Cloning of CAT genes in Satsuma mandarin and their expression characteristics in response to environmental stress and arbuscular mycorrhizal fungi

KEY MESSAGE

CitCAT1 and CitCAT2 were cloned and highly expressed in mature leaves. High temperatures up-regulated CitCAT1 expression, while low temperatures and Diversispora versiformis up-regulated CitCAT2 expression, maintaining a low oxidative damage. Catalase (CAT), a tetrameric heme-containing enzyme, removes hydrogen peroxide (H2O2) to maintain low oxidative damage in plants exposed to environmental stress. This study aimed to clone CAT genes from Citrus sinensis cv. "Oita 4" and analyze their expression patterns in response to environmental stress, exogenous abscisic acid (ABA), and arbuscular mycorrhizal fungal inoculation. Two CAT genes, CitCAT1 (NCBI accession: PP067858) and CitCAT2 (NCBI accession: PP061394) were cloned, and the open reading frames of their proteins were 1479 bp and 1539 bp, respectively, each encoding 492 and 512 amino acids predicted to be localized in the peroxisome, with CitCAT1 being a stable hydrophilic protein and CitCAT2 being an unstable hydrophilic protein. The similarity of their amino acid sequences reached 83.24%, and the two genes were distantly related. Both genes were expressed in stems, leaves, flowers, and fruits, accompanied by the highest expression in mature leaves. In addition, CitCAT1 expression was mainly up-regulated by high temperatures (37 °C), exogenous ABA, and PEG stress within a short period of time, whereas CitCAT2 expression was up-regulated by exogenous ABA and low-temperature (4 °C) stress. Low temperatures (0 °C) for 12 h just up-regulated CitCAT2 expression in Diversispora versiformis-inoculated plants, and D. versiformis inoculation up-regulated CitCAT2 expression, along with lower hydrogen peroxide and malondialdehyde levels in mycorrhizal plants at low temperatures. It is concluded that CitCAT2 has an important role in resistance to low temperatures as well as mycorrhizal enhancement of host resistance to low temperatures.

KN0901 to simultaneously remove atrazine and corn straw at low temperatures: From gene identification to empirical validation

Corn planting is often associated with serious atrazine pollution and excessive corn straw amounts, causing severe threats to environmental and ecological security, as well as to green agricultural development. In this context, a Paenarthrobacter sp. KN0901 strain was applied to simultaneously remove atrazine and straw at low temperatures. The results of whole genome sequencing indicated that KN0901 encoded over nine straw biodegradation-related enzymes. In addition, 100 % and 27.3 % of atrazine and straw were simultaneously degraded by KN0901 following an incubation period of seven days at 15 ºC and 180 rpm in darkness. The KN0901 strain maintained high atrazine and straw biodegradation rates under temperature and pH ranges of 4-25 ºC and 5-9, respectively. The simultaneous atrazine and corn straw additions improved the microbial growth and biodegradation rates by increasing the functional gene expression level, cell viability, inner membrane permeability, and extracellular polymeric substance contents of KN0901. The hydroponic experiment results demonstrated the capability of the KN0901 strain to mitigate the toxicity of atrazine to soybeans in four days under the presence of corn straw. The present study provides a new perspective on the development of bioremediation approaches and their application to restore atrazine-polluted cornfields with large straw quantities, particularly in cold areas.

Effects of appropriate low-temperature treatment on the yield and quality of pigmented potato (Solanum tuberosum L.) tubers

