Major Functional Groups Research Articles

Bioactive compound fromAspergillus terreusDMTMGK004 synergistically contributes towards potential anti-pathogenicity

This study focused on the evaluation of fungal compound for their anti-pathogenic potential against respiratory pathogens. Soil samples were collected from various geographical regions in Madurai, fungal strain was isolated and identified as Aspergillus terreusDMTMGK004 (MGK004). Secondary metabolites were extracted and evaluated for antioxidant potential. It exhibited significantly high anti-proliferative property against gastric adenocarcinoma (AGS) cell lines. Antimicrobial activity against Gram positive (Streptococcus pneumoniae) and Gram negative (Klebsiella pneumoniae and Haemophilus influenzae) respiratory pathogens were analysed and the minimum inhibitory concentration (MIC) values were determined. Furthermore, the time-killing assay illustrated that the metabolite eliminates 50% of the vegetative cells within few hours of the treatment. From the spectral data, the major functional groups present in the compound were determined as carbonyl group and phenolic hydroxyl group which contribute towards its bioactivity. The compound significantly depreciates the production of extracellular polysaccharides which results in the weakening of biofilm architecture and resistance towards serum killing and phagocytosis. It also induced cell membrane damage which leads to protein and nucleic acid leakage. Hence, the results of the present study could provide a better insinuation towards the formulation of new drug targeting respiratory pathogens. SIGNIFICANCE AND IMPACT OF THE STUDY: The ubiquitous fungi Aspergillus terreus is well known for its secondary metabolite production. The fungus was evaluated for production of antagonistic molecule to reduce the growth of infectious agents causing respiratory infections. It exhibited the biological means of antioxidant, anti-proliferative and anti-pathogenic compound production. The compound exhibits killing effect against respiratory pathogens within two hours. It induced cell membrane damage leading to protein and nucleic acid leakage. It significantly reduced the production of extracellular polysaccharides. The results provide needed information to design innovative strategies for targeting pathogenic factors of the respiratory pathogens instead of killing it precisely.

Unraveling the molecular interaction mechanism between graphene oxide and aromatic organic compounds with implications on wastewater treatment

Graphene oxide (GO) has been extensively applied in environmental and chemical engineering applications, such as wastewater remediation and organic compounds sensing, in which the adsorption of aromatic organic compounds (AOCs) (e.g., dyes, drugs and pesticides) on GO is commonly involved. Understanding the fundamental interaction mechanism of AOCs-GO is critical for these applications and designing advanced functional GO-based nanocomposites. In this work, for the first time, the nanomechanical interaction mechanism between GO and a model AOC molecule is quantitatively characterized using single-molecule force spectroscopy (SMFS) and density functional theory (DFT) simulations. The contributions of major functional groups of GO to the binding affinity and configurations of AOC/GO complex have been investigated. It is found that most binding events in the formation of AOC/GO complex should be attributed to the attraction between the cationic AOC molecule and the regions on GO with epoxy groups, the role of which has been overlooked previously, with an activation Gibbs energy for bond dissociation (ΔG) of −4.61 kcal mol−1. Surprisingly limited occurrence of binding events between the cationic AOC and the regions with ionized carboxylic groups on GO suggests that the role of electrostatic interaction has been overrated traditionally. Our results provide new nanomechanical insights into the interaction mechanism of AOCs-GO with useful implications for developing novel AOC/GO nanocomposites with environmental, biomedical and engineering applications.

Contributions of TaSUTs to grain weight in wheat under drought.

