Phenoloxidase Activity Research Articles

Effects of Two Commercial Protein Diets on the Health of Two Imago Ages of Apis mellifera L. Reared in Laboratory.

Simple SummaryBeekeepers often feed their bees with supplemented artificial diets. The formulation of an integrative diet for honey bee colonies able to prevent nutritional deficiencies is yet to be found. In this work, the effects of pollen diet substitution with commercial protein diets in newly emerged bees (that still feed a little on pollen) and in forager bees (that usually do not feed on pollen) were tested. Results obtained suggest that commercial protein diets do not compensate pollen diets in newly emerged bees and do not determine an increase in life span or immunity in forager bees. Further investigations on the effect of concentration and quality of proteins are desirable in order to provide beekeepers with scientific evidence on protein-based feeding.Protein-supplemented artificial diets are widely used by beekeepers during winter and whenever food availability is low, yet no data are available concerning their effects on bees’ health. In this work, the effects of two commercial diets enriched with 1.7% and 7.7% protein concentration on feed intake, survival rate, glucose oxidase, phenoloxidase and glutathione S-transferase in newly emerged and forager bees were tested. Administration of a 7.7% protein-enriched diet significantly reduced the lifespan of both newly emerged and forager bees, while only in foragers a significantly higher feed intake was recorded. In newly emerged bees, administration of a high-protein-enriched diet stimulated glucose oxidase production at the 10th day of feeding, determined a reduction of phenoloxidase and did not affect glutathione S-transferase activity. In forager bees, a high level of protein inclusion did not determine any significant variation in either glucose oxidase, phenoloxidase or glutathione S-transferase activity. Therefore, the results obtained in this investigation suggest that administration of commercial protein diets negatively affect honey bee health, determining an increase in mortality. Further investigations on the effect of concentration and quality of proteins are desirable to provide beekeepers with scientific evidence on protein feeding.

Parasite infection influences the biomarker response and locomotor activity of Gammarus fossarum exposed to conventionally-treated wastewater

Modern wastewater treatment plants cannot completely remove pollutants. Often, effluents entering the aquatic environment still contain micropollutants such as pharmaceuticals or pesticides, which may impose adverse effects on aquatic biota. At the same time, a large proportion of free-living aquatic species are known to be infected with parasites, which raises the question of interactions between environmental stressors (such as micropollutants) and parasite infection. We chose the freshwater amphipod Gammarus fossarum (Koch, 1835) as a test organism to investigate potential pollutant-parasite interactions. This gammarid is frequently used in ecotoxicological tests and is also commonly infected with larvae of the acanthocephalan parasite species Polymorphus minutus (Zeder, 1800) Lühe, 1911. We exposed infected and uninfected specimens of G. fossarum to conventionally-treated wastewater and river water in a 22-day flow channel experiment. The test organisms’ response was measured as mortality rates, concentrations or activities of five biomarkers, and overall locomotor activity. No significant differences were found between mortality rates of different exposure conditions. Contrastingly, three biomarkers (phenoloxidase activity, glycogen, and lipid concentrations) showed a significant increase in infected gammarids, while the effect of the water type was insignificant. Infected gammarids also showed a significantly higher locomotor activity in both water types. Our results suggest that the response of G. fossarum during the exposure experiments was mainly driven by parasite infection. This implies that parasites may act as additional biotic stressors in multiple stressor scenarios, and therefore, might play an important role when measuring the response of organisms to chemical stressors. Future ecotoxicological studies and assessments thus should consider parasite infection as an additional test parameter.

Protective effects of the biofloc system in Pacific white shrimp (Penaeus vannamei) culture against pathogenic Vibrio parahaemolyticus infection

