Phenoloxidase Research Articles

Detection and substrate portrayal on the serum phenoloxidase activity from the grub of rhinoceros beetle, Oryctes rhinoceros.

Phenoloxidase (PO) is a significant biomolecule involved in humoral defence mechanism of invertebrates. Spontaneous melanization of insect haemolymph is the major hinderance for studying PO activity, as haemolymph was collected devoid of phenylthiourea. In the study, no visible melanization was observed in crude serum from the grub of Oryctes rhinoceros up to 30 min of incubation amongst crude haemolymph, diluted haemolymph, crude serum and diluted serum that were subjected to visual observation for spontaneous melanization reaction. Accordingly, crude serum was taken for evaluating PO activity. At the same time, as PO substrates tend to auto-oxidize and provide false optical density value, tris-buffered saline devoid of any substrates were used as blank for PO assays. The ideal wavelength at which maximum PO activity occurred for each substrate, namely, tyrosine, tyramine, dopamine, L-dopa, DL-dopa, catechol, protocatechuic acid and pyrogallol was determined as 407, 410, 429, 465, 403, 466, 428 and 400 nm, respectively. Additionally, time course of oxidation for each phenolic substrate by the serum PO were examined and DL-dopa was identified as the specific substrate for serum PO in the grub of O. rhinoceros. Furthermore, maximum PO activity was observed at 5 min of incubation for 10 mM of DL-dopa that was considered as optimum concentration. The ideal pH and temperature for serum PO activity was observed as 7.5 and 20°C, respectively. These results suggested that standardizing a suitable substrate is an essential prerequisite to evaluate the real PO activity of serum which might significantly fluctuate in each insect model.

Effects of dietary peptidoglycan on Litopenaeus vannamei: Growth performance, disease resistance, non-specific immunity and transcriptome analysis of immune response

At present, peptidoglycan (PGN) is commonly used as an immunostimulant in shrimp. However, little has been known about its mechanism. In this study, comparative transcriptome analysis was employed to investigate the impact of dietary PGN on the immune response in Litopenaeus vannamei. A total of 720 healthy juvenile L. vannamei (initial weight 0.31 ± 0.05 g) were randomly evenly allocated to 18 fibreglass buckets as 6 groups, fed with six isonitrogen (41.05%) and isolipid diets (8.16%) containing PGN at the doses of 0 (control), 0.2, 1, 5, 25, and 125 mg/kg, respectively. After 8 weeks feeding trail, the growth performance, immunity, and transcriptome response of L. vannamei were analyzed. The results showed that the growth performance of L. vannamei was not significantly influenced by dietary PGN (P > 0.05). According to the analysis of weight gain rate (WGR), the optimum dietary PGN level was 71.46 mg/kg. Compared with the control group, the survival rate (SR) after Vibrio parahaemolyticus infection of L. vannamei were significantly increased by dietary PGN at 5 mg/kg and the SR after white spot syndrome virus (WSSV) infection was improved by dietary PGN at 25 mg/kg (P < 0.05). The superoxide dismutase (SOD), phenoloxidase (PO), catalase (CAT), lysozyme (LZM), acid phosphatase (ACP), and alkaline phosphatase (AKP) activities could be enhanced remarkably while the maleic dialdehyde (MDA) levels were significantly decreased by dietary PGN compared with the control group (P < 0.05). Transcriptome analysis showed that there were 1350 (902 down, 448 up) and 1697 (1183 down, 514 up) DEGs in the PGN5 and PGN25 when compared with the PGN0 group, respectively. Most DEGs were significantly enriched in immune and metabolism related signalling pathways, such as antigen processing and presentation, autophagy-animal, apoptosis-multiple species, carbohydrate digestion and absorption, and amino sugar and nucleotide sugar metabolism signalling pathway. Besides, the metabolism related signalling pathways occupied top significantly enriched placement. In conclusion, moderate dietary PGN could significantly improve the non-specific immunity of L. vannamei, presumably by modulating its metabolism.

The effects of a polystyrene nanoplastic on the immune response and gut microbiota of Eriocheir sinensis and its post-recovery state

Although there is increasing concern about the toxicity of nanoplastics, the effects of nanoplastic exposure and subsequent recovery on immune responses, as well as antioxidant responses and gut microbiota, in crustaceans are rarely reported. In this study, the nonspecific immunity and antioxidant defense of Eriocheir sinensis were evaluated after acute exposure to various concentrations (0, 2.5, 5, 10 and 20 mg/L) of 75-nm polystyrene nanoplastics (PS-NPs) for 48 h, as well as after 7 days of recovery from the nanoplastic environment. The results showed that, after 48 h of exposure, nanoplastics were observed in the gills, hepatopancreas and gut. However, no nanoplastics were found in the gut after 7 days of recovery. Under nanoplastic-induced stress, Hc, Relish, proPO, and LITAF mRNA levels increased in the gills and hepatopancreas for 48 h. Expression of the myd88, Hc, Relish and proPO genes decreased in the gills during the 7-day recovery period. Exposure to nanoplastics for 48 h and recovery for 7 days significantly decreased the activities of lysozyme (LZM) alkaline phosphatase (AKP), total superoxide dismutase (SOD) and phenoloxidase (POD) and, glutathione peroxidase (GPX) in the hepatopancreas. Meanwhile, the relative abundance of pathogens exposed to 10 mg/L nanoplastics for 48 h increased at the species level, and these pathogens decreased significantly in the 7-day recovery period. These results suggested that exposure to nanoplastics for 48 h affected the activities of immune system enzymes and expression of immune-related genes in Eriocheir sinensis and altered the diversity and composition of their gut microbiota. E. sinensis could not recover from damage to the hepatopancreas within a 7-day recovery period. The results of this study provided insight into the effects of nanoplastics on crustaceans and it filled a gap in research on crustacean recovery after exposure to nanoplastics.

Microplastics in feed cause sublethal changes in the intestinal microbiota and a non-specific immune response indicator of the freshwater crayfish Procambarus clarkii (Decapoda: Cambaridae).

Microplastics (MP) are a hazardous pollutant of global concern that threatens aquatic ecosystems and public health. We used the invasive, cosmopolitan, and environmentally versatile red swamp crayfish Procambarus clarkii as a model to study the effects of MP on the intestinal microbiome. Crayfish collected from the environment were compared with specimens exposed to recycled Polyethylene terephthalate (rPET) MP in feed (30%) for 96 h in the laboratory and a control group. We analyzed the 16S rRNA of the intestinal bacteria by PCR-DGGE and high-throughput sequencing. MP exposure caused dysbiosis of the intestinal microbiota, with an increase in Alphaproteobacteria and Actinobacteria. We detected higher abundance of opportunistic genera such as Klebsiella, Acinetobacter, Hydromonas, Pseudomonas, Gemmobacter, and Enterobacter on MP fed organisms. Moreover, MP exposure reduced the abundance of Clostridia and Bateroidetes, which are important for immune system development and pathogen prevention. Furthermore, MP exposure decreased the phenoloxidase (PO) immune response in crayfish. There was a significant difference in the richness of intestinal bacterial communities after consumption of food contaminated with MP, likely increasing the abundance of opportunistic bacteria in the intestinal microbiota. Our results suggest that MP alter the gut microbial composition and impair the health of P. clarkii.

Changes in the activity of soil enzymes after fire

Fire can have widespread impacts on biogeochemical processes of carbon (C) and nutrient cycling. Soil extracellular enzyme activity (EEA) plays crucial roles in biogeochemical processes, while the general response pattern of EEAs to fire remains elusive. Here, we synthesized 1064 paired observations of fire effects on eight soil EEAs of β-D-Cellobiosidase (CB), β-1,4-Glucosidase (BG), β-1,4-Xylosidase (XYL), N-acetyl-glucosaminidase (NAG), urease (URE), phosphatase (PHO), peroxidase (PER), and phenol oxidase (POX) from 51 publications on a global scale. Results showed that fire significantly decreased hydrolases of C acquisition (sum of CB, BG, and XYL), N acquisition (sum of URE and NAG), and P acquisition (PHO) EEAs by 21.0%, 25.5%, and 29.9%, respectively. In contrast, fire significantly enhanced oxidative enzyme (sum of PER and POX) activities by 12.4%. Among all experimental, environmental, and soil variables, ecosystem type and soil C and N had greater effects on the various responses of EEAs to fire across studies. In addition, changes in soil C and N pools and microbial biomass were positively correlated with changes in hydrolytic EEAs but negatively correlated with changes in oxidative EEAs. These results suggest that the differential fire effects on soil hydrolytic and oxidative EEAs may be a crucial mechanism regulating soil C and nutrient cycling following fire events.