The homologous genes to OsSUT1-5 in wheat were identified and detailed analysed. TaSUT1 was the predominant sucrose transporter group and it illustrated the genotypic variations towards drought during grain filling. Sucrose transporters (SUT) play crucial roles in wheat stem water soluble carbohydrate (WSC) remobilization to grain. To determine the major functional SUT gene groups in shoot parts of wheat during grain development, drought tolerant varieties, Westonia and Kauz, were investigated in field drought experiments. Fourteen homologous genes to OsSUT1-5 were identified on five homeologous groups, namely TaSUT1_4A, TaSUT1_4B, TaSUT1_4D; TaSUT2_5A, TaSUT2_5B, TaSUT2_5D; TaSUT3_1A, TaSUT3_1D; TaSUT4_6A, TaSUT4_6B, TaSUT4_6D; TaSUT5_2A, TaSUT5_2B, and TaSUT5_2D, and their gene structures were analysed. Wheat plants above the ground were harvested from pre-anthesis to grain maturity and the stem, leaf sheath, rachis, lemma and developing grain were used for analysing TaSUT gene expression. Grain weight, thousand grain weight, kernel number per spike, biomass and stem WSC were characterized. The study showed that among the five TaSUT groups, TaSUT1 was the predominant sucrose transporting group in all organs sampled, and the expression was particularly high in the developing grain. In contrast to TaSUT1, the gene expression levels of TaSUT2, TaSUT3 and TaSUT4 were lower, except for TaSUT3 which showed preferential expression in the lemma before anthesis. The TaSUT5 gene group was very weakly expressed in all tissues. The upregulated gene expression of TaSUT1 Westonia type in stem and grain reveal a crucial role in stem WSC remobilization to grain under drought. The high TaSUT1 gene expression and the significant correlations with thousand grain weight (TGW) and kernel number per spike demonstrated the contribution in Kauz's high grain yield in an irrigated environment and high TGW in Westonia under drought stress. Further molecular level identification is required for gene marker development.

Contingent factors explain average divergence in functional composition over 88 years of old field succession

Abstract “Old fields” are ecosystems that have been previously managed and subsequently abandoned, usually from agricultural use. These systems are classic testing grounds for hypotheses about community assembly. However, old field succession can be difficult to predict: seemingly similar fields often diverge in terms of species composition and environmental conditions. Here, we test the relative roles of contingency and stochasticity in driving vegetative successional dynamics. We draw on three decades of surveys in 24 old fields at the Cedar Creek Ecosystem Science Reserve (Minnesota, USA), and focus on five drivers that are known to shape local plant communities: soil fertility, fire, climate, competition, and demography. These drivers can contribute to contingency when they act consistently across fields and years (e.g., soil nitrogen accumulation, experimental fire regimes, or average climate), or to stochasticity when their effects are variable (e.g., annual variations in weather, or colonization and mortality events). We proceed in two steps. First, we fit regressions estimating abundance, colonization, and mortality for eight major functional groups in relation to these five drivers. We then use these regressions to parameterize a series of metacommunity simulation models, and test whether observed levels of stochasticity and variation in the drivers are sufficient to explain successional divergence. All drivers were significantly associated with plant species abundances, colonization, and mortality. Contingent factors strongly altered predicted successional trajectories. However, replicate simulations with similar conditions followed similar successional trajectories, suggesting that stochastic processes did not lead to divergence. This robustness of successional dynamics may be explained by compensatory trade‐offs. For example, species that were abundant late in succession typically suffered from low colonization rates and high mortality rates early in succession. Synthesis. Average successional dynamics among old fields at Cedar Creek follow largely consistent trends. Though dynamics of individual fields vary, much of this variation can be explained by contingent factors. Stochastic processes appear not to be sufficiently strong to create divergent successional trajectories among fields with similar sets of drivers. Our results therefore suggest that divergence among successional trajectories in chronosequences may be the result of predictable contingent factors, rather than unpredictable stochastic fluctuations.

Co-adsorption of Cd(II) and Sb(III) by ferrihydrite: a combined XPS and ITC study

Heavy metal and metalloid commonly coexist in soils and sediments, and interact frequently with various minerals. The coexistence of Sb and Cd is commonly observed in Sb mine area, but their co-adsorption behaviors to soil minerals still remain poorly understood. This study aimed to elucidate the co-adsorption characteristics of Cd(II) and Sb(III) by ferrihydrite (Fh) under anoxic condition. Batch experiments were performed to determine the sorption capacity of Cd(II) and Sb(III) in both single and binary systems. The major functional groups that were responsible for Cd(II) and Sb(III) sorption were determined by X-ray photoelectron spectroscopy (XPS), while the thermodynamic sorption mechanisms were elucidated using isothermal titration calorimetry. Cd(II) sorption on Fh increases with increasing pH levels (4–8) whereas Sb(III) sorption shows less variation with pH level variations. The Langmuir adsorption capacity is 55.54 mg/g for Cd(II) and 188.19 mg/g for Sb(III). In Cd–Sb binary systems, Cd(II) sorption is significantly diminished whereas Sb(III) uptake is close to single Sb(III) sorption. XPS indicates the Fe–OH groups are mainly responsible for the binding of Cd and Sb, possibly through the formation of inner-sphere complexes. This hypothesis is further confirmed by the positive entropy (ΔS) after Cd and/or Sb binding. A larger ΔS in the binary Cd–Sb titration than in their single titrations implies the formation of a ternary Fh–Sb–Cd complex, which results in a higher disorder of the sorption system. The presence of Sb(III) reduces Cd(II) sorption whereas Cd(II) has a negligible effect on Sb(III) sorption to ferrihydrite; moreover, Sb(III) and Cd(II) might form surface ternary complexes in binary systems. These new findings have important implications for predicting the sequestration, migration, and fate of Cd and Sb in soils.

