•Forest conversion significantly increased the ammonification rate.•Forest conversion decreased the nitrification and mineralization rates.•Forest conversion altered the function of the ...ectomycorrhizal community.•The ectomycorrhizal community is clearly linked to the altered N dynamics.•Some taxa of ectomycorrhizas are actively driving ecosystem processes.
The conversion of natural forests to plantations affects soil carbon (C) and nitrogen (N) dynamics. However, the underlying microbial mechanisms of C and N dynamics caused by forest conversion, particularly the functional role of ectomycorrhizal (ECM) fungi, remain largely unknown. Here, we investigated the soil and root-associated fungal communities, soil and ECM root enzyme activities, and C and N mineralization rates in natural forests and plantations in the western Sichuan subalpine coniferous forest. Soil fungal and root ECM fungal communities were determined by high-throughput and Sanger sequencing, respectively. ECM root surface enzymes were used to assess fungal function, while soil enzymes, C and N mineralization, were used to evaluate soil function.
Our results showed that clearing natural forests and converting them to plantations led to lower soil organic carbon (SOC), total nitrogen (TN), and pH, which drove changes in ECM and saprophytic (SAP) fungal communities. After forest conversion, the main difference in the fungal community was an increase in the ratio of ECM to SAP fungi. The most apparent change in the soil ECM fungal community is the shift of the dominant genera from Russula to Cortinarius and Piloderma. Subsequently, the function of the ECM fungal community was altered. The results indicated that the conversion of the natural forest to the plantation reduced ECM community β-glucosidase (βG), β-glucuronidase (βLU), N-acetyl-β-D-glucosaminidase (NAG), and acid phosphatase (AP) activities, and soil βG, NAG, and leucine aminopeptidase (LAP) activities. Among them, the activities of βG, βLU, and NAG in the ECM fungal community were significantly correlated with the activities of βG, βLU, and NAG in soil, respectively. Finally, we show that converting natural forests to plantations significantly increased the ammonification rate while decreasing the nitrification and mineralization rates. The close relationship between the relative abundance and diversity of the ECM fungal community, ECM communities and soil NAG, and N processes indicated that the changes in soil N dynamic after forest conversion were directly related to the changes in the ECM fungal community. Our results provide insight into soil C and N dynamics mechanisms resulting from forest conversion.
Here we combined microcalorimetry, enzyme activity measurements, and characterization of metal form in order to evaluate the effect of metal(loid)s on the activity of microbial community inhabiting ...tailings area with high toxic metal(loid)s concentration. Chromium (Cr), nickel (Ni), copper (Cu) and manganese (Mn) were the main pollutants. The exchangeable fractions (bioavailability) of Cu, Ni and Mn were higher in the tailings sample (Site Z), indicating a higher environmental risk. The total heat Qtotal (17,726.87 J/g), peak power Ppeak (541.42 μW/g) and growth rate constant k (0.11 h−1) of Site Z were higher than that of the polluted soil around tailings (Site Y). Such observation may be explained by physiological changes within the microbial community in response to high levels of heavy metal stress, thereby increasing respiration and improving microbial activity. In contrast, enzyme activities and enzyme activities index (GmeA) of Site Z were lower than the Site Y, which is strongly influenced by changes on physical-chemical properties (TN and TOC) and the presence of Cr, Mn, and Ni. Correlation coefficient and principal component analysis (PCA) indicate that GmeA is significantly correlated (p < 0.05 or p < 0.01) with environmental factors (EC, TOC and TN), Mn and Ni concentration, Ni bioavailability, and peak time (Tpeak). Therefore, GmeA represents a potential biological indicator for reporting the pollution degree in tailings area. Our results provide a theoretical basis for the prevention and control of pollution in non-ferrous metal(loid) tailings area.
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•Less than 11% of Cr, Ni, Cu and Mn is bioavailable in non-ferrous tailings soil.•Metal(loid)s affect microbial activity, being higher in tailings than surroundings.•Metal(loid)s and microbial activity significantly correlated to the GmeA.
•Temperature warming significantly decreased soil labile organic C fractions.•Long-term organic manure application increased soil labile organic C fractions.•Long-term fertilization significantly ...affected soil enzyme activities.•Warming governed soil enzyme activities by altering labile organic C fractions.
