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Becker, Kevin W., Felix J. Elling, Marcos Y. Yoshinaga, Andrea Söllinger, Tim Urich y Kai-Uwe Hinrichs. "Unusual Butane- and Pentanetriol-Based Tetraether Lipids in Methanomassiliicoccus luminyensis, a Representative of the Seventh Order of Methanogens". Applied and Environmental Microbiology 82, n.º 15 (13 de mayo de 2016): 4505–16. http://dx.doi.org/10.1128/aem.00772-16.
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ABSTRACTA new clade of archaea has recently been proposed to constitute the seventh methanogenic order, theMethanomassiliicoccales, which is related to theThermoplasmatalesand the uncultivated archaeal clades deep-sea hydrothermal ventEuryarchaeotagroup 2 and marine group IIEuryarchaeotabut only distantly related to other methanogens. In this study, we investigated the membrane lipid composition ofMethanomassiliicoccus luminyensis, the sole cultured representative of this seventh order. The lipid inventory ofM. luminyensiscomprises a unique assemblage of novel lipids as well as lipids otherwise typical for thermophilic, methanogenic, or halophilic archaea. For instance, glycerol sesterpanyl-phytanyl diether core lipids found mainly in halophilic archaea were detected, and so were compounds bearing either heptose or methoxylated glycosidic head groups, neither of which have been reported so far for other archaea. The absence of quinones or methanophenazines is consistent with a biochemistry of methanogenesis different from that of the methanophenazine-containing methylotrophic methanogens. The most distinctive characteristic of the membrane lipid composition ofM. luminyensis, however, is the presence of tetraether lipids in which one glycerol backbone is replaced by either butane- or pentanetriol, i.e., lipids recently discovered in marine sediments. Butanetriol dibiphytanyl glycerol tetraether (BDGT) constitutes the most abundant core lipid type (>50% relative abundance) inM. luminyensis. We have thus identified a source for these unusual orphan lipids. The complementary analysis of diverse marine sediment samples showed that BDGTs are widespread in anoxic layers, suggesting an environmental significance ofMethanomassiliicoccalesand/or related BDGT producers beyond gastrointestinal tracts.IMPORTANCECellular membranes of members of all three domains of life,Archaea,Bacteria, andEukarya, are largely formed by lipids in which glycerol serves as backbone for the hydrophobic alkyl chains. Recently, however, archaeal tetraether lipids with either butanetriol or pentanetriol as a backbone were identified in marine sediments and attributed to uncultured sediment-dwelling archaea. Here we show that the butanetriol-based dibiphytanyl tetraethers constitute the major lipids inMethanomassiliicoccus luminyensis, currently the only isolate of the novel seventh order of methanogens. Given the absence of these lipids in a large set of archaeal isolates, these compounds may be diagnostic for theMethanomassiliicoccalesand/or closely related archaea.
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Sinninghe Damsté, Jaap S., W. Irene C. Rijpstra, Ellen C. Hopmans, Johan W. H. Weijers, Bärbel U. Foesel, Jörg Overmann y Svetlana N. Dedysh. "13,16-Dimethyl Octacosanedioic Acid (iso-Diabolic Acid), a Common Membrane-Spanning Lipid of Acidobacteria Subdivisions 1 and 3". Applied and Environmental Microbiology 77, n.º 12 (22 de abril de 2011): 4147–54. http://dx.doi.org/10.1128/aem.00466-11.
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ABSTRACTThe distribution of membrane lipids of 17 different strains representing 13 species of subdivisions 1 and 3 of the phylumAcidobacteria, a highly diverse phylum of theBacteria, were examined by hydrolysis and gas chromatography-mass spectrometry (MS) and by high-performance liquid chromatography-MS of intact polar lipids. Upon both acid and base hydrolyses of total cell material, the uncommon membrane-spanning lipid 13,16-dimethyl octacosanedioic acid (iso-diabolic acid) was released in substantial amounts (22 to 43% of the total fatty acids) from all of the acidobacteria studied. This lipid has previously been encountered only in thermophilicThermoanaerobacterspecies but bears a structural resemblance to the alkyl chains of bacterial glycerol dialkyl glycerol tetraethers (GDGTs) that occur ubiquitously in peat and soil and are suspected to be produced by acidobacteria. As reported previously, most species also containediso-C15and C16:1ω7Cas major fatty acids but the presence ofiso-diabolic acid was unnoticed in previous studies, most probably because the complex lipid that contained this moiety was not extractable from the cells; it could only be released by hydrolysis. Direct analysis of intact polar lipids in the Bligh-Dyer extract of three acidobacterial strains, indeed, did not reveal any membrane-spanning lipids containingiso-diabolic acid. In 3 of the 17 strains, ether-boundiso-diabolic acid was detected after hydrolysis of the cells, including one branched GDGT containingiso-diabolic acid-derived alkyl chains. Since the GDGT distribution in soils is much more complex, branched GDGTs in soil likely also originate from other (acido)bacteria capable of biosynthesizing these components.
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Lopes dos Santos, Raquel A. y Christopher H. Vane. "Tracking natural organic carbon in the River Clyde, UK, using glycerol dialkyl glycerol tetraethers". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 108, n.º 2-3 (junio de 2017): 289–98. http://dx.doi.org/10.1017/s175569101800035x.
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ABSTRACTSurface sediments from a 100-km stretch of the River Clyde, UK, and its estuary were analysed for glycerol dialkyl glycerol tetraethers (GDGTs) to track the downstream changes in the source of organic matter (OM) and to evaluate the impact of urbanisation. Bacterial membrane lipids, named branched GDGTs (brGDGTs), produced in soils and rivers ranged from 1.6 to 58μgg−1 organic carbon (OC) and the isoprenoid GDGT crenarchaeol, mainly from marine archaea, ranged from 0.01 to 42μgg−1 OC. The highest brGDGT concentrations were in the upper river, in Glasgow city and in the outer estuary, suggesting higher soil-derived OM input. By contrast, crenarchaeol concentrations gradually increased from the tidal weir in Glasgow towards the sea. This spatial distribution of the tetraethers was reflected in the branched and isoprenoid tetraether (BIT) index, a proxy for soil versus marine carbon. The highest BIT values (1.0) occurred upstream, estuarine values ranged from 0.9 to 0.6 and the lowest values (0.4) were found in the outer estuary. An independent proxy for soil-derived OM, stable carbon isotope (δ13C) values, showed a comparable decrease in terrigenous OM contribution towards the sea, but was more variable compared to the BIT. Conversely, carbon/nitrogen (C/N) showed a constant trend, suggesting that it is not a reliable indicator of OM source in the Clyde. Neither BIT, δ13C nor C/N were able to reflect the input of urban effluents from Glasgow.
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Hu, Jianfang, Philip A. Meyers, Gukui Chen, Ping’an Peng y Qunhui Yang. "Archaeal and bacterial glycerol dialkyl glycerol tetraethers in sediments from the Eastern Lau Spreading Center, South Pacific Ocean". Organic Geochemistry 43 (febrero de 2012): 162–67. http://dx.doi.org/10.1016/j.orggeochem.2011.10.012.
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Schouten, Stefan, Marcel T. J. van der Meer, Ellen C. Hopmans, W. Irene C. Rijpstra, Anna-Louise Reysenbach, David M. Ward y Jaap S. Sinninghe Damsté. "Archaeal and Bacterial Glycerol Dialkyl Glycerol Tetraether Lipids in Hot Springs of Yellowstone National Park". Applied and Environmental Microbiology 73, n.º 19 (10 de agosto de 2007): 6181–91. http://dx.doi.org/10.1128/aem.00630-07.
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ABSTRACTGlycerol dialkyl glycerol tetraethers (GDGTs) are core membrane lipids originally thought to be produced mainly by (hyper)thermophilic archaea. Environmental screening of low-temperature environments showed, however, the abundant presence of structurally diverse GDGTs from both bacterial and archaeal sources. In this study, we examined the occurrences and distribution of GDGTs in hot spring environments in Yellowstone National Park with high temperatures (47 to 83°C) and mostly neutral to alkaline pHs. GDGTs with 0 to 4 cyclopentane moieties were dominant in all samples and are likely derived from both (hyper)thermophilicCrenarchaeotaandEuryarchaeota. GDGTs with 4 to 8 cyclopentane moieties, likely derived from the crenarchaeotal orderSulfolobalesand the euryarchaeotal orderThermoplasmatales, are usually present in much lower abundance, consistent with the relatively high pH values of the hot springs. The relative abundances of cyclopentane-containing GDGTs did not correlate with in situ temperature and pH, suggesting that other environmental and possibly genetic factors play a role as well. Crenarchaeol, a biomarker thought to be specific for nonthermophilic group ICrenarchaeota, was also found in most hot springs, though in relatively low concentrations, i.e., <5% of total GDGTs. Its abundance did not correlate with temperature, as has been reported previously. Instead, the cooccurrence of relatively abundant nonisoprenoid GDGTs thought to be derived from soil bacteria suggests a predominantly allochthonous source for crenarchaeol in these hot spring environments. Finally, the distribution of bacterial branched GDGTs suggests that they may be derived from the geothermally heated soils surrounding the hot springs.