The mitigation of vibriosis in shrimp culture could be accomplished by reducing the virulence of the pathogen or by increasing the immune response of the shrimp. This study aims to evaluate the application of a biofloc system in protecting Pacific white shrimp (Penaeus vannamei) from pathogenic Vibrio parahaemolyticus infection. Shrimp post-larvae (PL 20) with an average body weight of 0.041 ± 0.019 g were reared in an aquarium with a working volume of 33 L at a density of 3 L−1 for 21 days using two rearing systems, i.e., the biofloc system and the regular clear water system as control. In each system, the shrimp post-larvae were challenged by adding V. parahaemolyticus at different densities, 103, 105, and 107 CFU mL−1, while the negative control was performed by maintaining shrimp post-larvae in the clear water system without the addition of V. parahaemolyticus. The results of the in vitro experiment showed that the density and biofilm activity of V. parahaemolyticus reared in biofloc suspension was lower than that of the positive control (p < 0.05). The density of V. parahaemolyticus in shrimp rearing water was lower than that in the control at 105 CFU mL−1, especially on the 3rd day post-challenge, but there was no significant difference in the total presumptive Vibrio count between the biofloc treatment and the control. The survival, growth, and immune response parameters, such as total hemocyte count, phagocytic activity, respiratory burst, and phenoloxidase activity, of the shrimp, reared in the biofloc system were also higher than those of the positive control (p < 0.05), regardless of the density of V. parahaemolyticus. The present study demonstrated that the application of biofloc could significantly protect and increase the resistance of Pacific white shrimp against pathogenic V. parahaemolyticus infection.

Temperature-Induced Environmental Chain Reaction in Marine Sedimentation and Its Impact on Manila Clam Ruditapes philippinarum

Marine Heatwaves (MHWs) events have been increasing, causing severe impacts on marine ecosystems and aquaculture. In this study, the effects of temperature on changes in sediment dissolved oxygen (DO) and hydrogen sulfide (H2S) concentrations and their effects on the behavioral and physiological responses of a bivalve were investigated by simulating different sudden summer temperature change conditions. The results showed that temperature was an important factor affecting DO consumption and H2S release in sediments, and sediment type also played a key role. At higher temperatures, DO was consumed more rapidly and H2S release increased in sediments, and the DO was consumed and H2S released in sandy sediments was less than in silty sand sediments. The response of Manila clam’s exercise behavior under environmental pressure was also rapid. The excavation index of the Manila clam decreased with the DO consumption, indicating that the Manila clam could alter its burial depth and move toward the sediment-water interface when stressed. Compared with phenol oxidases (PO) activity being activated under experimental conditions, succinate concentrations only increased slightly at 32°C, and did not surpass the threshold indicative of anaerobic metabolism. However, when toxic substances such as H2S start to accumulate, they may damage the immune system and tissues of the Manila clam, thereby affecting its future survival. Therefore, when temperatures are high for long periods in summer, it is necessary to take timely action to prevent and guard against harm caused by DO and H2S to aquaculture organisms.

Effects of Janus kinase (JAK) on hemocyte proliferation and disease resistance in Scylla paramamosain

Janus kinase (JAK), a nonreceptor tyrosine kinase, is the JAK-signal transducer and activator of transcription (STAT) signaling pathway. In this study, RNA interference technology was used to knockdown the expression of JAK to explore the immune function of JAK in Scylla paramamosain. JAK expression was relatively high in the intestine and relatively low in the heart and hemocytes of S. paramamosain. JAK was highly expressed in all examined tissues of S. paramamosain after infection with white spot syndrome virus (WSSV) or Vibrio alginolyticus. The expression levels of Astakine, STAT, CAP, TLR, proPO, and CTL were downregulated, while MCM7, Myosin and Relish expression was upregulated in hemocytes at 24 h after injection of JAK-dsRNA. Astakine expression was significantly downregulated within 72 h after injection of JAK-dsRNA. The total hemocyte count and hemocyte proliferation were significantly decreased after treatment with Astakine-dsRNA or JAK-dsRNA. The results showed that JAK may promote hemocyte proliferation, probably by regulating Astakine expression. The activities of phenoloxidase, superoxide dismutase, and lysozyme were decreased significantly, while production of reactive oxygen species was increased significantly in hemocytes after treatment with JAK-dsRNA. After JAK knockdown, the phagocytosis rate of WSSV or V. alginolyticus in hemocytes was increased. After WSSV challenge, the WSSV copy number in the JAK-dsRNA-treated group was higher than that in the WSSV group. After V. alginolyticus challenge, the apoptosis rate of hemocytes in the JAK-dsRNA group was higher than that in the V. alginolyticus group. The mortality rate of WSSV or V. alginolyticus-infected crabs after JAK knockdown was higher than that of the infection group. These results suggest that JAK can regulate the expression of some immune-related genes, such as Astakine, to influence the innate immune response of S. paramamosain against pathogens (WSSV or V. alginolyticus), mostly by regulating enzyme activities, hemocyte phagocytosis and apoptosis.

