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Stable nitrogen isotope analysis of chlorophylls by gas chromatography–isotope ratio mass spectrometry
A100
Goldschmidt Conference Abstract 2006
Stable nitrogen isotope analysis of chlorophylls by gas chromatography– isotope ratio mass spectrometry Y. CHIKARAISHI1, Y. KASHIYAMA1, N.O. OGAWA1, H. KITAZATO1, S. NOMOTO2, N. OHKOUCHI1 1
Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Japan (ychikaraishi@ jamstec.go.jp) 2 Department of Chemistry, University of Tsukuba, Japan Compound-specific H, C and N isotope analyses by gas chromatography–isotope ratio mass spectrometry (GC/IRMS) have widely been used for various studies, because it allows a rapid and precise isotope analysis of specific molecules of a small amount (nanomolar amount of the element) in complex mixture. However, its application for tetrapyrrole pigments (i.e. chlorophylls) is limited due to their high molecular weight and conjugated structures. In this study, we developed a method to determine nitrogen isotopic composition (d15N) of chlorophylls, by the use of chemical degradation treatment prior to the isotope analysis. Chlorophylls were isolated by high-performance liquid chromatography. The isolated chlorophylls were transformed to pyropheophorbide derivatives by HCl treatment, and subsequently degraded to pyrrole units (maleimides) by chromic acid oxidation (Fig. 1). These chemical degradations have no substantial isotopic fractionation for chlorophyll nitrogen, and thus d15N values of the pyrrole units can be determined precisely by GC/IRMS. Analytical error (1r, standard deviation) of the isotope measurement was always better than ±0.5&, with the minimum sample amount of 15 ngN.
Microbial community structure at Champagne Pool, Waiotapu, New Zealand A. CHILDS1, B.W. MOUNTAIN1, R. O’TOOLE2 1
GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo, New Zealand ([email protected]) 2 School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand The unique geology and geochemistry of Champagne Pool, Waiotapu, New Zealand, has been well documented but to date there has been very little information on the relationship between microbial community structure and the physico-chemical environments in and around the pool. Champagne Pool contains alkalichloride water that maintains a constant 75 °C in which the pH is lowered to 5.5 due to the formation of bicarbonate from the ascending CO2. The water itself contains a variety of elements such as arsenic, antimony, sulfur, gold, silver, thallium, and mercury. Silica is precipitated out and deposited around the edge of the pool forming siliceous microstromatolites. This study aims to identify organisms around the margins of Champagne Pool and assess their spatial distribution with reference to the pool’s geochemistry. The sample site was divided into four zones spanning the margin of the pool: the sub-aqueous precipitate at 75 °C and pH 5.5; the air/water interface containing elemental sulfur and amorphous silica; the silica microstromatolites consisting of layers of microbes and precipitated silica which are kept moist by wave action, steam, and wicking effect; and the organic mat which coats the underside of the silica sinter ledge. This has a pH of 2.5 due to the oxidation of airborne H2S and is kept moist by steam emanating from the pool. Molecular methods were used to identify the community structure and relate this to the geochemical environment. Community genomic DNA was extracted and 16S ribosomal DNA amplified using a variety of universal and specific primers for archaea and bacteria. Sequences were then compared with current databases using BLAST. DGGE has been used to assess variation in microbial diversity associated with each cross-sectional zone. The sub-aqueous precipitate, sulfur and sinter samples showed a number of organisms that originate near the base of the 16S phylogeny tree including the archaeal families Sulfolobales, Thermoproteales, Desulfurococcales and Thermofilaceae. Bacteria identified to date include Thermodesulfobacterium and Aquificales. These results reveal a predominance of anaerobic sulphur-respiring microbes. The microbial mat revealed a different community containing b, d and c Proteobacteria, and Cyanidiaceae. doi:10.1016/j.gca.2006.06.114
Fig. 1. d15N values of the pyrrole units from chlorophyll a in Zea mays. The d15N values of chlorophyll a (+1.8&) and pyropheophorbide a methyl ester (+2.2&) are determined by Flash elemental analyzer-IRMS.
