Stimulation Of Enzyme Activity Research Articles

Pecan agroforestry systems improve soil quality by stimulating enzyme activity.

BackgroundForest and plantation intercropping are efficient agroforestry systems that optimize land use and promote agroforestry around the world. However, diverse agroforestry systems on the same upper-plantation differently affect the physical and chemical properties of the soil.MethodsThe treatments for this study included a single cultivation (CK) pecan control and three agroforestry systems (pecan + Paeonia suffruticosa + Hemerocallis citrina, pecan + Paeonia suffruticosa, and pecan + Paeonia lactiflora). Soil samples were categorized according to the sampling depth (0–20 cm, 20–40 cm, 40–60 cm).ResultsThe results demonstrated that the bulk density (BD) of soil under the pecan agroforestry system (PPH and PPL) was reduced by 16.13% and 7.10%, respectively, and the soil moisture content (MC) and total soil porosity (TPO) increased. Improvements in the physical properties of the soil under the PPS agroforestry system were not obvious when compared with the pecan monoculture. The soil total phosphorus (TP), total nitrogen (TN), available potassium (AK), and total carbon (TC) increased significantly, while the soil urease (S-UE), alkaline phosphatase (S-AKP), and 1,4-β-N-acetylglucosamines (S-NAG) enzyme activity also increased significantly, following agroforestry. Overall, the pecan agroforestry system significantly improved the physical properties of the pecan plantation soil, enriched the soil nutrients, and increased the activity of soil enzymes related to TC, TN, and TP cycles.

Enhancing Hydrogen Productivity of Photosynthetic Bacteria from the Formulated Carbon Source by Mixing Xylose with Glucose.

To develop an efficient photofermentative process capable of higher rate biohydrogen production using carbon components of lignocellulosic hydrolysate, a desired carbon substrate by mixing xylose with glucose was formulated. Effects of crucial process parameters affecting cellular biochemical reaction of hydrogen by photosynthetic bacteria (PSB), i.e., variation in initial concentration of total carbon, glucose content in initial carbon substrate, and light intensity, were experimentally investigated using response surface methodology (RSM) with a Box-Behnken design (BBD). Hydrogen production rate (HPR) in the maximum value of 30.6mLh-1 L-1 was attained under conditions of 39mM initial concentration of total carbon, 59% (mol/mol) glucose content in initial carbon substrate, and 12.6Wm-2 light intensity at light wavelength of 590nm. Synergic effects of metabolizing such a well-formulated carbon substrate for sustaining the active microbial synthesis to sufficiently accumulate biomass in bioreactor, as well as stimulating enzyme activity of nitrogenase for the higher rate biohydrogen production, were attributed to this carbon substrate that can enable PSB to maintain the relatively consistent microenvironment in suitable culture pH condition during the optimized photofermentative process.

Effects of Co-Applications of Biochar and Solid Digestate on Enzyme Activities and Heavy Metals Bioavailability in Cd-Polluted Greenhouse Soil

To deal with the problems of increasing the heavy metal (HM) bioavailability and declining the soil biological properties resulting from a direct application of solid digestate (SD). A low-temperature fruit biochar and pig-SD (BSD-0, BSD-1, BSD-2, BSD-4, BSD-8) co-application experiment was performed to evaluate enzyme activities and HM bioavailability in Cd-polluted greenhouse soil. The advantage of BSD co-applications compared to SD application was maintained the stable of pH and electrical conductivity (EC) in soil and was more effective to improve soil organic matter (OM). BSD-8 treatment significantly promoted the uptake of available nitrogen, available phosphorus, and available potassium by plants. The immobilization effect of BSD co-applications on Cu, Zn, and Cd was better than SD application. BSD-8 treatment has the best immobilization effect on Cd and the contents of bioavailable Cd was 0.167 mg kg−1. The optimal enzyme activities of invertase, urease, and alkaline phosphatase were shown in BSD-8 treatment, which were 0.027 mg glucose g−1 soil h−1, 88.654 mg NH3-N g−1 soil h−1, and 15.766 μmol PNP g−1 soil h−1, respectively. The activities of enzymes also were influenced by soil physicochemical properties and HM bioavailability. BSD-8 treatment was suggested as an appropriate mixing proportion to alleviate soil acidification and salinization, decreasing HM bioavailability and stimulating enzyme activities in Cd-polluted soil.

Influence of thermal assistance on the biodegradation of organics during food waste bio-drying: Microbial stimulation and energy assessment

Recently, bio-drying was highlighted in the drying pretreatment of high-moisture organic wastes for their energy recovery. In this study, to investigate the influences of thermal assistance on microbial stimulation and energy utilization in organic degradation, thermally assisted bio-drying (TB) was conducted on food waste (FW) and was compared with conventional bio-drying (CB) and thermal drying (TD). As expected, more water was removed in TB, which exhibited no lag phenomenon and intensified microbial activity. Corresponding with the stimulated enzyme activity, more readily degradable carbohydrates, lipids and lignocellulose were decomposed in TB than those in CB, and lipid degradation generated a significant proportion of the total bio-heat generated (43.13%–45.83%). Furthermore, according to the microbial analysis (qPCR and 16S rRNA gene sequencing), Bacillus was found to be the dominant genus involved in the degradation of organics during TB and CB. In the initial phase, rather than Weissella, as in CB, Ureibacillus was notable in TB for the degradation of readily degradable substrates. In the late phase, Pseudoxanthomonas and Saccharomonospora were enriched for degrading lignocellulose. In addition, heat balance and life-cycle energy assessment demonstrated that a small amount of thermal heat (11.96%) upgraded bio-drying with high energy efficiency. Compared with the CB and TD processes, the TB trial consumed less thermal energy (0.58 MJ/kg H2O) and achieved a higher energy output/input ratio (3.64). This research suggests that thermal assistance is a promising approach to enhancing FW bio-drying, which exhibits efficient drying performance and great potential for energy recovery.

G-Quadruplex loops regulate PARP-1 enzymatic activation.

G-Quadruplexes are non-B form DNA structures present at regulatory regions in the genome, such as promoters of proto-oncogenes and telomeres. The prominence in such sites suggests G-quadruplexes serve an important regulatory role in the cell. Indeed, oxidized G-quadruplexes found at regulatory sites are regarded as epigenetic elements and are associated with an interlinking of DNA repair and transcription. PARP-1 binds damaged DNA and non-B form DNA, where it covalently modifies repair enzymes or chromatin-associated proteins respectively with poly(ADP-ribose) (PAR). PAR serves as a signal in regulation of transcription, chromatin remodeling, and DNA repair. PARP-1 is known to bind G-quadruplexes with stimulation of enzymatic activity. We show that PARP-1 binds several G-quadruplex structures with nanomolar affinities, but only a subset promote PARP-1 activity. The G-quadruplex forming sequence found in the proto-oncogene c-KIT promoter stimulates enzymatic activity of PARP-1. The loop-forming characteristics of the c-KIT G-quadruplex sequence regulate PARP-1 catalytic activity, whereas eliminating these loop features reduces PARP-1 activity. Oxidized G-quadruplexes that have been suggested to form unique, looped structures stimulate PARP-1 activity. Our results support a functional interaction between PARP-1 and G-quadruplexes. PARP-1 enzymatic activation by G-quadruplexes is dependent on the loop features and the presence of oxidative damage.

Optimization of EDTA and citric acid for risk assessment in the remediation of lead contaminated soil

So far, more attention has been mostly paid to the effects of the chelates application to improve phytoextraction efficiency, but less information is available about their effects on the rhizosphere enzyme activities. A greenhouse study was conducted to investigate the effect of EDTA and citric acid (CA) (3 and 5 mmol/kg) on the Pb accumulation in plant organs, the dehydrogenase, urease and alkaline phosphomonoesterase activities, geometric mean of enzyme activities (GMea), total enzyme activity (TEA), and Shannon's diversity index. The application of EDTA harmed plant growth, whereas CA treatments improved plant growth. The 3 and 5 mmol/kg EDTA enhanced Pb accumulation in shoots by 2.6–6 and 1.7–3 times, respectively, in comparison with the control. Pb accumulation in roots after the CA application was significantly higher than control and EDTA treatments. The high dose of EDTA reduced the dehydrogenase and urease activities, GMea, TEA, and diversity of enzyme activities. In contrast, the low dose of EDTA increased the dehydrogenase and alkaline phosphomonoesterase activities, and enzyme-based indices compared with control treatment. In both high and low concentrations, CA significantly stimulated enzyme activities of the rhizosphere, as well as the enzyme-based indices, compared with control and EDTA treatments. CA increased Pb accumulation in the root while did not elevate Pb translocation to the shoot, and also improved the rhizosphere enzyme activities. Thus, we conclude that: i) the effect of EDTA on the Pb phytoextraction and rhizosphere enzyme activities depended on the dosage of EDTA used; ii) CA can be a more suitable choice to increase Pb phytostabilization due to enhancement of the rhizosphere microbial activities.