The effects of temperature changes on soil organic carbon (SOC), labile organic carbon fractions (microbial biomass carbon, MBC; dissolved organic carbon, DOC; particulate organic carbon, POC), and enzyme activities under long-term fertilization regimes as well as their relationships at different temperatures were investigated in this study. Soil samples were collected in the fluvo-aquic soil of a 26-year fertilizer trial in the North China Plain after maize harvest in 2012, and four treatments were selected: control of no fertilizer (CK), standard rate of mineral fertilizer treatment (SMF), standard rate of organic manure treatment with N input rate equal to SMF (SMA), and half-standard rate of organic manure plus half-standard rate of mineral fertilizer treatment (1/2(SMA+SMF)). We determined soil chemical properties and labile organic carbon fractions using standard methods and the activities of nine soil enzymes involved in C, N, and P cycling in a 21-day incubation experiment at different temperatures (5°C, 15°C, 25°C, and 35°C) by micro-plate fluorometric assay. Additionally, we investigated the relationships among them using redundancy analyses (RDA) at four temperatures. The results indicated that (1) temperature, fertilization, and their interaction had significant effects on SOC, MBC, DOC, POC, and most of the soil enzyme activities; (2) long-term organic manure treatments (SMA and 1/2(SMA+SMF)) significantly improved SOC, MBC, DOC, and POC contents and seven hydrolytic enzyme activities (α-1,4-glucosidase, β-1,4-glucosidase, β-1,4-xylosidase, cellobiohydrolase, L-leucine aminopeptidase, β-1,4-N-acetylglucosaminidase, phosphatase) at different temperatures, compared with the mineral fertilized treatment (SMF) and CK. However, oxidoreductases (peroxidase and phenol oxidase) showed the opposite trend with hydrolytic enzyme activities and had higher values in SMF and CK treatments; (3) SOC, MBC, DOC, POC, and most of the soil enzyme activities decreased with increasing temperature; (4) RDA revealed that the dominant factors of SOC and soil labile organic carbon fractions affecting soil enzyme activities were POC and SOC at 5°C, DOC and POC at 15°C, DOC and SOC at 25°C, and MBC, DOC, and SOC at 35°C. In conclusion, temperature changes significantly altered soil enzyme activities by driving changes in the rates of SOC decomposition and the fractions of soil labile organic carbon. Our conclusions have clear implications for soil ecosystem and biogeochemical cycles under climate change.
•Novel GSTD and GSTT proteins found P. vannamei.•GSTD and GSTT expression is higher in hepatopancreas than in gills and muscle.•Phenanthrene and naphthalene differentially induce GSTD and GSTT genes ...in shrimp.•GST activity was affected by phenanthrene exposure but not by naphthalene.•Glutathione concentrations were affected by the exposure to PAHs.
Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants ubiquitous in coastal ecosystems. The white shrimp Penaeus vannamei naturally inhabits in coastal areas and is cultivated in farms located nearby the oceans. PAHs can damage shrimp health, endanger natural populations, and lower shrimp aquaculture productivity. However, crustaceans have enzymes capable of metabolizing organic xenobiotics as PAHs and to neutralize reactive oxygen species (ROS) produced during xenobiotics metabolism. An important superfamily of xenobiotic-metabolizing and antioxidant enzymes are glutathione S-transferases (GSTs). In white shrimp, some GSTs are known, but they have been scarcely studied in response to PAHs. In this study we report the molecular cloning and bioinformatic characterization of two novel nucleotide sequences corresponding to cytosolic GSTs belonging the Delta and Theta classes (GSTD and GSTT). Both proteins genes have tissue-specific patterns of expression under normal conditions, that do not necessarily relate to GST activity and glutathione content. The expression of the GSTD and GSTT, GST activity and glutathione content was analyzed in juvenile P. vannamei exposed to two PAHs, naphthalene (NAP) and phenanthrene (PHE) in sub-lethal concentrations for 96 h. GSTD expression was up-regulated by the two PAHs, while GSTT expression was only induced by NAP. In contrast, GST activity towards CDNB was only up-regulated by PHE, suggesting differential effects of PAHs at gene and protein level. On the other hand, lower reduced glutathione content (GSH) caused by PAHs indicates its utilization for detoxification or antioxidant defenses. However, the GSH/GSSG did not change by PAHs treatment, indicating that shrimp can maintain redox balance during short-term sub-lethal exposure to NAP and PHE. Despite the variations in the responses to NAP and PHE, all these results suggest that the GSTD and GSTT genes could be useful biomarkers for PAH exposure in P. vannamei.