Temperature is one of the important environmental factors affecting plant growth, yield and quality. Moreover, appropriately low temperature is also beneficial for tuber coloration. The red potato variety Jianchuanhong, whose tuber color is susceptible to temperature, and the purple potato variety Huaxinyangyu, whose tuber color is stable, were used as experimental materials and subjected to 20 °C (control check), 15 °C and 10 °C treatments during the whole growth period. The effects of temperature treatment on the phenotype, the expression levels of structural genes related to anthocyanins and the correlations of each indicator were analyzed. The results showed that treatment at 10 °C significantly inhibited the potato plant height, and the chlorophyll content and photosynthetic parameters in the leaves were reduced, and the enzyme activities of SOD and POD were significantly increased, all indicating that the leaves were damaged. Treatment at 10 °C also affected the tuberization of Huaxinyangyu and reduced the tuberization and coloring of Jianchuanhong, while treatment at 15 °C significantly increased the stem diameter, root-to-shoot ratio, yield and content of secondary metabolites, especially anthocyanins. Similarly, the expression of structural genes were enhanced in two pigmented potatoes under low-temperature treatment conditions. In short, proper low temperature can not only increase yield but also enhance secondary metabolites production. Previous studies have not focused on the effects of appropriate low-temperature treatment during the whole growth period of potato on the changes in metabolites during tuber growth and development, these results can provide a theoretical basis and technical guidance for the selection of pigmented potatoes with better nutritional quality planting environment and the formulation of cultivation measures.

Exploring the mechanism of blindness physiopathy in Brassica oleracea var italica L. by comprehensive transcriptomics and metabolomics analysis

Blindness is a physiopathy characterized by apical abortion that particularly affects the Brassica family. The occurrence of blindness has been related to exposure to low temperatures during early developmental stages. However, the causes of this selective sensitivity and how they affect the correct development remain unknown. In this study, we investigated the mechanisms involved in the occurrence of blindness in broccoli plants. The analysis of RNAseq, focused on membrane transporters and the synthesis pathways of glucosinolates and phenolics, was related with physiological changes in nutrient and water uptake, gas exchange, and metabolism. Comparative gene expression analysis between control and blindness-affected broccoli plants revealed distinct regulation patterns in roots and shoots, leading to reduced synthesis of glucosinolates and phenolics. Additionally, the expression levels of aquaporins and potassium transporters were found to be associated with mineral and water transport. In this way, our results revealed the causes of blindness by identifying differentially expressed genes, highlighting those related to secondary metabolism, as well as genes involved in water and nutrient uptake and transport as the crucial involved in the physiopathy appearance.

Macroscopic sample shape effect on pulse electron double resonance (PELDOR) signal

Pulse electron double resonance (PELDOR), also called double electron-electron resonance (DEER), is a technique capable of measuring the strength of electron spin dipolar interactions, revealing spin-spin distance distributions in ordered and disordered solid materials. Previous work has shown that PELDOR signals acquire an out-of-phase component under conditions of high electron spin polarization, such as at low temperatures and high fields. In this paper, we show theoretically and experimentally that the size and sign of this effect depends on the macroscopic shape of the sample and its orientation in the external magnetic field. This effect is caused by dipolar interactions between distant spins and provides new insights into the fundamental physics of PELDOR.

Does biochar in combination with compost effectively promote phytostabilization of heavy metals in soil under different temperature regimes?

The article presents the effect of a combined amendment, i.e., biochar+compost (BC), on the process of Cd, Cu, Ni, Pb and Zn immobilization in soil cultivated with L. perenne under freezing and thawing conditions (FTC). In particular, the speciation analysis of the examined elements in phytostabilized soils based on their response using the sequential extraction, and the variability of the soil microbiome using 16S rRNA gene amplicon sequencing were systematically assessed. Metal stability in soils was evaluated by the reduced distribution index (Ir). Plants were grown in pots for 52 days under greenhouse conditions. After termination, phytostabilization was continued in a temperature chamber for 64 days to provide FTC. As a result, it was noted that biomass yield of L. perenne was promoted by BC (39 % higher than in the control pots) and reduced by FTC (45 % lower than in the BC-enriched soil not exposed to FTC). An efficacious level of phytostabilization, i.e., higher content of heavy metals in plant roots, was found in the BC-enriched soil, regardless of the changes in soil temperature conditions. BC improved soil pH before applying FTC more than after applying FTC. BC had the greatest impact on increasing Cu stability by redistributing it from the F1 and F2 fractions to the F3 and F4 fractions. For most metals, phytostabilization under FTC resulted in an increase in the proportion of the F1 fraction and a decrease in its stability. Only for Pb and Zn, FTC had greater impact on their stability than BC addition. In all soil samples, the core genera with about 2-3 % abundances were Sphingomonas sp. and Mycobacterium sp. FTC favored the growth of Bacteroidetes and Proteobacteria in soil. Microbial taxa that coped well with FTC but only in the absence of BC were Rhodococcus, Alkanindiges sp., Flavobacterium sp., Williamsia sp. Thermomonas sp.

