Biosynthesis of 3-methylhopanoids by purple non-sulfur anoxygenic phototrophs
Abstract
We have recently discovered that three purple non-sulfur (PNS) anoxygenic phototrophs isolated from marine, hypersaline, and hot spring environments synthesize 3-methylbacteriohopanepolyols (3-MeBHPs). These compounds were previously thought to be exclusively made by oxygen requiring methanotrophic and acetic acid bacteria, and have long been considered a signal for methanotrophy in the rock record. However, our cultures are the first example of both the production of 3-MeBHPs by phototrophic bacteria and their production under anoxic conditions. Preliminary PNS pure culture experiments have revealed that both total BHP and 3-MeBHP increased relative to total membrane fatty acid with increasing pH. We also observed a concomitant increase in cyclopropane fatty acid (cy19), indicating a membrane response to pH stress. We are currently investigating the cellular function of these compounds in PNS, namely we are characterizing the role of hopanoids in pH homeostasis. We are also performing detailed compound-specific C isotopic studies, as preliminary analyses indicate that the PNS 3-MeBHPs will be distinguishable from methanotrophic 3-MeBHPs in the rock record. The overarching goal of this work is to link the laboratory and environmental experiments to ensure that the observations made with pure cultures reflect the biosynthesis of 3-MeBHPs in the environment. Such a relationship is necessary for properly interpreting the occurrence of these compounds in the sedimentary rock record.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.B41A0397P
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0444 Evolutionary geobiology;
- BIOGEOSCIENCESDE: 0463 Microbe/mineral interactions;
- BIOGEOSCIENCESDE: 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES