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Stable isotope switching (SIS): a new stable isotope probing (SIP) approach to determine carbon flow in the soil food web and dynamics in organic matter pools
Author(s) -
Maxfield P. J.,
Dildar N.,
Hornibrook E. R. C.,
Stott A. W.,
Evershed R. P.
Publication year - 2012
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6172
Subject(s) - chemistry , isotopes of carbon , stable isotope probing , isotope analysis , isotope ratio mass spectrometry , stable isotope ratio , soil water , environmental chemistry , population , isotope , organic matter , microbial food web , carbon fibers , soil carbon , mass spectrometry , total organic carbon , bacteria , chromatography , soil science , nutrient , phytoplankton , ecology , organic chemistry , microorganism , materials science , environmental science , sociology , composite number , composite material , biology , genetics , quantum mechanics , physics , demography
RATIONALE Recent advances in stable isotope probing (SIP) have allowed direct linkage of microbial population structure and function. This paper details a new development of SIP, Stable Isotope Switching (SIS), which allows the simultaneous assessment of carbon (C) uptake, turnover and decay, and the elucidation of soil food webs within complex soils or sedimentary matrices. METHODS SIS utilises a stable isotope labelling approach whereby the 13 C‐labelled substrate is switched part way through the incubation to a natural abundance substrate. A 13 CH 4 SIS study of landfill cover soils from Odcombe (Somerset, UK) was conducted. Carbon assimilation and dissimilation processes were monitored through bulk elemental analysis isotope ratio mass spectrometry and compound‐specific gas chromatography/combustion/isotope ratio mass spectrometry, targeting a wide range of biomolecular components including: lipids, proteins and carbohydrates. RESULTS Carbon assimilation by primary consumers (methanotrophs) and sequential assimilation into secondary (Gram‐negative and ‐positive bacteria) and tertiary consumers (Eukaryotes) was observed. Up to 45% of the bacterial membrane lipid C was determined to be directly derived from CH 4 and at the conclusion of the experiment ca. 50% of the bulk soil C derived directly from CH 4 was retained within the soil. CONCLUSIONS This is the first estimate of soil organic carbon derived from CH 4 and it is comparable with levels observed in lakes that have high levels of benthic methanogenesis. SIS opens the way for a new generation of SIP studies aimed at elucidating total C dynamics (incorporation, turnover and decay) at the molecular level in a wide range of complex environmental and biological matrices. Copyright © 2012 John Wiley & Sons, Ltd.