Local canopy diversity does not influence phenotypic expression and plasticity of tree seedlings exposed to different resource availabilities

Species diversity seems to favour the environmental heterogeneity and habitat complexity, which in turn favour the selection of greater levels of phenotypic plasticity of plant species. While recent evidence suggested that local species diversity and environmental heterogeneity act as selective pressures over mean traits and plasticity for herbs, which adjust their traits to the identity and species richness of their neighbors, little is known for tree species. Here, we investigated shifts in the phenotypic expression and plasticity of seedlings of two functional groups (broadleaved and conifers) coming from communities with different canopy species richness in two contrasting forest types (a hemiboreal and a Mediterranean forest). We carried out a greenhouse experiment to test the response of seedlings to different light and nutrient availability, measuring different functional traits related to resource acquisition. Our results indicated that seedlings coming from monospecific and more diverse communities had similar phenotypic expression and response capacity to the study treatments. This finding suggests that canopy species richness did not exert a detectable selective pressure on tree phenotypes and plasticity at this early stage. Additionally, we found great differences in the phenotypic expression and plasticity between the two major functional groups (conifers and broadleaved species). Specifically, we found that broadleaves reached higher mean values in key functional traits by a greater plasticity to both light and nutrient treatment than coniferous species, mainly in the Mediterranean forest. This finding suggests that broadleaved species potentially have a higher capacity to respond to future changing environmental conditions than conifers at early stages, conferring an advantage that can be crucial for the species competitive ability for resources and, therefore, for survival.

Free radicals and ultrafine particulate emissions from the co-pyrolysis of Croton megalocarpus biodiesel and fossil diesel

BackgroundThe atmosphere has become a major transport corridor for free radicals and particulate matter from combustion events. The motivation behind this study was to determine the nature of particulate emissions and surface bound radicals formed during the thermal degradation of diesel blends in order to assess the health and environmental hazards of binary transport fuels.MethodologyAccordingly, this contribution explored the interactions that occur when Croton megalocarpus biodiesel and fossil diesel in the ratio of 1:1 by weight were co-pyrolyzed in a quartz reactor at a residence time of 0.5 s under an inert flow of nitrogen at 600 °C. The surface morphology of the thermal char formed were imaged using a Feld emission gun scanning electron microscope (FEG SEM) while Electron paramagnetic resonance spectrometer (EPR) was used to explore the presence of free radicals on the surface of thermal char. Molecular functional groups adsorbed on the surface of thermal char were explored using Fourier transform infrared spectroscopy (FTIR).ResultsFTIR spectrum showed that the major functional groups on the surface of the char were basically aromatic and some methylene groups. The particulate emissions detected in this work were ultrafine (~ 32 nm). The particulates are consistent with the SEM images observed in this study. Electron paramagnetic resonance results gave a g-value of 2.0027 characteristic of carbon-based radicals of aromatic nature. Spectral peak-to-peak width (∆Hp-p) obtained was narrow (4.42 G).ConclusionsThe free radicals identified as carbon-based are medically notorious and may be transported by various sizes of particulate matter on to the surface of the human lung which may trigger cancer and pulmonary diseases. The nanoparticulates determined in this work can precipitate severe biological health problems among humans and other natural ecosystems.

Conversion of solid waste to activated carbon to improve landfill sustainability.

