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Assessing the metabolism of sedimentary microbial communities using the hydrogen isotopic composition of fatty acids
Organic Geochemistry ( IF 3 ) Pub Date : 2018-10-01 , DOI: 10.1016/j.orggeochem.2018.07.011
Sandra M. Heinzelmann , Laura Villanueva , Yvonne A. Lipsewers , Danielle Sinke-Schoen , Jaap S. Sinninghe Damsté , Stefan Schouten , Marcel T.J. van der Meer

Abstract The hydrogen isotopic composition of fatty acids (FAs) has previously been shown to reflect the metabolism of microorganisms in pure culture, but has rarely been tested in the environment. Here, we report the abundance and hydrogen isotopic composition of polar lipid derived FAs extracted from surface sediments of the saline Lake Grevelingen (The Netherlands), at two different stations and during two seasons with oxic bottom water conditions during spring and hypoxic to anoxic conditions during late summer. These data are compared with the bacterial diversity revealed by 16S rRNA gene amplicon sequencing. All measured FAs were depleted in deuterium relative to the bottom water by 103‰ to 267‰. FAs associated with heterotrophic bacteria (i-15:0 and ai-15:0) showed the smallest fractionation (−103‰ to −185‰) while those derived from pelagic photoautotrophic phytoplankton (20:5) showed the largest fractionation (−230‰ to −267‰). Overall, the hydrogen isotope fractionation reflected in the majority of the more commonly occurring FAs (14:0, 16:0, 16:1ω7) is relatively large (−172‰ to −217‰). Together with the high relative abundance of the 20:5 FA, this suggests a substantial contribution from dead pelagic biomass settling from the water column to the sedimentary polar lipid derived FA pool and not from the in situ microbial communities. Therefore, the majority of the isotope signal in the fatty acids from surface sediments might not represent the general metabolism of the active sedimentary communities. Therefore, the input of pelagic biomass into sedimentary environments may bias the information contained in the hydrogen isotopic composition of FAs.

中文翻译:

使用脂肪酸的氢同位素组成评估沉积微生物群落的代谢

摘要 脂肪酸 (FA) 的氢同位素组成先前已被证明可以反映纯培养物中微生物的代谢,但很少在环境中进行测试。在这里,我们报告了从盐水湖 Grevelingen(荷兰)的表层沉积物中提取的极性脂质衍生 FAs 的丰度和氢同位素组成,在两个不同的站点和两个季节,春季底水条件为含氧量,低氧到缺氧条件下为夏末。这些数据与 16S rRNA 基因扩增子测序揭示的细菌多样性进行了比较。相对于底水,所有测量的 FA 都消耗了 103‰ 至 267‰ 的氘。与异养细菌相关的 FA(i-15:0 和 ai-15: 0) 表现出最小的分馏(-103‰ 至-185‰),而来自远洋光合自养浮游植物(20:5)的那些表现出最大的分馏(-230‰ 至-267‰)。总体而言,反映在大多数更常见的 FA(14:0、16:0、16:1ω7)中的氢同位素分馏相对较大(-172‰ 至 -217‰)。连同 20:5 FA 的高相对丰度,这表明从水柱沉降到沉积极性脂质衍生的 FA 池的死远洋生物量的重要贡献,而不是来自原位微生物群落。因此,来自表层沉积物的脂肪酸中的大部分同位素信号可能不代表活跃沉积群落的一般代谢。所以,
更新日期:2018-10-01
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