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Zink, Klaus-G., Marcus J. Vandergoes, Kai Mangelsdorf, Ann C. Dieffenbacher-Krall y Lorenz Schwark. "Application of bacterial glycerol dialkyl glycerol tetraethers (GDGTs) to develop modern and past temperature estimates from New Zealand lakes". Organic Geochemistry 41, n.º 9 (septiembre de 2010): 1060–66. http://dx.doi.org/10.1016/j.orggeochem.2010.03.004.
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Blank, P. N., A. A. Barnett, T. A. Ronnebaum, K. E. Alderfer, B. N. Gillott, D. W. Christianson y J. A. Himmelberger. "Structural studies of geranylgeranylglyceryl phosphate synthase, a prenyltransferase found in thermophilic Euryarchaeota". Acta Crystallographica Section D Structural Biology 76, n.º 6 (29 de mayo de 2020): 542–57. http://dx.doi.org/10.1107/s2059798320004878.
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Archaea are uniquely adapted to thrive in harsh environments, and one of these adaptations involves the archaeal membrane lipids, which are characterized by their isoprenoid alkyl chains connected via ether linkages to glycerol 1-phosphate. The membrane lipids of the thermophilic and acidophilic euryarchaeota Thermoplasma volcanium are exclusively glycerol dibiphytanyl glycerol tetraethers. The first committed step in the biosynthetic pathway of these archaeal lipids is the formation of the ether linkage between glycerol 1-phosphate and geranylgeranyl diphosphate, and is catalyzed by the enzyme geranylgeranylglyceryl phosphate synthase (GGGPS). The 1.72 Å resolution crystal structure of GGGPS from T. volcanium (TvGGGPS) in complex with glycerol and sulfate is reported here. The crystal structure reveals TvGGGPS to be a dimer, which is consistent with the absence of the aromatic anchor residue in helix α5a that is required for hexamerization in other GGGPS homologs; the hexameric quaternary structure in GGGPS is thought to provide thermostability. A phylogenetic analysis of the Euryarchaeota and a parallel ancestral state reconstruction investigated the relationship between optimal growth temperature and the ancestral sequences. The presence of an aromatic anchor residue is not explained by temperature as an ecological parameter. An examination of the active site of the TvGGGPS dimer revealed that it may be able to accommodate longer isoprenoid substrates, supporting an alternative pathway of isoprenoid membrane-lipid synthesis.
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Stadnitskaia, Alina, Marianne Baas, Michael K. Ivanov, Tjeerd C. E. Van Weering y Jaap S. Sinninghe Damsté. "Novel archaeal macrocyclic diether core membrane lipids in a methane-derived carbonate crust from a mud volcano in the Sorokin Trough, NE Black Sea". Archaea 1, n.º 3 (2003): 165–73. http://dx.doi.org/10.1155/2003/329175.
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A methane-derived carbonate crust was collected from the recently discovered NIOZ mud volcano in the Sorokin Trough, NE Black Sea during the 11th Training-through-Research cruise of the R/V Professor Logachev. Among several specific bacterial and archaeal membrane lipids present in this crust, two novel macrocyclic diphytanyl glycerol diethers, containing one or two cyclopentane rings, were detected. Their structures were tentatively identified based on the interpretation of mass spectra, comparison with previously reported mass spectral data, and a hydrogenation experiment. This macrocyclic type of archaeal core membrane diether lipid has so far been identified only in the deep-sea hydrothermal vent methanogenMethanococcus jannaschii. Here, we provide the first evidence that these macrocyclic diethers can also contain internal cyclopentane rings. The molecular structure of the novel diethers resembles that of dibiphytanyl tetraethers in which biphytane chains, containing one and two pentacyclic rings, also occur. Such tetraethers were abundant in the crust. Compound-specific isotope measurements revealed δ13C values of –104 to –111‰ for these new archaeal lipids, indicating that they are derived from methanotrophic archaea acting within anaerobic methane-oxidizing consortia, which subsequently induce authigenic carbonate formation.
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Rodrigo-Gámiz, M., S. W. Rampen, H. de Haas, M. Baas, S. Schouten y J. S. Sinninghe Damsté. "Constraints on the applicability of the organic temperature proxies U<sup>K'</sup><sub>37</sub>, TEX<sub>86</sub> and LDI in the subpolar region around Iceland". Biogeosciences 12, n.º 22 (19 de noviembre de 2015): 6573–90. http://dx.doi.org/10.5194/bg-12-6573-2015.
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Abstract. Subpolar regions are key areas for studying natural climate variability due to their high sensitivity to rapid environmental changes, particularly through sea surface temperature (SST) variations. Here, we have tested three independent organic temperature proxies (UK'37; TEX86; and the long-chain diol index, LDI) regarding their potential applicability for SST reconstruction in the subpolar region around Iceland. UK'37, TEX86 and TEXL86 temperature estimates from suspended particulate matter showed a substantial discrepancy with instrumental data, while long-chain alkyl diols were below the detection limit at most of the stations. In the northern Iceland Basin, sedimenting particles revealed a seasonality in lipid fluxes, i.e., high fluxes of alkenones and glycerol dialkyl glycerol tetraethers (GDGTs) were measured during late spring and during summer and high fluxes of long-chain alkyl diols during late summer. The flux-weighted average temperature estimates had a significant negative (ca. 2.3 °C for UK'37) and positive (up to 5 °C for TEX86) offset with satellite-derived SSTs and temperature estimates derived from the underlying surface sediment. UK'37 temperature estimates from surface sediments around Iceland correlate well with summer mean sea surface temperatures, while TEX86-derived temperatures correspond with both annual and winter mean 0–200 m temperatures, suggesting a subsurface temperature signal. Anomalous LDI-SST values in surface sediments and low mass flux of 1,13- and 1,15-diols compared to 1,14-diols suggest that Proboscia diatoms are the major sources of long-chain alkyl diols in this area rather than eustigmatophyte algae, and therefore the LDI cannot be applied in this region.
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Zhang, Zhe-Xuan, Edith Parlanti, Christelle Anquetil, Jérôme Morelle, Anniet M. Laverman, Alexandre Thibault, Elisa Bou y Arnaud Huguet. "Environmental controls on the distribution of brGDGTs and brGMGTs across the Seine River basin (NW France): implications for bacterial tetraethers as a proxy for riverine runoff". Biogeosciences 21, n.º 9 (7 de mayo de 2024): 2227–52. http://dx.doi.org/10.5194/bg-21-2227-2024.
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Abstract. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial lipids that have been widely used as environmental proxies in continental paleorecords. Another group of related lipids, branched glycerol monoalkyl glycerol tetraethers (brGMGTs), has recently been proposed as a potential paleotemperature proxy. Nevertheless, the sources and environmental dependencies of both brGDGTs and brGMGTs along the river–sea continuum are still poorly understood, complicating their application as paleoenvironmental proxies in some aquatic settings. In this study, the sources of brGDGTs and brGMGTs and the potential factors controlling their distributions are explored across the Seine River basin (NW France), which encompasses the freshwater-to-seawater continuum. BrGDGTs and brGMGTs were analyzed in soils, suspended particulate matter (SPM), and sediments (n=237) collected along the land–sea continuum of the Seine basin. Both types of compounds (i.e., brGDGTs and brGMGTs) are shown to be produced in situ, in freshwater and saltwater, based on their high concentrations and distinct distributions in aquatic settings (SPM and sediments) vs. soils. Redundancy analysis further shows that both salinity and nitrogen dominantly control the brGDGT distributions. Furthermore, the relative abundance of 6-methyl vs. that of 5-methyl brGDGTs (the IR6Me ratio), the total nitrogen (TN), the δ15N, and the chlorophyll a concentration co-vary in a specific geographical zone with low salinity, suggesting that 6-methyl brGDGTs are preferentially produced under low-salinity and high-productivity conditions. In contrast to brGDGTs, the brGMGT distribution appears to be primarily regulated by salinity, with a distinct influence on the individual homologues. Salinity is positively correlated with homologues H1020a and H1020b and negatively correlated with compounds H1020c and H1034b in SPM. This suggests that bacteria living in freshwater preferentially produce compounds H1020c and H1034b, whereas bacteria that primarily grow in saltwater appear to be predominantly responsible for the production of homologues H1020a and H1020b. Based on the abundance ratio of the freshwater-derived compounds (H1020c and H1034b) vs. their saltwater-derived homologues (H1020a and H1020b), a novel proxy, the Riverine IndeX (RIX), is proposed to trace riverine organic matter inputs, with high values (>0.5) indicating a higher riverine contribution. We successfully applied RIX to the Godavari River basin (India) and a paleorecord across the upper Paleocene and lower Eocene from the Arctic Coring Expedition at Lomonosov Ridge, showing its potential applicability to both modern samples and paleorecords.