The potential of different ripeness of blood oranges (Citrus sinensis L. Osbeck) for sale in advance after low-temperature storage: Anthocyanin enhancements, volatile compounds, and taste attributes

To explore the optimal early harvest time similar to the ripe fruit qualities, the effects of storage temperatures on maturity indexes, weight losses, colour parameters, anthocyanin profiles, volatile and taste components of blood oranges at six different maturity levels were investigated. Total anthocyanin contents of cold-treated fruits increased to or exceed that of ripe fruits (0.24 ± 0.12 mg/100 g), and fruits harvested from 260 d and 280 d after anthesis shared similar individual anthocyanin profiles to ripe fruits during storage at 8 °C for 30 d and 20 d (III-30 d and IV-20 d groups), respectively. Moreover, comparative analyses of e-nose and e-tongue demonstrated the distances of volatile components and scores of taste attributes including sourness, saltiness, bitterness, sweetness, and umami in III-30 d and IV-20 d groups were close to that of ripe fruits, indicating that the fruits could be sold about 20 to 30 d ahead of the season.

Cross-linked amorphous potassium titanate Nanobelts/Titanium carbide MXene nanoarchitectonics for efficient sodium storage at low temperature

One of the major challenges to improving the performance of sodium-ion batteries at low temperatures is to develop effective anode materials with novel structures and fast reaction kinetics. Currently, converting electrode materials from the crystalline to amorphous state is an effective approach to fabricate the electrode material with high sodium storage performance. Herein, a three-dimensional (3D) cross-linked heterostructure with one-dimensional (1D) amorphous potassium titanate (KTiOx) nanobelts in-situ grown on two-dimensional (2D) titanium carbide (Ti2CTx) nanosheets (a-KTiOx/Ti2CTx) was fabricated through alkalization of the multilayered Ti2CTx MXene, which exhibits remarkable sodium storage performance at both room and low temperatures. The heterostructure prepared by the combination of 1D amorphous nanobelts and 2D conductive nanosheets enables efficient strain alleviation in the electrode, a high capacitive contribution to charge storage, rapid ionic diffusion kinetics, and robust electrode integrity, thus enhancing the sodium storage performance. In particular, reversible capacities of 221.9, 144.2 and 112.6 mAh/g can be achieved at 0.1 A/g after 100 cycles at 25, 0 and -25 °C, respectively. This study provides significant insights into the construction of MXene-based electrode materials for sodium storage at low temperatures.

Chronic cold exposure modulates genes related to feeding and immune system in Nile tilapia (Oreochromis niloticus)