The effect of banana blossom on growth performance, immune response, disease resistance, and anti-hypothermal stress of Macrobrachium rosenbergii

Banana (Musa acuminata) blossom contains high nutritional value and bioactive compounds. In this study, Macrobrachium rosenbergii were fed with diets containing banana blossom powder (BBP) at 10 and 20 g kg−1, hot-banana blossom (BBH) extract at 10 and 20 g kg−1, and the basal diet for 56 days. The growth performance, physiological response and immune parameters were evaluated. The results showed that a significantly higher percentage weight gain (PWG) and percentage length gain (PLG) in prawns fed with BBH diet. The feed efficiency (FE) significantly increased in prawns fed BBP. The prawn fed both BBH and BBP diet showed higher survival rate than control group. The prawn fed with BBH showed a significant increase in total haemocyte count (THC) and different haemocyte count (DHC), whereas phenoloxidase (PO) activity and respiratory bursts (RBs) significant increase in prawns fed both BBP and BBH diet. Furthermore, M. rosenbergii fed with both BBP and BBH diets showed significantly higher phagocytic activity and clearance efficiency against Lactococcus garvieae infection. At the end of the 56 days of feeding trial, the susceptibility of prawns to L. garvieae infection and hypothermal (18 °C) stress were evaluated. The results showed that prawns fed BBH diets had a significantly higher survival rate against L. garvieae than those of fed with the basal diet. Anti-hypothermal stress was observed in prawns fed both BBP and BBH diets showing no significant difference in haemolymph glucose in prawns subjected to 18 °C and 28 °C, whereas the norepinephrine level in haemolymph of prawns fed with BBH diets subjected to 18 °C was significantly lower than in prawns subjected to 28 °C. In summary, we recommend addition of hot-banana blossom extract to the diet of M. rosenbergii at 20 g kg−1 to promote growth performance, improve physiological function, enhance immunity, increase anti-hypothermal stress, and to increase resistance against L. gavieae.

The effects of Anoectochilus roxburghii polysaccharides on the innate immunity and disease resistance of Procambarus clarkii

Anoectochilus roxburghii polysaccharides (ARPs) are composed of glucose (75.71%) and galactose (14.53%) with α-type glycosidic chains, and the sugar chains contained the functional groups of S=O, C=O, and -COO-. A white spot syndrome virus (WSSV) infection experiment was performed to determine the effect of ARPs on the innate immunity of crayfish. Dietary ARPs were proven to increase the survival of WSSV-infected crayfish up to 40%. It was also found that ARPs could up-regulate the expression level of multiple immune genes, including crustin 1, proPO, Toll-like receptors, c-type-lectin, and decrease the expression of NF-κB. Additionally, ARPs promoted phenoloxidase (PO), superoxide dismutase (SOD), catalase (CAT), and lysozyme (LZM) activity in crayfish. The apoptosis of hemocytes in crayfish was promoted by ARPs, whether challenged or not. This study showed that ARPs could be used as a potential source of therapeutic or preventive drugs to regulate crayfish immunity and increase the survival rate of crayfish infected with WSSV.

Effects of pyroligneous acid on life history and physiology of two pyralid pests of stored products