doi:10.1016/j.gca.2006.06.113
Goldschmidt Conference Abstract 2006
Stable nitrogen isotope analysis of chlorophylls by gas chromatography– isotope ratio mass spectrometry Y. CHIKARAISHI1, Y. KASHIYAMA1, N.O. OGAWA1, H. KITAZATO1, S. NOMOTO2, N. OHKOUCHI1 1
Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Japan (ychikaraishi@ jamstec.go.jp) 2 Department of Chemistry, University of Tsukuba, Japan Compound-specific H, C and N isotope analyses by gas chromatography–isotope ratio mass spectrometry (GC/IRMS) have widely been used for various studies, because it allows a rapid and precise isotope analysis of specific molecules of a small amount (nanomolar amount of the element) in complex mixture. However, its application for tetrapyrrole pigments (i.e. chlorophylls) is limited due to their high molecular weight and conjugated structures. In this study, we developed a method to determine nitrogen isotopic composition (d15N) of chlorophylls, by the use of chemical degradation treatment prior to the isotope analysis. Chlorophylls were isolated by high-performance liquid chromatography. The isolated chlorophylls were transformed to pyropheophorbide derivatives by HCl treatment, and subsequently degraded to pyrrole units (maleimides) by chromic acid oxidation (Fig. 1). These chemical degradations have no substantial isotopic fractionation for chlorophyll nitrogen, and thus d15N values of the pyrrole units can be determined precisely by GC/IRMS. Analytical error (1r, standard deviation) of the isotope measurement was always better than ±0.5&, with the minimum sample amount of 15 ngN.
Microbial community structure at Champagne Pool, Waiotapu, New Zealand A. CHILDS1, B.W. MOUNTAIN1, R. O’TOOLE2 1
GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo, New Zealand ([email protected]) 2 School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand The unique geology and geochemistry of Champagne Pool, Waiotapu, New Zealand, has been well documented but to date there has been very little information on the relationship between microbial community structure and the physico-chemical environments in and around the pool. Champagne Pool contains alkalichloride water that maintains a constant 75 °C in which the pH is lowered to 5.5 due to the formation of bicarbonate from the ascending CO2. The water itself contains a variety of elements such as arsenic, antimony, sulfur, gold, silver, thallium, and mercury. Silica is precipitated out and deposited around the edge of the pool forming siliceous microstromatolites. This study aims to identify organisms around the margins of Champagne Pool and assess their spatial distribution with reference to the pool’s geochemistry. The sample site was divided into four zones spanning the margin of the pool: the sub-aqueous precipitate at 75 °C and pH 5.5; the air/water interface containing elemental sulfur and amorphous silica; the silica microstromatolites consisting of layers of microbes and precipitated silica which are kept moist by wave action, steam, and wicking effect; and the organic mat which coats the underside of the silica sinter ledge. This has a pH of 2.5 due to the oxidation of airborne H2S and is kept moist by steam emanating from the pool. Molecular methods were used to identify the community structure and relate this to the geochemical environment. Community genomic DNA was extracted and 16S ribosomal DNA amplified using a variety of universal and specific primers for archaea and bacteria. Sequences were then compared with current databases using BLAST. DGGE has been used to assess variation in microbial diversity associated with each cross-sectional zone. The sub-aqueous precipitate, sulfur and sinter samples showed a number of organisms that originate near the base of the 16S phylogeny tree including the archaeal families Sulfolobales, Thermoproteales, Desulfurococcales and Thermofilaceae. Bacteria identified to date include Thermodesulfobacterium and Aquificales. These results reveal a predominance of anaerobic sulphur-respiring microbes. The microbial mat revealed a different community containing b, d and c Proteobacteria, and Cyanidiaceae. doi:10.1016/j.gca.2006.06.114
Fig. 1. d15N values of the pyrrole units from chlorophyll a in Zea mays. The d15N values of chlorophyll a (+1.8&) and pyropheophorbide a methyl ester (+2.2&) are determined by Flash elemental analyzer-IRMS.
doi:10.1016/j.gca.2006.06.113