Using hydrothermal biofilm geochemical signatures to generate predictions of elemental behavior with implications for gene hunting, biogeochemical rate measurements, and novel biosignatures
Abstract
The inorganic geochemical composition of hydrothermal biofilms may provide novel ways to interpret isotopic, molecular, and genomic data from active or fossil hydrothermal systems. In order to better constrain the composition of living biofilms, hydrothermal water samples, bulk biofilm samples, and contextual samples including soil, sinter, and non-hydrothermal biomass were collected from dozens of siliceous sinter-depositing hot springs spread out over five separate thermal areas in Yellowstone National Park. Sampled hot springs varied in temperature (boiling to 35 C), pH (2.1 to 8.7), spatial proximity (less than a meter to tens of kilometers of separation), and geochemical composition. Analysis of major and trace element abundances, in conjunction with stable isotopic carbon and nitrogen values, was conducted for the biofilms within the context of environmental inputs. Geochemical analysis of biofilms from the source and outflow channel of one circum-neutral hot spring (‘Bison Pool’) provides context for connecting biofilm carbon fractionation patterns and nitrogen isotopic values with metagenomic analysis for carbon fixation pathways and nitrogen uptake pathways of the same biofilms. Assessment of major and trace element compositions of the biofilms from this hot spring led to the development of aluminum-normalized concentration ratio (ANCR) plots. Analysis of ANCR calculations for water and biofilms collected from Bison Pool indicate that there are groups of elements that exhibit similar patterns of behavior, including mono and divalent cations and silica (Li, Na, Mg, Si, K, Ca, Mn, Rb, Sr, Tl), and oxy-hydroxy anions (B, C, N, P, V, Ga, Ge, As, Mo, Sn, Sb, W). Combining isotopic and metagenomic data with these groupings provides a framework for novel predictions about carbon fractionation pathways, nitrogen uptake pathways, and elemental uptake and utilization methods that could operate in other hydrothermal biofilm communities. We find that each hot spring ecosystem we have studied has unique carbon and nitrogen isotopic signatures, and diverse ranges of elemental patterns. ANCR plots indicate active elemental enrichment or depletion, and variations in the specific behavior of elements within ANCR-defined groups suggests that diverse biofilms have distinct elemental processing modes. These variations lead to predictions that can guide searches for specific gene occurrences, gene expression experiments, and biogeochemical rate measurements.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.B23D0408H
- Keywords:
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- 0424 BIOGEOSCIENCES / Biosignatures and proxies;
- 0450 BIOGEOSCIENCES / Hydrothermal systems;
- 0465 BIOGEOSCIENCES / Microbiology: ecology;
- physiology and genomics;
- 0489 BIOGEOSCIENCES / Trace element cycling