Natural products derived from plant materials, such as wood vinegar (pyroligneous acid; PA), have shown toxicity to insects in previous studies; however, the impact of this substance on physiology and life history of stored product insects is unknown. Thus, the current study aimed to determine the effects of PA on two prominent stored product moths, Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae). LC50/24h values of PA were determined for both species and first instar larvae were fed on an artificial diet containing LC50 concentrations of PA for their entire life cycle. Final instar larvae were selected for biochemical analysis while life history parameters were assayed in female adults that emerged from treated larvae. In both species, significantly lower activities of digestive enzymes (α-amylase, protease, and lipase) and detoxifying enzymes (carboxylesterase, monooxygenase cytochrome P450, and glutathione S-transferase) were observed in treated larvae relative to untreated larvae. In contrast, antioxidant enzyme activities (superoxide dismutase, phenoloxidase, and ascorbate peroxidase) were significantly elevated in treated larvae compare to controls in both species. Moreover, larvae of both species tended to have lower levels of energy reserves, such as proteins, lipids, and carbohydrates, and adults exhibited reduced longevity, fecundity, and oviposition periods in comparison to untreated larvae. Finally, GC-MS analysis of the PA used for this study demonstrated that phenolic compounds and organic acids were the largest constituents. These results indicate that consumption of PA leads to the induction of to the antioxidant system, the inhibition of detoxification and digestion enzyme activities as well as reduced levels of energy reserves. Cumulatively, these effects resulted in reduced longevity and fecundity compared to control insects. This study expands our knowledge of the impacts of PA on physiology and life history for two prominent pests of stored products.

Fitness cost of malathion resistance in Egyptian Culex pipiens populations.

The extensive use of insecticides in agriculture and public health has resulted in the rapid development of insecticide resistance in mosquito populations. Therefore, in this study, we aimed to evaluate insecticide resistance costs on the fitness of Culex pipiens. Two Cx. pipiens field populations (Beheira malathion-resistant and Gharbia malathion-susceptible) were compared to the reference (sensitive) population. The biochemical composition and expression of four genes relevant to insecticide resistance were estimated in third instar larvae. Adult survival, female fecundity and egg hatchability were also determined. As per our findings, it was found that the total protein and carbohydrate contents in Beheira malathion-resistant larvae were significantly lower than that in the reference larvae. Beheira malathion-resistant larvae had higher phenoloxidase (PO) specific activity than the reference population. In terms of the relevant genes, only cytochrome P450 (CYP6F1) expression showed elevated levels in the Gharbia malathion-susceptible population compared to the Beheira malathion-resistant population. In esterases (Estα and Estβ) and glutathione S-transferase, the tested populations did not show any significant differences. Compared to the reference mosquito population, Gharbia malathion-susceptible Cx. pipiens males exhibited significantly longer median survival. Female fecundity and hatchability showed nonsignificant differences among the populations tested. In conclusion, malathion resistance can induce lower protein and carbohydrate contents, but higher PO activity in larvae.

Long-term impact of integrated nutrient management on sustainable yield index of rice and soil quality under acidic inceptisol

ABSTRACT An in-depth knowledge on impact of integrated nutrient management (INM) practice on yield sustainability and soil quality is important to scale INM practice across regions. Therefore, field experiment was initiated in 2006, which consisted of five treatments: absolute control, 100% recommended doses of nitrogen (N), phosphorus (P) and potassium (K) (RDF), 50% recommended doses of NP + 100% K + biofertilizers, 50% recommended doses of NP + 100% K + 1 t ha−1 enriched compost (ECM) and 25% recommended doses of NP + 100% K + 2 t ha−1 ECM (25RDF + 2ECM). The use of 25RDF + 2ECM increased soil organic carbon by 32 and 24% over control and RDF, respectively, at 0–5 cm soil layer. It also increased soil microbial biomass carbon, microbial phosphorus and phenol oxidase activity by 13.7, 20.9 and 55.7% than RDF, respectively, at 0–5 cm layer. Notably, phenol oxidase activity, pH, DTPA-extractable iron, available K, mineral N and microbial biomass phosphorus came out as the key indicators of soil quality in acidic soil after 10 years. The study recommends that INM practice comprising ECM and reduced inorganic fertilizers could enhance soil quality and yield sustainability of rice in the long-run in acidic soil ecology.