Nile tilapia is the fourth most produced species in the global aquiculture panorama. This species requires water temperatures higher than 16 °C to grow and survive, and so, little is known about the effects of low temperatures on genes related to food intake and inflammatory responses. This study brought insights about the modulation of genes in different tissues of Nile tilapia chronically exposed to low temperatures. Thus, sixty animals were divided in two experimental groups: a control group in which the animals remained at the optimum temperature of 24 °C; and an exposed to cold group, in which a decrease in the water temperature was applied until reaching 15 °C. These conditions were maintained for 28 days. Blood samples were collected for flow cytometry analysis, while brain, spleen, liver, and kidney tissues were collected for total RNA extraction, followed by quantitative PCR (RT-qPCR). For genes related to feeding process pathway, it was observed an upregulation in pyy and a downregulation of npy and cart gene expression. Also, pro-inflammatory cytokine genes were modulated in the spleen, kidney and liver with a higher expression of il-1b and tnfα and a reduction in the il-8 and nf-κβ gene expressions in the group exposed to 15 °C. The fish exposed to cold presented higher serum cortisol levels than the ones from control group. The blood cell analysis showed a lower level of membrane fluidity and a higher DNA fragmentation and cell disruption in the group exposed to cold. These findings suggest an important effect of a stressful situation in the tilapia organism due to cold exposure. This study brings insights on tilapia wellbeing under low temperature stress. It can be a first step to understanding the appropriate way to cope with cold impacts on aquaculture.

Vitamin E protects from lipid peroxidation during winter stress in the seagrass Cymodocea nodosa

Adjustments in the antenna size and α-tocopherol contents provide protection from sustained damage in leaves of a seagrass, while low vitamin E contents appear to be enough to protect rhizomes (which appear to be more cold tolerant than leaves). Despite low temperatures can adversely affect the proper growth and development of marine angiosperms, by, among other processes, increasing reactive oxygen species production and causing oxidative damage to lipid membranes, the role of vitamin E in seagrasses, such as Cymodocea nodosa has not been explored thus far. Here, we aimed to better understand the possible role of this chain-breaking (peroxyl radical-trapping) antioxidant in response to low temperatures, and most particularly in relation to the occurrence of photo-inhibition and lipid peroxidation. Low temperatures caused an important desiccation of leaves, but not of rhizomes, which were much more tolerant to cold stress than leaves. Cold stress during winter was associated with chlorophyll loss and transient photo-inhibition, as indicated by reversible reductions in the F_v/F_m ratio. Adjustments in pigment antenna size and vitamin E contents per unit of chlorophyll during winter may help protect the photosynthetic apparatus from sustained photo-inhibitory damage and lipid peroxidation events in leaves. Rhizomes also accumulated significant amounts of vitamin E, although to a much lesser extent than leaves, and kept protected from lipid peroxidation during winter, as indicated by malondialdehyde contents, a product from secondary lipid peroxidation. It is concluded that vitamin E can help protect both leaves and rhizomes from lipid peroxidation, although cold stress during winter can cause transient photo-inhibition of the photosynthetic apparatus, in C. nodosa.

Enhancing anammox resistance to low operating temperatures with the use of PVA gel beads

Low temperatures, or a sudden decrease in operating temperature, can seriously inhibit anammox activity, it is, therefore, important to maintain anammox activities at a low temperature. In this study, the use of gel beads to enhance the resistance of anammox biomass to a low temperature was investigated. The performance of three reactors: R1 without gel beads; R2 with polyvinyl alcohol/chitosan (PVA/CS); R3 with PVA/CS/Fe, was studied and compared in a temperature transition from 35 to 8 °C. When the operating temperature was ≥25 °C, there was little difference in nitrogen removal among the three reactors. Decreasing the temperature to < 25 °C created obvious difference between R1 and R2/R3. R1 had a nitrogen removal efficiency (NRE) of 33.1 ± 25.3% at 10 °C, significantly lower than that of R2 (90.5 ± 2.5%) or R3 (87.7 ± 11.1%). Unclassified Candidatus Brocadiaceae was the dominant genus at 10 °C, with an abundance of 44.4, 56.5 and 58.7% in R1, R2 and R3, respectively. These differences were attributed to the use of gel beads, which promoted the granulation of both the non-immobilized sludge and the immobilized biomass, resulting in higher anammox activities in R2/R3. The non-immobilized sludge of R1 was dominated by small particles (<300 μm) at 10 °C, while in R2 and R3 large particles (1000-2000 μm) were the main components. Furthermore, the immobilized biomass on gel beads exhibited much higher anammox activity and maintained a relatively high level of nitrate reductase and nitrite reductase in response to the temperature decrease. The Fe²⁺/Fe³⁺ in the PVA/CS/Fe gel beads further promoted microbial aggregation and led to an improved performance in R3 compared to R2. The results of this study demonstrate an effective approach to increase anammox resistance at low operating temperatures.

