Methodologies for Extracellular Enzyme Assays from Wetland Soils

Dunn, Christian; Jones, Timothy G. J.; Girard, Astrid; Freeman, Chris

doi:10.1007/s13157-013-0475-0

Cited by 64 publications

(31 citation statements)

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“…Phosphomonoesterases were found to have the highest activities despite the inherent overestimation of phosphodiesterase activities when using MUF-tagged substrates (Sirová et al, 2013). The opposite trend was observed for glycopyranoside, part of the cellulose degradation pathway (Dunn et al, 2013), which showed consistently higher activity (69 % p =< 0.05) under anoxic conditions (Fig. 6b).…”

Section: Hydrolytic Enzyme Activitiesmentioning

confidence: 88%

“…Degradation rates for phosphomonoesters, phosphodiesters and pyrophosphate were determined fluorometrically through use of the MUF-tagged substrates: MUF phosphate (MUP), bis(MUF)phosphate (DiMUP, Chem-Impex International) and MUF pyrophosphate (PYRO-P, Chem-Impex International) respectively. Additionally MUF β-D-glucopyranoside (MUGb) was used in order to compare phosphatase enzyme activity to the activity of β-glucosidase (cellulase) (Dunn et al, 2013). Enzyme activities were determined using a microplate reader (Flexstation3, Molecular Devices) using a modification of Deng et al (2013).…”

Section: Extracellular Enzyme Assaysmentioning

confidence: 99%

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Sediment phosphorus speciation and mobility under dynamic redox conditions

Parsons¹,

Rezanezhad²,

O’Connell³

et al. 2017

Biogeosciences

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Abstract. Anthropogenic nutrient enrichment has caused phosphorus (P) accumulation in many freshwater sediments, raising concerns that internal loading from legacy P may delay the recovery of aquatic ecosystems suffering from eutrophication. Benthic recycling of P strongly depends on the redox regime within surficial sediment. In many shallow environments, redox conditions tend to be highly dynamic as a result of, among others, bioturbation by macrofauna, root activity, sediment resuspension and seasonal variations in bottom-water oxygen (O 2 ) concentrations. To gain insight into the mobility and biogeochemistry of P under fluctuating redox conditions, a suspension of sediment from a hypereutrophic freshwater marsh was exposed to alternating 7-day periods of purging with air and nitrogen gas (N 2 ), for a total duration of 74 days, in a bioreactor system. We present comprehensive data time series of bulk aqueous-and solidphase chemistry, solid-phase phosphorus speciation and hydrolytic enzyme activities demonstrating the mass balanced redistribution of P in sediment during redox cycling. Aqueous phosphate concentrations remained low (∼ 2.5 µM) under oxic conditions due to sorption to iron(III) oxyhydroxides. During anoxic periods, once nitrate was depleted, the reductive dissolution of iron(III) oxyhydroxides released P. However, only 4.5 % of the released P accumulated in solution while the rest was redistributed between the MgCl 2 and NaHCO 3 extractable fractions of the solid phase. Thus, under the short redox fluctuations imposed in the experiments, P remobilization to the aqueous phase remained relatively limited. Orthophosphate predominated at all times during the experiment in both the solid and aqueous phase. Combined P monoesters and diesters accounted for between 9 and 16 % of sediment particulate P. Phosphatase activities up to 2.4 mmol h −1 kg −1 indicated the potential for rapid mineralization of organic P (P o ), in particular during periods of aeration when the activity of phosphomonoesterases was 37 % higher than under N 2 sparging. The results emphasize that the magnitude and timing of internal P loading during periods of anoxia are dependent on both P redistribution within sediments and bottom-water nitrate concentrations.

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Section: Hydrolytic Enzyme Activitiesmentioning

confidence: 88%

Section: Extracellular Enzyme Assaysmentioning

confidence: 99%

Sediment phosphorus speciation and mobility under dynamic redox conditions

Parsons¹,

Rezanezhad²,

O’Connell³

et al. 2017

Biogeosciences

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“…The activity of a range of hydrolase enzymes (namely; β-D-glucosidase, sulphatase, β-D-xylosidase, N-acetyl-B-D-glucosaminidase and phosphatase) was calculated from a series of peat slurries made with varying concentrations of Ca lignosulphonate using the protocol as outlined by Dunn et al (2014). These slurries were made and stored in the same way as described before, and were left for 24 hours before the assays were conducted.…”

Section: Peatmentioning

confidence: 99%

The role of molecular weight in the enzyme-inhibiting effect of phenolics: the significance in peatland carbon sequestration

Dunn

Freeman

2018

Ecological Engineering

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Northern peatlands store 455 Pg of carbon-a third of the entire global carbon store. Carbon accumulates because phenolic inhibitors slow the rate of decomposition to below that of photosynthetic production. The disproportionate importance of phenolics in peatlands is related to the unique properties of waterlogged peat soils suppressing the activity of phenol oxidase; one of the few enzymes capable of breaking these inhibitors down. This permits accumulation of phenolic compounds that are potent inhibitors of hydrolase enzymes-major agents in the breakdown of organic matter. In our study we investigate the importance of molecular weight of natural phenolic inhibitors on microbial decomposition in peat. We found the higher the molecular weight, of a phenolic compound, the greater its inhibitory effect on the breakdown of organic matter.

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“…Analysis of hydrolase activity was measured using a method modified from Freeman et al (1995), using 1 cm 3 of soil. Further information concerning the enzyme assays can be found in Dunn et al (2013).…”

Section: Laboratory Analysismentioning

confidence: 99%