Understanding how conservation tillage promotes soil carbon accumulation: Insights into extracellular enzyme activities and carbon flows between aggregate fractions

Conservation tillage has been shown to mitigate climate change by promoting the sequestration of soil carbon (C) in agroecosystems. However, knowledge on how conservation tillage accumulates soil organic C (SOC), especially at the aggregate scale, remains limited. This study aimed to clarify the effects of conservation tillage on SOC accumulation by measuring hydrolytic and oxidative enzyme activities and C mineralization in aggregates and developing an extended scheme of C flows between aggregate fractions using the 13C natural abundance (δ13C) method. Topsoils (0–10 cm) were sampled from a 21-year tillage experiment located in the Loess Plateau of China. Compared with conventional (CT) and reduced tillage with straw removal (RT), no-till (NT) and subsoiling with straw mulching (SS) enhanced the proportions of macro-aggregates (> 0.25 mm) (by 12–26%) and SOC contents in bulk soils and all aggregate fractions (by 12–53%). In bulk soils and all aggregate fractions, SOC mineralization and the activities of hydrolases (β-1,4-glucosidase, β-acetylglucosaminidase, β-xylosidase, and cellobiohydrolase) and oxidases (peroxidase and phenol oxidase) were 9–35% and 8–56% lower, respectively, under NT and SS than under CT and RT. Partial least squares path model revealed that reductions in the activities of hydrolases and oxidases and increases in macro-aggregation decreased SOC mineralization in bulk soils and macro-aggregates. Furthermore, Δ13C values (aggregate-associated δ13C − bulk-soil δ13C) increased with decreasing size of soil aggregates, suggesting that C is younger in larger aggregates than in smaller aggregates. The probability of C flows from large to small soil aggregates was lower under NT and SS than under CT and RT, indicating that young SOC with low rates of decomposition in macro-aggregates was better protected under NT and SS. Overall, NT and SS enhanced SOC accumulation in macro-aggregates by decreasing the activities of hydrolases and oxidases and C flows from macro- to micro-aggregates, which promoted C sequestration in soils. The present study provides improved insights into the mechanism and prediction of soil C accumulation under conservation tillage.

Several Characteristics of Oidiodendron maius G.L. Barron Important for Heather Plants' Controlled Mycorrhization.

Oidiodendron maius G.L. Barron is a recognized fungal species capable of forming ericoid mycorrhiza with various positive effects on host plants; therefore, newly found and previously uncharacterized O. maius strains may be valuable for heather plants' controlled mycorrhization. Characteristics of the O. maius F3860 strain were studied, i.e., mycelium growth on various nutrient media and the ability to secrete auxins and enzymes. O. maius F3860 grew rapidly on malt extract agar and potato dextrose agar. It was also able to grow on nutrient media suitable for heather plant cultivation. The presence of the flavonoids rutin and quercetin increased the mycelium growth rate compared to the control, starting from the 8th to the 13th days of cultivation. The ability to secrete auxins was confirmed with bioassay and thin-layer chromatography, and their content, as well as phytase activity, was estimated spectrophotometrically. Both in nutrient media with tryptophan and without it, O. maius F3860 secreted about 6 μg IAA/mL growth medium. O. maius F3860 possessed extracellular phytase, protease, and phenol oxidase activities. The investigation indicates O. maius F3860's promise for heather seedling inoculation as an approach to increase their fitness.

Effects of dietary soluble β-1,3-glucan on the growth performance, antioxidant status, and immune response of the river prawn (Macrobrachium nipponense).

The effects of dietary β-1,3-glucan on the growth performance, body composition, hepatopancreas tissue structure, antioxidant activities, and immune response of the river prawn (Macrobrachium nipponense) were investigated. In total, 900 juvenile prawns were fed one of five diets with different contents of β-1,3-glucan (0%, 0.1%, 0.2%, and 1.0%) or 0.2% curdlan for 6 weeks. The growth rate, weight gain rate, specific growth rate, specific weight gain rate, condition factor, and hepatosomatic index of juvenile prawns fed 0.2% β-1,3-glucan were significantly higher than those fed 0% β-1,3-glucan and 0.2% curdlan (p < 0.05). The whole-body crude lipid content of prawns supplemented with curdlan and β-1,3-glucan was significantly higher than that of the control group (p < 0.05). The antioxidant and immune enzyme activities of superoxide dismutase (SOD), total antioxidant capacity (T-AOC), catalase (CAT), lysozyme (LZM), phenoloxidase (PO), acid phosphatase (ACP), and alkaline phosphatase (AKP) in the hepatopancreas of juvenile prawns fed 0.2% β-1,3-glucan were significantly higher than those of the control and 0.2% curdlan groups (p < 0.05), and tended to increase and then decrease with increasing dietary β-1,3-glucan. The highest malondialdehyde (MDA) content was observed in juvenile prawns without β-1,3-glucan supplementation. The results of real-time quantitative PCR indicated that dietary β-1,3-glucan promoted expression of antioxidant and immune-related genes. Binomial fit analysis of weight gain rate and specific weight gain rate showed that the optimum β-1,3-glucan requirement of juvenile prawns was 0.550%-0.553%. We found that suitable dietary β-1,3-glucan improved juvenile prawns growth performance, antioxidant capacity, and non-specific immunity, which provide reference for shrimp healthy culture.

