Multiple Enzyme Analyzer (MEA): Steps toward the in situ detection of microbial community ectoenzyme activities

Jaeger, Stephanie A.; Gaas, Brian M.; Klinkhammer, Gary P.; Ammerman, James W.

doi:10.4319/lom.2009.7.716

Cited by 4 publications

(1 citation statement)

References 34 publications

(33 reference statements)

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“…Blanks were assessed using boiled seawater, and linearity of the assay was checked weekly with a set of MUF standards (Sigma-Aldrich). Activities were calculated according to Jaeger et al (2009).…”

Section: Methodsmentioning

confidence: 99%

Arsenic and phosphorus biogeochemistry in the ocean: Arsenic species as proxies for P‐limitation

Wurl

Zimmer

Cutter

2013

Limnology & Oceanography

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Arsenic and phosphorus are biochemically very similar, and hence arsenate (As 5+ ) is toxic by interfering with the energy metabolism, in particular during P limitation. However, many phytoplankton detoxify As by reducing arsenate to arsenite (As 3+ ), and/or methylating it to mono and dimethyl As. Such As detoxification becomes operative in oligotrophic waters when phosphate concentrations are below those for As; therefore, we evaluated the potential use of these detoxification products as indicators of P limitation by measuring As speciation during the US GEOTRACES North Atlantic transect. The distribution of As 3+ concentrations in surface waters is similar to that of N : P ratios and alkaline phosphatase activity (APA), two conventional proxies for P-limitation. As 3+ concentrations have a very similar relationship to phosphate as APA to phosphate, and therefore indicate the potential of As 3+ as proxy for P-limitation. From the relationship to phosphate we derived threshold values of As 3+ concentration to indicate moderate and extreme P-limitation. We then applied these threshold values to assess P-limitation with high horizontal resolution in the North Atlantic, improving on the contradictory assessments using the conventional proxies. Our new evaluation is consistent with the general concept that the North Atlantic is moderately to extremely limited in phosphate.Arsenic and phosphorus are biochemically very similar, so that phytoplanktonic uptake of arsenate (As 5+ ) induces toxic effects due to its substitution in the adenotriphosphate (ATP) cycle, effectively decoupling the energy metabolism (Lehninger 1975). Many phytoplankton species evolved different strategies to ameliorate the toxic effects of As 5+ , including reduction to arsenite (As 3+ ) and methylation to monomethyl-(MMAs) and dimethylarsenic (DMAs). These detoxification products are less harmful and easier to excrete (Andreae and Klumpp 1979;Sanders and Riedel 1993;Hellweger et al. 2003). Hellweger et al. (2003) proposed a mechanistic model with a limited methylation capacity due to slower kinetics compared with the preceding reduction. Such capacity may be exceeded during luxury P uptake because the chances of taking up As 5+ increase with higher rates of P uptake. Hellweger et al. (2003) proposed that exceeding methylation capacity leads to the excretion of the reduced As 3+ . Surface waters of oligotrophic central gyres have particularly high As : P ratios, with As 5+ concentrations in a range of 10-15 nmol L 21 (Cutter et al. 2001;Cutter and Cutter 2006), while phosphate is typically within a range of 0.2-10 nmol L 21 (Wu et al.

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Section: Methodsmentioning

confidence: 99%

Arsenic and phosphorus biogeochemistry in the ocean: Arsenic species as proxies for P‐limitation

Wurl

Zimmer

Cutter

2013

Limnology & Oceanography

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Advances in Biochemical Indices of Zooplankton Production

Yebra

Kobari

Sastri

et al. 2017

Advances in Marine Biology

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Quantification of small-scale heterogeneity in aquatic aminopeptidase activity

Gaas

Ammerman

2020

Aquat. Microb. Ecol.

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Leucine aminopeptidase (LAP) is one of the enzymes involved in the hydrolysis of peptides, and is sometimes used to indicate potential nitrogen limitation in microbes. Small-scale variability has the potential to confound interpretation of underlying patterns in LAP activity in time or space. An automated flow-injection analysis instrument was used to address the small-scale variability of LAP activity within contiguous regions of the Hudson River plume (New Jersey, USA). LAP activity had a coefficient of variation (CV) of ca. 0.5 with occasional values above 1.0. The mean CVs for other biological parameters—chlorophyll fluorescence and nitrate concentration—were similar, and were much lower for salinity. LAP activity changed by an average of 35 nmol l-1 h-1 at different salinities, and variations in LAP activity were higher crossing region boundaries than within a region. Differences in LAP activity were ±100 nmol l-1 h-1 between sequential samples spaced <10 m apart. Variogram analysis indicated an inherent spatial variability of 52 nmol l-1 h-1 throughout the study area. Large changes in LAP activity were often associated with small changes in salinity and chlorophyll fluorescence, and were sensitive to the sampling frequency. This study concludes that LAP measurements in a sample could realistically be expected to range from zero to twice the average, and changes between areas or times should be at least 2-fold to have some degree of confidence that apparent patterns (or lack thereof) in activity are real.

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Multiple Enzyme Analyzer (MEA): Steps toward the in situ detection of microbial community ectoenzyme activities

Cited by 4 publications

References 34 publications

Arsenic and phosphorus biogeochemistry in the ocean: Arsenic species as proxies for P‐limitation

Arsenic and phosphorus biogeochemistry in the ocean: Arsenic species as proxies for P‐limitation

Advances in Biochemical Indices of Zooplankton Production

Quantification of small-scale heterogeneity in aquatic aminopeptidase activity

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