Heterogeneous composite wastes from landfills were evaluated as precursors for the generation of activated carbon (AC). A single-step chemical activation process was applied involving irradiation with microwave energy and impregnation with KOH. The average percentage yield of AC from active landfill precursor was higher than that from closed landfill for all depths sampled. Increase in impregnation ratio and irradiation power decreased the average percentage yield for both landfill precursors (active: 38.1 to 33.1%; closed: 42.1 to 33.3%). The optimum pH range for adsorption of methylene blue was pH 6-7, while adsorption increased with increase in temperature over the range 30 to 50°C. Carbonyl and hydroxyl groups were the major functional groups on the surface of AC. The properties of the AC are potentially suitable for the removal of cationic dyes and pollutants. AC generated from the landfill composite was comparable to that from other biomass being managed through AC generation. This is the first report to demonstrate the possible reuse of landfill composite as AC. The reuse option of landfill composite could provide a means of sustainable management of landfilled municipal waste.

Diel light cycle as a key factor for modelling phytoplankton biogeography and diversity

Understanding the mechanisms driving species biogeography and biodiversity remains a major challenge in phytoplankton ecology. Using a model of two phytoplankton species with a gleaner-opportunist trade-off and competing for light and a limiting nutrient, we show that the diel light cycle may be an essential factor to explain large-scale ecological patterns. When only the seasonal light cycle is considered (control scenario) the model predicts that, independently of the nutrient supply, gleaners should dominate across all latitudes and opportunists can obtain a temporal niche only at high latitudes. However, the diel light cycle makes the competition outcome also a function of nutrient supply by affecting the amplitude of diel nutrient oscillations, with gleaners dominating when nutrient supply is low, opportunists when nutrient supply is high, and both species coexisting at intermediate levels of nutrient supply. The combined effects of seasonal and diel light cycles (diel scenario) shape a latitudinal diversity gradient with decreasing diversity towards higher latitudes and a unimodal dependence of diversity on nutrient supply and, therefore, on ecosystem productivity. The proposed mechanism can help interpret the biogeography of major phytoplankton functional groups in the global ocean and link them with large-scale biodiversity patterns.

The role of major functional groups: Multi-evidence from the binding experiments of heavy metals on natural fulvic acids extracted from lake sediments

Fulvic acid (FA) plays a key role in governing the environmental geochemistry behavior of heavy metals. In this work, the roles of major functional groups were investigated based on binding experiments of heavy metals on natural FA extracted from lake sediments. The results showed that the adsorption capacities were ranked as Cu2+ > Pb2+ >Cd2+. The differences of peak area at 3412, 1713, 617and 2430 cm−1 pre- and post-binding reactions in FTIR spectra suggested that phenolic, carboxyl and nitrogen-containing groups were the major functional groups providing sites binding heavy metals. Moreover, the results of bi-Langmuir model and the ionic strength effects jointly indicated that electrostatic attraction was the key mechanism during the adsorption process. The fitted results of Ligand-binding model suggested that the major functional groups in FA were classified into two types binding sites: weak (i.e. phenolic and carboxyl groups) and strong binding sites (i.e. nitrogen-containing groups). Additionally, there might be p-benzoquinone-like formed in FA which were then reduced to hydroquinone during the adsorption process, corresponding to the changing of peak area at 1614 and 830 cm−1 in FTIR spectra, the occurrence of Peak C in Fluorescence excitation-emission matrix (EEM) spectra and the ratios of H/C (<1) and O/C (≈1). The organic matter in sediments from Lake Wuliangsuhai presented similar characteristics with terrestrial plants due to the lake characterized by Phragmites australis and Potamogeton pectinatus L. being the dominant species, which shared large proportions of woody tissues as well as waxy hydrocarbons resembling that of terrestrial plants. This work is useful to insight the environmental effects of FA on heavy metals in environment.

Aqueous extract of broccoli mediated synthesis of CaO nanoparticles and its application in the photocatalytic degradation of bromocrescol green.

CaO nanoparticles have been prepared using CaCl2 and aqueous extract of broccoli as a precursor and reducing agent, respectively. Different volumes of the aqueous broccoli extract were utilised to obtain Ca(OH)2 and subsequent calcination gave CaO nanoparticles. The synthesised CaO was confirmed by powder X-ray diffraction (XRD). The morphology was studied using transmittance electron microscopy (TEM), and the surface composition of Ca(OH)2 was explored using Fourier transform infrared spectroscopy. The major functional groups present in the capping material responsible for the reduction of the metal salt and the surface passivation of Ca(OH)2 were identified. The XRD pattern revealed cubic phase for all the CaO nanoparticles, and the crystallite size was estimated using Scherrer's equation showed a variation which is dependent on the volume of the extract used. TEM analysis showed different shapes, while the selected area electron diffraction (SAED) results confirmed the crystallinity of the nanoparticles. Thermogravimetric analysis of Ca(OH)2 showed the decomposition product to be CaO. Sample C3, which has the smallest particle size, was used as a catalyst for the degradation of bromocresol green via photo irradiation with ultraviolet light and the result revealed a degradation efficiency of 60.1%.