Carbon sequestration and the enzymic latch mechanism in red, black and white mangrove soils of Florida USA

Mangrove swamps are important habitat types providing vital ecological services, such as protection of coastlines from erosion and extreme weather conditions including hurricanes, recycling of nutrients and sequestration of carbon. Mangrove swamps support a wide range of biodiversity, improve water quality, provide fish for local communities. They are also used as a source of wood fuel, medication as well as for harvesting honey for the local population. Soil samples for laboratory analyses were collected from red (Rhizophora mangle), black (Avicennia germinans) and white (Laguncularia racemose) mangroves in Florida, USA to determine the biogeochemistry processes. Results of analyses indicated that the red mangrove soil is the most efficient for carbon sequestration. It had the lowest phenol oxidase activity (206.15 nmol dicq g-1 h-1), highest phenolic concentration (262.33 µg g-1) and lowest hydrolase enzyme activity (β-glucosidase) (3.04 nmol g-1 min-1) and, as a result, the highest concentration of soil organic matter (SOM) (57.9%). It is believed that the high soil water content (84.2%).) of the red mangrove, due to its proximity to the sea, is a key driver of these observations. The 'enzymic latch' mechanism appears to be prevalent in the red mangrove soil, in particular, allowing these ecosystems to be effective at carbon storage hence, could serve as an important natural tool in mitigating the effect of climate change. Preservation and conservation of mangrove swamps is vital in balancing the effect of global warming.

Effects of histamine on the neuroendocrine-immune regulatory network in the Pacific white shrimp, Litopenaeus vannamei

In shrimp culture, feed made from stale fishmeal and decomposition of dead shrimp easily produces large amounts of histamine in the water environment, which will cause disease outbreaks. Simultaneously, in the internal environment of crustaceans, histamine is a short-acting biogenic amine that can act as a neurotransmitter and regulate immunity. To investigate the effects of histamine on the neuroendocrine-immune network of crustaceans, a histamine injection experiment was carried out on Litopenaeus vannamei in this study. The results showed that the neuroendocrine factors, including hormones (corticotrophin-releasing hormone, adrenocorticotropic hormone) and biogenic amines (dopamine, noradrenaline), in the histamine injection groups increased significantly at 6 h, while the 5-hydroxytryptamine concentration was significantly decreased at 12 h. The intracellular signaling pathways, including the PKC pathway (phospholipase C, diacylglycerol and protein kinase C), the RAP1 pathway (RAS-associated protein and integrin αIIbβ3), the PI3K/PKB pathway (phosphoinositide 3-kinase, phosphatidylinositol (3,4,5)-trisphosphate and protein kinase B) and the MAPK pathway (rat sarcoma protein and extracellular signal-regulated kinase) in the histamine injection groups all decreased significantly after 6 h and shared a similar trend. The immune parameters, including total hemocyte count, cell viability, phagocytic activity, phenoloxidase activity of hemocyte, antibacterial activity, bacteriolytic activity and hemagglutinating activity, all decreased significantly in the histamine injection group after 6 h, while phenoloxidase activity of plasma increased significantly. In addition, the antioxidant parameters (superoxide dismutase, catalase and glutathione peroxidase) in the histamine injection group were significantly increased. These results indicated that histamine might regulate the prophenoloxidase system via the PKC pathway, further influence the antibacterial and bacteriolytic activities, regulate hemagglutinating activity via the PKC-RAP1 pathway, regulate the total hemocyte count and cell viability via the PKC -PI3K/PKB pathway, and regulate phagocytic activity via the PKC -PI3K/PKB -MAPK pathway. Meanwhile, histamine may also affect the activities of antioxidant enzymes via the RAP1 pathway and the PKC-PI3K/PKB pathway. Therefore, it may be concluded that the neuroendocrine-immunoregulatory network plays a principal role in histamine regulation and causes immune and antioxidant defense in L. vannamei.

Dietary supplementation of Chlorella vulgaris improved growth performance, immunity, intestinal microbiota and stress resistance of juvenile narrow clawed crayfish, Pontastacus leptodactylus Eschscholtz, 1823

