Temperature and pH control on lipid composition of silica sinters from diverse hot springs in the Taupo Volcanic Zone, New Zealand.

Gurpreet Kaur,Matthew B Stott,Bruce W Mountain,Ellen C Hopmans,Richard D Pancost

doi:10.1007/s00792-014-0719-9

Abstract

Microbial adaptations to environmental extremes, including high temperature and low pH conditions typical of geothermal settings, are of interest in astrobiology and origin of life investigations. The lipid biomarkers preserved in silica deposits associated with six geothermal areas in the Taupo Volcanic Zone were investigated and variations in lipid composition as a function of temperature and pH were assessed. Lipid analyses reveal highly variable abundances and distributions, reflecting community composition as well as adaptations to extremes of pH and temperature. Biomarker profiles reveal three distinct microbial assemblages across the sites: the first in Champagne Pool and Loop Road, the second in Orakei Korako, Opaheke and Ngatamariki, and the third in Rotokawa. Similar lipid distributions are observed in sinters from physicochemically similar springs. Furthermore, correlation between lipid distributions and geothermal conditions is observed. The ratio of archaeol to bacterial diether abundance, bacterial diether average chain length, degree of GDGT cyclisation and C31 and C32 hopanoic acid indices typically increase with temperature. At lower pH, the ratio of archaeol to bacterial diethers, degree of GDGT cyclisation and C31 and C32 hopanoic acid indices are typically higher. No trends in fatty acid distributions with temperature or pH are evident, likely reflecting overprinting due to population influences.

Highlights

The study of geothermal environments and their microbial inhabitants is crucial to unravelling the origins and diversification of life on Earth and the discovery of life elsewhere in the universe (e.g. Stetter 1996)
Bacterial non-isoprenoidal diethers were attributed to Thermodesulfobacteriales (Thermodesulfbacterium hydrogeniphilum) and Aquificales (Venenivibrio stagnispumantis) (Table 2), consistent with DNA analyses of Champagne Pool sinters and waters (Hetzer et al 2007; Childs et al 2008), whereas archaeol and glycerol dialkyl glycerol tetraethers (GDGTs) were attributed to Sulfolobales (Sulfurisphaera ohwakuensis) and/or Thermofilum-like populations (Table 2; Hetzer et al 2007)
Lowmolecular weight (LMW) fatty acids have a range of potential sources, branched fatty acids were attributed to Thermodesulfobacteriales (Langworthy et al 1983)

Summary

Introduction

The study of geothermal environments and their microbial inhabitants is crucial to unravelling the origins and diversification of life on Earth and the discovery of life elsewhere in the universe (e.g. Stetter 1996). Silica deposits and associated microbiology have been studied in hot springs from diverse settings, including Yellowstone National Park, USA (Jahnke et al 2001; Guidry and Chafetz 2003; Pepe-Ranney et al 2012), Krisuvik, Iceland (Schultzelam et al 1995; Konhauser et al 2001; Tobler and Benning 2011) and the Taupo Volcanic Zone (TVZ), New Zealand (Jones et al 2001; Mountain et al 2003; Pancost et al 2005, Childs et al 2008; Kaur et al 2011a, b). The diverse and characteristic hydrocarbon structures of lipids have a high preservation potential and are entrained. Our recent work confirmed the preservation of a wide range of diagnostic lipid biomarkers in geothermal silica sinters and demonstrated their potential in the reconstruction of geothermal microbiology (Pancost et al 2005, 2006; Kaur et al 2008, 2011a, b)

Methods

Results

Conclusion