Plastics accumulating in the environment, especially microplastics (defined as particles <5 mm), can lead to a range of problems and potential loss of ecosystem services. Polyhydroxyalkanoates (PHAs) ...are biodegradable plastics used in mulch films, and in packaging material to minimize plastic waste and to reduce soil pollution. Little is known, however, about the effect of microbioplastics on soil-plant interactions, especially soil microbial community structure and functioning in agroecosystems. For the first time, we combined zymography (to localize enzyme activity hotspots) with substrate-induced growth respiration to investigate the effect of PHAs addition on soil microbial community structure, growth, and exoenzyme kinetics in the microplastisphere (i.e. interface between soil and microplastic particles) compared to the rhizosphere and bulk soil. We used a common PHAs biopolymer, poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and showed that PHBV was readily used by the microbial community as a source of carbon (C) resulting in an increased specific microbial growth rate and a more active microbial biomass in the microplastisphere in comparison to the bulk soil. Higher β-glucosidase and leucine aminopeptidase activities (0.6–5.0 times higher Vmax) and lower enzyme affinities (1.5–2.0 times higher Km) were also detected in the microplastisphere relative to the rhizosphere. Furthermore, the PHBV addition changed the soil bacterial community at different taxonomical levels and increased the alpha diversity, as well as the relative abundance of Acidobacteria and Verrucomicrobia phyla, compared to the untreated soils. Overall, PHBV addition created soil hotspots where C and nutrient turnover is greatly enhanced, mainly driven by the accelerated microbial biomass and activity. In conclusion, microbioplastics have the potential to alter soil ecological functioning and biogeochemical cycling (e.g., SOM decomposition).
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•Microplastisphere (soil-MPs interface) is localized and visualized by zymography.•MPs stimulates microbial turnover and nutrient efficiency in microplastisphere.•MPs increases soil enzyme activity and shifts bacterial community to K-strategy.•MPs have the potential to alter soil functioning and biogeochemical cycling.
Ecoenzymatic stoichiometry links microbial decomposition with nutrient mineralization and improves our understanding of nutrient cycling in terrestrial ecosystems. Microbial C:N:P acquisition in the ...topsoil converged at a ratio of 1:1:1 in global ecosystems. However, whether the ratio of microbial acquisition is stable in forest soils, and is applicable among different soil depths remain unknown.
Based on large‐scale soil sampling in China's forests, we examined the patterns and environmental drivers of the eight most‐widely measured enzyme activities and the relevant stoichiometry.
We found that the ratio of C:N:P acquisition significantly deviated from 1:1:1. The specific enzyme activities (normalized by SOC) did not change significantly with latitude except those for xylosidase and acid phosphatase. Similarly, only the C:P acquisition ratio increased with latitude. Vertically, the specific activities of C‐acquiring enzymes mainly increased, N‐acquiring enzymes decreased and P‐acquiring enzymes did not change with soil depth. Moreover, all ratios of microbial acquisition decreased, and the percentage of recalcitrant C increased significantly with increasing depth. Our study also showed that temperature and soil C:N ratio were the important factors in explaining the variations in specific enzyme activities and microbial nutrient acquisition, respectively.
Our results indicated that no constant microbial C:N:P acquisition ratio can be widely recognized, and that SOC quality changed from labile to recalcitrant with depth. We highlight that depth‐dependent enzymatic processes should be considered in future SOC dynamic models.
A free Plain Language Summary can be found within the Supporting Information of this article.
A free Plain Language Summary can be found within the Supporting Information of this article.
Herein, we report a bottom-up approach to assemble a series of stochastic DNA walkers capable of probing dynamic interactions occurring at the bio–nano interface. We systematically investigated the ...impact of varying interfacial factors, including intramolecular interactions, orientation, cooperativity, steric effect, multivalence, and binding hindrance on enzymatic behaviors at the interfaces of spherical nucleic acids. Our mechanistic study has revealed critical roles of various interfacial factors that significantly alter molecular binding and enzymatic behaviors from bulk solutions. The improved understanding of the bio–nano interface may facilitate better design and operation of nanoparticle-based biosensors and/or functional devices. We successfully demonstrate how improved understanding of the bio–nano interface help rationalize the design of amplifiable biosensors for nucleic acids and antibodies.
•The 200μmolL−1 SNP treatment extended shelf life of broccoli florets.•The SNP treatment enhanced the activity of antioxidant enzymes in broccoli.•The SNP treatment delayed the chlorophyll ...degradation in broccoli.•The SNP treatment regulated the gene expression of chlorophyll-degrading enzymes.
