Incomplete recovery of intact polar glycerol dialkyl glycerol tetraethers from lacustrine suspended biomass
Weber, Y.; Sinninghe Damsté, J.S.; Hopmans, E.C.; Lehmann, M.F.; Niemann, H. (2017). Incomplete recovery of intact polar glycerol dialkyl glycerol tetraethers from lacustrine suspended biomass. Limnol. Oceanogr., Methods 15(9): 782–793. https://dx.doi.org/10.1002/lom3.10198 In: Limnology and Oceanography: Methods. American Society of Limnology and Oceanography: Waco, Tex.. ISSN 1541-5856; e-ISSN 1541-5856, more |   |
| Authors | | Top | - Weber, Y.
- Sinninghe Damsté, J.S., more
- Hopmans, E.C., more
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| Abstract | Branched and isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) are membrane lipids of bacteria andarchaea, respectively, and their core lipid distributions are used as proxy indicators in paleolimnological studies.In addition, the amount and composition of intact polar lipid (IPL) GDGTs yield information on thepresence and abundance of GDGT-producing microbes within the water column. GDGTs are, however, notalways easily recovered from cultured microbial cells by commonly applied extraction methods, and thismay also apply to suspended particulate matter (SPM) in aquatic systems. In order to investigate potentialbiases induced by incomplete GDGT recovery, we analyzed both core- and IPL-GDGTs in SPM from LakeLugano (Switzerland) using (1) ultrasonic solvent extraction with mixtures of methanol (MeOH) anddichloromethane (DCM), and (2) two modifications of the Bligh–Dyer (BD) protocol. Acid hydrolysis of thepost-extraction residues revealed that particularly branched GDGTs were poorly recovered from SPM by theMeOH/DCM mixtures (25–62%). Much better extraction yields (> 85%) were achieved with the BD method,however, during subsequent phase separation, up to 75% of the extracted branched IPL-GDGTs partitionedinto the aqueous phosphate buffer that is usually discarded. In contrast, when this buffer was substitutedwith 5% trichloroacetic acid, only 13% were lost into the aqueous phase. Depending on the protocol used,the distribution of the IPL-derived GDGTs varied substantially. Our results indicate that both bacterial- andarchaeal IPL-GDGTs can be difficult to extract from lacustrine microbial communities, and caution is advisedwhen targeting the “viable” GDGT pool. |
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