Triploid Fujian oyster (Crassostrea angulata) is crucial to aquaculture and coastal ecosystems because of its accelerated growth and heightened resilience against environmental stressors. In light of ...the increasing prevalence of nanoplastic pollution in the ocean, understanding its potential impact on this organism, particularly its adaptive responses, is of paramount importance. Despite this, the effects of nanoplastic pollution on the physiology of C. angulata remain largely unexplored. In this study, we explored the responses of triploid Fujian oysters to nanoplastic stress during a 14-day exposure period, employing an integrative methodology that included physiological, metabolomic, and 16S rRNA sequencing analyses. Our results demonstrate that the oysters exhibit a strong adaptive response to nanoplastic exposure, characterized by alterations in enzyme activity, metabolic pathways, and microbial community composition, indicative of an adaptive recovery state as opposed to a disordered state. Oysters subjected to elevated nanoplastic levels exhibited adaptive responses primarily by boosting the activity of the antioxidant enzyme catalase and elevating the levels of antioxidants such as adenosine, 3-(4-hydroxyphenyl)pyruvate, D-sorbitol, d-mannose, and unsaturated fatty acids, as well as the functional amino acids l-proline and l-lysine. Nanoplastic treatment also resulted in increased activity of succinate dehydrogenase, a key component of energy metabolism, and increased contents of intermediate metabolites or products of energy metabolism, such as adenosine monophosphate, adenosine, guanosine, creatine, and thiamine. Nanoplastic treatment led to an increase in the abundance of certain advantageous genera of gut bacteria, specifically Phaeobacter and Nautella. The observed adaptive response of triploid Fujian oysters to nanoplastic stress provides valuable insights into the mechanisms underpinning resilience in marine bivalves.
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•Triploid Fujian oysters show strong adaptive response to nanoplastic stress.•Nanoplastic exposure alters enzyme activity, metabolic pathways, and microbial community.•Adaptive recovery state indicates resilience in marine organisms.•Findings can inform strategies to enhance resistance of aquatic species.•Study contributes to preservation of marine ecosystem health.
Nutrient availability and plant diversity are two important factors determining crop productivity in agricultural ecosystems, but little is known about the underlying mechanisms shaping microbial ...communities and their regulatory roles in soil biological activity and function. Here, we explored the impacts of fertilization regimes and crop rotations on soil physicochemical properties, crop yield and bacterial and fungal community structures in a 26-year field experiment. The critical determinants for regulating soil enzyme activity profiles involved in carbon (C), nitrogen (N) and phosphorus (P) cycling were identified by the partial least squares path model (PLS-PM). Long-term inorganic or organic fertilization significantly increased soil total N by 27%–77% and crop yield by 237%–419% and decreased soil pH by an average of 0.4 units when compared with non-fertilized control. Soil bacteria were more sensitive than fungi to the fertilization practices. Nutrient additions enriched copiotrophic taxa affiliated to the Pseudomonadaceae and Cytophagaceae bacterial families, but reduced some Acidobacteria such as subgroup 4 RB41, which was the most sensitive biomarker responding to no fertilization. Conversely, fungi were more active in response to crop conversion from wheat-maize to wheat-soybean rotation, leading to a 3-fold enhancement of an unclassified Sordariomycetes family in soybean-based rotation. PLS-PM revealed that fertilization-induced increases in soil enzyme activities were regulated by the bacterial community, while plant-driven alterations in yield, organic C input and soil aggregate-size distribution played an important role for fungal development, which, however, had no significant link to soil enzyme activity profiles. Our results suggest that different response patterns of soil bacteria and fungi to agricultural practices might have consequences for ecosystem function.
•Agricultural practices can impact soil biotic communities in diverse manners.•Soil bacteria were more sensitive than fungi to changes in soil nutrient status.•Soil fungi were more active than bacteria in response to crop-type conversion.•Bacterial community was a key factor to explain the changes in enzyme activities.