Production and partial purification by PEG/citrate ATPS of a β-galactosidase from the new promising isolate Cladosporium tenuissimum URM 7803

β-Galactosidase production, partial purification and characterization by a new fungal were investigated. Partial purification was performed by aqueous two-phase system (ATPS) using polyethylene glycol (PEG) molar mass, PEG concentration, citrate concentration and pH as the independent variables. Purification factor (PF), partition coefficient (K) and yield (Y) were the responses. After identification by rDNA sequencing and classification as Cladosporium tenuissimum URM 7803, this isolate achieved a maximum cell concentration and β-galactosidase activity of 0.48 g/L and 462.1 U/mL, respectively. β-Galactosidase partitioned preferentially for bottom salt-rich phase likely due to hydrophobicity and volume exclusion effect caused in the top phase by the high PEG concentration and molar mass. The highest value of PF (12.94) was obtained using 24% (w/w) PEG 8000 g/mol and 15% (w/w) citrate, while that of Y (79.76%) using 20% (w/w) PEG 400 g/mol and 25% (w/w) citrate, both at pH 6. The enzyme exhibited optimum temperature in crude and ATPS extracts in the ranges 35–50 °C and 40–55 °C, respectively, and optimum pH in the range 3.0–4.5, with a fall of enzyme activity under alkaline conditions. Some metal ions and detergents inhibited, while others stimulated enzyme activity. Finally, C. tenuissimum URM 7803 β-galactosidase showed a profile suitable for prebiotics production.

Nitrogen fertilisation in tropical pastures: what are the impacts of this practice?

It is estimated that approximately 47% of the world’s ruminant meat and milk is produced in tropical and subtropical regions, with pasture comprising the main food base of these animals. Nitrogen fertilisation is an essential practice for the maintenance of pasture productivity, considering that a deficiency of this nutrient is a primary factor in triggering pasture degradation. In addition to directly influencing the photochemical and biochemical phases of photosynthesis, nitrogen stimulates enzyme activity and the synthesis of enzymes responsible for fixing CO2 (Rubisco in C3 plants and phosphoenolpyruvate carboxylase in C4 plants), thus increasing the efficiency of atmospheric CO2 capture. All of these physiological processes are easily observed macroscopically in the characteristics of forage plants. This review examines the impact of nitrogen fertilisation in tropical pastures on the main components of production systems (soil, plants and animals), describes the results obtained in different situations and highlights the most efficient ways of producing meat without environmental impacts.

Combined biochar and nitrogen application stimulates enzyme activity and root plasticity

Biochar (BC) and nitrogen (N) fertilizers are frequently applied to improve soil properties and increase crop productivity. Nonetheless, our mechanistic understanding of plant-soil interactions under single or combined application of BC and N remains incomplete. For the first time, we applied a split-root system to evaluate how BC or N contributes to the changes in soil enzyme activities, N and phosphorus (P) cycling as well as root plasticity. Left and right parts of rhizoboxes were filled with silty-clay loamy soil amended with BC (15 g kg−1 soil, from wheat straw, 300 °C), N (0.05 g KNO3-N kg−1 soil) or a control (no amendments), resulting in the following combinations: BC/Control, N/Control, BC/N. Soil enzyme activities, available N and P, root morphology and plant biomass were analyzed after plant harvest.Plant biomass (shoot + root) ranged from 0.56 g pot−1 (BC/Control) to 0.91 g pot−1(BC/N). The decreased soil bulk density and increased P availability in the BC compartment (BC/Control and BC/N) stimulated root length by 1.4–1.8 times – an effect that was independent of N availability in the same rhizobox. Biochar stimulated activities of β-glucosidase and leucine aminopeptidase (by 33–39%) compared to N due to the coupling of C, N and P cycles in BC/N treated soil. Nitrogen fertilization also increased β-glucosidase activity compared to the unfertilized control, whereas root elongation remained unaffected. Thus, the combined application of BC/N had more efficient benefits for plant growth than BC or N alone. This is linked with i) the stimulation of enzyme activities at the BC locations to reduce N limitation for both microorganisms and plants, and ii) an increase of fine root production to improve N uptake efficiency. Thus, combined BC/N application is potentially especially sustainable to overcome nutrient limitation as well as to maintain crop productivity because it accelerates root-microbial interactions.

