Role of 3-Methylhopanoids in Environmental Hot Spring Anoxygenic Phototrophic Bacteria
Abstract
Microbes are the oldest, most numerous, and most diverse group of organisms on Earth. Despite their central role in sustaining the biogeochemical cycles of our planet today, little is known about the microbes of the early Earth due to a lack of diagnostic morphologic fossils. Biomarkers, membrane lipids that readily fossilize, record microbial inputs to the sediments and can provide a longstanding record of microbial life. Furthermore, because of their durability and longevity, biomarker molecules can be used to detect life in ancient sediments. To understand what the nature of that life may have been, the biosynthesis, taxonomic extent, and physiological role of modern biomarker homologs in living microbes must be known.
Our research aims to characterize the biosynthesis, distribution, and physiological function of cyclic triterpenoid lipids in a diversity of microbes. Recently, we identified the production of a key lipid biomarker, 3-methylhopanoid (3-MeBHP), traditionally attributed to aerobic organisms, in Rhodopila sp. LVNP - a novel purple non-sulfur (PNS) anoxygenic phototroph we isolated from an acidic (pH 3.9) sulfidic hot spring in Lassen Volcanic National Park. We sequenced the genome of Rhodopila sp. LVNP and determined it contained a suite of known lipid biomarker biosynthesis genes documented in other microbes including the hpnR gene required for 3-MeBHP production. This work has the potential to challenge the standing interpretation of 3-MeBHPs as biomarkers of aerobiosis in the rock record. In this acidic, sulfidic hot spring we report the unique community composition and lipid biomarker profiles. We compare seasonal environmental factors in inducing certain biomarker production. There is little previously known about the in situ lipid biomarker production in living microbial mats and biofilms in this natural environment. Modern hydrothermal systems, such as the hot springs that Rhodopila inhabits, are thought to be analogs of habitats present on the early Earth. For this reason, these environments are potentially relevant models for the study of the origin and evolution of photosynthetic systems.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B53E2450M
- Keywords:
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- 0424 Biosignatures and proxies;
- BIOGEOSCIENCES;
- 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES;
- 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY;
- 4924 Geochemical tracers;
- PALEOCEANOGRAPHY