Insoluble prokaryotic membrane lipids in a Sphagnum peat: Implications for organic matter preservation

Torres, Lidia Chaves; Pancost, Richard D.

doi:10.1016/j.orggeochem.2015.12.013

Cited by 14 publications

(25 citation statements)

References 149 publications

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“…It is also highly variable, as reflected by those ranges, amongst the three samples measured here. With the exception of archaeol, which has not been observed previously in IOM of peat and marine sediments, these findings are consistent with previous work from profoundly different settings (Chaves Torres & Pancost, ; Chaves Torres et al., ).…”

Section: Discussionsupporting

confidence: 93%

“…Here, we focus on the comparison of prokaryotic membrane lipids obtained from solvent extraction, BD and Sox, versus the analogues in IOM fractions, BHy and AMe. These findings are interpreted in the context of previous findings from a peat profile (Chaves Torres & Pancost, ) and coastal marine sediments (Chaves Torres et al., ), which were explored using the same methodology as in the current TVZ silica sinters. This allows us to explore the implications of insolubisation on the determination and interpretation of lipid biomarkers.…”

Section: Discussionsupporting

confidence: 61%

“…Additionally, i‐GDGTs of all extracts were analysed via HPLC‐MS. All instrumental details for lipid analysis are published elsewhere (Chaves Torres & Pancost, ). We target particular prokaryotic lipids, such as (see Appendix) branched FAs (I–IV), hopanoids (V, VI), DAGEs (VII), archaeol (VIII) and i‐GDGTs (IX–XIV).…”

Section: Methodsmentioning

confidence: 99%

“…This represents only a small percentage (<3.5%) of the total organic carbon (TOC) of the sinters (see Supporting information), but it is crucial for understanding the partitioning of these biomarkers. Finally, the use of prokaryotic lipids as biomarkers in the current study enables a comparison to previous work on peat (Chaves Torres & Pancost, ) and marine sediments (Chaves Torres, Melbourne, Hernandez‐Sanchez, Inglis, & Pancost, ), and therefore, to assess whether previous findings apply in a setting where there is no wider OM matrix, that is whether previously observed patterns for IOM occurrence/formation are consistent across the geosphere.…”

Section: Introductionmentioning

confidence: 90%

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Selective chemical degradation of silica sinters of the Taupo Volcanic Zone (New Zealand). Implications for early Earth and Astrobiology

et al. 2019

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Most organic matter (OM) on Earth occurs as kerogen‐like materials, that is naturally formed macromolecules insoluble with standard organic solvents. The formation of this insoluble organic matter (IOM) is a topic of much interest, especially when it limits the detection of compounds of geomicrobiological interest. For example, studies that search for biomarker evidence of life on early Earth or other planets usually use solvent‐based extractions. This leaves behind a pool of OM as unexplored post‐extraction residues, potentially containing diagnostic biomarkers. Since the IOM has an enhanced potential for preservation compared to soluble OM, analysing IOM‐released biomarkers can also provide even deeper insights into the ecology of ancient settings, with implications for early Earth and Astrobiology investigations. Here, we analyse the prokaryotic lipid biosignature within soluble and IOM of the Taupo Volcanic Zone (TVZ) silica sinters, which are key analogues in the search for life. We apply sequential solvent extractions and a selective chemical degradation upon the post‐solvent extraction residue. Moreover, we compare the IOM from TVZ sinters to analogous studies on peat and marine sediments to assess patterns in OM insolubilisation across the geosphere. Consistent with previous work, we find significant but variable proportions—1%–45% of the total prokaryotic lipids recovered—associated with IOM fractions. This occurs even in recently formed silica sinters, likely indicating inherent cell insolubility. Moreover, archaeal lipids seem more prone to insolubilisation as compared to the bacterial analogues, which might enhance their preservation and also bias overall biomarkers interpretation. These observations are similar to those observed in other settings, confirming that even in a setting where the OM derives predominantly from prokaryotic sources, patterns of IOM formation/occurrence are conserved. Differences with other settings, however, such as the occurrence of archaeol in IOM fractions, could be indicative of different mechanisms for IOM formation that merit further exploration.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 61%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 90%

