteritis pathogens (p ≤ 0.05) when compared to control. An increase in bodyweight as compared to control (from 1845.8±20.9 to 1936.4±17.9 g, p = 0.046) occurred in 36-day-old chickens fed Stafac® 110 but not the probiotic strain but not the probiotic strain, despite recovery of gut microbiota in the chickens fed B. subtilis. A 7.1 % increase infiber digestibility (p = 0.0027) occurred in broilers fed dietary probiotic and a 2.3 % increase (p = 0.047) in those fed the dietary antibiotic, which may be due to the action of cellulolytic microorganisms. Therefore, a dietary B. subtilis-based probiotic which promotes recovery of gut microbiota and increases fiber digestibility in feeds for broiler chickens can be an effective alternative to the virginiamycin-based antibiotic Stafac® 110.

THE IMPACT OF VIRGINIAMICIN AND PROBIOTICS ON INTESTI-NAL MICROBIOME AND GROWTH PERFORMANCE TRAITS OF CHICKEN (Gallus gallus L.) BROILERS

Today, there is great interest in the development of environmentally friendly feed additives for poultry farming as a worthy alternative to antibiotics capable of positively modulating the microbiota to control pathogenic microorganisms. However, very few studies have been devoted to comparing the effects of probiotics and antibiotics on the structure of the gut microbiome in broilers. In this study, we compared the composition of the intestinal microbiota and zootechnical parameters in chickens of the Cobb 500 cross during the starter, growth and finishing periods when a probiotic (Bacillus subtilis in the composition of Cellobacterin®-T) or an antibiotic (Stafac® 110 based on virginiamycin) was added to the diet and showed that the B. subtilis strain accelerates the formation of intestinal microflora. The probiotic also reduces the number of microorganisms of the Campylobacteriaceae family which includes many types of gastroenteritis pathogens, and also increases the digestibility of fiber. T-RFLP analysis and qPCR method were used to assess changes in the intestinal microbiota of Cobb 500 broiler chickens fed a Bacillus subtilis-based dietary probiotic and virginiamycin-based dietary antibiotic Stafac® 110. On day 14, the total counts of cecal bacteria, as compared to control, were 9.1 times higher (p ≤ 0.05) in broilers fed Stafac® 110, and 54.2 times higher (p ≤ 0.001) when fed B. subtilis preparation. This indicates rapid microbial colonization of gastrointestinal tract of the chickens fed Stafac® 110 and B. subtilis. T-RFLP analysis revealed two dominant cecal phyla, Firmicutes and Proteobacteria, while phyla Actinobacteria, Bacteroidetes, and Fusobacteriawere less abundant. The taxa are detected which ferment non-starch polysaccharides to produce short-chain fatty acids, inhibit the competing pathogens due to production of bacteriocins, and acidize the chyme as synthesize organic acids. Administration of the dietary antibiotic mostly positively influences the cecal microbiota, e.g., the cellulolytic bacteria and Clostridia forms involved in the synthesis of organic acids became more abundant (p ≤ 0.05). Similar beneficial effects, e.g., an increase in Clostridia counts (p ≤ 0.05) compared to control, occurred when the probiotic strain was administered. On day 14 of rearing, the dietary antibiotic and probiotic reduced abundance of Campylobacteriaceae family comprising gastroenteritis pathogens (p ≤ 0.05) when compared to control. An increase in bodyweight as compared to control (from 1845.8±20.9 to 1936.4±17.9 g, p = 0.046) occurred in 36-day-old chickens fed Stafac® 110 but not the probiotic strain but not the probiotic strain, despite recovery of gut microbiota in the chickens fed B. subtilis. A 7.1 % increase infiber digestibility (p = 0.0027) occurred in broilers fed dietary probiotic and a 2.3 % increase (p = 0.047) in those fed the dietary antibiotic, which may be due to the action of cellulolytic microorganisms. Therefore, a dietary B. subtilis-based probiotic which promotes recovery of gut microbiota and increases fiber digestibility in feeds for broiler chickens can be an effective alternative to the virginiamycin-based antibiotic Stafac® 110.

Metaproteomic investigation of functional insight into special defined microbial starter on production of fermented rice with melanogenesis inhibition activity.

