13 research outputs found
Environmental and biochemical controls on the molecular distribution and stable isotope composition of leaf wax biomarkers
Leaf wax n-alkyl lipids are increasingly used as proxies in palaeoclimate studies. Palaeovegetation assemblages are reconstructed from their molecular distribution patterns, while their δ13C and δ2H signals are thought to reflect plant-environment interactions and palaeohydrological shifts, respectively. Such applications depend, however, upon these compounds faithfully recording environmental conditions. To explore the influence of environmental, physical and biochemical controls on n-alkane composition, leaf waxes from seven UK saltmarsh plants were analysed over two growing seasons. Linked analysis of sedimentary n-alkanes enabled further investigation of leaf wax biomarker integration into saltmarsh sediments. The molecular distribution and concentration of n-alkanes from the saltmarsh plants varied significantly. Bulk and n-alkane δ13C recorded different seasonal shifts, with a range of up to 13Ⱐin the offset between bulk and n-alkane 13C/12C values. This
indicated that post-photosynthetic 13C/12C fractionation may be an important additional control on n-alkane δ13C signals. n-Alkane δ2H also varied among the sampled species by >100â°, and could not be explained by physical processes controlling the movement of water inside/outside and within leaves. Comparison with the 2H/1H of chloroplast-synthesised compounds (fatty acids, phytol) suggested
these differences instead reflected the varied biochemical mechanisms operating in the chloroplast and cytosol. Sedimentary biomarker analysis further highlighted that small/moderate vegetation change could drive shifts of ~40â° in sedimentary nalkane 2H/1H, while using globally averaged âtypicalâ values to correct for fractionation between source water and n-alkane 2H/1H may not be representative of a specific geographical location. Results demonstrate: (i) the importance of biochemical mechanisms in controlling the molecular and isotopic composition of n-alkyl lipids; and (ii) the need to further constrain the influence of vegetation change on the isotope composition of sedimentary n-alkanes. Future research should address these areas in other biomes and depositional environments, to ensure accurate interpretation of modern and ancient leaf wax lipid data
Molecular and isotopic investigations of pottery and âcharred remainsâ from Sannai Maruyama and Sannai Maruyama No. 9, Aomori Prefecture.
This paper presents a preliminary study of the analysis of organic residues of Early and Middle Jomon pottery and âcharred remains.â Samples are taken from the Sannai Maruyama site and the Sannai Maruyama No. 9 site in Aomori City, Aomori Prefecture in northern Japan. The following questions are addressed in this study: (i) Do organic residues survive in association with pottery vessels and charred remains? (ii) Can the residues be identified based on molecular and isotopic criteria applied in other investigations? (iii) Are the residues associated with the charred remains common to the residues associated with the pottery vessels? (iv) How do these residues contribute to our understanding of food processing and consumption? Results of our analysis indicate that the lipid composition of the pottery extracts is remarkably similar although some of the sherds exhibited better preservation and a wider range of molecules were detected albeit in lower abundance. There is a marked contrast with the composition of the lipid extracts of the âcharred remains.â The lipid compositions of sample sets from Sannai Maruyama and Sannai Maruyama No. 9 suggest aquatic resources in the pottery but with a plant contribution. The âcharred remainsâ from Sannai Maruyama contain plant tissues most likely with a high starch composition such as nuts. Lipids were recovered from the majority of the samples
First molecular and isotopic evidence of millet processing in prehistoric pottery vessels
Analysis of organic residues in pottery vessels has been successful in detecting a range of animal and plant products as indicators of food preparation and consumption in the past. However, the identification of plant remains, especially grain crops in pottery, has proved elusive. Extending the spectrum is highly desirable, not only to strengthen our understanding of the dispersal of crops from centres of domestication but also to determine modes of food processing, artefact function and the culinary significance of the crop. Here, we propose a new approach to identify millet in pottery vessels, a crop that spread throughout much of Eurasia during prehistory following its domestication, most likely in northern China. We report the successful identification of miliacin (olean-18-en-3β-ol methyl ether), a pentacyclic triterpene methyl ether that is enriched in grains of common/broomcorn millet (Panicum miliaceum), in Bronze Age pottery vessels from the Korean Peninsula and northern Europe. The presence of millet is supported by enriched carbon stable isotope values of bulk charred organic matter sampled from pottery vessel surfaces and extracted n-alkanoic acids, consistent with a C4 plant origin. These data represent the first identification of millet in archaeological ceramic vessels, providing a means to track the introduction, spread and consumption of this important crop
Ancient lipids document continuity in the use of early hunter-gatherer pottery through 9,000 years of Japanese prehistory