The remediation of heavy metal-contaminated soils is a great challenge for global environmental sciences and engineering. To control the ecological risks of heavy metal-contaminated soil more ...effectively, the present study focused on the combination of soil washing (with FeCl3) and in situ immobilization (with lime, biochar, and black carbon). The results showed that the removal rate of Cd, Pb, Zn, and Cu was 62.9%, 52.1%, 30.0%, and 16.7%, respectively, when washed with FeCl3. After the combined remediation (immobilization with 1% (w/w) lime), the contaminated soils showed 36.5%, 73.6%, 70.9%, and 53.4% reductions in the bioavailability of Cd, Cu, Pb, and Zn (extracted with 0.11M acetic acid), respectively, than those of the soils washed with FeCl3 only. However, the immobilization with 1% (w/w) biochar or 1% (w/w) carbon black after washing exhibited low effects on stabilizing the metals. The differences in effects between the immobilization with lime, biochar, and carbon black indicated that the soil pH had a significant influence on the lability of heavy metals during the combined remediation process. The activity of the soil enzymes (urease, sucrase, and catalase) showed that the addition of all the materials, including lime, biochar, and carbon black, exhibited positive effects on microbial remediation after soil washing. Furthermore, lime was the most effective material, indicating that low soil pH and high acid-soluble metal concentrations might restrain the activity of soil enzymes. Soil pH and nutrition were the major considerations for microbial remediation during the combined remediation. These findings suggest that the combination of soil washing and in situ immobilization is an effective method to amend the soils contaminated with multiple heavy metals.
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•Soil washing combined with lime addition can effectively amend metal-polluted soil.•pH is a crucial factor to control heavy metal lability in the combined remediation.•Soil enzyme activities are greatly influenced by pH and acid-soluble metal contents.
Intensified anthropogenic activities will increase rates of nitrogen (N) deposition over the next decades, especially in the tropics. There are urgent needs to know how soil microbial community in ...N-rich tropical forests responds to long-term N deposition. This study examined effects of long-term N additions on soil microbial biomass (determined by chloroform fumigation), microbial community composition (based on phospholipid fatty acids, PLFAs), and microbial enzyme activities, using an ongoing experimental N additions field in an N-rich tropical forest of South China. There were four N additions levels: no additions (Control); 50 kg N ha−1 yr−1 (Low-N); 100 kg N ha−1 yr−1 (Medium-N), and 150 kg N ha−1 yr−1 (High-N). Results showed that long-term N additions significantly decreased microbial biomass carbon (MBC) and nitrogen (MBN), but had little effects on total PLFAs. However, elevated N inputs significantly reduced the relative abundance of bacterial PLFAs, especially gram-negative bacterial PLFAs with higher gram-positive bacteria: gram-negative bacteria ratio in N treatment plots. Although N additions did not change fungi: bacteria ratio, the proportion of arbuscular mycorrhizal fungi increased significantly with N additions. Long-term N additions greatly increased bacterial stress indexes and enhanced specific enzyme activity (activity per unit of microbial biomass) involved in carbon, nitrogen and phosphorus mineralization. Meanwhile, shifts in microbial community composition and specific enzyme activity were correlated well with soil pH and available N. These results suggest that N-mediated environmental stresses can play an important role in shaping microbial community, and that soil microbes will invest more resources on enzyme production in N-rich forest under elevated N deposition.
•Nitrogen additions decreased microbial biomass carbon and nitrogen.•Nitrogen additions shifted microbial community composition.•Bacterial stress indexes increased with elevated nitrogen inputs.•Nitrogen additions enhanced both absolute and specific enzyme activity.
Bio-production of optically pure l-lactic acid from food waste has attracted much interest as it can treat organic wastes with simultaneous recovery of valuable by-products. However, the yield of ...l-lactic acid was very low and no optically pure l-lactic acid was produced in the literature due to (1) the lower activity of enzymes involved in hydrolysis and l-lactic acid generation, and (2) the participation of other enzymes related to d-lactic acid and acetic and propionic acids production. In this paper, a new strategy was reported for effective production of optically pure l-lactic acid from food waste at ambient temperature, i.e. via regulating key enzyme activity by sewage sludge supplement and intermittent alkaline fermentation. It was found that not only optically pure l-lactic acid was produced, but the yield was enhanced by 2.89-fold. The mechanism study showed that the activities of enzymes relevant to food waste hydrolysis and lactic acid production were enhanced, and the key enzymes related to volatile fatty acids and d-lactic acid generations were severally decreased or inhibited. Also, the microbes responsible for l-lactic acid production were selectively proliferated. Finally, the pilot-scale continuous experiment was conducted to testify the feasibility of this new technique.
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•A new process for enhancing optically pure l-lactic acid production was reported.•Synergistic effect between food waste and sludge on hydrolysis was observed.•Intermittent alkaline fermentation led to exclusively l-lactic acid generation.•The pilot-scale experiment testified the feasibility of this new technique.
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