Effect of Clostridium butyricum on intestinal microbiota and resistance to Vibrio alginolyticus of Penaeus vannamei

In order to evaluate the effect of Clostridium butyricum (C. butyricum) feeding on intestinal microorganisms and protection against infection by Vibrio alginolyticus (V. alginolyticus) in Penaeus vannamei (P. vannamei). We set up two groups, CG30 (fed normal feed) and CB30 (fed feed supplemented with C. butyricum), for the 30d C. butyricum feeding test, and four groups, CG (CG30 group injected with PBS), CB (CB30 group injected with PBS), VACG (CG30 group injected with V. alginolyticus), and VACB (CB30 group injected with V. alginolyticus), for the 24 h infection test. The protective effect of C. butyricum against acute V. alginolyticus infection in P. vannamei was explained in terms of survival, histopathology, changes in enzyme activity, transcriptome analysis, and immune-related genes. We found that feeding C. butyricum significantly altered intestinal microbial populations' abundance and significantly reduced Vibrio spp. In the V. alginolyticus stress test, C. butyricum improved the survival rate and alleviated pathological changes in hepatopancreatic tissues, alleviated the reduction of superoxide dismutase (SOD) and phenoloxidase (PO) activity caused by infection, and increased the lysozyme content in P. vannamei. VACB group compared with the VACG group, 1730 up-regulated differentially expressed genes (DEGs) and 2029 down-regulated DEGs were screened. Quantitative real-time PCR (qRT-PCR) showed that dietary supplementation with C. butyricum suppressed the upregulation of alkaline phosphatase (AKP) transcription factors and the downregulation of prophenoloxidase (proPO), alpha-2-macroglobulin (A2M), and anti-lipopolysaccharide factor (ALF) induced by V. alginolyticus infection. In conclusion, feed supplementation with C. butyricum changed P. vannamei's population ratio of intestinal microorganisms. Moreover, C. butyricum has the potential to act as an inhibitor of V. alginolyticus infection and enhance the resistance of P. vannamei to V. alginolyticus infection.

Influence of Asafoetida Extract on the Virulence of the Entomopathogenic Nematode Steinernema carpocapsae and Its Symbiotic Bacterium Xenorhabdus nematophila in the Host Pyrrhocoris apterus.

Nematode-microbe symbiosis plays a key role in determining pathogenesis against pests. The modulation of symbiotic bacteria may affect the virulence of entomopathogenic nematodes (EPNs) and the biological management of pests. We tested the influence of asafoetida (ASF) extract on the virulence of Steinernema carpocapsae and its symbiotic bacterium, Xenorhabdus nematophila, in Pyrrhocoris apterus. A total of 100 mg of ASF killed 30% of EPNs in 48 h, while P. apterus remained unaffected. The EPNs pre-treated with 100 mg of ASF influenced P. apterus's mortality by 24-91.4% during a period of 24 to 72 h. The topical application of ASF acted as a deterrent to S. carpocapsae, lowering host invasion to 70% and delaying infectivity with 30% mortality for 168 h. Interestingly, Steinernema's symbiotic bacterium, Xenorhabdus, remained unaffected by ASF. An in vitro turbidity test containing 100 mg of ASF in a medium increased the growth rate of Xenorhabdus compared to a control. A disc diffusion assay confirmed the non-susceptibility of Xenorhabdus to ASF compared to a positive control, streptomycin. Pro-phenol oxidase (PPO) and phenol oxidase (PO) upregulation showed that ASF influences immunity, while EPN/ASF showed a combined immunomodulatory effect in P. apterus. We report that ASF modulated the virulence of S. carpocapsae but not that of its symbiotic bacterium, X. nematophila, against P. apterus.