Elevated CO2 mitigates the negative effect of CeO2 and Cr2O3 nanoparticles on soil bacterial communities by alteration of microbial carbon use

The interactive effects of elevated atmospheric CO2 and nanoparticles (NPs) on the structure and function of soil bacterial community remain unknown. Here we compared the impacts of CeO2 (nCeO2) and Cr2O3 (nCr2O3) nanoparticles on the taxonomic compositions and functional attributes of bacterial communities under elevated CO2 (eCO2). The stimulated enzyme activities (dehydrogenase, acid phosphatase and urease), increased microbial biomass carbon (MBC), and higher bacterial alpha-diversity were observed under the combined effects of eCO2 and NPs compared to the single NP treatment, indicating eCO2 could mitigate the adverse effect of NPs on soil microorganisms. NPs and eCO2 are important factors influencing the alpha- and beta-diversity (17% and 18% of variations were explained) as well as functional profile (20% and 26% of variations were explained) of bacterial communities. Rising CO2 level promoted the resilience of NP-resistant bacterial populations, primarily the members of Alphaproteobacteria, Gammaproteobacteria and Bacteroidia, which are also characterized by the fast carbon use capability. Moreover, the significantly (P < 0.05) higher metabolic quotient (qCO2), reduced available carbon and overrepresented carbon metabolism genes at eCO2vs. ambient CO2 (aCO2) indicate the acceleration of available carbon turnover in NP-exposed soils. Correlation analysis revealed that mitigation of NPs toxicity by eCO2 could be attributed to the remarkable decline of bioavailable metals disassociated from NPs and available carbon level, as well as promotion of the rapid carbon-metabolizing microbes. Our study pointed out the positive role of eCO2 in alleviating the adverse effect of NPs on microbiological soil environment, and results can serve as important basis in establishing guidelines for lowering the ecotoxicity of NPs.

Management of barley net blotch using Trichoderma asperellum (T34), eugenol, non-traditional compounds and fungicides

Barley plants (cv. Giza 2000) are infected by Drechslera teres which causes net blotch disease symptoms and yield losses. Plants were treated with commercial molecular products such as Trichoderma asperilium (T34), eugenol compared to non-traditional compounds (potassium silicate, nano-selenium) and fungicides (Maven, Montoro, and Decent) which selected from 12 treatments according to their important effects on infected barley plants. Bio-arc, Tilt, Rush up, Curve, and Amisto treatments were left out because of their lower efficiency of some treatments and similarity of the active ingredients of some other of them.Disease severity (%) was significantlty decreased as a result of the selected treatments, except eugenol which showed less reduction than the control. Disease symptoms were suppressed and electrolyte leakage % was reduced significantly due to all treatments than the control treatment. As a consequence of treatments, endogenous reactive oxygen species (ROS) such as superoxide (O2−) was significantly elevated early after the inoculation, consequently, later on catalase (CAT), peroxidase (POX), and polyphenol oxidase (PPO) activities were increased significantly than the control. Elevated levels of O2− early after inoculation could play essential role in killing or suppressing the fungus and inhibiting disease symptoms as well as stimulated enzyme activities. Interestingly, the treatments were effective so that the yield characters (1000 K.W. and grain yield/plo) were increased significantly than the control treatment. These results indicated that the biological commercial product of Trichoderma asperilium 34 and non-traditional biological compounds in this research study are so effective and could be used as an alternative to fungicides.