A microscopy-based approach for determining growth probability and lag time of individual bacterial cells

The development of relevant predictive models for single-cell lag time and growth probability near growth limits is of critical importance for predicting pathogen behavior in foods. The classical methods for data acquisition in this field are based on turbidity measurements of culture media in microplate wells inoculated with approximately one bacterial cell per well. Yet, these methods are labour intensive and would benefit from higher throughput. In this study, we developed a quantitative experimental method using automated microscopy to determine the single-cell growth probability and lag time. The developed method consists of the use of direct cell observation with phase-contrast microscopy equipped with a 100× objective and a high-resolution device camera. The method is not a time-lapse method but is based on the observation of high numbers of colonies for a given time. Automation of image acquisition and image analysis was used to reach a high throughput. The single-cell growth probabilities and lag times of four strains of Listeria monocytogenes were determined at 4 °C. The microscopic method was shown to be a promising method for the determination of individual lag times and growth probability at the single-cell level.

Performance of the anammox process treating low-strength municipal wastewater under low temperatures: Effect of undulating seasonal temperature variation

In the anammox process treating low-strength municipal wastewater, the effect of common seasonal temperature variation (15.1 °C-22.2 °C) on performance was studied. In autumn and winter, the nitrogen removal rate (NRR) decrement of 0.038kgN/(m³·d) (17.9 °C → 15.1 °C) was nearly threefold higher than 0.014kgN/(m³·d) (22.2 °C → 17.9 °C), which showed that lower temperature laid more negative impact on nitrogen removal. ¹⁵N isotope tracing tests confirmed that the contribution of denitrification to nitrogen removal was far less than anammox, and anammox contributed more at 15.1 °C (91.7%) than 21.9 °C (78.9%). Anammox bacteria could adapt to lower temperature after short-term acclimatization, especially the dominant genus Ca. Brocadia increased from 1.8% to 2.5% and its abundance was significantly correlated with nitrogen consumption (p < 0.05). Above findings suggest that the adaptability of Ca. Brocadia could provide the possibility to maintain nitrogen removal performance at lower temperature. In spring, the improved maximum anammox activity from 2.85 to 3.23mgNH₄⁺-N/(gVSS·h) indicated the recovered removal capacity.

Optical measurement platform of temperature-dependent interaction between nanoliposomes and a polymer-grafted surface

In this study, we report an opto-microfluidic platform integrated with dark-field light scattering imaging and fluorescence microspectroscopy to investigate the temperature-dependent behavior of nanoliposomes. This newly developed experimental platform enabled both in situ measurements of the temperature of the sample solution and observation of individual nanoliposomes. As a proof-of-concept, the temperature-dependent interaction between 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) nanoliposomes and a poly(ethylene glycol) (PEG) grafted surface was investigated using this opto-microfluidic platform. Temperature-dependent detachment behavior of DLPC nanoliposomes, which was because of the phase transition of DLPC, was observed. The opto-microfluidic platform for individual nanoparticle measurements may become a powerful tool for investigating temperature-dependent physicochemical properties of nanoparticles in aqueous solution.