A 63- day feeding trial was conducted to study the effect of fishmeal substitution levels with Chlorella vulgaris meal (25, 50, 75 and 100%) on the growth performance, nutrient digestibility, immune responses and the stress resistance of juvenile narrow clawed crayfish, Pontastacus leptodactylus (6.19 ± 0.13 g). The highest values of final weight (25.52 g), specific growth rate (2.24% body weight day−1), protein efficiency ratio (3.24), the protein productive value (54.67%), in vivo ADCOM (88.40%) and in vivo ADCCP (93.50%) and the lowest feed conversion ratio (1.49) were observed in the juvenile crayfish fed the diet containing 75% fishmeal substituted level with chlorella meal (p < 0.05). With an increment in the dietary inclusion level of chlorella meal, the activities of alkaline protease (r2 = 0.97), lipase (r2 = 0.98), amylase (r2 = 0.97), phenoloxidase (r2 = 0.98), superoxide dismutase (r2 = 0.99), lysozyme (r2 = 0.96) and nitric oxide synthase (r2 = 0.98) were promoted as a third-order polynomial regression model (p < 0.05). There was an increasing trend in Lactobacillus count (r2 = 0.99) and a decreasing trend in Escherichia coli count (r2 = 0.97) with an increase in the fishmeal substitution level with chlorella meal. Based on the broken line regression model, the dietary fishmeal substitution level (%) with chlorella meal for maximum growth (SGR) and weight gain values and minimum FCR value of crayfish were estimated to be 85.49%, 78.14% and 78.13%, respectively.

Enzymatic activity and functional diversity of soil microorganisms along the soil profile – A matter of soil depth and soil-forming processes

Most studies concerning soil microorganisms and enzymes are focused on the upper horizons of the soil profile even though they transform soil organic matter at every depth of the soil profile. The aim of this study was to determine how the soil microbial functional diversity and enzymatic activity changed as a function of depth across the soil profiles which developed on the same parent material (glacial till) but differed in their soil-forming processes thereby resulting in the formation of different reference soil groups (RSG) (Luvisols, Gleysols and Stagnosols). Four soil profiles were excavated at different sites that are located in two mesoregions of the South Baltic Lake District (central Poland) in fields with alfalfa (Medicago sativa L.) in the fourth year of its cultivation. Using the soil samples collected in June 2019, we assessed the oxidoreductase activity (DHA – dehydrogenases, POX – phenol oxidase, PER – peroxidase), the fluorescein diacetate hydrolysis (FDAH) rate, the microbial biomass carbon and nitrogen (MBC, MBN) content, the number of microbial groups and the related physico-chemical properties. The community-level physiological profiles of the soil microorganisms were evaluated using the Biolog EcoPlate™ method. In general, the highest level of enzymatic activity per soil mass unit was found in the Ap horizons, whereas the dehydrogenases activity and FDAH decreased gradually with depth, while the phenol oxidase and peroxidase activity revealed no consistent trends between the sub-surface horizons. The specific enzymatic activity, expressed per unit of soil TOC and MBC, was more variable in response to profile depth than the enzymatic activity, which was expressed per soil mass, and this did not allow for clear trends to be determined. Also, the specific activity was different with regard to the intracellular and extracellular enzymes. The DHA/MBC ratio was markedly higher in the Ap horizons (all profiles) and generally decreased with depth. The phenol oxidase and peroxidase activities, expressed in the terms of the MBC content, did not exhibit any clear trends in the studied profiles, however, they reached their highest levels in the deepest layers in all of them. The abundance of all of the microbial groups was generally highest in the Ap horizon and decreased sharply with depth. A greater abundance of microbial groups was found in the gleyic horizons of the Gleysols and Stagnosols as compared to the upper and lower horizons. The highest average well color development (AWCD) under aerobic conditions was observed in the Ap genetic horizons (with the exception of the Haplic Luvisol profile), while the highest values of AWCD in anaerobic conditions were found in the illuvial and gleyic horizons. In contrast to the AWCD, the Shannon diversity index (H) and Shannon evenness index (S) (equal usage of compounds) indices were more similar in the compared horizons. Our findings suggest that the studied microbial properties in the Ap horizons were primarily determined by the TOC content, while their activity in the sub-surface layers was also affected by factors associated with soil-forming processes.

Land-Use Change Enhanced SOC Mineralization but Did Not Significantly Affect Its Storage in the Surface Layer.