Expression of the Xylanase Gene from Paenibacillus brasilensis X1 in Pichia pastoris and Characteristics of the Recombinant Enzyme

The heterologous expression, isolation, and characterization of a novel xylanase from Paenibacillus brasilensis are described. The xyl1 gene from the Paenibacillus brasilensis strain X1 VKPM B-13092, which consists of 639 nucleotides, encodes a secreted endo-1,4-β-xylanase (EC 3.2.1.8) containing 184 amino acids and 28 residues of the putative signal peptide in the N-terminal region. The nucleotide sequence of the xyl1 gene and the amino acid sequence of the mature Xyll protein have the greatest homology with the Bacillus subtilis endo-1,4-β-xylanase sequences (78 and 83%, respectively). A gene fragment encoding the mature protein was expressed in Pichia pastoris. The purified recombinant Xyl1 enzyme was able to use birch xylan and arabinoxylan as substrates. With birch xylan, the optimal pH for the enzymatic reaction was 6.0, the optimal temperature was 40–50°C, and Km and Vmax, were equal to 1.1288 mg/mL and 5124.3 μmol/(min mg), respectively. The recombinant Xyl1 protein showed high pH and thermal stability, and the resistance to digestive enzymes and xylanase protein inhibitors from cereals. It was also shown that Mn2+ and Со2+ ions stimulate enzyme activity.

Effect of organic soil amendments on soil quality in oil palm production

Soil quality (SQ) evaluation is an essential tool for the enhancement of agricultural soil management and use. An array of soil attributes, termed soil quality indicators, are used in soil quality estimation due to their sensitivity to disturbance from management practices. Therefore, the objective of this study was to assess the soil quality (using multivariate ordination technique) of oil palm (Elaeis guineensis, Jacq.) plantations amended with on-farm biomass. The experimental sites were three oil palm plantations located in the southernmost Pattani province of Thailand namely, Ban Chamao (BC), Ban Lipasango (BL) and Ban Bothong (BB) fertilised with fish effluent (FE), empty fruit bunch (EFB) compost and NPK (plus EFB mulch), respectively with completely randomised block design. A minimum dataset (MDS) of soil indicators were defined using multivariate principal component analysis (PCA). The selected MDS comprised mainly geometric mean of microbial enzyme activity (GME), available phosphorus (AP) and moisture content (MC) with per cent contribution towards soil quality index (SQI) (assessed based on PCA after scoring by normalised linear function) in the order: GME (77.3%) > AP (13.6%) > MC (9.1%). Essentially, the activity of enzymes is a crucial ecosystem function (nutrient cycling), further indicating that decreases in soil enzyme activities can be signal for a decline in SQ. GME, AP, and MC effectively differentiated the oil palm plantations and could be important not only in monitoring soil quality enhancement in the present study locations but also in a similar tropical environment with similar edaphic conditions. SQI was not significantly different between the BB (0.81) and BL (0.79) plantations (p = 0.46). However, both BB and BL were higher than in BC (0.65). BB and BL showed low geometric mean of microbial biomass GMB, high soil pH, C, N, GME and qCO2 (metabolic quotient, i.e., the amount of CO2 respired per unit microbial biomass), while the fish effluent amended BC plantation showed the opposite. EFB contains a substantial quantity of nutrients and organic matter (OM) capable of reducing soil acidity, stimulating enzyme activity, and enriching the soil with nutrients with the resultant improvement in SQ. Therefore, a regular practice of returning EFB (either as compost or mulch, with or without mineral NPK) to the soil should be encouraged for smallholder oil palm plantations to improve soil quality and serves as an alternative channel for on-farm biomass disposal.

Carboxylate-functionalized foldamer inhibitors of HIV-1 integrase and Topoisomerase 1: artificial analogues of DNA mimic proteins.

Inspired by DNA mimic proteins, we have introduced aromatic foldamers bearing phosphonate groups as synthetic mimics of the charge surface of B-DNA and competitive inhibitors of some therapeutically relevant DNA-binding enzymes: the human DNA Topoisomerase 1 (Top1) and the human HIV-1 integrase (HIV-1 IN). We now report on variants of these anionic foldamers bearing carboxylates instead of phosphonates. Several new monomers have been synthesized with protecting groups suitable for solid phase synthesis (SPS). Six hexadecaamides have been prepared using SPS. Proof of their resemblance to B-DNA was brought by the first crystal structure of one of these DNA-mimic foldamers in its polyanionic form. While some of the foldamers were found to be as active as, or even more active than, the original phosphonate oligomers, others had no activity at all or could even stimulate enzyme activity in vitro. Some foldamers were found to have differential inhibitory effects on the two enzymes. These results demonstrate a strong dependence of inhibitory activity on foldamer structure and charge distribution. They open broad avenues for the development of new classes of derivatives that could inhibit the interaction of specific proteins with their DNA target thereby influencing the cellular pathways in which they are involved.