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Sinninghe Damsté, Jaap S., W. Irene C. Rijpstra, Ellen C. Hopmans, Bärbel U. Foesel, Pia K. Wüst, Jörg Overmann, Marcus Tank et al. "Ether- and Ester-Boundiso-Diabolic Acid and Other Lipids in Members of Acidobacteria Subdivision 4". Applied and Environmental Microbiology 80, n.º 17 (13 de junio de 2014): 5207–18. http://dx.doi.org/10.1128/aem.01066-14.
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ABSTRACTRecently,iso-diabolic acid (13,16-dimethyl octacosanedioic acid) has been identified as a major membrane-spanning lipid of subdivisions 1 and 3 of theAcidobacteria, a highly diverse phylum within theBacteria. This finding pointed to theAcidobacteriaas a potential source for the bacterial glycerol dialkyl glycerol tetraethers that occur ubiquitously in peat, soil, lakes, and hot springs. Here, we examined the lipid composition of seven phylogenetically divergent strains of subdivision 4 of theAcidobacteria, a bacterial group that is commonly encountered in soil. Acid hydrolysis of total cell material releasediso-diabolic acid derivatives in substantial quantities (11 to 48% of all fatty acids). In contrast to subdivisions 1 and 3 of theAcidobacteria, 6 out of the 7 species of subdivision 4 (excepting “CandidatusChloracidobacterium thermophilum”) containediso-diabolic acid ether bound to a glycerol in larger fractional abundance thaniso-diabolic acid itself. This is in agreement with the analysis of intact polar lipids (IPLs) by high-performance liquid chromatography-mass spectrometry (HPLC-MS), which showed the dominance of mixed ether-ester glycerides.iso-Diabolic acid-containing IPLs were not identified, because these IPLs are not released with a Bligh-Dyer extraction, as observed before when studying lipid compositions of subdivisions 1 and 3 of theAcidobacteria. The presence of ether bonds in the membrane lipids does not seem to be an adaptation to temperature, because the five mesophilic isolates contained a larger amount of ether lipids than the thermophile “Ca. Chloracidobacterium thermophilum.” Furthermore, experiments withPyrinomonas methylaliphatogenesdid not reveal a major influence of growth temperature over the 50 to 69°C range.
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Zander, Paul D., Daniel Böhl, Frank Sirocko, Alexandra Auderset, Gerald H. Haug y Alfredo Martínez-García. "Reconstruction of warm-season temperatures in central Europe during the past 60 000 years from lacustrine branched glycerol dialkyl glycerol tetraethers (brGDGTs)". Climate of the Past 20, n.º 4 (8 de abril de 2024): 841–64. http://dx.doi.org/10.5194/cp-20-841-2024.
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Abstract. Millennial-scale climate variations during the last glacial period, such as Dansgaard–Oeschger (DO) cycles and Heinrich events, have been extensively studied using ice core and marine proxy records. However, there is a limited understanding of the magnitude of these temperature fluctuations in continental regions, and questions remain about the seasonal signal of these climate events. This study presents a 60 000-year-long temperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) extracted from lake sediments from the Eifel Volcanic Field, Germany. brGDGTs are bacterial membrane-spanning lipids that are known to have a strong relationship with temperature, making them suitable for temperature reconstructions. We test several temperature calibration models on modern samples taken from soils and multiple maar lakes. We find a negative bias in brGDGT-based temperature estimates associated with water depth and anoxic conditions that can be corrected for by accounting for a brGDGT isomer that is only produced in anoxic conditions. The corrected temperature reconstruction correlates with proxy and climate model estimates of temperature spanning the same time period, validating the calibration approach we selected. However, millennial-scale variability is significantly dampened in the brGDGT record, and in contrast to other Northern Hemisphere climate records, during several Heinrich stadials, temperatures actually increase. We demonstrate that these apparent discrepancies can be explained by the unique seasonal response of the brGDGT paleothermometer to temperatures of months above freezing (TMAF). Our data support the view that warm-season temperatures in Europe varied minimally during the last glacial period and that abrupt millennial-scale events were defined by colder, longer winters. Our continuous high-resolution temperature reconstruction provides important information about the magnitude of seasonal climate variability during the last glacial period that can be used to test climate models and inform studies of paleoecological change.
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Weber, Yuki, Jaap S. Sinninghe Damsté, Jakob Zopfi, Cindy De Jonge, Adrian Gilli, Carsten J. Schubert, Fabio Lepori, Moritz F. Lehmann y Helge Niemann. "Redox-dependent niche differentiation provides evidence for multiple bacterial sources of glycerol tetraether lipids in lakes". Proceedings of the National Academy of Sciences 115, n.º 43 (9 de octubre de 2018): 10926–31. http://dx.doi.org/10.1073/pnas.1805186115.
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Terrestrial paleoclimate archives such as lake sediments are essential for our understanding of the continental climate system and for the modeling of future climate scenarios. However, quantitative proxies for the determination of paleotemperatures are sparse. The relative abundances of certain bacterial lipids, i.e., branched glycerol dialkyl glycerol tetraethers (brGDGTs), respond to changes in environmental temperature, and thus have great potential for climate reconstruction. Their application to lake deposits, however, is hampered by the lack of fundamental knowledge on the ecology of brGDGT-producing microbes in lakes. Here, we show that brGDGTs are synthesized by multiple groups of bacteria thriving under contrasting redox regimes in a deep meromictic Swiss lake (Lake Lugano). This niche partitioning is evidenced by highly distinct brGDGT inventories in oxic vs. anoxic water masses, and corresponding vertical patterns in bacterial 16S rRNA gene abundances, implying that sedimentary brGDGT records are affected by temperature-independent changes in the community composition of their microbial producers. Furthermore, the stable carbon isotope composition (δ13C) of brGDGTs in Lake Lugano and 34 other (peri-)Alpine lakes attests to the widespread heterotrophic incorporation of 13C-depleted, methane-derived biomass at the redox transition zone of mesotrophic to eutrophic lake systems. The brGDGTs produced under such hypoxic/methanotrophic conditions reflect near-bottom water temperatures, and are characterized by comparatively low δ13C values. Depending on climate zone and water depth, lake sediment archives predominated by deeper water/low-13C brGDGTs may provide more reliable records of climate variability than those where brGDGTs derive from terrestrial and/or aquatic sources with distinct temperature imprints.
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D'Anjou, R. M., J. H. Wei, I. S. Castañeda, J. Brigham-Grette, S. T. Petsch y D. B. Finkelstein. "High-latitude environmental change during MIS 8–12: biogeochemical evidence from Lake El'gygytgyn, Far East Russia". Climate of the Past Discussions 8, n.º 5 (28 de septiembre de 2012): 4745–77. http://dx.doi.org/10.5194/cpd-8-4745-2012.
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Abstract. Marine Isotope Stages (MIS) 11 has been proposed as an analog for the present interglacial; however, terrestrial records of this time period are rare. Sediments from Lake El'gygytgyn (67°30´ N, 172°5´ E) in Far East Russia contain a 3.56 Ma record of climate variability from the Arctic. Here, we present an organic geochemical reconstruction of environmental and climatic changes from MIS 8 through 12 (289 to 460 ka). Terrestrial vegetation changes, as revealed by plant leaf wax (n-alkane) indices and concentrations of arborinol (a biomarker for trees), show increased tree cover around the lake during interglacial periods, with higher concentrations observed during MIS 11 as compared to MIS 9. A similar pattern is also observed in records of aquatic productivity revealed by molecular indicators from dinoflagellates (dinosterol), eustigmatophyte algae (long-chain (C28–C32) 1,15 n-alkyl diols) in addition to short-chain nalkanes, where aquatic productivity is highest during MIS 11. Changes recorded in these molecular proxies track relative temperature variability as recorded by the MBT/CBT paleothermometer, based on branched glycerol dialkyl glycerol tetraethers (GDGTs). Additionally, relative MBT/CBT temperature changes generally track pollen and diatom δ18O temperature estimates, compiled by other studies, which suggest glacial–interglacial temperature changes of ~ 9–12 °C. These records of environmental and climatic change indicate Arctic sensitivity to external forcings such as orbital variability and atmospheric greenhouse gas concentrations. Overall, this study indicates that organic geochemical analyses of the Lake El'gygytgyn sediment archive can provide critical insight into the response of lake ecosystems and their sensitivity in high latitude regions.
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Niemann, H., A. Stadnitskaia, S. B. Wirth, A. Gilli, F. S. Anselmetti, J. S. Sinninghe Damsté, S. Schouten, E. C. Hopmans y M. F. Lehmann. "Bacterial GDGTs in Holocene sediments and catchment soils of a high Alpine lake: application of the MBT/CBT-paleothermometer". Climate of the Past 8, n.º 3 (7 de mayo de 2012): 889–906. http://dx.doi.org/10.5194/cp-8-889-2012.