Efficient removal of hazardous lead, cadmium, and arsenic from aqueous environment by iron oxide modified clay-activated carbon composite beads

Abstract The present communication addresses the removal of toxic lead, cadmium, and arsenic using iron oxide modified clay-activated carbon composite beads from aqueous solutions. The SEM-EDX analysis was conducted to study the heterogeneity of the surface and the elemental composition of the composite beads. The specific surface area of the composite beads was found to be 433 m2/g. Furthermore, the XRD pattern indicates the intercalation of iron particles between the layers of bentonite clay. The FT-IR analysis suggests that the hydroxyl, carboxyl, and Fe-O were the major functional groups responsible for the removal of lead, cadmium, and arsenic. The Langmuir monolayer sorption capacity of Pb(II), Cd(II) and As(V) were observed to be 74.2, 41.3 and 5.0 mg/g respectively. Kinetic studies indicate that intra-particle diffusion plays a significant role in the removal of these three toxic pollutants. In addition, the composite beads were applied for the adsorption of a ternary mixture of subjected pollutants at low concentrations and found efficient to remove these pollutants up to an acceptable permissible limit of drinking water. The significances of this study propose the potential of composite beads for purifying the water containing toxic pollutants, viz., lead, cadmium, and arsenic.

Identification of polysaccharides extracted from pea pod by-products and evaluation of their biological and functional properties

A three-variable Box-Behnken design was employed to obtain the best possible combination of extraction time, ratio (raw material/water) and extraction temperature to allow maximum extraction yield of polysaccharides from pea pod (PPP). The preferred extraction conditions were: extraction time 195 min, extraction temperature 70 °C and ratio of raw material/water 1/40. Under these conditions, the experimental yield was 16.21 ± 1.12%, which is in close agreement with the value predicted by response surface methodology model yield (16.08 ± 0.95%). The molecular weight distribution of PPP showed two peaks with MW of 5217 kDa and 50 kDa, respectively. The main monosaccharides in PPP were galactose, xylose and arabinose, whereas the major functional groups identified from FT-IR spectrum included CO, OH and CH. In addition, PPP had high 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and a moderate reducing power. The antibacterial activity of PPP was also observed against the tested microorganisms and at 50 mg/mL PPP could inhibit the growth of the Gram-negative and Gram-positive bacteria. Generally, these results suggest that the PPP has significant antioxidant activity and good antibacterial activity and can potentially be used as additive in food, pharmaceutical and cosmetic preparations.

Quantifying cell densities and biovolumes of phytoplankton communities and functional groups using scanning flow cytometry, machine learning and unsupervised clustering.

Scanning flow cytometry (SFCM) is characterized by the measurement of time-resolved pulses of fluorescence and scattering, enabling the high-throughput quantification of phytoplankton morphology and pigmentation. Quantifying variation at the single cell and colony level improves our ability to understand dynamics in natural communities. Automated high-frequency monitoring of these communities is presently limited by the absence of repeatable, rapid protocols to analyse SFCM datasets, where images of individual particles are not available. Here we demonstrate a repeatable, semi-automated method to (1) rapidly clean SFCM data from a phytoplankton community by removing signals that do not belong to live phytoplankton cells, (2) classify individual cells into trait clusters that correspond to functional groups, and (3) quantify the biovolumes of individual cells, the total biovolume of the whole community and the total biovolumes of the major functional groups. Our method involves the development of training datasets using lab cultures, the use of an unsupervised clustering algorithm to identify trait clusters, and machine learning tools (random forests) to (1) evaluate variable importance, (2) classify data points, and (3) estimate biovolumes of individual cells. We provide example datasets and R code for our analytical approach that can be adapted for analysis of datasets from other flow cytometers or scanning flow cytometers.

Temperature-dependent optical constants of liquid isopropanol, n-butanol, and n-decane.