The Stimulatory Effects of Nanochitin Whisker on Carbon and Nitrogen Metabolism and on the Enhancement of Grain Yield and Crude Protein of Winter Wheat.

Nanochitin whisker (NC) with a cationic nature could enhance plant photosynthesis, grain yield, and quality of wheat, but have not been systematically studied. This study was designed to investigate the stimulatory effects of NC on dry matter (DM) and nitrogen (N) accumulation and translocation, and on the metabolism of carbon (C) and N in later growth stages of winter wheat to reveal the enhancement mechanism of grain yield and crude protein concentration. Different parts of NC-treated plants from pot grown experiments were collected at the pre- and post-anthesis stages. The accumulation, translocation, and contributions of DM and N from pre-anthesis vegetation organs to grains, as well as key metabolic enzyme activities, including sucrose phosphate synthase (SPS) and phosphoenolpyruvate carboxylase (PEPC), were examined. The results showed that, at an application rate of 6 mg·kg−1 of NC in the soil, the accumulation of DM and N were significantly enhanced by 16.2% and 38.8% in pre-anthesis, and by 15.4% and 30.0% in post-anthesis, respectively. Translocation of N and DM in the post-anthesis periods were enhanced by 38.4% and 50.9%, respectively. NC could also stimulate enzyme activities, and increased 39.8% and 57.1% in flag leaves, and by 36.0% and 58.8% in spikes, respectively, at anthesis. SPS and PEPC increased by 28.2% and 45.1% in flag leaves, and by 42.2% and 56.5% in spikes, respectively, at 15 days after anthesis. The results indicated that the NC promoted N metabolism more than C metabolism, and resulted in the enhancement of grain yield by 27.56% and of crude protein concentration in grain by 13.26%, respectively.

Short-term dynamics of soil organic matter fractions and microbial activity in smallholder potato-legume intercropping systems

Continuous cultivation of potato (Solanum tuberosum L.) in monoculture systems represents the greatest factor deteriorating soil organic matter (SOM) in smallholder farms. With an aim to breaking this norm, a 2-year field trial intercropping potato with two legumes: lima bean (Phaseolus lunatus) and dolichos (Lablab purpureus), was conducted in the upper-midland (1552 meters above sea level (masl.)), lower-highland (1854 masl.) and upper-highland (2552 masl.) agro-ecologies of Kenya. Residues from each cropping system were quantified at the end of each season and incorporated back into the soil at start of the subsequent season. A combined physical and density fractionation was used to separate the soil in macro-aggregates (>250 μm), micro-aggregates (250–50 μm) and silt plus clay fractions (<50 μm), while SOM was partitioned into labile (density of 1.65 to 1.85 g cm−3) and stable (2.60 g cm−3) fractions. Microbial biomass contents were determined by chloroform fumigation while enzymatic activities were assessed by hydrolyses of fluorescein diacetate and dehydrogenase. Compared to sole potato, intercropping increased the contents of light fraction organic matter by 12–28%, dissolved organic matter by 7–21% and microbial biomass by 15–38%, thus stimulating enzyme activities. Trends in soil microbial respiration followed those of enzyme activity and were 20–34% higher in intercropping than in sole potato. Intercropping ensured high residue returns which got short-term residence within the macro-aggregates, thus ensuring steady supply of substrates to the soil microbes. These results affirm legume intercropping as a possible entry point to restoring the impoverished soil quality in smallholder potato farming systems.

Tuning stress in bacteria

Signaling In Gram-positive bacteria, protein arginine phosphorylation plays a role in the stress response by regulating transcription and marking aberrant proteins for degradation. Through structural and functional studies of the arginine kinase McsB, Suskiewicz et al. show that the bacterial phospho-signaling system goes beyond linear on-off pathways. The McsB active site is related to that in phosphagen kinases, which are animal enzymes that catalyze phosphorylation of guanido compounds, but the catalytic domain is modified so that MscB binds arginine residues that are part of a polypeptide chain rather than in small compounds. McsB acts more efficiently as a dimer, and phosphoarginine binding to the dimerization domain further stimulates enzyme activity. This additional control, superimposed on the slower transcriptional control, is likely to be important for a fast and robust stress response. Nat. Chem. Biol. 15 , 510 (2019).