The effect of differences in soil water content on microbial and enzymatic properties across the soil profiles

The differences in soil water content across the soil profiles produce changes in soil microbial and enzymatic properties, which play a major role in the transformation of soil organic matter. Permanent water saturation contributes to the formation of gleyic/stagnic horizons which have reducing conditions, this leads to a depletion in soil oxygen and changes in soil properties. To assess the effect of water content, we compared soil properties in the gleyic/stagnic horizons to the oxidative layers, which occurred at the same/similar depth in other profiles. The enzymatic activity and the number of microbial groups were assessed in eight soil profiles located in central Poland.The studied properties responded differently to the water content. As expected, nitrate-reductase activity and the nitrate content were significantly higher in gleyic/stagnic than in oxidative conditions, while the opposite trend was found for phenol oxidase, urease, N-acetyl-glucosaminidase activity and the fungi number. No clear response in the total bacteria and facultative anaerobic bacteria (Bfa) count toward oxidation-reduction conditions was found. The dehydrogenases did not have a higher activity in the gleyic/stagnic as compared to the oxidative horizons and did not correlate significantly with the Bfa count. Differences in enzyme activities may be caused by the fact that the variation in frequency and duration of the reducing conditions in the soils may be insufficient to affect the short-term dynamics of these enzymes. The higher activity of some hydrolases in the reducing horizons may also be associated with the greater carbon and nitrogen content in these horizons.

Anaerobic phloroglucinol degradation by Clostridium scatologenes.

Polyphenols are abundant in nature, and their anaerobic biodegradation by gut and soil bacteria is a topic of great interest. The O2 requirement of phenol oxidases is thought to explain the microbial inertness of phenolic compounds in anoxic environments, such as peatlands, termed the enzyme latch hypothesis. A caveat of this model is that certain phenols are known to be degraded by strict anaerobic bacteria, although the biochemical basis for this process is incompletely understood. Here, we report the discovery and characterization of a gene cluster in the environmental bacterium Clostridium scatologenes for the degradation phloroglucinol (1,3,5-trihydroxybenzene), a key intermediate in the anaerobic degradation of flavonoids and tannins, which constitute the most abundant polyphenols in nature. The gene cluster encodes the key C-C cleavage enzyme dihydrophloroglucinol cyclohydrolase, as well as (S)-3-hydroxy-5-oxo-hexanoate dehydrogenase and triacetate acetoacetate-lyase, which enable phloroglucinol to be utilized as a carbon and energy source. Bioinformatics studies revealed the presence of this gene cluster in phylogenetically and metabolically diverse gut and environmental bacteria, with potential impacts on human health and carbon preservation in peat soils and other anaerobic environmental niches. IMPORTANCE This study provides novel insights into the microbiota's anaerobic metabolism of phloroglucinol, a critical intermediate in the degradation of polyphenols in plants. Elucidation of this anaerobic pathway reveals enzymatic mechanisms for the degradation of phloroglucinol into short-chain fatty acids and acetyl-CoA, which are used as a carbon and energy source for bacterium growth. Bioinformatics studies suggested the prevalence of this pathway in phylogenetically and metabolically diverse gut and environmental bacteria, with potential impacts on carbon preservation in peat soils and human gut health.

Integrating microbiome and transcriptome analyses to understand the effect of replacing fishmeal with Tenebrio molitor meal in Pacific white shrimp (Litopenaeus vannamei) diets