The earliest pots in the world are from East Asia and date to the Late Pleistocene. However, ceramic vessels were only produced in large numbers during the warmer and more stable climatic conditions of the Holocene. It has long been assumed that the expansion of pottery was linked with increased sedentism and exploitation of new resources that became available with the ameliorated climate, but this hypothesis has never been tested. Through chemical analysis of their contents, we herein investigate the use of pottery across an exceptionally long 9,000-y sequence from the JĹmon site of Torihama inwestern Japan, intermittently occupied from the Late Pleistocene to the mid-Holocene. Molecular and isotopic analyses of lipids from 143 vessels provides clear evidence that pottery across this sequence was predominantly used for cooking marine and freshwater resources, with evidence for diversification in the range of aquatic products processed during the Holocene. Conversely, there is little indication that ruminant animals or plants were processed in pottery, although it is evident from the faunal and macrobotanical remains that these foods were heavily exploited. Supported by other residue analysis data from Japan, our results show that the link between pottery and fishing was established in the Late Paleolithic and lasted well into the Holocene, despite environmental and socio-economic change. Cooking aquatic products in pottery represents an enduring social aspect of East Asian hunter-gatherers, a tradition based on a dependable technology for exploiting a sustainable resource in an uncertain and changing world
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A mechanistic understanding of polyethylene biodegradation by the marine bacterium Alcanivorax
Polyethylene (PE) is one of the most recalcitrant carbon-based synthetic materials produced and, currently, the most ubiquitous plastic pollutant found in nature. Over time, combined abiotic and biotic processes are thought to eventually breakdown PE. Despite limited evidence of biological PE degradation and speculation that hydrocarbon-degrading bacteria found within the plastisphere is an indication of biodegradation, there is no clear mechanistic understanding of the process. Here, using high-throughput proteomics, we investigated the molecular processes that take place in the hydrocarbon-degrading marine bacterium Alcanivorax sp. 24 when grown in the presence of low density PE (LDPE). As well as efficiently utilising and assimilating the leachate of weathered LDPE, the bacterium was able to reduce the molecular weight distribution (M from 122 to 83Â kg/mol) and overall mass of pristine LDPE films (0.9 % after 34 days of incubation). Most interestingly, Alcanivorax acquired the isotopic signature of the pristine plastic and induced an extensive array of metabolic pathways for aliphatic compound degradation. Presumably, the primary biodegradation of LDPE by Alcanivorax sp. 24 is possible via the production of extracellular reactive oxygen species as observed both by the material's surface oxidation and the measurement of superoxide in the culture with LDPE. Our findings confirm that hydrocarbon-biodegrading bacteria within the plastisphere may in fact have a role in degrading PE
Tracing higher plant inputs to coastal sediments: an integrated isotopic and molecular approach for forensic investigation
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Understanding 2H/1H systematics of leaf wax n-alkanes in coastal plants at Stiffkey saltmarsh, Norfolk, UK
Interpretation of sedimentary n-alkyl lipid d2H data is complicated by a limited understanding of factors controlling interspecies variation in biomarker 2H/1H composition. To distinguish between the effects of interrelated environmental, physical and biochemical controls on the hydrogen isotope composition of n-alkyl lipids, we conducted linked d2H analyses of soil water, xylem water, leaf water and n-alkanes from a range of C3 and C4 plants growing at a UK saltmarsh (i) across multiple
sampling sites, (ii) throughout the 2012 growing season, and (iii) at different times of the day. Soil waters varied isotopically by up to 35& depending on marsh sub-environment, and exhibited site-specific seasonal shifts in d2H up to a maximum of 31 per mil. Maximum interspecies variation in xylem water was 38 per mil, while leaf waters differed seasonally by a maximum of 29 per mil. Leaf wax n-alkane 2H/1H, however, consistently varied by over 100 per mil throughout the 2012 growing season, resulting in an interspecies range in the ewax/leaf water values of -79 per mil to â227 per mil. From the discrepancy in the magnitude of these isotopic differences, we conclude that mechanisms driving variation in the 2H/1H composition of leaf water, including (i) spatial changes in soil water 2H/1H, (ii) temporal changes in soil water 2H/1H, (iii) differences in xylem water 2H/1H, and (iv) differences in leaf water evaporative 2H-enrichment due to varied plant life forms, cannot explain the range of n-alkane d2H values we observed. Results from this study suggests that accurate reconstructions of palaeoclimate regimes from sedimentary n-alkane d2H require further research to constrain those biological mechanisms influencing species-specific differences in 2H/1H fractionation during lipid biosynthesis, in particular where plants have developed biochemical adaptations to water-stressed conditions. Understanding how these mechanisms interact with environmental conditions will be crucial to ensure accurate
interpretation of hydrogen isotope signals from the geological record