Optimizing sample pretreatment for compound-specific stable carbon isotopic analysis of amino sugars in marine sediment
Author:
Zhu R., Lin Y.-S.ORCID, Lipp J. S., Meador T. B.ORCID, Hinrichs K.-U.
Abstract
Abstract. Amino sugars are quantitatively significant constituents of soil and marine sediment, but their sources and turnover in environmental samples remain poorly understood. The stable carbon isotopic composition of amino sugars can provide information on the lifestyles of their source organisms and can be monitored during incubations with labeled substrates to estimate the turnover rates of microbial populations. However, until now, such investigation has been carried out only with soil samples, partly because of the much lower abundance of amino sugars in marine environments. We therefore optimized a procedure for compound-specific isotopic analysis of amino sugars in marine sediment employing gas chromatography-isotope ratio mass spectrometry. The whole procedure consisted of hydrolysis, neutralization, enrichment, and derivatization of amino sugars. Except for the derivatization step, the protocol introduced negligible isotopic fractionation, and the minimum requirement of amino sugar for isotopic analysis was 20 ng, i.e. equivalent to ~ 8 ng of amino sugar carbon. Our results obtained from δ13C analysis of amino sugars in selected marine sediment samples showed that muramic acid had isotopic imprints from indigenous bacterial activities, whereas glucosamine and galactosamine were mainly derived from organic detritus. The analysis of stable carbon isotopic compositions of amino sugars opens a promising window for the investigation of microbial metabolisms in marine sediments and the deep marine biosphere.
Publisher
Copernicus GmbH
Reference46 articles.
1. Aluwihare, L. I. and Meador, T. B. (Eds.): Chemical composition of marine dissolved organic nitrogen, in: Nitrogen in the Marine Environment, Elsevier, Oxford, UK, 95–140, 2008. 2. Aluwihare, L. I., Repeta, D. J., Pantoja, S., and Johnson, C. G.: Two chemically distinct pools of organic nitrogen accumulate in the ocean, Science, 308, 1007–1010, 2005. 3. Amelung, W., Cheshire, M. V., and Guggenberger, G.: Determination of neutral and acidic sugars in soil by capillary gas-liquid chromatography after trifluoroacetic acid hydrolysis, Soil Biol. Biochem., 28, 1631–1639, 1996. 4. Amelung, W., Zhang, X., Flach, K. W., and Zech, W.: Amino sugars in native grassland soils along a climosequence in North America, Soil Sci. Soc. Am. J., 63, 86–92, 1999. 5. Bai, Z., Bode, S., Huygens, D., Zhang, X., and Boeckx, P.: Kinetics of amino sugar formation from organic residues of different quality, Soil Biol. Biochem., 57, 814–821, 2012.
|
|