Microbial communities and biogenic Mn-oxides in an on-site biofiltration system for cold Fe-(II)- and Mn(II)-rich groundwater treatment

This study investigated relationships between microbial communities, groundwater chemistry, and geochemical and mineralogical characteristics in field-aged biofilter media from a two-stage, pilot-scale, flow-through biofiltration unit designed to remove Fe(II) and Mn(II) from cold groundwater (8 to 15 °C). High-throughput 16S rRNA gene amplicon sequencing of influent groundwater and biofilter samples (solids, effluents, and backwash water) revealed significant differences in the groundwater, Fe filter, and Mn filter communities. These community differences reflect conditions in each filter that select for populations that biologically oxidize Fe(II) and Mn(II) in the two filters, respectively. Genera identified in both filters included relatives of known Fe(II)-oxidizing bacteria (FeOB), Mn(II)-oxidizing bacteria (MnOB), and ammonia-oxidizing bacteria (AOB). Relatives of AOB and nitrite-oxidizing bacteria were abundant in sequencing reads from both filters. Relatives of FeOB in class Betaproteobacteria dominated the Fe filter. Taxa related to Mn-oxidizing organisms were minor members of the Mn-filter communities; intriguingly, while Alphaproteobacteria dominated (40 ± 10% of sequencing reads) the Mn filter community, these Alphaproteobacteria did not classify as known MnOB. Isolates from Fe and Mn filter backwash enrichment studies provide insight on the identity of MnOB in this system. Novel putative MnOB isolates included Azospirillum sp. CDMB, Solimonas soli CDMK, and Paenibacillus sp. CDME. The isolate Hydrogenophaga strain CDMN can oxidize Mn(II) at 8 °C; this known FeOB is likely capable of Mn(II) oxidation in this system. Synchrotron-based X-ray near-edge spectroscopy (XANES) coupled with electron paramagnetic resonance (EPR) revealed the dominant Mn-oxide that formed was biogenic birnessite. Co-existence of amorphous and crystallized Mn-oxide surface morphologies on the Mn-filter media suggest occurrence of both biological and autocatalytic Mn(II) oxidation in the biofilter. This study provides evidence that biofiltration is a viable approach to remove iron, manganese, and ammonia in cold groundwater systems, and that mineralogical and microbiological approaches can be used to monitor biofiltration system efficacy and function.

Plasma membrane ATPase and the aquaporin HvPIP1 in barley brassinosteroid mutants acclimated to high and low temperature

The integral parts of the cell membranes are the functional proteins, which are crucial for cell life. Among them, proton-pumping ATPase and aquaporins appear to be of particular importance. There is some knowledge about the effect of the temperature during plant growth, including stress-inducing temperatures, on the accumulation of the membrane proteins: plasma membrane H⁺-ATPase and aquaporins, but not much is known about the effect of the phytohormones (i.e. brassinosteroids (BR)) on control of accumulation of these proteins. The aim of our study was to answer the question of how a BR deficit and disturbances in the BR perception/signalling affect the accumulation of plasma membrane H⁺-ATPase (PM H⁺-ATPase), the aquaporin HvPIP1 transcript and protein in barley growing at 20 °C and during its acclimation at 5 °C and 27 °C. For the studies, the BR-deficient mutant 522DK (derived from the wild-type Delisa), the BR-deficient mutant BW084 and the BR-signalling mutant BW312 and their wild-type Bowman were used. Generally, temperature of growth was significant factor influencing on the level of the accumulation of the H⁺-ATPase and HvPIP1 transcript and the PM H⁺-ATPase and HvPIP1 protein in barley leaves. The level of the accumulation of the HvPIP1 transcript decreased at 5 °C (compared to 20 °C), but was higher at 27 °C than at 20 °C in the analyzed cultivars. In both cultivars the protein HvPIP1 was accumulated in the highest amounts at 27 °C. On the other hand, the barley mutants with a BR deficiency or with BR signalling disturbances were characterised by an altered accumulation level of PM H⁺-ATPase, the aquaporin HvPIP1 transcript and protein (compared to the wild types), which may suggest the involvement of brassinosteroids in regulating PM H⁺-ATPase and aquaporin HvPIP1 at the transcriptional and translational levels.