The effect of an exogenous application of sodium nitroprusside (SNP) on the shelf life, antioxidant enzyme and chlorophyll-degrading enzyme activity, and chlorophyll-degradation related gene expression was investigated in stored broccoli. The preliminary results indicated that the 200μmolL−1 SNP treatment had the greatest effect on extending shelf life of broccoli florets so this concentration was used in the remainder of the study. The SNP treatment delayed chlorophyll degradation, thus color was maintained and shelf-life was extended. The activity of the antioxidant enzymes, catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) was all enhanced while glutathione reductase (GR) activity was inhibited throughout the storage. Relative to the untreated control, the SNP treatment suppressed the activity of the chlorophyll-degrading enzymes, chlorophyllase (Chlase), chlorophyll-degrading peroxidase (Chl-POX), Mg-dechelatase (MD), and pheophytinase (PPH), and also suppressed chlorophyllase I (BoCHL1), chlorophyllase II (BoCHL2), chlorophyllase III (BoCLH3) and pheophorbide a oxygenase (BoPAO) gene expression during the entire storage period. In summary, 200μmolL−1 SNP treatment of broccoli extends shelf life, enhances oxidative stress tolerance by enhancing the activity of antioxidant enzymes, and inhibits the activity of chlorophyll-degrading enzymes and related gene expression. The combined effect delayed the yellowing of broccoli florets by inhibiting chlorophyll degradation, thus extending the shelf life of broccoli florets.
•Joint effects of heavy metals and soil properties on soil enzyme activities were determined.•Arylsulfatase could be used as an indicator to study the toxicity of heavy metals.•Changes of ...arylsulfatase activity with SOM content fitted well an exponential model.•The model illustrated the offset of SOM to heavy metal toxicity on soil enzymes activities.
Soil enzyme activities are greatly influenced by soil properties and could be significant indicators of heavy metal toxicity in soil for bioavailability assessment. Two groups of experiments were conducted to determine the joint effects of heavy metals and soil properties on soil enzyme activities. Results showed that arylsulfatase was the most sensitive soil enzyme and could be used as an indicator to study the enzymatic toxicity of heavy metals under various soil properties. Soil organic matter (SOM) was the dominant factor affecting the activity of arylsulfatase in soil. A quantitative model was derived to predict the changes of arylsulfatase activity with SOM content. When the soil organic matter content was less than the critical point A (1.05% in our study), the arylsulfatase activity dropped rapidly. When the soil organic matter content was greater than the critical point A, the arylsulfatase activity gradually rose to higher levels showing that instead of harm the soil microbial activities were enhanced. The SOM content needs to be over the critical point B (2.42% in our study) to protect its microbial community from harm due to the severe Pb pollution (500mgkg−1 in our study). The quantitative model revealed the pattern of variation of enzymatic toxicity due to heavy metals under various SOM contents. The applicability of the model under wider soil properties need to be tested. The model however may provide a methodological basis for ecological risk assessment of heavy metals in soil.
Extracellular enzymes catalyze rate‐limiting steps in soil organic matter decomposition, and their activities (EEAs) play a key role in determining soil respiration (SR). Both EEAs and SR are highly ...sensitive to temperature, but their responses to climate warming remain poorly understood. Here, we present a meta‐analysis on the response of soil cellulase and ligninase activities and SR to warming, synthesizing data from 56 studies. We found that warming significantly enhanced ligninase activity by 21.4% but had no effect on cellulase activity. Increases in ligninase activity were positively correlated with changes in SR, while no such relationship was found for cellulase. The warming response of ligninase activity was more closely related to the responses of SR than a wide range of environmental and experimental methodological factors. Furthermore, warming effects on ligninase activity increased with experiment duration. These results suggest that soil microorganisms sustain long‐term increases in SR with warming by gradually increasing the degradation of the recalcitrant carbon pool.
The links between extracellular enzyme activities (EEAs) and soil respiration (SR) under warming scenarios remain poorly understood, despite both EEAs and SR are highly sensitive to temperatures. By synthesizing data from 56 studies, we showed that warming significantly increased ligninase activity by 21.4% and SR by 15.8%, while warming had no effect on cellulase activity. Moreover, increases in ligninase activity were positively correlated with SR and warming duration. These results reveal a novel mechanism that warming‐induced shifts in carbon‐degrading EEAs could contribute to the self‐reinforcing SR to long‐term climate warming.