With the increasing price and demand for fishmeal (FM) in aquaculture feeds, Tenebrio molitor (TM), an insect species known as yellow mealworm, is becoming an attractive alternative to FM in the aquaculture industry. This study investigated the effect on growth, enzyme activity, resistance to Vibrio parahaemolyticus, intestinal microbiota, and hemolymph transcriptome in Litopenaeus vannamei (Pacific white shrimp) of replacing up to 45% of FM with TM. L. vannamei (initial weight: 0.42 ± 0.01 g) were fed with diets that replaced FM with TM at 0% (TM0, control), 15% (TM15), 30% (TM30), and 45% (TM45). The results showed that dietary TM30 significantly increased the final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) of L. vannamei (P < 0.05) when compared with TM0. For the enzyme activity of serum, alkaline phosphatase (AKP), catalase (CAT), superoxide dismutase (SOD), phenoloxidase (PO), and lysozyme (LZM) differed significantly in TM45 compared with TM0 (P < 0.05), and malondialdehyde (MDA) decreased. The trypsin in the intestine significantly increased in TM45 compared with TM0 (P < 0.05). In the shrimps challenged with V. parahaemolyticus (1.3 × 107 CFU/mL), survival rates were not significantly different between groups. The alpha diversity indicators were significantly affected by feeding different levels of TM (P < 0.05), and beta diversity analysis showed that the four groups differed significantly (P < 0.05). Based on IndVal values, eight families were distinguished. RNA-seq analysis showed that the most enriched pathway was ‘Metabolism of xenobiotics by cytochrome P450’. Some DEGs (differentially expressed genes) of the cytochrome P450 pathway correlated with the abundance of intestine bacteria at the family level. This study provides an insight into the mechanisms associated with molecular and microbiota responses to the effects of substituting TM for FM on L. vannamei, as well as suggests that TM is a potential protein source for farmed L. vannamei, possibly improving its antioxidant capacity, immunity, and resistance to disease via the cytochrome P450 pathway.

Extracellular enzyme activities response to nitrogen addition in the rhizosphere and bulk soil: A global meta-analysis

Plant roots play a crucial role in acquiring available nutrients and regulating microbial decomposition, leading to faster nutrient cycling in the rhizosphere than in bulk soil. With increasing nitrogen (N) loading, rhizosphere processes may become more crucial than bulk soil processes for accurately predicting nutrient cycling process changes. However, it remains unclear how the rhizosphere and bulk soil extracellular enzyme activities (EEAs) respond to N addition on a global scale. Therefore, we used a global meta-analysis to examine the effects of N addition on EEAs involved in carbon (C), N, and phosphorus (P) acquisition in paired rhizosphere and bulk soils, based on 1992 observations from 40 studies. Overall, N addition significantly increased β-xylosidase (BXYL) activity by 17.0% in bulk soil, together with urease (URE) activity in both the rhizosphere (25.3%) and bulk soil (33.6%). In addition, N addition marginally significantly decreased phenol oxidase (PHEO) activity in the rhizosphere (−18.4%), as well as peroxidase (PERO) activity in both the rhizosphere (−12.6%) and bulk soil (−13.6%). The reductions may be caused by fungi: bacteria ratio and Gram+ bacteria: Gram− bacteria ratio (F: B and G+: G−, respectively) reductions. We also found that EEAs (e.g., acid/alkaline phosphatase (AP) and PHEO) did not always have a simple linear relationship with higher N addition rate and duration. Additionally, the responses of β-1,4-N-acetyl-glucosaminnidase (NAG) and PHEO significantly increased with increase in mean annual temperature (MAT), whereas those of microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) significantly decreased with increase in mean annual precipitation (MAP). Moreover, the responses of PHEO and PERO significantly decreased along altitudinal gradients. Furthermore, we found that the N sensitivity of rhizosphere C-acquisition (BG, PHEO, and PERO) and P-acquisition (AP) enzyme activities was significantly lower than that of bulk soil, but no significant difference was noted in N-acquisition enzyme activities except for the NAG which exhibited marginal significant differences between the rhizosphere and bulk soil. Our results suggest that EEAs in the rhizosphere and bulk soil have different response patterns, and these differences might mainly be caused by soil nutrient availability and microbial attributes. These results deepen our understanding of rhizosphere and bulk soil nutrient cycling processes under increasing N loading. They also provide extensive evidence and a basis for the parameterization of global nutrient cycling models that incorporate rhizosphere responses to climate change.

Aspergillus niger confers health benefits and modulates the gut microbiota of juvenile Pacific white shrimp (Penaeus vannamei) under farming conditions