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Abstract. A novel proxy for continental mean annual air temperature (MAAT) and soil pH, the MBT/CBT-paleothermometer, is based on the temperature (T) and pH-dependent distribution of specific bacterial membrane lipids (branched glycerol dialkyl glycerol tetraethers – GDGTs) in soil organic matter. Here, we tested the applicability of the MBT/CBT-paleothermometer to sediments from Lake Cadagno, a high Alpine lake in southern Switzerland with a small catchment of 2.4 km2. We analysed the distribution of bacterial GDGTs in catchment soils and in a radiocarbon-dated sediment core from the centre of the lake, covering the past 11 000 yr. The distribution of bacterial GDGTs in the catchment soils is very similar to that in the lake's surface sediments, indicating a common origin of the lipids. Consequently, their transfer from the soils into the sediment record seems undisturbed, probably without any significant alteration of their distribution through in situ production in the lake itself or early diagenesis of branched GDGTs. The MBT/CBT-inferred MAAT estimates from soils and surface sediments are in good agreement with instrumental values for the Lake Cadagno region (~0.5 °C). Moreover, downcore MBT/CBT-derived MAAT estimates match in timing and magnitude other proxy-based T reconstructions from nearby locations for the last two millennia. Major climate anomalies recorded by the MBT/CBT-paleothermometer are, for instance, the Little Ice Age (~14th to 19th century) and the Medieval Warm Period (MWP, ~9th to 14th century). Together, our observations indicate the quantitative applicability of the MBT/CBT-paleothermometer to Lake Cadagno sediments. In addition to the MWP, our lacustrine paleo T record indicates Holocene warm phases at about 3, 5, 7 and 11 kyr before present, which agrees in timing with other records from both the Alps and the sub-polar North-East Atlantic Ocean. The good temporal match of the warm periods determined for the central Alpine region with north-west European winter precipitation strength implies a strong and far-reaching influence of the North Atlantic Oscillation on continental European T variations during the Holocene.
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Niemann, H., A. Stadnitskaia, S. B. Wirth, A. Gilli, F. S. Anselmetti, J. S. Sinninghe Damsté, S. Schouten, E. C. Hopmans y M. F. Lehmann. "Bacterial GDGTs in Holocene sediments and catchment soils of a high-alpine lake: application of the MBT/CBT-paleothermometer". Climate of the Past Discussions 7, n.º 5 (19 de octubre de 2011): 3449–88. http://dx.doi.org/10.5194/cpd-7-3449-2011.
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Abstract. A novel proxy for continental mean annual air temperature (MAAT) and soil-pH, the MBT/CBT-paleothermometer, is based on the temperature (T) and pH-dependent distribution of specific bacterial membrane lipids (branched glycerol dialkyl glycerol tetraethers – GDGTs) in soil organic matter. Here, we tested the applicability of the MBT/CBT-paleothermometer to sediments from Lake Cadagno, a small high-alpine lake in southern Switzerland with a small catchment of 2.4 km2. We analysed the distribution of bacterial GDGTs in catchment soils and in a radiocarbon-dated sediment core from the centre of the lake, covering the entire Holocene. The composition of bacterial GDGTs in soils are almost identical to that in the lake's surface sediments, indicating a common origin of the lipids. Consequently, their transfer from the soils into the sediment record is undisturbed, apparently without any significant alteration of their distribution through in situ production or early diagenesis of branched GDGTs. The MBT/CBT-inferred MAAT-estimates from soils and surface sediments are in good agreement with instrumental values for the Lake Cadagno region (~0.5 °C). Moreover, downcore MBT/CBT-derived MAAT-estimates match in timing and magnitude other proxy-based T-reconstructions from nearby locations for the last two millennia. Major climate anomalies recorded by the MBT/CBT-paleothermometer are, for instance, the Little Ice Age (~14th to 19th century) and the Medieval Warm Period (~10th to 14th century). Together, our observations confirm the applicability of the MBT/CBT-paleothermometer to Lake Cadagno sediments. Consistent with other T-records from both the Alps and from the subpolar NE-Atlantic, our lacustrine paleotemperature record indicates Holocene MAAT-variations with an apparent cyclicity of ~2 kyr. The good temporal match of the warm periods determined for the S-Alpine region with NW-European winter precipitation strength implies a strong and far-reaching influence of the North Atlantic Oscillation on continental European Holocene T-variations.
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D'Anjou, R. M., J. H. Wei, I. S. Castañeda, J. Brigham-Grette, S. T. Petsch y D. B. Finkelstein. "High-latitude environmental change during MIS 9 and 11: biogeochemical evidence from Lake El'gygytgyn, Far East Russia". Climate of the Past 9, n.º 2 (8 de marzo de 2013): 567–81. http://dx.doi.org/10.5194/cp-9-567-2013.
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Abstract. Marine isotope stages (MIS) 11 has been proposed as an analog for the present interglacial; however, terrestrial records of this time period are rare. Sediments from Lake El'gygytgyn (67°30' N, 172°5' E) in Far East Russia contain a 3.56 Ma record of climate variability from the Arctic. Here, we present the first terrestrial Arctic reconstruction of environmental and climatic changes from MIS 8 through 12 (289 to 464 ka) using organic geochemical proxies. Terrestrial vegetation changes, as revealed by plant leaf wax (n-alkane) indices and concentrations of arborinol (a biomarker for trees), show increased tree cover around the lake during interglacial periods, with higher concentrations observed during MIS 11 as compared to MIS 9. A similar pattern is also observed in records of aquatic productivity revealed by molecular indicators from dinoflagellates (dinosterol), eustigmatophyte algae (long-chain (C28–C32) 1, 15 n-alkyl diols) in addition to short-chain n-alkanes, where aquatic productivity is highest during MIS 11. Changes recorded in these molecular proxies show a similar structure to relative temperature variability as recorded by the MBT/CBT (Methylation of Branched Tetraether/Cyclization of Branched Tetraether) paleothermometer, based on branched glycerol dialkyl glycerol tetraethers (GDGTs). Additionally, relative MBT/CBT temperature changes generally track pollen and diatom δ18O temperature estimates, compiled by other studies, which suggest glacial-interglacial temperature changes of ~ 9 to 12 °C. These records of environmental and climatic change indicate Arctic sensitivity to external forcings such as orbital variability and atmospheric greenhouse gas concentrations. Overall, this study indicates that organic geochemical analyses of the Lake El'gygytgyn sediment archive can provide critical insight into the response of lake ecosystems and their sensitivity in high latitude regions.
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van Bree, Loes G. J., Francien Peterse, Allix J. Baxter, Wannes De Crop, Sigrid van Grinsven, Laura Villanueva, Dirk Verschuren y Jaap S. Sinninghe Damsté. "Seasonal variability and sources of in situ brGDGT production in a permanently stratified African crater lake". Biogeosciences 17, n.º 21 (13 de noviembre de 2020): 5443–63. http://dx.doi.org/10.5194/bg-17-5443-2020.
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Abstract. Lake sediments are important archives of continental climate history, and their lipid biomarker content can be exploited to reconstruct paleoenvironmental conditions. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial membrane lipids widely used in paleoclimate studies to reconstruct past temperature. However, major gaps still exist in our understanding of the environmental controls on in situ (i.e. aquatic) production in lake systems. In Lake Chala, a permanently stratified tropical crater lake in East Africa, we determined the concentrations and fractional abundances of individual brGDGTs along depth profiles of suspended particulate matter collected monthly from September 2013 to January 2015 and in settling particles collected monthly at 35 m water depth from August 2010 to January 2015 and compared these brGDGT distributions with those in surficial lake bottom sediments and catchment soils. We find that brGDGTs are primarily produced within the water column and that their concentrations and distributions vary greatly with depth and over time. Comparison with concentration–depth profiles of the monthly distribution and abundance of bacterial taxa, based on 16S rRNA gene amplicon sequencing and quantification, indicates that Acidobacteria are likely not the main producers of brGDGTs in Lake Chala. Shallowing of the oxic–anoxic boundary during seasonal episodes of strong water column stratification promoted production of specific brGDGTs in the anoxic zone. BrGDGT distributions in the water column do not consistently relate with temperature, pH, or dissolved-oxygen concentration but do respond to transitions between episodes of strong stratification and deep (but partial) lake mixing, as does the aquatic bacterial community. Hence, the general link between brGDGT distributions and temperature in brGDGT-based paleothermometry is more likely driven by a change in bacterial community composition than by membrane adaptation of specific members of the bacterial community to changing environmental conditions. Although temperature is not the principal driver of distributional changes in aquatic brGDGTs in this system, at least not during the 17-month study period, abundance-weighted and time-integrated averages of brGDGT fractional abundance in the 53-month time series of settling particles reveal systematic variability over longer timescales that indirectly relates to temperature. Thus, although we do not as yet fully understand the drivers of modern-day brGDGT fluxes and distributions in Lake Chala, our data do support the application of brGDGT paleothermometry to time-integrated archives such as sediments. Highlights. BrGDGTs in the tropical African lake Chala are produced in situ. Acidobacteria are not the dominant source of aquatic brGDGTs. Stratification and mixing drive aquatic brGDGT production and their signature.
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Lengger, S. K., Y. A. Lipsewers, H. de Haas, J. S. Sinninghe Damsté y S. Schouten. "Lack of <sup>13</sup>C-label incorporation suggests low turnover rates of thaumarchaeal intact polar tetraether lipids in sediments from the Iceland shelf". Biogeosciences 11, n.º 2 (17 de enero de 2014): 201–16. http://dx.doi.org/10.5194/bg-11-201-2014.
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Abstract. Thaumarchaeota are amongst the most abundant microorganisms in aquatic environments, however, their metabolism in marine sediments is still debated. Labeling studies in marine sediments have previously been undertaken, but focused on complex organic carbon substrates which Thaumarchaeota have not yet been shown to take up. In this study, we investigated the activity of Thaumarchaeota in sediments by supplying different 13C-labeled substrates which have previously been shown to be incorporated into archaeal cells in water incubations and/or enrichment cultures. We determined the incorporation of 13C-label from bicarbonate, pyruvate, glucose and amino acids into thaumarchaeal intact polar lipid-glycerol dibiphytanyl glycerol tetraethers (IPL-GDGTs) during 4–6 day incubations of marine sediment cores from three sites on the Iceland shelf. Thaumarchaeal intact polar lipids, in particular crenarchaeol, were detected at all stations and concentrations remained constant or decreased slightly upon incubation. No 13C incorporation in any IPL-GDGT was observed at stations 2 (clay-rich sediment) and 3 (organic-rich sediment). In bacterial/eukaryotic IPL-derived fatty acids at station 3, contrastingly, a large uptake of 13C label (up to + 80‰ ) was found. 13C was also respired during the experiment as shown by a substantial increase in the 13C content of the dissolved inorganic carbon. In IPL-GDGTs recovered from the sandy sediments at station 1, however, some enrichment in δ13C (1–4‰ ) was detected after incubation with bicarbonate and pyruvate. The low incorporation rates suggest a low activity of Thaumarchaeota in marine sediments and/or a low turnover rate of thaumarchaeal IPL-GDGTs due to their low degradation rates. Cell numbers and activity of sedimentary Thaumarchaeota based on IPL-GDGT measurements may thus have previously been overestimated.
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Lengger, S. K., Y. A. Lipsewers, H. de Haas, J. S. Sinninghe Damsté y S. Schouten. "Lack of <sup>13</sup>C-label incorporation suggests low turnover rates of thaumarchaeal intact polar tetraether lipids in sediments from the Iceland Shelf". Biogeosciences Discussions 10, n.º 8 (6 de agosto de 2013): 12807–47. http://dx.doi.org/10.5194/bgd-10-12807-2013.
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Abstract. Thaumarchaeota are amongst the most abundant microorganisms in aquatic environments, however, their metabolism in marine sediments is still debated. Labeling studies in marine sediments have previously been undertaken, but focused on complex organic carbon substrates which Thaumarchaeota have not yet been shown to take up. In this study, we investigated the activity of Thaumarchaeota in sediments by supplying different 13C-labeled substrates which have previously been shown to be incorporated into archaeal cells in water incubations and/or enrichment cultures. We determined the incorporation of 13C-label from bicarbonate, pyruvate, glucose and amino acids into thaumarchaeal intact polar lipid-glycerol dibiphytanyl glycerol tetraethers (IPL-GDGTs) during 4–6 day incubations of marine sediment cores from three different sites on the Iceland Shelf. Thaumarchaeal intact polar lipids were detected at all stations and concentrations remained constant or decreased slightly upon incubation. No 13C incorporation in any IPL-GDGT was observed at stations 2 (clay-rich sediment) and 3 (organic-rich sediment). In bacterial/eukaryotic IPL-derived fatty acids at station 3, contrastingly, a large uptake of 13C label (up to &plus;80‰) was found. 13C was also respired during the experiment as shown by a substantial increase in the 13C content of the dissolved inorganic carbon. In IPL-GDGTs recovered from the sandy sediments at station 1, however, some enrichment in 13C (1–4‰) was detected after incubation with bicarbonate and pyruvate. The low incorporation rates suggest a low activity of Thaumarchaeota in marine sediments and/or a low turnover rate of thaumarchaeal IPL-GDGTs due to their low degradation rates. Cell numbers and activity of sedimentary Thaumarchaeota based on IPL-GDGT measurements may thus have previously been overestimated.
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Vinçon-Laugier, Arnauld, Cristiana Cravo-Laureau y Vincent Grossi. "Selective preservation among bacterial alkyl glycerol ether lipid structures during long term oxic and anoxic incubation". Organic Geochemistry 125 (noviembre de 2018): 24–28. http://dx.doi.org/10.1016/j.orggeochem.2018.08.009.
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Jabeen, Asma, Rida Batool y Nazia Jamil. "Micrococcus yunnanensis and Psychrobacter sp. as Potential Producers of Polymers from Hot Spring". Industria: Jurnal Teknologi dan Manajemen Agroindustri 11, n.º 1 (30 de abril de 2022): 1–9. http://dx.doi.org/10.21776/ub.industria.2022.011.01.1.
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Polyhydroxyalkanoates (PHAs) and exopolysaccharides (EPSs) are biopolymers bacteria under nutrient-limiting conditions. In this study, bacterial strains were isolated from hot springs. Soil samples were collected from Tatta Pani, Azad Kashmir, Pakistan. Bacterial strains AJ2 and AJ3 were selected due to their ability to produce PHAs and EPSs. Phylogenetic analysis showed that strain AJ2 was Micrococcus yunnanensis and AJ3 was Psychrobacter sp. Three carbon sources (glucose, glycerol, and molasses) were used for polymer production. The effect of high pH (8) and high temperature (55 °C) was checked on PHAs and EPSs production. The highest yield of PHAs was given by strain AJ3 (89.43%) with molasses. When grown at 55 °C for 24 hours, strain AJ3 showed the highest PHAs accumulation, 79% with glucose. At alkaline pH 8, strain AJ3 gave 34% PHAs with molasses. The highest EPSs production was observed for strain AJ3. AJ3 gave 70g/L of EPSs with both glucose and glycerol. The amplification of the phaC gene was done to confirm the genetic basis of PHAs production. FTIR analysis showed clear bands at 1722 cm-1 and 2925 cm-1 representing the carbonyl and alkyl groups of PHAs, respectively.
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Hepp, Johannes, Imke Kathrin Schäfer, Verena Lanny, Jörg Franke, Marcel Bliedtner, Kazimierz Rozanski, Bruno Glaser, Michael Zech, Timothy Ian Eglinton y Roland Zech. "Evaluation of bacterial glycerol dialkyl glycerol tetraether and <sup>2</sup>H–<sup>18</sup>O biomarker proxies along a central European topsoil transect". Biogeosciences 17, n.º 3 (12 de febrero de 2020): 741–56. http://dx.doi.org/10.5194/bg-17-741-2020.
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Abstract. Molecular fossils, like bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs), and the stable isotopic composition of biomarkers, such as δ2H of leaf wax-derived n-alkanes (δ2Hn-alkane) or δ18O of hemicellulose-derived sugars (δ18Osugar), are increasingly used for the reconstruction of past climate and environmental conditions. Plant-derived δ2Hn-alkane and δ18Osugar values record the isotopic composition of plant source water (δ2Hsource-water and δ18Osource-water), which usually reflects mean annual precipitation (δ2Hprecipiation and δ18Oprecipiation), modulated by evapotranspirative leaf water enrichment and biosynthetic fractionation (εbio). Accuracy and precision of respective proxies should be ideally evaluated at a regional scale. For this study, we analysed topsoils below coniferous and deciduous forests as well as grassland soils along a central European transect in order to investigate the variability and robustness of various proxies and to identify effects related to vegetation. Soil pH values derived from brGDGTs correlate reasonably well with measured soil pH values but are systematically overestimated (ΔpH = 0.6±0.6). The branched vs. isoprenoid tetraether index (BIT) can give some indication whether the pH reconstruction is reliable. Temperatures derived from brGDGTs overestimate mean annual air temperatures slightly (ΔTMA=0.5 ∘C ± 2.4). Apparent isotopic fractionation (εn-alkane/precipitation and εsugar∕precipitation) is lower for grassland sites than for forest sites due to signal damping; i.e. grass biomarkers do not record the full evapotranspirative leaf water enrichment. Coupling δ2Hn-alkane with δ18Osugar allows us to reconstruct the stable isotopic composition of the source water more accurately than without the coupled approach (Δδ2H = ∼-21 ‰ ± 22 ‰ and Δδ18O = ∼-2.9 ‰ ± 2.8 ‰). Similarly, relative humidity during daytime and the vegetation period (RHMDV) can be reconstructed using the coupled isotope approach (ΔRHMDV=∼-17±12). Especially for coniferous sites, reconstructed RHMDV values as well as source water isotope composition underestimate the measured values. This can likely be explained by understorey grass vegetation at the coniferous sites contributing significantly to the n-alkane pool but only marginally to the sugar pool in the topsoils. Vegetation-dependent variable signal damping and εbio (regarding 2H between n-alkanes and leaf water) along our European transect are difficult to quantify but likely contribute to the observed underestimation in the source water isotope composition and RH reconstructions. Microclimate variability could cause the rather large uncertainties. Vegetation-related effects do, by contrast, not affect the brGDGT-derived reconstructions. Overall, GDGTs and the coupled δ2Hn-alkane–δ18Osugar approach have great potential for more quantitative paleoclimate reconstructions.
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Fletcher, Tamara L., Lisa Warden, Jaap S. Sinninghe Damsté, Kendrick J. Brown, Natalia Rybczynski, John C. Gosse y Ashley P. Ballantyne. "Evidence for fire in the Pliocene Arctic in response to amplified temperature". Climate of the Past 15, n.º 3 (19 de junio de 2019): 1063–81. http://dx.doi.org/10.5194/cp-15-1063-2019.
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Abstract. The mid-Pliocene is a valuable time interval for investigating equilibrium climate at current atmospheric CO2 concentrations because atmospheric CO2 concentrations are thought to have been comparable to the current day and yet the climate and distribution of ecosystems were quite different. One intriguing, but not fully understood, feature of the early to mid-Pliocene climate is the amplified Arctic temperature response and its impact on Arctic ecosystems. Only the most recent models appear to correctly estimate the degree of warming in the Pliocene Arctic and validation of the currently proposed feedbacks is limited by scarce terrestrial records of climate and environment. Here we reconstruct the summer temperature and fire regime from a subfossil fen-peat deposit on west–central Ellesmere Island, Canada, that has been chronologically constrained using cosmogenic nuclide burial dating to 3.9+1.5/-0.5 Ma. The estimate for average mean summer temperature is 15.4±0.8 ∘C using specific bacterial membrane lipids, i.e., branched glycerol dialkyl glycerol tetraethers. This is above the proposed threshold that predicts a substantial increase in wildfire in the modern high latitudes. Macro-charcoal was present in all samples from this Pliocene section with notably higher charcoal concentration in the upper part of the sequence. This change in charcoal was synchronous with a change in vegetation that included an increase in abundance of fire-promoting Pinus and Picea. Paleo-vegetation reconstructions are consistent with warm summer temperatures, relatively low summer precipitation and an incidence of fire comparable to fire-adapted boreal forests of North America and central Siberia. To our knowledge, this site provides the northernmost evidence of fire during the Pliocene. It suggests that ecosystem productivity was greater than in the present day, providing fuel for wildfires, and that the climate was conducive to the ignition of fire during this period. The results reveal that interactions between paleo-vegetation and paleoclimate were mediated by fire in the High Arctic during the Pliocene, even though CO2 concentrations were similar to modern values.
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Schubotz, Florence, Sitan Xie, Julius S. Lipp, Kai-Uwe Hinrichs y Stuart G. Wakeham. "Intact polar lipids in the water column of the eastern tropical North Pacific: abundance and structural variety of non-phosphorus lipids". Biogeosciences 15, n.º 21 (6 de noviembre de 2018): 6481–501. http://dx.doi.org/10.5194/bg-15-6481-2018.
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Abstract. Intact polar lipids (IPLs) are the main building blocks of cellular membranes and contain chemotaxonomic, ecophysiological and metabolic information, making them valuable biomarkers in microbial ecology and biogeochemistry. This study investigates IPLs in suspended particulate matter (SPM) in the water column of the eastern tropical North Pacific Ocean (ETNP), one of the most extensive open-ocean oxygen minimum zones (OMZs) in the world, with strong gradients of nutrients, temperature and redox conditions. A wide structural variety in polar lipid head-group composition and core structures exists along physical and geochemical gradients within the water column, from the oxygenated photic zone to the aphotic OMZ. We use this structural diversity in IPLs to evaluate the ecology and ecophysiological adaptations that affect organisms inhabiting the water column, especially the mid-depth OMZ in the context of biogeochemical cycles. Diacylglycerol phospholipids are present at all depths, but exhibit the highest relative abundance and compositional variety (including mixed acyl/ether core structures) in the upper and core OMZ where prokaryotic biomass was enriched. Surface ocean SPM is dominated by diacylglycerol glycolipids that are found in photosynthetic membranes. These and other glycolipids with varying core structures composed of ceramides and hydroxylated fatty acids are also detected with varying relative abundances in the OMZ and deep oxycline, signifying additional non-phototrophic bacterial sources for these lipids. Betaine lipids (with zero or multiple hydroxylations in the core structures) that are typically assigned to microalgae are found throughout the water column down to the deep oxycline but do not show a depth-related trend in relative abundance. Archaeal IPLs comprised of glycosidic and mixed glycosidic-phosphatidic glycerol dibiphytanyl glycerol tetraethers (GDGTs) are most abundant in the upper OMZ, where nitrate maxima point to ammonium oxidation but increase in relative abundance in the core OMZ and deep oxycline. The presence of non-phosphorus “substitute” lipids within the OMZ suggest that the indigenous microbes might be phosphorus limited (P starved) at ambient phosphate concentrations of 1 to 3.5 µM, although specific microbial sources for many of these lipids still remain unknown.
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Jahnke, Linda L., Wolfgang Eder, Robert Huber, Janet M. Hope, Kai-Uwe Hinrichs, John M. Hayes, David J. Des Marais, Sherry L. Cady y Roger E. Summons. "Signature Lipids and Stable Carbon Isotope Analyses of Octopus Spring Hyperthermophilic Communities Compared with Those ofAquificales Representatives". Applied and Environmental Microbiology 67, n.º 11 (1 de noviembre de 2001): 5179–89. http://dx.doi.org/10.1128/aem.67.11.5179-5189.2001.
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ABSTRACT The molecular and isotopic compositions of lipid biomarkers of cultured Aquificales genera have been used to study the community and trophic structure of the hyperthermophilic pink streamers and vent biofilm from Octopus Spring. Thermocrinis ruber, Thermocrinis sp. strain HI 11/12,Hydrogenobacter thermophilus TK-6,Aquifex pyrophilus, and Aquifex aeolicusall contained glycerol-ether phospholipids as well as acyl glycerides. The n-C20:1 andcy-C21 fatty acids dominated all of theAquificales, while the alkyl glycerol ethers were mainly C18:0. These Aquificales biomarkers were major constituents of the lipid extracts of two Octopus Spring samples, a biofilm associated with the siliceous vent walls, and the well-known pink streamer community (PSC). Both the biofilm and the PSC contained mono- and dialkyl glycerol ethers in which C18 and C20 alkyl groups were prevalent. Phospholipid fatty acids included both the Aquificales n-C20:1 andcy-C21, plus a series ofiso-branched fatty acids (i-C15:0 toi-C21:0), indicating an additional bacterial component. Biomass and lipids from the PSC were depleted in13C relative to source water CO2 by 10.9 and 17.2‰, respectively. The C20–21 fatty acids of the PSC were less depleted than the iso-branched fatty acids, 18.4 and 22.6‰, respectively. The biomass of T. rubergrown on CO2 was depleted in 13C by only 3.3‰ relative to C source. In contrast, biomass was depleted by 19.7‰ when formate was the C source. Independent of carbon source, T. ruber lipids were heavier than biomass (+1.3‰). The depletion in the C20–21 fatty acids from the PSC indicates thatThermocrinis biomass must be similarly depleted and too light to be explained by growth on CO2. Accordingly,Thermocrinis in the PSC is likely to have utilized formate, presumably generated in the spring source region.
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Grossi, Vincent, Damien Mollex, Arnauld Vinçon-Laugier, Florence Hakil, Muriel Pacton y Cristiana Cravo-Laureau. "Mono- and Dialkyl Glycerol Ether Lipids in Anaerobic Bacteria: Biosynthetic Insights from the Mesophilic Sulfate Reducer Desulfatibacillum alkenivorans PF2803T". Applied and Environmental Microbiology 81, n.º 9 (27 de febrero de 2015): 3157–68. http://dx.doi.org/10.1128/aem.03794-14.