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Selective chemical degradation of silica sinters of the Taupo Volcanic Zone (New Zealand). Implications for early Earth and Astrobiology

et al. 2019

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“…It has previously been reported that not all GDGTs present in lake sediments, soils, and/or peatlands are accessible through common extraction techniques (i.e., P‐BD, Soxhlet‐, and accelerated solvent extraction) (Huguet et al c , d ; Tierney et al ; Chaves Torres and Pancost ). In all of these studies, considerable amounts of GDGTs could still be released from the post‐extraction residues by acid hydrolysis, giving rise to the hypothesis that parts of the GDGT pool had been “insolubilized” (i.e., by encapsulation in organic macromolecules, in organo‐mineral complexes, or in soil‐ or sediment aggregates; see Lützow et al for review).…”

Section: Discussionmentioning

confidence: 99%

Incomplete recovery of intact polar glycerol dialkyl glycerol tetraethers from lacustrine suspended biomass

Weber

Damsté

Hopmans

et al. 2017

Limnol. Oceanogr. Methods

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Branched and isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) are membrane lipids of bacteria and archaea, 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 the presence and abundance of GDGT‐producing microbes within the water column. GDGTs are, however, not always easily recovered from cultured microbial cells by commonly applied extraction methods, and this may also apply to suspended particulate matter (SPM) in aquatic systems. In order to investigate potential biases induced by incomplete GDGT recovery, we analyzed both core‐ and IPL‐GDGTs in SPM from Lake Lugano (Switzerland) using (1) ultrasonic solvent extraction with mixtures of methanol (MeOH) and dichloromethane (DCM), and (2) two modifications of the Bligh–Dyer (BD) protocol. Acid hydrolysis of the post‐extraction residues revealed that particularly branched GDGTs were poorly recovered from SPM by the MeOH/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 partitioned into the aqueous phosphate buffer that is usually discarded. In contrast, when this buffer was substituted with 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‐ and archaeal IPL‐GDGTs can be difficult to extract from lacustrine microbial communities, and caution is advised when targeting the “viable” GDGT pool.

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Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids

Naafs

Inglis

Zheng

et al. 2017

Geochimica et Cosmochimica Acta

213

175

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International audienceGlycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from Bacteria and Archaea that are ubiquitous in a range of natural archives and especially abundant in peat. Previous work demonstrated that the distribution of bacterial branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors such as mean annual air temperature (MAAT) and soil pH. However, the influence of these parameters on brGDGT distributions in peat is largely unknown. Here we investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the world with a broad mean annual air temperature (−8 to 27 °C) and pH (3–8) range and present the first peat-specific brGDGT-based temperature and pH calibrations. Our results demonstrate that the degree of cyclisation of brGDGTs in peat is positively correlated with pH, pH = 2.49 x CBTpeat + 8.07 (n = 51, R2 = 0.58, RMSE = 0.8) and the degree of methylation of brGDGTs is positively correlated with MAAT, MAATpeat (°C) = 52.18 x MBT5me’ – 23.05 (n = 96, R2 = 0.76, RMSE = 4.7 °C). These peat-specific calibrations are distinct from the available mineral soil calibrations. In light of the error in the temperature calibration (∼ 4.7 °C), we urge caution in any application to reconstruct late Holocene climate variability, where the climatic signals are relatively small, and the duration of excursions could be brief. Instead, these proxies are well-suited to reconstruct large amplitude, longer-term shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit spanning the late glacial period (∼15.2 kyr), we demonstrate that MAATpeat yields absolute temperatures and relative temperature changes that are consistent with those from other proxies. In addition, the application of MAATpeat to fossil peat (i.e. lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We conclude that there is clear potential to use brGDGTs in peats and lignites to reconstruct past terrestrial climate

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Insoluble prokaryotic membrane lipids in a Sphagnum peat: Implications for organic matter preservation

Cited by 14 publications

References 149 publications

Selective chemical degradation of silica sinters of the Taupo Volcanic Zone (New Zealand). Implications for early Earth and Astrobiology

Selective chemical degradation of silica sinters of the Taupo Volcanic Zone (New Zealand). Implications for early Earth and Astrobiology

Incomplete recovery of intact polar glycerol dialkyl glycerol tetraethers from lacustrine suspended biomass

Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids

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