There is growing interest in the use of probiotics as an alternative strategy for the promotion of growth rates and prevention of diseases in aquaculture. In this study, abalone Haliotis diversicolor ...were fed with different probiotic-supplemented diets for 180 days, containing Bacillus stratosphericus A3440, Phaeobacter daeponensis AP1220, and a mixture of the two strains. Probiotic supplementation significantly increased shell length and wet weight of juvenile abalone (p < 0.05). Compared with those non-treatment group, trypsin and lipase activities were increased significantly in the gastrointestinal tract of animals fed with A3440 or bacterial mixture (p < 0.05). A subsequent ten-day of challenging trial against Vibrio harveyi, the animals with AP1220 had ~90% survival rate as against ~60% survival rate for the non-treated animals. Likewise, in situ glutathione peroxidase, catalase, alkaline phosphatase, acid phosphatase, and superoxide dismutase assays showed that the probiotics significantly improved immune response of H. diversicolor (p < 0.05). 13,622 OTUs were obtained from abalone intestine microbiome by 16S rRNA high-throughput sequencing. Microbial diversity indices and richness estimates in the non-treated group declined before and after Vibrio infection trial. Conversely, these indexes enhanced to different levels in probiotics treatments, and the A3440 group restored and reached the highest value. Cluster analysis showed that probiotic could re-establish and subsequently balance the gut microbial community after the challenge trial. Furthermore, these potential probiotics had a positive effect on the number of beneficial endogenous bacteria in the abalone gut, such as bacilli and actinobacterial species. Thus, dietary administration of B. stratosphericus, P. daeponensis and their mixture could improve the nutrient and health status of abalone H. diversicolor.
•China is the most important abalone-producing country in the world. But the application of probiotics was limited.•The evaluation of the gut microbiome associated with host after probiotic supplementation, are less in China.•This study assessed effects of probiotics on growth, immune responses and pathogenic resistance of juvenile abalone.•By conjoint analysis of the growth-survival and gut microbiome, the possible mechanism of probiotics was elaborated.
Variability in the activity and composition of soil microbial communities may have important implications for the suite of microbially-derived ecosystem functions upon which agricultural systems ...rely, particularly organic agriculture. An on-farm approach was used to investigate microbial communities and soil carbon (C) and nitrogen (N) availability on 13 organically-managed fields growing Roma-type tomatoes, but differing in nutrient management, across an intensively-managed agricultural landscape in the Central Valley of California. Soil physicochemical characteristics, potential activities of nine soil enzymes involved in C, N, phosphorus (P), and sulfur (S) cycling, and fatty acid methyl esters (FAMEs) were measured during the growing season and evaluated with multivariate approaches. Soil texture and pH in the 0–15 cm surface layer were similar across the 13 fields, but there was a three-fold range of soil C and N as well as substantial variation in inorganic N and available P that reflected current and historical management practices. Redundancy analysis showed distinct profiles of enzyme activities across the fields, such that C-cycling enzyme potential activities increased with inorganic N availability while those of N-cycling enzymes increased with C availability. Although FAMEs suggested that microbial community composition was less variable across fields than enzyme activities, there were slight community differences that were related to organic amendments (manure vs. composted green waste). Overall, however, the general similarity among fields for particular taxonomic indicators, especially saprophytic fungi, likely reflects the high disturbance and low complexity in this landscape. Variation in potential enzyme activities was better accounted for with soil physicochemical characteristics than microbial community composition, suggesting high plasticity of the resident microbial community to environmental conditions. These patterns suggest that, in this landscape, differences in organic agroecosystem management have strongly influenced soil nutrients and enzyme activity, but without a major effect on soil microbial communities. The on-farm approach provided a wide range of farming practices and soil characteristics to reveal how microbially-derived ecosystem functions can be effectively manipulated to enhance nutrient cycling capacity.
•Soil microbial community activity and composition was investigated in 13 organic fields.•C-cycling enzyme activities increased with inorganic N availability.•N-cycling enzyme activities increased with C availability.•Microbial community composition was differentiated by organic amendment applied.
Fluoxetine (FLX), an emerging pollutant, has been detected in the sewage and excess sludge (ES) at substantial levels. So far, however, the impacts of FLX on the ES anaerobic digestion and the ...related mechanisms have never been investigated. In this work, the effects of FLX on the ES anaerobic digestion were explored by the batch test under moderate temperature condition. The results indicated the effect of FLX on ES digestion was dose-dependent. When FLX was at a low dose (0.1 mg/kg), FLX had no significant impact on the methane generation from the ES digestion. However，when FLX was 2.0 mg/kg, the cumulative methane production was only 91.2 ± 4.3 mL/g volatile suspended solids (VSS), which was about 59.9 ± 3.4% of the blank (without FLX). Mechanisms revealed that the presence of FLX has inhibited hydrolysis, acidification and methanogenesis. Enzyme activity analysis showed that FLX inhibited the activities of key enzymes in the process of hydrolysis, acidification and methanogenesis. The results of this work are of great significance to explain the role of FLX in the process of ES fermentation, and provide some reference for the subsequent utilization of ES.
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•The effect of FLX on ES digestion was explored for the first time.•The presence of FLX reduced methane accumulation from ES.•High content of FX inhibited ES hydrolysis and acidification process.
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