Liquid isopropanol, n-butanol, and n-decane are combustible organic compounds that are frequently used in theoretical and experimental researches on fuel combustion. In this work, the temperature-dependent optical constants of liquid isopropanol, n-butanol, and n-decane in the region 500-5500 cm-1 at ambient pressure are measured using the combined ellipsometry-transmission method. In the combined method, the optical constants are first measured by a modified ellipsometry method, and then the absorption indices for weak absorption regions are obtained by the transmission method using the refractive indices measured by the modified ellipsometry method. The refractive indices of liquid isopropanol, n-butanol, and n-decane are within the range from 1.3 to 1.45 in the studied wavelength and temperature region. The absorption indices of these liquids range from 10-5 to 10-1. In the temperature range studied, the refractive indices decrease with increasing temperature in an approximately linear manner, but the effects of the temperature on the absorption indices are much smaller. The characteristic wavenumbers of the main absorption peaks are consistent with the vibrational frequencies of major functional groups.

Probing the DOM-mediated photodegradation of methylmercury by using organic ligands with different molecular structures as the DOM model

Photodegradation is the main depletion pathway for methylmercury (MeHg) in surface water. The formation of MeHg-dissolved organic matter (DOM) complexes has been found to be a key step in MeHg photodegradation. However, the major functional groups involved in the DOM-mediated process have yet to be clearly resolved. In this work, we systematically investigated the effects of DOM molecular structures on MeHg photodegradation by using a variety of organic ligands with different functional groups (e.g., thiosalicylate, thiophenol, and thioaniline). The results showed that thiol and phenyl groups may be the major functional groups governing DOM-mediated MeHg photodegradation, with photodegradation rates also dependent on the type (carboxyl, hydroxyl, and amino group) and position (ortho-, meta-, and para-) of other chemical substituents. The addition of “non-photochemically active” thiol ligands (e.g., mercaptoethanol and dithiothreitol) and high concentrations of Cl− can significantly inhibit the o-thiosalicylate-induced MeHg photodegradation, indicating that complexation of MeHg with these ligands is necessary for MeHg photodegradation. Sparging with O2 had a negligible effect on MeHg photodegradation, while sparging with N2 significantly enhanced MeHg photodegradation. This finding suggests that MeHg photodegradation may be a reductive process, which was further supported by identification of the degradation products of MeHg. A possible protonolysis mechanism of MeHg photodegradation in the presence of o-thiosalicylate was then proposed based on the findings of this study.

Context-dependent interactions and the regulation of species richness in freshwater fish

Species richness is regulated by a complex network of scale-dependent processes. This complexity can obscure the influence of limiting species interactions, making it difficult to determine if abiotic or biotic drivers are more predominant regulators of richness. Using integrative modeling of freshwater fish richness from 721 lakes along an 11o latitudinal gradient, we find negative interactions to be a relatively minor independent predictor of species richness in lakes despite the widespread presence of predators. Instead, interaction effects, when detectable among major functional groups and 231 species pairs, were strong, often positive, but contextually dependent on environment. These results are consistent with the idea that negative interactions internally structure lake communities but do not consistently ‘scale-up’ to regulate richness independently of the environment. The importance of environment for interaction outcomes and its role in the regulation of species richness highlights the potential sensitivity of fish communities to the environmental changes affecting lakes globally.

Zooplankton From a Reef System Under the Influence of the Amazon River Plume.

At the mouth of the Amazon River, a widespread carbonate ecosystem exists below the river plume, generating a hard-bottom reef (∼9500 km2) that includes mainly large sponges but also rhodolith beds. The mesozooplankton associated with the pelagic realm over the reef formation was characterized, considering the estuarine plume and oceanic influence. Vertical hauls were carried out using a standard plankton net with 200 μm mesh size during September 2014. An indicator index was applied to express species importance as ecological indicators in community. Information on functional traits was gathered for the most abundant copepod species. Overall, 179 zooplankton taxa were recorded. Copepods were the richest (92 species), most diverse and most abundant group, whereas meroplankton were rare and less abundant. Species diversity (>3.0 bits.ind-1) and evenness (>0.6) were high, indicating a complex community. Small holoplanktonic species dominated the zooplankton, and the total density varied from 107.98 ind. m-3 over the reef area to 2,609.24 ind. m-3 in the estuarine plume, with a significant difference between coastal and oceanic areas. The most abundant copepods were the coastal species ithona plumifera and Clausocalanus furcatus and early stages copepodites of Paracalanidae. The holoplanktonic Oikopleura, an important producer of mucous houses, was very abundant on the reefs. The indicator species index revealed three groups: (1) indicative of coastal waters under the influence of the estuarine plume [Euterpina acutifrons, Parvocalanus crassirostris, Oikopleura (Vexillaria) dioica and Hydromedusae]; (2) characterized coastal and oceanic conditions (Clausocalanus); (3) characterized the reef system (O. plumifera). Two major copepods functional groups were identified and sorted according to their trophic strategy and coastal-oceanic distribution. The species that dominated the coastal area and the area over the rhodolith beds are indicators of the estuarine plume and are mixed with species of the North Brazil Current. These species practically disappear offshore, where occur oceanic species commonly found in other oligotrophic tropical areas. This ecosystem shows a mixture of estuarine, coastal and oceanic communities coexisting in the waters over the Amazon reefs, with no significant differences among these areas. However, the MDS clearly separated the communities along the salinity gradient in the plume.

