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Yellowstone National Park is a prime location to study biological adaptations to a wide range of temperatures and geochemical conditions. Lipids were extracted and quantified from thermophilic microbial communities sampled along the temperature (29-91°C) and chemical gradients of four alkaline Yellowstone hot springs. I observed that decreased alkyl chain carbon content, increased degree of unsaturation, and a shift from ether to ester linkage caused a downstream increase in the average oxidation state of carbon (ZC) I hypothesized these adaptations were selected because they represent cost-effective solutions to providing thermostable membranes.
This hypothesis was explored by assessing the relative energetic favorability of autotrophic reactions to form alkyl chains from known concentrations of dissolved inorganic species at elevated temperatures. I found that the oxidation-reduction potential (Eh) predicted to favor formation of sample-representative alkyl chains had a strong positive correlation with Eh calculated from hot spring water chemistry (R2 = 0.72 for the O2/H2O redox couple). A separate thermodynamic analysis of bacteriohopanepolyol lipids found that predicted equilibrium abundances of observed polar headgroup distributions were also highly correlated with Eh of the surrounding water (R2= 0.84). These results represent the first quantitative thermodynamic assessment of microbial lipid adaptation in natural systems and suggest that observed lipid distributions represent energetically cost-effective assemblages along temperature and chemical gradients.
Sulfur oxidation is a process that is seen a wide variety of places. One particular place is Yellowstone national park where an abundance of hot springs are present. These acidic and hot places are prime locations for sulfur oxidation to occur. At a very basic level this is thought of as Sulfur, oxygen, and water forming sulfate and hydrogen. Many other reactions occur when an organism performs these processes, and many enzymes are used for this. This paper aimed to create, balance, and analyze the reactions involved in the paper Sulfur Oxidation in the Acidophilic Autotrophic Acidithiobacillus spp. (Wang et al., 2019) Once these reactions were balanced thermodynamic properties were found to evaluate the Gibbs Free Energy of these reactions. This allowed for a unique energy-based view of how this web of reactions relate to each other.