Fermentation of rice grains requires diverse metabolic enzymes to be synchronously synthesized by the microbial community. Although many studies have used a metaproteomic approach to investigate the roles of microorganisms in improving the flavor of fermented foods, their roles in producing compounds with biological activity have not yet been reported. In a previous study the ferment obtained from unpolished black rice (UBR) fermented with a defined microbial starter (De-E11), comprised of Rhizopus oryzae, Saccharomycopsis fibuligera, Saccharomyces cerevisiae, and Pediococcus pentosaceus, (fermented UBR; FUBR) showed a strong melanogenesis inhibition activity in B16F10 melanoma cells. Hence, in this study, the roles of these microorganisms in producing the melanogenesis inhibitor(s) in FUBR was investigated using a metaproteomic approach. The melanogenesis inhibition activity of the FUBR liquid (FR-Liq) was found to increase with longer fermentation times. R. oryzae and S. cerevisiae were the major hosts of proteins related to the biosynthesis of melanogenesis inhibitor(s) in the FUBR. During fermentation, the enzymes involved in the degradation of UBR and in the carbohydrate metabolic process were identified. These enzymes were associated with the process of releasing of bioactive compound(s) from UBR and the synthesis of organic acids from the microorganisms, respectively. In addition, enzymes involved in the synthesis of some known melanogenesis inhibitor(s) and in the degradation of the melanogenesis stimulator (arsenate) were detected. Varying the combination of microorganisms in the De-E11 starter to produce the FR-Liq revealed that all four microorganisms were required to produce the most potent melanogenesis inhibition activity. Taken together with the metaproteomics results, this suggested that the microorganisms in De-E11 synchronously synthesize the FR-Liq with melanogenesis inhibition activity. In conclusion, this information on the metaproteome in FUBR will increase our understanding of the microbial metabolic modes and could lead to knowledge-based improvements in the fermented rice process to produce melanogenesis inhibitor(s).

Current advance in biological production of short-chain organic acid.

As natural metabolites, organic acids have been widely applied in food, pharmaceutical, and bio-based materials industries. Particularly, the short-chain organic acids, including C2, C3, C4, C5, and C6 organic acids, are necessary intermediate metabolites in cells and are also alternatives to some commercial chemical products. As the necessary metabolites in cells, most major short-chain organic acids can be produced through microbial fermentation. Specifically, with the development of synthetic biology, metabolic engineering could endow cells with the ability to produce more short-chain organic acid products including propionic acid, pyruvate, lactic acid, 3-hydroxypropionic acid, malic acid, succinic acid, fumaric acid, butyric acid, itaconic acid, α-ketoglutaric acid, glutaric acid, citric acid, gluconic acid, muconic acid, adipic acid, xylonic acid, and so on. The recent advances in the biological production of short-chain organic acids, as well as the challenges and perspectives, are summarized in this review to promote the generation of microbial cell factories for the production of short-chain organic acids.Key points• Outlines the production strategy of short-chain organic acids• Provide guidance for efficient synthesis of short-chain organic acids• Impacts the necessary factor of acid resistance on the successful production of host cells.

Combination of Trace Metal to Improve Solventogenesis of Clostridium carboxidivorans P7 in Syngas Fermentation.

Higher alcohols such as butanol (C4 alcohol) and hexanol (C6 alcohol) are superior biofuels compared to ethanol. Clostridium carboxidivorans P7 is a typical acetogen capable of producing C4 and C6 alcohols natively. In this study, the composition of trace metals in culture medium was adjusted, and the effects of these adjustments on artificial syngas fermentation by C. carboxidivorans P7 were investigated. Nickel and ferrous ions were essential for growth and metabolite synthesis during syngas fermentation by P7. However, a decreased dose of molybdate improved alcohol fermentation performance by stimulating carbon fixation and solventogenesis. In response to the modified trace metal composition, cells grew to a maximum OD600nm of 1.6 and accumulated ethanol and butanol to maximum concentrations of 2.0 and 1.0 g/L, respectively, in serum bottles. These yields were ten-fold higher than the yields generated using the original composition of trace metals. Furthermore, 0.5 g/L of hexanol was detected at the end of fermentation. The results from gene expression experiments examining genes related to carbon fixation and organic acid and solvent synthesis pathways revealed a dramatic up-regulation of the Wood–Ljungdahl pathway (WLP) gene cluster, the bcs gene cluster, and a putative CoA transferase and butanol dehydrogenase, thereby indicating that both de novo synthesis and acid re-assimilation contributed to the significantly elevated accumulation of higher alcohols. The bdh35 gene was speculated to be the key target for butanol synthesis during solventogenesis.