Heavy metals interact with the microbial community and affect biogas production in anaerobic digestion: A review

Heavy metals (HMs), which accumulate in digestion substrates, such as plant residues and livestock manure, can affect biogas yields during anaerobic digestion (AD). Low concentration of Cu2+ (0–100 mg/L), Fe2+ (50–4000 mg/L), Ni2+ (0.8–50 mg/L), Cd2+ (0.1–0.3 mg/L), and Zn2+ (0–5 mg/kg) promote biogas production, while high concentrations inhibit AD. Trace amounts of HMs are necessary for the activity of some enzymes. For example, Cu2+ and Cd2+ serve as cofactors in the catalytic center of cellulase and stimulate enzyme activity. High contents of Cd2+ and Cu2+ inhibit enzyme activity by disrupting protein structures. Trace amounts of HMs stimulate the growth and activity of methanogens, while high levels have toxic effects on methanogens. HMs affect the hydrolysis, acidification, and other biochemical reactions of organics in AD by changing the enzyme structure and they also impact methanogen growth. A better understanding of the impact of HMs on AD can provide valuable insights for improving the digestion of poultry manure and plant residues contaminated with HMs, as well as help mitigate HMs pollution. Although several studies have been conducted in this field, few comprehensive reviews have examined the effect of many common HMs on AD. This review summarizes the effects of HMs on the biogas production efficiency of AD and also discusses the effects of HMs on the activities of enzymes and microbial communities.

Dopamine binding directly up-regulates (Na+, K+)-ATPase activity in the gills of the freshwater shrimp Macrobrachium amazonicum

We examined the effects of exogenous dopamine on gill (Na+, K+)-ATPase activity in vitro in microsomal preparations from juvenile or adult freshwater shrimp, Macrobrachium amazonicum. Dopamine had no effect on enzyme activity in juveniles but stimulated activity in adult shrimp gills by ≈35%. Stimulation of the gill (Na+, K+)-ATPase in adult shrimps by 100 mmol L−1 dopamine was characterized kinetically by varying ATP, MgATP, and Na+ and K+ concentrations, together with inhibition by ouabain. Dopamine stimulated ATP hydrolysis by ≈40% obeying Michaelis-Menten kinetics, reaching VM = 190.5 ± 15.7 nmol Pi min−1 mg−1 protein, KM remaining unaltered. Stimulation by Na+ (≈50%) and K+ (≈25%) revealed distinct kinetic profiles: although KM values were similar, Na+ stimulation followed cooperative kinetics, contrasting with the Michaelian kinetics seen for K+. Stimulation by MgATP increased activity by ≈30% with little change in KM. Similar saturation profiles were seen for ouabain inhibition with very similar calculated KI values. Our findings suggest that dopamine may be involved in hemolymph sodium homeostasis by directly binding to the gill (Na+, K+)-ATPase at a site different from ouabain, thus stimulating enzyme activity in an ontogenetic stage-specific manner. However, dopamine binding does not affect enzyme affinity for cations and ouabain. This is the first report of the direct action of dopamine in stimulating the crustacean gill (Na+, K+)-ATPase.

The involvement of NO in ABA-delayed the senescence of cut roses by maintaining water content and antioxidant enzymes activity

Abscisic acid (ABA) coordinates plant growth and development as internal signals. Nitric oxide (NO) as an essential endogenous signal molecule may prolong the vase life of cut flowers. However, the interaction of between ABA and NO during postharvest life of perishable horticultural products was not clear. Here, cut roses were used to investigate the interaction between NO and ABA during the senescence of cut flowers. The results showed that ABA increased the vase life and flower diameter of cut roses in a dose-dependent manner, with maximal biological responses at 0.5 μM. Sodium tungstate, an NO biosynthesis inhibitor, significantly suppressed the vase life and diameter enhanced by ABA, indicating that endogenous NO might be involved in ABA-regulated cut flower senescence. ABA and a NO donor sodium nitroprusside (SNP) effectively increased leaf relative water content and reduced the rate of water loss via inducing stomatal closure. ABA and NO treatments significantly increased the activity of superoxide dismutase, peroxidase and ascorbate peroxidase and the content of leaf chlorophyll. Sodium tungstate also prevented the effects of ABA mentioned above. Altogether, NO may play a crucial role in ABA-delayed the senescence of cut roses by retarding water loss, stimulating enzyme activity and maintaining leaf chlorophyll content.