Carbon isotopic fractionation in heterotrophic microbial metabolism

Blair, Neal E.; Leu, Andy O.; Munoz, Elaine F.; Olsen, Jan Vidar; Kwong, Eva; Marais, Des

doi:10.1128/aem.50.4.996-1001.1985

Cited by 374 publications

(202 citation statements)

References 32 publications

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“…Our previous studies Hopkins et al, 2008a) indicated an important contribution from lacustrine detritus, but the present study confirms that the lacustrine material subsidizes the terrestrially derived organic matter arising from either endolithic organisms or mosses, or both. The small relative 13 C depletion of CO2 (by no more than 3‰ relative to the soil) produced during decomposition of lacustrine detritus is consistent with the preferential loss of 12 CO2 during decomposer respiration (Blair et al, 1985). It cannot account for the GV soils being more 13 C-depleted (by 5-10‰) than the lacustrine detritus because preferential loss of 12 C in CO2 from decomposer respiration would lead to the soils being less, not more, 13 C-depleted.…”

Section: Provenance Of the Soil Organic Mattermentioning

confidence: 78%

Isotopic evidence for the provenance and turnover of organic carbon by soil microorganisms in the Antarctic dry valleys

Hopkins

Sparrow

Gregorich

et al. 2009

Environmental Microbiology

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SummaryThe extremely cold and arid Antarctic dry valleys are one of the most environmentally harsh terrestrial ecosystems supporting organisms in which the biogeochemical transformations of carbon are exclusively driven by microorganisms. The natural abundance of 13 C and 15 N in source organic materials and soils have been examined to obtain evidence for the provenance of the soil organic matter and the C loss as CO2 during extended incubation (approximately 1200 days at 10°C under moist conditions) has been used to determine the potential decay of soil organic C. The organic matter in soils remote from sources of liquid water or where lacustrine productivity was low had isotope signatures characteristic of endolithic (lichen) sources, whereas at more sheltered and productive sites, the organic matter in the soils that was a mixture mainly lacustrine detritus and moss-derived organic matter. Soil organic C declined by up to 42% during extended incubation under laboratory conditions (equivalent to 50-73 years in the field on a thermal time basis), indicating relatively fast turnover, consistent with previous studies indicating mean residence times for soil organic C in dry valley soils in the range 52-123 years and also with recent inputs of relatively labile source materials.

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Section: Provenance Of the Soil Organic Mattermentioning

confidence: 78%

Isotopic evidence for the provenance and turnover of organic carbon by soil microorganisms in the Antarctic dry valleys

Hopkins

Sparrow

Gregorich

et al. 2009

Environmental Microbiology

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“…Considering that the non-protein carbon sources had a d 13 C value of )11&, the observed d 13 C values would require an unreasonably large discrimination against 12 C during microbial biosynthesis. Previous work suggests that microbial synthesis of amino acids by heterotrophic microbes has modest discrimination values and often discriminates against 13 C (Blair et al 1985;Macko et al 1987). Because an incorrect estimate of d M will lead to biased estimates of p M (%), the model needs to be constrained with realistic values for d M .…”

Section: H O W M U C H D O E S M I C R O B I O T a C O N T R I B U T mentioning

confidence: 99%

Contributions of direct incorporation from diet and microbial amino acids to protein synthesis in Nile tilapia

et al. 2011

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Summary 1.Further advancement in the use of stable isotope analysis in animal ecology and physiology requires a better understanding of how organisms incorporate the macromolecular elements they consume into the tissues they biosynthesize. 2. Mixing models used to infer diets from isotopic data assume that assimilated macromolecules are dissembled into elements and then reassembled in animal tissues. 3. To test this assumption, we fed Nile tilapia diets with contrasting levels of protein and in which the carbon isotopic composition of protein differed from that of other macronutrients (carbohydrates and lipids). We then analysed the d13 C values of individual tilapia amino acids using compound-specific stable isotope analysis (CSIA). 4. C values of their corresponding dietary amino acid as protein intake increased. This pattern is consistent with assimilation of indispensable amino acids of microbial origin by tilapias fed low protein food. 6. Our results suggest that the assumptions of mixing models are sound in situations where omnivores consume protein-deficient diets, as the elemental constituents used to biosynthesize amino acids in tissues may be derived from various ingested macromolecules (e.g. protein, carbohydrates, or lipids) and their elemental components. In contrast, for omnivores that consume sufficient amounts of protein, macromolecular (e.g. protein) routing likely occurs and mixing model assumptions are violated. 7. Our study shows that CSIA is a novel method to quantify the contribution of symbiotic microbes to the amino acid homeostasis of animals.