Hydrogen sulphide alleviates iron deficiency by promoting iron availability and plant hormone levels in Glycine max seedlings

BackgroundHydrogen sulphide (H2S) is involved in regulating physiological processes in plants. We investigated how H2S ameliorates iron (Fe) deficiency in soybean (Glycine max L.) seedlings. Multidisciplinary approaches including physiological, biochemical and molecular, and transcriptome methods were used to investigate the H2S role in regulating Fe availability in soybean seedlings.ResultsOur results showed that H2S completely prevented leaf interveinal chlorosis and caused an increase in soybean seedling biomass under Fe deficiency conditions. Moreover, H2S decreased the amount of root-bound apoplastic Fe and increased the Fe content in leaves and roots by regulating the ferric-chelate reductase (FCR) activities and Fe homeostasis- and sulphur metabolism-related gene expression levels, thereby promoting photosynthesis in soybean seedlings. In addition, H2S changed the plant hormone concentrations by modulating plant hormone-related gene expression abundances in soybean seedlings grown in Fe-deficient solution. Furthermore, organic acid biosynthesis and related genes expression also played a vital role in modulating the H2S-mediated alleviation of Fe deficiency in soybean seedlings.ConclusionOur results indicated that Fe deficiency was alleviated by H2S through enhancement of Fe acquisition and assimilation, thereby regulating plant hormones and organic acid synthesis in plants.

CONTENT of ORGANIC ACIDS in the CULTURAL MEDIUM of Bacillus subtilis IMV B-7023 at CULTIVATION WITH DIFFERENT SOURCES of the PHOSPHORUS NUTRIENT

The strain Bacillus subtilis IMV B-7023 is part of the complex bacterial preparation Azogran for crop production. This bacterium has the ability to increase the availability of phosphorus for plants through the synthesis of different organic acids. Using GS-MS, the qualitative and quantitative composition of organic acids in the culture medium of bacilli was investigated depending on the source of phosphorus nutrition in the nutrient medium. It was established that B. subtilis IMV B-7023 synthesizes the greatest amount of organic acids at cultivation in a glucose-mineral medium with calcium glycerophosphate after 24 hours. Among them: acetic, isobutyric, butyric, isovaleric, valeric, caproic, enanthic, caprylic, pelargonic. The content of the acetic acid was 32.5 µg/mL and prevailed over other acids. In the presence of calcium glycerophosphate as the sole source of carbon and phosphate nutrition, the concentration of butyric acid increased by 14.5 µg/mL, valeric – by 17.0 µg/mL, caproic – by 36.6 µg/mL, caprylic – by 9.3 µg/mL, and pelargonic – by 13.1 µg/mL, compared with the previous variant. In the presence of Ca3(PO4)2, B. subtilis IMV B-7023 produced the acetic and isobutyric acids. The concentrations of these compounds reached a maximum (300.0 and 90.0 μg/mL) after 48 hours of cultivation of bacteria, and then decreased.

Impact of high atmospheric CO2 concentrations on the seasonality of water-related processes, gas exchange, and carbohydrate metabolism in coffee trees under field conditions

Increasing atmospheric CO2 concentrations ([CO2]) are unequivocal, widespread, and responsible for increased mean global temperatures and altered precipitation patterns. In this context, among the topics that need to be better understood are the changes in the water-related processes and gas exchange properties of plants grown under these conditions. Notably, the effects of climate change on coffee (Coffea spp.) production are particularly concerning given the importance of this commodity. Especially, it has been reported that coffee trees exhibit better photosynthetic efficiency when grown at higher [CO2] levels. In order to elucidate the mechanisms involved with this response, the seasonality of water-related processes, gas exchange, and carbohydrate metabolism were investigated using C. arabica var. Red Catuai grown at ambient and high [CO2] under field conditions, at a free-air CO2 enrichment (FACE) facility for coffee, in Brazil. The trees were evaluated fortnightly, from November to February (hot and rainy—summer) and from June to September (cold and dry—winter). It was found that C. arabica trees grown under high [CO2] conditions exhibited increased photosynthetic rates (averaging 121% higher in summer and 45% higher in winter) in both seasons, without displaying any significant changes in the seasonal photosynthesis pattern. Additionally, there was a tendency for the coffee trees grown at high [CO2] to exhibit increased levels of soluble carbohydrates, organic acids, and amino acids in the leaves. Our findings suggest that coffee trees adapt to increased [CO2] through increased photosynthetic rates, enhanced stomatal conductance regulation, and augmented carbohydrate and organic acid synthesis. It is plausible that these features could help mitigate the effects caused by climate change.