IntroductionThe fungus Aspergillus niger is found to be predominant in the body of Pacific white shrimp (Penaeus vannamei); however, its role in shrimp’s health has not been explored. This study aimed to evaluate the influences of A. niger on growth, antioxidative activity, immune response, and gut microbiota of juvenile Pacific white shrimps under farming conditions.MethodsShrimps (2.30±1.05 g) were fed diets supplemented with 0 (control), 1.5 (A1.5), or 3.0 g/kg diet of A. niger (A3.0) for one month. At the end of the study, the growth, antioxidant enzyme activity and immune parameters, and gut microbiota in shrimps fed with different experimental diets were analyzed.ResultsThe results showed a significant increase in weight gain, specific growth rate, and length gain of shrimps in A1.5, compared with other groups (P&amp;lt;0.05). With the exception of lysozyme in both A1.5 and A3.0, which were lower than in the control, the activity of superoxide dismutase (SOD), catalase, acid phosphatase, alkaline phosphatase, and phenol oxidase was higher than those in the control. Gene expressions of SOD, anti-lipopolysaccharide factor-ALF1, and ALF2 (in A1.5 and A3.0) and nitric oxide synthase, penaeidin-PEN2 (in A1.5) and PEN3 and PEN4 (in A3.0) were significantly up-regulated compared to the control (P&amp;lt;0.05). The addition of A. niger increased diversity and separated the microbial community in the gut of shrimps. At the phylum level, Firmicutes and Bacteroidota were dominant, and Proteobacteria was less abundant in the A1.5 and A3.0, as compared to the control. At the genus level, the relative abundance of Vibrio, Marivita, and Roseobacter was increased but Ruegeria was decreased in A1.5 and A3.0 when compared to the control. The genera Edwardsiella, Clostridium sensu stricto 1, and Shimia in the A1.5 were higher than in the control.DiscussionThese findings demonstrated the beneficial effects of A. niger on growth, health, and changes in the gut microbiota in shrimps under farming conditions. The recommended concentration of A. niger in the diet for shrimps is 1.5 g/kg diet.

Extracellular vesicles secreted by Brugia malayi microfilariae modulate the melanization pathway in the mosquito host

Vector-borne, filarial nematode diseases cause significant disease burdens in humans and domestic animals worldwide. Although there is strong direct evidence of parasite-driven immunomodulation of mammalian host responses, there is less evidence of parasite immunomodulation of the vector host. We have previously reported that all life stages of Brugia malayi, a filarial nematode and causative agent of Lymphatic filariasis, secrete extracellular vesicles (EVs). Here we investigate the immunomodulatory effects of microfilariae-derived EVs on the vector host Aedes aegypti. RNA-seq analysis of an Ae. aegypti cell line treated with B. malayi microfilariae EVs showed differential expression of both mRNAs and miRNAs. AAEL002590, an Ae. aegypti gene encoding a serine protease, was shown to be downregulated when cells were treated with biologically relevant EV concentrations in vitro. Injection of adult female mosquitoes with biologically relevant concentrations of EVs validated these results in vivo, recapitulating the downregulation of AAEL002590 transcript. This gene was predicted to be involved in the mosquito phenoloxidase (PO) cascade leading to the canonical melanization response and correspondingly, both suppression of this gene using RNAi and parasite EV treatment reduced PO activity in vivo. Our data indicate that parasite-derived EVs interfere with critical immune responses in the vector host, including melanization.

The selective regulation of immune responses by matrix metalloproteinase MMP14 in Ostrinia furnacalis.

Matrix metalloproteinases (MMPs) are crucial for tissue remodeling and immune responses in insects, yet it remains unclear how MMPs affect the various immune processes against pathogenic infections and whether the responses vary among insects. In this study, we used the lepidopteran pest Ostrinia furnacalis larvae to address these questions by examining the changes of immune-related gene expression and antimicrobial activity after the knockdown of MMP14 and bacterial infections. We identified MMP14 in O. furnacalis using the rapid amplification of complementary DNA ends (RACE), and found that it was conserved and belonged to the MMP1 subfamily. Our functional investigations revealed that MMP14 is an infection-responsive gene, and its knockdown reduces phenoloxidase (PO) activity and Cecropin expression, while the expressions of Lysozyme, Attacin, Gloverin, and Moricin are enhanced after MMP14 knockdown. Further PO and lysozyme activity determinations showed consistent results with gene expression of these immune-related genes. Finally, the knockdown of MMP14 decreased larvae survival to bacterial infections. Taken together, our data indicate that MMP14 selectively regulates the immune responses, and is required to defend against bacterial infections in O. furnacalis larvae. Conserved MMPs may serve as a potential target for pest control using a combination of double-stranded RNA and bacterial infection.