To achieve carbon (C) neutrality and mitigate climate change, it is crucial to understand how converting natural forests to agricultural plantations influences soil organic C (SOC) mineralization. In this study, we investigated the impact of converting evergreen broadleaf forests (EBF) to extensively managed Moso bamboo (Phyllostachys edulis (Carriere) J. Houzeau) plantations (MBP) in subtropical China on SOC mineralization rate; the concentrations of labile SOC fractions such as dissolved organic C (DOC), microbial biomass C (MBC), and readily oxidizable C (ROC); the activities of C-degrading enzymes (cellobiohydrolase and phenol oxidase); and the abundance of C-degrading enzyme-encoding genes (cbhI and lcc). Three paired soil samples were taken from the surface layer (0–20 cm) of adjacent EBF-MBP sites in Anji County, Zhejiang province. Results showed that converting EBF to MBP significantly increased the SOC mineralization rate as well as soil pH, MBC, cellobiohydrolase, and phenol oxidase activities, and cbhI gene abundance, but did not change other soil properties described above. In addition, structural equation modelling (SEM) showed that the conversion increased SOC mineralization rate through increasing soil pH, cbhI gene abundance, MBC, and cellobiohydrolase and phenol oxidase activities. Our novel finding that converting EBF to extensively managed MBP enhanced SOC mineralization via increasing the activities of C-degrading enzymes suggests that C-degrading enzymes were a key factor regulating SOC mineralization in the extensively managed subtropical bamboo plantations.

An improved Amplex Red‐based fluorometric assay of phenol oxidases and peroxidases activity: A case study on Haplic Chernozem

AbstractThe initial steps of complex organic matter degradation in soil comprise several oxidative processes catalysed by phenol oxidases and peroxidases. Commonly, their activity is determined by colorimetric approaches based on a range of substrates, making comparison between studies difficult. To improve this shortcoming, we conducted a calibration procedure for assessing phenol oxidase and peroxidase activities in soils by a sensitive fluorometric assay. This assay is based on the colourless and non‐fluorescent Amplex Red® reagent as a substrate, which forms a fluorescent product, resorufin, upon oxidation. Commercially available resorufin was used as a standard for calibration. We applied Michaelis–Menten kinetics to determine functional traits of phenol oxidases and peroxidases in a case study on Haplic Chernozem from different land‐use and climate treatments of a field experiment. The kinetic parameters, limit of detection and limit of quantification demonstrated a high sensitivity of the fluorometric assay to differences caused by these treatments. For the total oxidative enzymes, the catalytic efficiency (Kcat, calculated as Vmax/Km) was 30% higher in the cropland compared with the pasture plot. However, compared with soil samples collected from ambient climatic conditions, Kcat of total oxidoreductases was 60% lower in cropland exposed to elevated air temperature and drought. The phenol oxidase activity was substantially higher than peroxidase activity in cropland land use. However, higher Kcat of peroxidase than phenol oxidase resulted in 60% faster substrate turnover under both climatic conditions. In our case study, the Amplex Red‐based assay enabled rapid and high‐throughput analyses of phenol oxidase and peroxidase activity in soil. The sensitivity of this assay for soil enzymology applications needs further testing for a larger range of soils and environmental conditions.Highlights A novel fluorometric assay of phenol oxidase and peroxidase activity in soil is proposed Resorufin fits very well for calibration simplifying the comparisons between studies Phenol oxidase and peroxidase displayed apparent Michaelis–Menten kinetics Amplex Red was sensitive for land‐use and climate treatments on Haplic Chernozem

Classic Hoarding Cages Increase Gut Bacterial Abundance and Reduce the Individual Immune Response of Honey Bee (Apis mellifera) Workers.

Laboratory experiments have advanced our understanding of honey bee (Apis mellifera) responses to environmental factors, but removal from the hive environment may also impact physiology. To examine whether the laboratory environment alters the honey bee gut bacterial community and immune responses, we compared bacterial community structure (based on amplicon sequence variant relative abundance), total bacterial abundance, and immune enzyme (phenoloxidase and glucose oxidase) activity of cohort honey bee workers kept under laboratory and hive conditions. Workers housed in the laboratory showed differences in the relative abundance of their core gut taxa, an increase in total gut bacterial abundance, and reduced phenoloxidase activity, compared to bees housed in hives.

The Combined Use of Pediococcus pentosaceus and Fructooligosaccharide Improves Growth Performance, Immune Response, and Resistance of Whiteleg Shrimp Litopenaeus vannamei Against Vibrio parahaemolyticus.