Exogenous Abscisic Acid Alleviates Harmful Effect of Salt and Alkali Stresses on Wheat Seedlings.

Exogenous hormones play an important role in plant growth regulation and stress tolerance. However, little is known about the effect of exogenous abscisic acid (ABA) on wheat seedlings under salt and alkali stresses. Here, a pot experiment of saline and alkaline stresses (0 and 100 mmol/L) in which ABA water solution (0, 50 and 100 μmol/L) was sprayed on wheat seedlings was conducted to study the alleviative effectiveness of ABA on salt and alkali stresses. After spraying ABA (50 μmol·L−1), shoot biomass increased 19.0% and 26.7%, respectively. The Na+ content in shoots reduced from 15-fold and 61.5-fold to 10-fold and 37.3-fold in salt and alkali stresses, compared to controls. In addition, proline and organic acid synthesis in shoots also reduced significantly, but the soluble sugar content increased under alkali stress. A high concentration of ABA (100 μmol·L−1) had no significant effects on biomass and ion content in wheat seedlings under both stresses. In conclusion, foliar application of ABA with moderate concentration could effectively accelerate shoot growth of salt-induced wheat seedlings by adjusting the levels of ions and organic solutes.

Sugar Alcohols and Organic Acids Synthesis in Yarrowia lipolytica: Where Are We?

Sugar alcohols and organic acids that derive from the metabolism of certain microorganisms have a panoply of applications in agro-food, chemical and pharmaceutical industries. The main challenge in their production is to reach a productivity threshold that allow the process to be profitable. This relies on the construction of efficient cell factories by metabolic engineering and on the development of low-cost production processes by using industrial wastes or cheap and widely available raw materials as feedstock. The non-conventional yeast Yarrowia lipolytica has emerged recently as a potential producer of such metabolites owing its low nutritive requirements, its ability to grow at high cell densities in a bioreactor and ease of genome edition. This review will focus on current knowledge on the synthesis of the most important sugar alcohols and organic acids in Y. lipolytica.

Citrate synthesis and exudation confer Al resistance in alfalfa (Medicago sativa L.)

Alfalfa is the most important forage legume but sensitive to aluminum (Al), which largely limits its growth in acid soils. To improve Al resistance in alfalfa, responses to Al toxicity were investigated for understanding of the mechanisms of Al resistance in alfalfa. Growth performance and Al resistance in forty-two cultivars was evaluated. Organic acids synthesis and exudation as well as the key genes in response to Al were investigated. Alfalfa cultivars showed diversity in Al resistance. Compared to the sensitive cultivar ‘Magnum 801’, the Al resistant cultivar ‘WL414’ had higher relative root elongation in response to Al toxicity, with less accumulation of Al. Al activated citrate and malate exudation in alfalfa, with higher citrate exudation and concentration as well as higher levels of citrate synthase (CS) activity, MsCS, MsALMT1, and MsMATE22 transcripts in root apex in WL414 than in Magnum 801. Citrate exudation is the major mechanism in Al resistance in alfalfa. Alfalfa cultivars had diversity in Al resistance. Citrate synthesis and exudation plays a key role in Al resistance in alfalfa. Higher levels of citrate concentration and exudation are associated with Al resistance in Al resistant cultivar as compared with the sensitive cultivar.