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ABSTRACTBacterial glycerol ether lipids (alkylglycerols) have received increasing attention during the last decades, notably due to their potential role in cell resistance or adaptation to adverse environmental conditions. Major uncertainties remain, however, regarding the origin, biosynthesis, and modes of formation of these uncommon bacterial lipids. We report here the preponderance of monoalkyl- and dialkylglycerols (1-O-alkyl-, 2-O-alkyl-, and 1,2-O-dialkylglycerols) among the hydrolyzed lipids of the marine mesophilic sulfate-reducing proteobacteriumDesulfatibacillum alkenivoransPF2803Tgrown onn-alkenes (pentadec-1-ene or hexadec-1-ene) as the sole carbon and energy source. Alkylglycerols account for one-third to two-thirds of the total cellular lipids (alkylglycerols plus acylglycerols), depending on the growth substrate, with dialkylglycerols contributing to one-fifth to two-fifths of the total ether lipids. The carbon chain distribution of the lipids ofD. alkenivoransalso depends on that of the substrate, but the chain length and methyl-branching patterns of fatty acids and monoalkyl- and dialkylglycerols are systematically congruent, supporting the idea of a biosynthetic link between the three classes of compounds. Vinyl ethers (1-alken-1′-yl-glycerols, known as plasmalogens) are not detected among the lipids of strain PF2803T. Cultures grown on different (per)deuteratedn-alkene,n-alkanol, andn-fatty acid substrates further demonstrate that saturated alkylglycerols are not formed via the reduction of hypothetic alken-1′-yl intermediates. Our results support an unprecedented biosynthetic pathway to monoalkyl/monoacyl- and dialkylglycerols in anaerobic bacteria and suggest thatn-alkyl compounds present in the environment can serve as the substrates for supplying the building blocks of ether phospholipids of heterotrophic bacteria.
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Ahrendt, Tilman, Hendrik Wolff y Helge B. Bode. "Neutral and Phospholipids of the Myxococcus xanthus Lipodome during Fruiting Body Formation and Germination". Applied and Environmental Microbiology 81, n.º 19 (10 de julio de 2015): 6538–47. http://dx.doi.org/10.1128/aem.01537-15.
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ABSTRACTMyxobacteria are well-known for their complex life cycle, including the formation of spore-filled fruiting bodies. The model organismMyxococcus xanthusexhibits a highly complex composition of neutral and phospholipids, including triacylglycerols (TAGs), diacylglycerols (DAGs), phosphatidylethanolamines (PEs), phosphatidylglycerols (PGs), cardiolipins (CLs), and sphingolipids, including ceramides (Cers) and ceramide phosphoinositols (Cer-PIs). In addition, ether lipids have been shown to be involved in development and signaling. In this work, we describe the lipid profile ofM. xanthusduring its entire life cycle, including spore germination. PEs, representing one of the major components of the bacterial membrane, decreased by about 85% during development from vegetative rods to round myxospores, while TAGs first accumulated up to 2-fold before they declined 48 h after the induction of sporulation. Presumably, membrane lipids are incorporated into TAG-containing lipid bodies, serving as an intermediary energy source for myxospore formation. The ceramides Cer(d-19:0/iso-17:0) and Cer(d-19:0/16:0) accumulated 6-fold and 3-fold, respectively, after 24 h of development, identifying them to be novel putative biomarkers forM. xanthussporulation. The most abundant ether lipid, 1-iso-15:0-alkyl-2,3-di-iso-15:0-acyl glycerol (TG1), exhibited a lipid profile different from that of all TAGs during sporulation, reinforcing its signaling character. The absence of all these lipid profile changes in mutants during development supports the importance of lipids in myxobacterial development. During germination of myxospores, only thede novobiosynthesis of new cell membrane fatty acids was observed. The unexpected accumulation of TAGs also during germination might indicate a function of TAGs as intermediary storage lipids during this part of the life cycle as well.
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Zhang, Zhe‐Xuan, Jiwei Li, Hongxuan Lu, Huan Yang, Yige Zhang, Yongjie Tang, Meiyan Fu y Xiaotong Peng. "Bacterial glycerol tetraethers as a potential tool to trace marine methane cycling". Limnology and Oceanography, 20 de noviembre de 2023. http://dx.doi.org/10.1002/lno.12462.
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AbstractBranched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial lipids that can be preserved in sedimentary archives for tens of millions of years and are ubiquitous in diverse environments, including cold seep systems. Their potential implications for detecting methane activity in deep time are, however, hampered by the multiple sources of brGDGTs in cold seeps and the lack of evidence of their stable carbon isotopes. Here, we show that brGDGTs in cold seeps are characterized by depleted stable carbon isotopic compositions of the alkyl moieties (δ13C = −32.9‰ to −82.7‰), indicating a methane metabolizing community origin, which is supported by the association between 16S rRNA genes and brGDGTs. We further identify unique seep‐derived brGDGT signals from the global published dataset by a tree‐based machine‐learning algorithm. This trained model, named light gradient‐boosting machine classification for paleoSEEP (GBM_SEEP), is further applied on a paleorecord across the Paleocene–Eocene Thermal Maximum (PETM), which suggests potential methane emission events during the PETM recovery phase. Collectively, our study links brGDGT production in cold seeps with methane metabolizing communities and provides a potential strategy to capture significant methane emission events using the machine‐learning model, which warrants further investigation.
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Zeng, Zhirui, Huahui Chen, Huan Yang, Yufei Chen, Wei Yang, Xi Feng, Hongye Pei y Paula V. Welander. "Identification of a protein responsible for the synthesis of archaeal membrane-spanning GDGT lipids". Nature Communications 13, n.º 1 (22 de marzo de 2022). http://dx.doi.org/10.1038/s41467-022-29264-x.
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AbstractGlycerol dibiphytanyl glycerol tetraethers (GDGTs) are archaeal monolayer membrane lipids that can provide a competitive advantage in extreme environments. Here, we identify a radical SAM protein, tetraether synthase (Tes), that participates in the synthesis of GDGTs. Attempts to generate a tes-deleted mutant in Sulfolobus acidocaldarius were unsuccessful, suggesting that the gene is essential in this organism. Heterologous expression of tes homologues leads to production of GDGT and structurally related lipids in the methanogen Methanococcus maripaludis (which otherwise does not synthesize GDGTs and lacks a tes homolog, but produces a putative GDGT precursor, archaeol). Tes homologues are encoded in the genomes of many archaea, as well as in some bacteria, in which they might be involved in the synthesis of bacterial branched glycerol dialkyl glycerol tetraethers.
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Xiao, Wenjie, Yunping Xu, Donald E. Canfield, Frank Wenzhöfer, Chuanlun Zhang y Ronnie N. Glud. "Strong linkage between benthic oxygen uptake and bacterial tetraether lipids in deep-sea trench regions". Nature Communications 15, n.º 1 (23 de abril de 2024). http://dx.doi.org/10.1038/s41467-024-47660-3.
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AbstractOxygen in marine sediments regulates many key biogeochemical processes, playing a crucial role in shaping Earth’s climate and benthic ecosystems. In this context, branched glycerol dialkyl glycerol tetraethers (brGDGTs), essential biomarkers in paleoenvironmental research, exhibit an as-yet-unresolved association with sediment oxygen conditions. Here, we investigated brGDGTs in sediments from three deep-sea regions (4045 to 10,100 m water depth) dominated by three respective trench systems and integrated the results with in situ oxygen microprofile data. Our results demonstrate robust correlations between diffusive oxygen uptake (DOU) obtained from microprofiles and brGDGT methylation and isomerization degrees, indicating their primary production within sediments and their strong linkage with microbial diagenetic activity. We establish a quantitative relationship between the Isomerization and Methylation index of Branched Tetraethers (IMBT) and DOU, suggesting its potential validity across deep-sea environments. Increased brGDGT methylation and isomerization likely enhance the fitness of source organisms in deep-sea habitats. Our study positions brGDGTs as a promising tool for quantifying benthic DOU in deep-sea settings, where DOU is a key metric for assessing sedimentary organic carbon degradation and microbial activity.
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Zeng, Zhiyu, Wenjie Xiao, Fengfeng Zheng, Yufei Chen, Yuanqing Zhu, Jiwei Tian y Chuanlun Zhang. "Enhanced production of highly methylated brGDGTs linked to anaerobic bacteria from sediments of the Mariana Trench". Frontiers in Marine Science 10 (18 de agosto de 2023). http://dx.doi.org/10.3389/fmars.2023.1233560.
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Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial membrane lipids that are widely used in terrestrial paleoclimatic reconstructions. Recent studies have reported that brGDGTs can also be produced by marine bacteria. However, the environmental factors influencing marine-derived brGDGTs and their source organisms remain largely unknown. Here, we investigated the distribution and composition of brGDGTs and a suite of their putative derivatives called overly branched GDGTs (obGDGTs) in the Mariana Trench core sediments (water depth 8300 m, core length 320 cm), as well as the composition of bacterial communities. The ratio of the branched over isoprenoid tetraethers (BIT) was 0.03-0.21 (average 0.07; SD = 0.04; n = 21) and the ratio ΣIIIa/ΣIIa of brGDGTs was 0.93-7.47 (average 3.39; SD = 1.73; n = 21), which support the in situ production of brGDGTs. Co-occurrence network analysis revealed that a total of 33 types of bacteria at the order level (e.g., Armatimonadota DG-56, Proteobacteria Rhodospirillales, Chloroflexi SAR202_clade) were closely related to the distribution of brGDGTs and obGDGTs, which could be potential sources for these compounds. The abrupt increase in brGDGT and obGDGT concentrations in deeper oxygen-depleted sediments and their good correlations with anaerobic bacterial abundances suggest that these brGDGTs and obGDGTs may be produced by anaerobic bacteria residing in the anoxic sediments. Considerable variation in the degrees of methylation and cyclization of brGDGTs (obGDGTs) under different redox conditions indicate that sediment oxygen levels may have a profound impact on the presence and abundance of brGDGTs and obGDGTs, which should be considered when applying them for paleo-temperature or pH reconstructions. This study shows that brGDGTs and obGDGTs obtained from the Mariana Trench were probably produced by a variety of bacterial phyla indigenous in the hadal ocean, which are different from Acidobacteria commonly considered to be major terrestrial sources of brGDGTs.