Oxidative attack during temperature fluctuation challenge compromises liver protein homeostasis of a temperate fish model

Seasonal variations in water temperature are a natural stressor of temperate fish that affect growth performance and metabolism globally. Gilthead sea bream is one of the most economically interesting species in the Mediterranean; but its liver metabolism is affected by the cold season. However, the effects of cold on protein turnover mechanisms have hardly been studied. Here, we study the relationship between liver oxidative status and protein homeostasis pathways during a 50-day low temperature period at 14 °C, and subsequent recovery at two times: 7 days (early recovery) and 30 days (late recovery). Liver redox status was determined by measuring oxidised lipids and proteins, the glutathione redox cycle and major antioxidant enzymes activities. Protein turnover was analysed via liver protein expression of HSP70 and HSP90; proteasome 26S subunits and polyubiquitination, as markers of the ubiquitin-proteasome system (UPS); and cathepsin D, as a lysosomal protease. Low temperature exposure depressed antioxidant enzyme activities, affecting the glutathione redox cycle and reducing total glutathione levels. Both the UPS and lysosomal pathways were also depressed and consequently, oxidised protein accumulated in liver. Interestingly, both protein oxidation and polyubiquitination tagging depended on protein molecular weight. Despite all these alterations, temperature recovery reverted most consequences of the cold at different rates: with delayed recovery of total glutathione levels and oxidised protein degradation with respect to enzyme activities recovery. All these findings demonstrate that protein liver homeostasis is compromised after chronic cold exposure and could be the cause of liver affectations reported in aquaculture of temperate fish.

Hysteresis of Low-Temperature Thermal Conductivity and Boson Peak in Glassy (g) As2S3: Nanocluster Contribution

Experimental results of the thermal conductivity (k(T)) of nanostructured g-As₂S₃ during cooling and heating processes within the temperature range from 2.5 to 100 K have been analysed. The paper has considered thermal conductivity is weakly temperature k(T) dependent from 2.5 to 100 K showing a plateau in region from 3.6 to 10.7 K during both cooling and heating regimes. This paper is the first attempt to consider the k(T) hysteresis above plateau while heating in the range of temperature from 11 to 60 K. The results obtained have not been reported yet in the scientific literature. Differential curve Δk(T) of k(T) (heating k(T) curve minus cooling k(T) curve) possesses a complex asymmetric peak in the energy range from 1 to 10 meV. Δk(T) reproduces the density of states in a g(ω)/ω ² representation estimated from a boson peak experimentally obtained by Raman measurement within the range of low and room temperatures. Theoretical and experimental spectroscopic studies have confirmed a glassy structure of g-As₂S₃ in cluster approximation. The origin of the low-frequency excitations resulted from a rich variety of vibrational properties. The nanocluster vibrations can be created by disorder on atomic scale.

Low-temperature Raman spectra of the 2-(α-methylbenzylamino)-5-nitropyridine crystal

The polar organic 2-(α-methylbenzylamino)-5-nitropyridine crystal (MBANP) has been studied by Raman spectroscopy at low temperatures (from 300 to 10K). The effect of temperature change on the vibrational spectrum is discussed with the aid of DFT calculations. The behavior of the Raman spectra indicates that MBANP molecules present a different conformation at low temperatures associated with the rotation of the phenyl and pyridine rings. Temperature-dependent X-ray measurements and differential scanning calorimetry (DSC) analysis were utilized as complementary techniques to investigate the structural stability of MBANP crystal.

Seasonal-related effects on ammonium removal in activated carbon filter biologically enhanced by heterotrophic nitrifying bacteria for drinking water treatment

To determine the potential effects of seasonal changes on water temperature and water quality upon removal of ammonium and organic carbon pollutants and to characterize the variations in microbial characteristics, a pilot-scale activated carbon filter biologically enhanced with heterotrophic nitrifying bacteria was investigated for 528 days. The results show that 69.2 ± 28.6% of ammonium and 23.1 ± 11.6% of the dissolved organic carbon were removed by the biologically enhanced activated carbon (BEAC) reactor. It is shown that higher biodegradable dissolved organic carbon enhances ammonium removal, even at low temperatures. The C/N ratio consumed by the BEAC reactor reached a steady value (i.e., 3.3) after 2 months of operation. Despite seasonal fluctuations and competition of the indigenous community, the heterotrophic nitrifying bacteria (Acinetobacter sp. HRBLi 16 and Acinetobacter harbinensis strain HITLi 7) remained relatively stable. The amount of carbon source was the most significant environmental parameter and dramatically affected the microbial community compositions in the BEAC reactor. The present study provides new insights into the application of a BEAC reactor for ammonium removal from drinking water, resisting strong seasonal changes.