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“…The isotopic content of microorganisms depends on that of their substrate: on assimilatory fractionation, but also on the availability of the substrate (Mariotti 1982). They are probably enriched in 13 C relative to litter (Blair et al 1985, Gleixner et al 1993, Å gren et al 1996; but see also Creach [1995]), but it is difficult to generalize about nitrogen enrichment, since contradictory results have been found (Macko and Estep 1984, Ziemans et al 1984, Macko et al 1987, Melillo et al 1989. For now, we can hypothesize that microorganisms are a potential food source for detritivores that is enriched in 13 C, compared to original leaf tissues in the litter, but it is not possible to say whether they are enriched or depleted in 15 N. Nadelhoffer and Fry (1988) showed that different biochemical components of the litter had very similar ␦ 15 N values.…”

Section: Isotopic Signals In the Soil And Littermentioning

confidence: 99%

What Can Stable Isotopes (δ 15 N and δ 13 C) Tell about the Food Web of Soil Macro-Invertebrates?

Ponsard¹,

Arditi²

2000

Ecology

115

181

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Animals reflect the stable isotope ratios (␦ 15 N and ␦ 13 C) of their diet, with a slight enrichment in 15 N that allows the use of ␦ 15 N as a trophic-level indicator. Stable isotope contents were measured for the litter, soil, and macro-invertebrates of three temperate deciduous forest sites, in spring, summer, and autumn, to study the trophic structure of this community. No distinct trophic structure could be derived from measurements of ␦ 13 C. In contrast, when the ␦ 15 N values of all animal species were grouped together, the hypothesis of an isotopically similar diet was rejected. Therefore, the community spreads over more than one trophic level and was subdivided into detritivores and predators. The potential detritivore food sources in the forest litter and soil showed a variety of isotopic ratios. Despite this fact, the variance of the isotopic ratios of the detritivorous species was not larger than what could be expected from interspecific variability of trophic isotopic enrichment alone. This was also the case for the predators in most of the sample sets. However, in some cases this variance was significantly larger, due to a small number of species with high ␦ 15 N values. The ␦ 15 N values of the detritivores indicated that the mean ␦ 15 N value of their food was close to that measured for the superficial litter layers. The difference in ␦ 15 N between detritivores and predators was highly significant and never significantly different from the value expected for one trophic transfer (3.4‰), although often slightly higher. Most of the litter macro-invertebrate community we studied can therefore be described as belonging to two trophic levels, one feeding on the superficial litter layers (or on soil fractions that have a similar ␦ 15 N value), and a second trophic level feeding on the first, with some indication of intraguild predation among the predators.Between-site differences of up to 7‰ were found for ␦ 15 N in the litter, and the ␦ 15 N values of the whole animal community were shifted in accordance with the local value of the litter ␦ 15 N. Therefore, the trophic structure must be studied in relation to the local isotopic content of the litter. Seasonal differences in isotopic ratios of the litter or animal samples were neither large nor consistent. These findings indicate similar trophic structure of the communities at the three sites and during the three sampling periods.

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Carbon isotopic fractionation in heterotrophic microbial metabolism

Cited by 374 publications

References 32 publications

Isotopic evidence for the provenance and turnover of organic carbon by soil microorganisms in the Antarctic dry valleys

Isotopic evidence for the provenance and turnover of organic carbon by soil microorganisms in the Antarctic dry valleys

Contributions of direct incorporation from diet and microbial amino acids to protein synthesis in Nile tilapia

What Can Stable Isotopes (δ 15 N and δ 13 C) Tell about the Food Web of Soil Macro-Invertebrates?

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