Sorption mechanism of zinc on reed, lignin, and reed- and lignin-derived biochars: kinetics, equilibrium, and spectroscopic studies

Biochar is considered as a substitute for stabilizing heavy metals, yet systematic studies regarding the stabilization mechanism of Zn on biochars from different biomass sources under different pyrolysis temperatures are still lacking. This study was endeavored to assess the sorption behavior and mechanism of Zn on pristine reed, lignin, and reed- and lignin-derived biochars at different pyrolysis temperatures (350, 450, and 550 °C). Batch experiments were performed to investigate the Zn sorption on pristine reed, lignin, and their derived biochars. Major functional groups on the surface of samples were measured using Fourier transform infrared (FTIR) spectroscopy and Boehm titration method, while the speciation and binding mechanisms were elucidated using X-ray absorption near-edge structure (XANES). The FTIR results showed an abrupt decline in the oxygen-containing functional groups with elevating pyrolysis temperature. The total amount of three acidic functional groups (carboxyl, lactone, phenol) was highest (2.39 mmol/g) in lignin, and it significantly decreased in reed- and lignin-derived biochars (0.05–0.94 mmol/g). Lignin exhibited the highest sorption capacity to Zn (qe = 3360 mg/kg) in the batch sorption experiments, while the sorption capacities for biochars were reduced with increasing pyrolysis temperature, irrespective of biomass sources. The XANES results indicated that soil organic matter (SOM), iron, and phosphate mineral components in the tested sorbents played an indispensable role in Zn immobilization. A large fraction of Zn-OM complex was observed in lignin due to its highest abundance of acidic functional group, leading to the highest sorption capacity for lignin toward Zn. The combination of XANES with FTIR, Boehm titration, batch sorption, and kinetic experiments altogether revealed that the decline in sorption capacity of Zn on reed- and lignin-derived biochars with elevating pyrolysis temperature was attributed to the loss in O-containing functional groups. The complexation of Zn with surface functional groups contributed to the Zn sorption on reed, lignin, and their derived biochars. The projected results will not only provide the detailed stabilization mechanism of Zn on lignin and reed- and lignin-derived biochars but also develop a novel and effective material (lignin) for heavy metal remediation.

The role of species turnover in structuring bacterial communities in a local scale in the cactus rhizosphere

Cereus jamacaru is a native cactus in the semiarid biome caatinga able to withstand long periods of drought. Here, we studied the rhizosphere microbiome of this cactus to understand how precipitation affects the assembly of bacterial communities from the taxonomical and functional perspectives. We selected three C. jamacaru plants in the caatinga biome, sampled the rhizosphere soil from the same plants during rainy and dry seasons and performed shotgun sequencing from total DNA isolated from rhizosphere using Ion Torrent technology. Acidobacteria, Actinobacteria and Proteobacteria showed increase in relative abundance during the rainy season when compared to dry season. Five major functional groups were significantly different, including differences in amino acids and derivatives, carbohydrates, protein metabolism, respiration, and RNA metabolism. Taxonomically, the assembly of bacterial communities follows a neutral model. The assembly of bacterial communities in the rhizosphere of C. jamacaru is affected by precipitation resulting in different taxonomical and functional community patterns during dry and rainy seasons. We attribute these differences on rhizosphere communities composition to dispersal limitation of microorganisms caused by low pore connectivity due to low water content in the soil, which leads to spatially isolate communities during the dry season.