Dicyclohexylcarbodiimide and disodium succinate regulate the browning development in fresh longan pericarp by modulating the antioxidant system and the metabolisms of membrane lipids and phenolics

In this study, the effects of dicyclohexylcarbodiimide (DCC) and disodium succinate (DS) treatments on the pericarp browning (PB) development in postharvest longan were elucidated by measuring PB-related phenotypes and the metabolisms of antioxidants, membrane lipids, and phenolics. Compared to the control, DCC-treated longan displayed the higher levels of PB index, CMP, ROS, PA, DAG, and SFAs, the higher activities of POD, PPO, and MLMEs including PLD, PC-PLC, PI-PLC, lipase, and LOX, and the higher expression levels of DlPPO1, DlPOD1, and genes encoding MLMEs. In contrast, the lower levels of chromaticity values, pigments, TP, PC, PI, and USFAs, the lower activities of RSEs including SOD, CAT, and APX, the lower expression levels of genes encoding RSEs, and a lower non-enzymatic antioxidant capacity were also noted in DCC-treated longan. These results imply that the exacerbated PB induced by DCC was associated with the activation of MLMEs by up-regulating the expression of genes encoding MLMEs, which expedited the damage of cell membrane. This membrane damage was also regulated by the accelerated accumulation of ROS triggered by DCC. The increased membrane permeability after the damage prompted an enzymatic oxidation between phenol oxidase and phenolics. However, the opposite effect occurred in the DS-treated longan.

Exploring the Role of Stumps in Soil Ecology: A Study of Microsite Organic Carbon and Enzyme Activities in a Larix olgensis Henry Plantation

Stumps are a significant component of coarse woody debris in plantations, but their effect on microsite soil organic carbon (C) and enzyme activities remains understudied. Soil (Alfisol) samples were collected at varying distances from larch (Larix olgensis Henry) stumps and at different soil depths (0–20 cm and 20–40 cm) to analyze soil total organic C (TOC), particulate organic C (POC), easily oxidizable C (EOC), microbial biomass C (MBC), and enzyme activities. Results indicated that stumps significantly affected TOC and POC contents, with the greatest horizontal range of impact reaching up to 15 cm in both the topsoil and subsoil layers. Stumps also significantly affected MBC content, with the greatest horizontal range of impact reaching up to 55 cm in the subsoil layer. EOC content was the most affected, with the stumps’ impact extending to 55 cm in both soil layers. Additionally, the study showed that stumps had a significant impact on the activities of β-glucosidase and β-cellobiohydrolase, with the greatest horizontal range of impact reaching up to 15 cm for glucosidase and 35 cm for cellobiohydrolase in the topsoil layer. Stumps also significantly affected the activities of phenol oxidase and peroxidase, with the maximum horizontal range of stump impact extending up to 35 cm for phenol oxidase and 55 cm for peroxidase in the topsoil layer. This study enhances our understanding of the role of stumps in plantation ecosystems and offers valuable insights for future management strategies to maintain soil fertility and improve site productivity.

Nanobioremediation: a bacterial consortium-zinc oxide nanoparticle-based approach for the removal of methylene blue dye from wastewater.

Industrial effluents carrying dyes are considered a major environmental threat in the present era. Methylene blue (MB) dye is one of the key dyes of the thiazine group of dyes. It is broadly used in medical, textile, and various fields and is well known for its carcinogenicity and methemoglobin nature. Bacterial and other microbes-mediated bioremediation is becoming an emerging and significant section for the treatment of wastewater. Isolated bacteria were used for the bioremediation and nanobioremediation of methylene blue dye under varying conditions and parameters. A comparative study was conducted for the remediation of methylene blue dye using bacterial consortium, potential bacteria (isolated by scale-up method), and potential bacteria within zinc oxide nanoparticles. The decolorizing ability of bacteria was analyzed by UV visible spectrophotometer after stirring and static incubation in different time intervals of the isolates. Growth parameters and environmental parameters which include pH, initial dye concentration, and dose of nanoparticles were optimized with the minimal salt medium. An enzyme assay study was also done to check the effect of dye and nanoparticles on bacterial growth and the mode of action of degradation. The authors found that potential bacteria within ZnO nanoparticles showed enhanced decolorization efficiency (95.46% at pH 8) due to the properties of nanoparticles. On the other hand, the decolorization of MB dye by potential bacteria and the bacterial consortium was about 89.08 and 76.3%, respectively, for a 10-ppm dye concentration. During the enzyme assays study, the highest activity was observed for phenol oxidase, nicotinamide adenine dinucleotide (NADH), 2,6-Dichloroindophenol(DCIP), and laccase for nutrient broth having MB dye, MB dye, and ZnO NPs, while no such change was observed for manganese peroxidase enzyme activity. Nanobioremediation is a promising approach to removing such pollutants from the environment.