In this study, we evaluated the effect of probiotic bacteria Pediococcus pentosaceus supplemented at different inclusion levels in a control diet [basal diet containing 0.5% fructooligosaccharide (FOS)] on the growth performance, feed conversion ratio, immune response, and the disease resistance of whiteleg shrimp Litopenaeus vannamei juveniles against Vibrio parahaemolyticus. A control diet with 0.5% FOS but without P. pentosaceus supplementation (Control) was prepared. In addition, three other test diets were also formulated: control diet supplemented with P. pentosaceus at (i) 1 × 106 cfu g–1 diet (P1), (ii) 1 × 107 cfu g–1 diet (P2), or (iii) 1 × 108 cfu g–1 diet (P3). After a 60-day feeding trial, the experimental shrimps were challenged with V. parahaemolyticus. The results showed that dietary supplementation of P. pentosaceus significantly improved the growth performance and immune responses of L. vannamei juveniles. The juveniles that were fed with a P2 or P3 diet recorded the maximum increase in the final body weight, final length, weight gain, and survival rate. The total hemocyte counts, phenoloxidase, and lysozyme activity of shrimp fed with either of these two diets were significantly enhanced. The results also showed that juveniles fed with a P2 or P3 diet exhibited significantly lower mortality when challenged with V. parahaemolyticus. Overall results suggested that a combination of P. pentosaceus at the inclusion level of 1 × 107 cfu g–1 diet (P2) and 0.5% FOS could be considered as a potential synbiotic formulation for improving the growth, health, and robustness of L. vannamei.

Bioaccumulation of arsenic and immunotoxic effect in white shrimp (Penaeus vannamei) exposed to trivalent arsenic

Trivalent arsenic (As (III)) contamination in the marine environment can produce adverse effects in crustaceans. The present study investigated the chronic toxicity of As (III) in white shrimp (Penaeus vannamei) by analyzing the tissue bioaccumulation and non-specific immune responses. Shrimps were exposed to 0 (control), 50, 500, and 2500 μg/L of As (III) for 21 days. The results showed that the hepatopancreas was the main tissue of arsenic accumulation in white shrimp. The cumulative concentration of total arsenic and inorganic arsenic but not arsenobetaine was positively correlated with the exposure concentration. In vitro As (III) treatment (0–2500 μg/L) with haemocytes isolated from healthy shrimp did not cause the cytotoxicity, but this arsenic treatments inhibited the phagocytic rate and O2− production. Moreover, the decrease of total haemocyte count and the inhibition of phagocytic rate, phagocytic index, O2− production and phenoloxidase activity were observed in white shrimp under the exposure of As (III) over a period of 21 days. This study revealed that chronic As (III) stress could disturb arsenic metabolism and immune responses in P. vannamei.

Effect of plant phenolic compounds on the hemocyte concentration and antioxidant enzyme activity in Hyphantria cunea (Drury, 1773) (Lepidoptera: Arctiidae) larvae infected by Hyphantria cunea granulovirus

The aim of this study was to determine the effects of phenolic substances in different plants (mulberry, apple, walnut and plum) on hemocyte counts and antioxidant enzyme activities of Hyphantria cunea larvae infected with Hyphantria cunea granulovirus (HycuGV) and uninfected. In the study, the phenolic contents of plant materials were firstly determined. Then, the effects of these ingredients on hemocyte counts and antioxidant enzyme activities of infected and uninfected larvae were determined. As a result of the study, the hemocyte counts of all groups increased with the infection was determined. In enzyme activity, the phenoloxidase (PO) activities of larvae fed on apple leaves and plum leaves containing rosmarinic acid and protocatechuic acid increased with infection was determined. The amounts of malondialdehyde (MDA) decreased in all groups as a result of viral infection. While the highest superoxide dismutase (SOD) and catalase (CAT) activities among both infected and uninfected larvae were in the plum groups with the highest amount of chlorogenic acid, the lowest glutathione peroxidase (GSH-Px) activities were also in these groups. All this showed that different phenolic contents of host plants affected the hemocyte counts and antioxidant enzyme activities of H. cunea larvae.