Genomic Analysis of Bacillus megaterium NCT-2 Reveals Its Genetic Basis for the Bioremediation of Secondary Salinization Soil

Bacillus megaterium NCT-2 is a nitrate-uptake bacterial, which shows high bioremediation capacity in secondary salinization soil, including nitrate-reducing capacity, phosphate solubilization, and salinity adaptation. To gain insights into the bioremediation capacity at the genetic level, the complete genome sequence was obtained by using a multiplatform strategy involving HiSeq and PacBio sequencing. The NCT-2 genome consists of a circular chromosome of 5.19 Mbp and ten indigenous plasmids, totaling 5.88 Mbp with an average GC content of 37.87%. The chromosome encodes 5,606 genes, 142 tRNAs, and 53 rRNAs. Genes involved in the features of the bioremediation in secondary salinization soil and plant growth promotion were identified in the genome, such as nitrogen metabolism, phosphate uptake, the synthesis of organic acids and phosphatase for phosphate-solubilizing ability, and Trp-dependent IAA synthetic system. Furthermore, strain NCT-2 has great ability of adaption to environments due to the genes involved in cation transporters, osmotic stress, and oxidative stress. This study sheds light on understanding the molecular basis of using B. megaterium NCT-2 in bioremediation of the secondary salinization soils.

QTL mapping of seed germination-related traits in <italic>Brassica napus</italic> L. under aluminum toxicity stress

<p indent=0mm>With the aggravation of soil acidification, aluminum toxicity has become one of the important stress factors that affect crop seed germination quality and crop yield. There have been many reports on QTL mapping and candidate gene screening for aluminum tolerance related traits in crops, but few reports on QTL mapping for aluminum tolerance during germination in <italic>Brassica napus</italic> L. The seed germination test was conducted on the recombinant inbred line population treated with <sc>80 µg mL^-1</sc> aluminum solution and with distilled water as control. Germination potential was investigated at <sc>3 d,</sc> germination rate was investigated at <sc>7 d,</sc> root length, bud length and dry weight were measured, and the relative values of various characters were calculated. Based on 6K SNP chip and combined with high density genetic linkage map, we detected 23 QTLs for five traits in rape germination period. QTLs for relative germination potential, relative germination rate, relative root length, relative bud length and relative dry weight were 9, 1, 4, 5, and 4 respectively, covering A and C genomes, with LOD values from 3.00 to 5.26, and interpretable phenotypic variation from 7.70% to 13.10%. According to the confidence interval sequence of each QTL, 30 candidate genes related to aluminum stress were screened. <italic>ALMT1</italic> gene and <italic>MATE</italic> gene are related to the synthesis and secretion of organic acids, which mainly enhance the aluminum tolerance of plants through the secretion of organic acids such as malic acid, citric acid and oxalic acid. <italic>STOP1</italic> gene, <italic>NAC </italic>gene and <italic>RAP2.4 </italic>gene all belong to transcription activation factors, which enhance the resistance of plants by inducing the expression of aluminum tolerance genes. ABC transporter, membrane protein transporter, GDSL lipase enhance aluminum tolerance of plants by reducing accumulation of toxic substances on plasma membrane or discharging toxic substances out of body. Peroxidase and cytochrome P450 are genes related to oxidative stress, which have the functions of preventing oxidative damage of plant cells and resisting stress. At the same time, many genes encoding stress proteins were found, which play an important role in various stress reactions. The results of this study provide a theoretical basis for the cultivation of aluminum-tolerant rape varieties and the functional research of subsequent genes.

Influence of plant immunity inducers on the quality of apple fruit in Abkhazia

The quality of fruit depends largely on the growing area of the crop, the intensity of disease development, damage by pests, as well as on the treatment of plants with compounds of various chemical natures. When introducing the immunity inducers Albit® (poly-beta-hydroxybutyric acid), Immunocytophyte® (arachidonic acid ethyl ether) and Ecogel® (chitosan lactate) into apple tree protection systems, an urgent task is to study their influence on the quality of fruits. Research was conducted on apple trees (cultivars Idared and Golden Rangers) in the conditions of the Republic of Abkhazia (Gulripsh district). When treated with immunity inducers, the genotypic features of the cultivars were clearly revealed. For the susceptible Idared cultivar, it is more significant to use Ecogel®, which causes the active synthesis of soluble solids, pectin, soluble sugars, ascorbic acid, and as a result, an increase in the sugar-acid index. At the same time, a relatively resistant cultivar Golden Rangers has a similar effect when treated with Immunocytophyte®. Treatment with Albit® has the same effect on the synthesis of soluble organic acids in the fruits of the studied apple cultivars, reducing their amount. The results obtained indicate the need for a cultivar-specific approach in the application and selection of plant immunity inducers.