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Zang, Jingjie, Huan Yang, Jiahao Zhang, Huiru Tang y Liangcheng Tan. "Application of microbial membrane tetraether lipids in speleothems". Frontiers in Ecology and Evolution 11 (2 de mayo de 2023). http://dx.doi.org/10.3389/fevo.2023.1117599.
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Glycerol dialkyl glycerol tetraethers (GDGTs), which are derived from microbial membranes, occur widely in soils, peats, lake sediments, marine sediments, hot springs, and other environments. GDGTs respond sensitively to environmental changes and have become an important tool in paleoenvironmental reconstruction. However, their application in speleothems, one of the most important archives of the study of past climates, has been quite limited. In this paper, we review the recent progress in the study of GDGTs in speleothems, from their sources to their distribution characteristics and paleoenvironmental applications. GDGTs in speleothems have been shown to come from dripping water, and cave systems. The distribution of GDGTs in speleothems shows that archaeal isoprenoid GDGTs (isoGDGTs) dominate over bacterial branched GDGTs (brGDGTs). The proxies based on isoGDGTs (TEX86) and brGDGTs (MBT/CBT) are correlated with temperature, which may offer promising potential methods for reconstructing terrestrial palaeotemperature. Ultimately, we discuss the difficulties and problems to be solved in studying speleothem GDGTs and the possible future directions for this field.
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Wang, Yipeng, Jialei Yang, Guichen Wang, Yinyi Zhang, Rui Zhang, Tiegang Li, James Russell et al. "Source Identification of brGDGTs in the Surface Sediments of the East China Sea". Frontiers in Earth Science 9 (31 de enero de 2022). http://dx.doi.org/10.3389/feart.2021.796539.
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Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are components of bacterial membranes in terrestrial soils, which are widely used in paleoenvironmental reconstruction in global terrestrial soils and marine sediments. In marine sediments, the mixed sources of brGDGTs complicate the applications of brGDGT-related indicators in reconstructing terrestrial environments. In this study, we reported the spatial distribution of brGDGT-related indicators (MBTʹ 5ME, CBTʹ 5ME, #Ringstetra, and IIIa/IIa) in surface sediments from the East China Sea (ECS). MBTʹ 5ME and CBTʹ 5ME showed a stepped trend from the inner shelf to the outer shelf, and #Ringstetra and ∑IIIa/∑IIa values in sediments of the ECS are distinct compared with those in the catchment soils, suggesting marine in situ production of brGDGTs. We also examined the existence of marine in situ brGDGTs and quantitatively determined the contributions of terrestrial and in situ production of brGDGTs. This study reported mixed sources of soil-derived brGDGTs were dominant, and marine in situ brGDGTs were overprinted. Our results indicate that there were predominantly marine in situ brGDGTs (avg. 60.5 ± 5.5%) in the outer shelf due to the weak riverine transportation and were characterized by high #Ringstetra and IIIa/IIa.
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O’Beirne, Molly D., Wesley P. Scott, Sergio Contreras, A. Araneda, E. Tejos, J. Moscoso y Josef P. Werne. "Distribution of branched glycerol dialkyl glycerol tetraether (brGDGT) lipids from soils and sediments from the same watershed are distinct regionally (central Chile) but not globally". Frontiers in Earth Science 12 (17 de abril de 2024). http://dx.doi.org/10.3389/feart.2024.1383146.
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Quantitative reconstructions of past continental climates are vital for understanding contemporary and past climate change. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are unique bacterial lipids that have been proposed as universal paleothermometers due to their correlation with temperature in modern settings. Thus, brGDGTs may serve as a crucial paleotemperature proxy for understanding past climate variations and improving regional climate projections, especially in critical but under constrained regions. That said, complications can arise in their application due to varying source contributions (e.g., soils vs. peats vs. lacustrine). As such, this study investigates brGDGT distributions in Chilean lake surface sediments and corresponding watershed soils to determine the source of brGDGTs to lake sediments. Global datasets of brGDGTs in lake sediments and soils were additionally compiled for comparison. Distinct brGDGT distributions in Chilean lakes and soils indicate minimal bias from soil inputs to the lacustrine sediments as well as in situ lacustrine production of brGDGTs, which supports the use of brGDGTs in lake sediments as reliable paleotemperature proxies in the region. The ΣIIIa/ΣIIa ratio, initially promising as a brGDGT source indicator in marine settings, shows global complexities in lacustrine settings, challenging the establishment of universal thresholds for source apportionment. That said, we show that the ratio can be successfully applied in Chilean lake surface sediments. Direct comparisons with watershed soils and further research are crucial for discerning brGDGT sources in lake sediments and improving paleotemperature reconstructions on regional and global scales moving forward. Overall, this study contributes valuable insights into brGDGT variability, essential for accurate paleoreconstructions.
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Kalpana, M. S., Joyanto Routh, Susanne Fietz, Mahjoor A. Lone y Augusto Mangini. "Sources, Distribution and Paleoenvironmental Application of Fatty Acids in Speleothem Deposits From Krem Mawmluh, Northeast India". Frontiers in Earth Science 9 (5 de julio de 2021). http://dx.doi.org/10.3389/feart.2021.687376.
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Integrated multiproxy geochemical studies are essential to reconstruct the paleoenvironment through different time scales. Pristine terrestrial archives such as speleothems provide an excellent opportunity to study these changes by measuring the stable isotope and biomarker trends preserved in these records. Here, we investigated fatty acids in drip water, moonmilk, and a stalagmite (KM-1) retrieved from Krem Mawmluh in northeast India to constrain the sources and distribution of these compounds. Besides, we tested their compatibility with established glycerol dialkyl glycerol tetraethers and stable isotope proxies in KM-1 to probe the use of fatty acid-derived proxies for paleoclimate reconstruction. We observe a similar composition of fatty acids in drip water as well as the cave deposits with significantly higher concentrations of fatty acids in drip water (10.6–124 μg/L) and moonmilk (1.32–16.5 μg/g) compared to the stalagmite (0.67–2.09 μg/g). In KM-1 stalagmite, fatty acids and the presence of azelaic acid transported from surface soils indicate that these compounds are derived from bacterial activity both within the cave and the overlying soil cover. The branched C15 fatty acid index (iso+anteiso C15/nC15) increases during the Holocene, suggesting enhanced microbial production under warm/wet conditions. Fluctuations in the fatty acid indices coincide with abrupt shifts in the TEX86 and BIT proxies reflecting the warm/wet Holocene and cold/dry Late Pleistocene. These trends imply the potential use of fatty acids for reconstructing past climate changes in speleothems but need more analytical reference points to provide statistical data.
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Zhu, Zeyang, Jing Wu, Guoqiang Chu, Patrick Rioual, Jiaxin Lu, Luo Wang y Jiaqi Liu. "Summer warming during Heinrich Stadial 1 in Northeast China". Geology, 26 de febrero de 2024. http://dx.doi.org/10.1130/g51881.1.
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The last deglaciation is considered a key period for exploring the underlying dynamics of temperature changes because it was characterized by multiple millennial-scale abrupt climatic events. However, the limited number of quantitative temperature records in Northeast (NE) China covering the last deglaciation hampers a complete understanding of the mechanisms and processes behind the temperature changes that occurred in that region. Here, we present a quantitative reconstruction of summer temperature over the last deglaciation based on bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs) analyzed from the sediment sequence of Lake Kielguo, a small volcanic lake in NE China. The results show that summer temperature was lowest during the interval ca. 20−18.2 calibrated (cal.) k.y. B.P. with a value of ∼11.1 °C and increased by ∼1.9 °C during Heinrich Stadial 1 (HS1) and by ∼2.7 °C during the transition to the Bølling-Allerød (B-A). The summer temperatures during the B-A warm interval and Younger Dryas cold interval were ∼14.1 °C and ∼12.0 °C, respectively. The summer temperature record from the Lake Kielguo sediment sequence indicates that summer warming dominated the climate change state during HS1 in East Asia, which is different from the cooling pattern controlled by winter temperatures in the North Atlantic and Greenland realms. This distinction can be explained by weakened winter cooling signals triggered by the collapse of Atlantic Meridional Overturning Circulation when these signals propagated to East Asia, and increased summer temperature warming controlled by orbital and greenhouse gases during HS1 in East Asia.