Characteristics of pellets with immobilized activated sludge and its performance in increasing nitrification in sequencing batch reactors at low temperatures

Immobilized pellets obtained by means of entrapping activated sludge in waterborne polyurethane were successfully adapted in ammonium (NH4(+)-N) synthetic wastewater. Its physicochemical characteristics were determined using scanning electron microscope, pyrosequencing, and microelectrodes, and its influence on the nitrification process in sequencing batch reactors (SBRs) at low temperatures was evaluated. A large number of rod-shaped bacteria were observed on the surface of the immobilized pellet, in which Rudaea spp. (Xanthomonadaceae family) was an important bacterial component (23.44% of the total bacteria). The oxygen uptake rate of immobilized pellets reached 240.83±15.59 mgO2/(L·hr), and the oxygen was primarily consumed by the bacteria on the pellet surfaces (0-600 μm). The dosing of the pellets (30 mL/L) into an SBR significantly improved the nitrification efficiency at low temperatures of 7-11°C, achieving an average NH4(+)-N removal of 84.09%, which is higher than the removal of 67.46% observed for the control group.

Ammonium removal of drinking water at low temperature by activated carbon filter biologically enhanced with heterotrophic nitrifying bacteria

We sought to confirm whether use of Acinetobacter strains Y7 and Y16, both strains of heterotrophic nitrifying bacteria, was practical for removing ammonium (NH4 (+)-N) from drinking water at low temperatures. To test this, ammonium-containing drinking water was treated with strains Y7 and Y16 at 8 and 2 °C. Continuous ammonium treatment was conducted in order to evaluate the performance of three biologically enhanced activated carbon (BEAC) filters in removing ammonium. The three BEAC filters were inoculated with strain Y7, strain Y16, and a mixture of strains Y7 and Y16, respectively. A granular activated carbon (GAC) filter, without inoculation by any strains, was tested in parallel with the BEAC filters as control. The results indicated that NH4 (+)-N removal was significant when a BEAC filter was inoculated with the mixture of strains Y7 and Y16 (BEAC-III filter). Amounts of 0.44 ± 0.05 and 0.25 ± 0.05 mg L(-1) NH4 (+)-N were removed using the BEAC-III filter at 8 and 2 °C, respectively. These values were 2.8-4.0-fold higher than the values of ammonium removal acquired using the GAC filter. The synergistic effect of using strains Y7 and Y16 in concert was the cause of the high-ammonium removal efficiency achieved by using the BEAC-III filter at low temperatures. In addition, a high C/N ratio may promote NH4 (+)-N removal efficiency by improving biomass and microbial activity. This study provides new insight into the use of biofilters to achieve biological removal of ammonium at low temperature.

Chlorophyll a fluorescence and CO2 exchange of Umbilicaria aprina under extreme light stress in the cold

A lichen growing in a continental Antarctic region with low temperatures and strong irradiance in summer was investigated for evidence of photoinhibition. Field experiments with Umbilicaria aprina from a sheltered site with heavy snowpack showed no effects of photoinhibition when the lichen was exposed to strong sun irradiance for nearly 11 h a day. This was evident from CO₂ exchange and simultaneous chlorophyll a fluorescence measurements. CO₂ exchange was also not affected if quartz glass allowing greater UV penetration, was used as a lid for the cuvette. The dependency of net photosynthesis on photosynthetic photon flux density suggests that the lichen is photophilous.