Factors Controlling the Distribution of Archaeal Tetraethers in Terrestrial Hot Springs

Abstract

Glycerol dialkyl glycerol tetraethers (GDGTs) found in hot springs reflect the abundance and community structure of Archaea in these extreme environments. The relationships between GDGTs, archaeal communities, and physical or geochemical variables are underexamined to date and when reported often result in conflicting interpretations. Here, we examined profiles of GDGTs from pure cultures of Crenarchaeota and from terrestrial geothermal springs representing a wide distribution of locations, including Yellowstone National Park (United States), the Great Basin of Nevada and California (United States), Kamchatka (Russia), Tengchong thermal field (China), and Thailand. These samples had temperatures of 36.5 to 87°C and pH values of 3.0 to 9.2. GDGT abundances also were determined for three soil samples adjacent to some of the hot springs. Principal component analysis identified four factors that accounted for most of the variance among nine individual GDGTs, temperature, and pH. Significant correlations were observed between pH and the GDGTs crenarchaeol and GDGT-4 (four cyclopentane rings, m/z 1,294); pH correlated positively with crenarchaeol and inversely with GDGT-4. Weaker correlations were observed between temperature and the four factors. Three of the four GDGTs used in the marine TEX 86 paleotemperature index (GDGT-1 to -3, but not crenarchaeol isomer) were associated with a single factor. No correlation was observed for GDGT-0 (acyclic caldarchaeol): it is effectively its own variable. The biosynthetic mechanisms and exact archaeal community structures leading to these relationships remain unknown. However, the data in general show promise for the continued development of GDGT lipid-based physiochemical proxies for archaeal evolution and for paleo-ecology or paleoclimate studies.

Contribution of river‐borne soil organic carbon to the Gulf of Lions (NW Mediterranean)

“…These results are in good agreement with a previous study of globally distributed soils by Weijers et al (2006b), showing that the relative abundance of crenarchaeol in soils was higher with increasing pH values. Pearson et al (2008) also showed that the abundance of crenarchaeol occurring in terrestrial hot springs was positively correlated with pH. However, Nicol et al (2008) showed that autotrophic archaeal ammonia oxidation occurred predominantly in acid soils and that the abundance of ammonia-oxidizing Crenarcheota decreased with increasing soil pH values.…”

Confounding effects of oxygen and temperature on the TEX 86 signature of marine Thaumarchaeota

“…The GDGT composition of the cultured thermophilic AOA Nitrosocaldus yellowstonii and members of Crenarchaeota vary with pH (20,(45)(46)(47). However, for the highly buffered ocean, pH variability is relatively small, and thus would not be expected to significantly bias reconstructed SST.…”

Global Occurrence of Archaeal amoA Genes in Terrestrial Hot Springs

“…It is possible that these genes derive from archaea within the Great Basin hot spring crenarchaeal cluster I (GBSHSC1), which was designated to describe the dominant archaeal 16S rRNA genes recovered from several 56 to 67°C spring systems in the Great Basin, including Surprise Valley (13). The Surprise Valley and Eagleville samples that were the source for cluster A1.1 amoA alleles also contained a preponderance of crenarchaeol relative to other GDGTs (28,29,44). However, in the absence of a pure or highly enriched culture of GBSHSC1, amoA gene alleles from these springs cannot be linked definitively to either 16S rRNA phylotypes or particular membrane lipids.…”

“…Similar amoA genes were amplified using PCR from hot spring sediment samples from a variety of Yellowstone springs (5). In culture, the pre-dominant membrane lipid of "Candidatus Nitrosocaldus yellowstonii" was the glycerol dialkyl glycerol tetraether (GDGT) crenarchaeol, confirming a thermophilic source for crenarchaeol in hot spring environments (28,29,34,44). Finally, a third study coupled rate measurements of complete nitrification by the 15 NO 3 Ϫ isotope pool dilution approach in two 84 to 85°C hot springs in Iceland, with the identification of crenarchaeol in one hot spring (30).…”