Below are recent projects that are completed and most representative of my work. You can find more on my Google Scholar.
Currently at UCSB, I am combining cultivation, field sampling, and flow cytometry to develop a targeted cell sorting and genome amplification method for understudied and/or (un)cultured archaea, with the goal of applying the approach to answer questions about the origin of the eukaryotic cell as well as the evolution and ecology of archaea.
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Isotopic fingerprints of microbial methane: application of methane clumped isotope analysis
Stable carbon and hydrogen isotope ratios have been widely used to identify the sources of a potent greenhouse gas, methane. The abundance of multiply-substituted or “clumped” isotopologues of methane provides additional and independent information about the origin and history of methane. However, these isotopic tools do not always lead to consistent interpretations. Through cultivation experiments, isotope analyses, and bio-isotopic model, we show that it is important to consider physiological state and energy availability when we interpret isotope data for microbial methane, providing new insights to the isotopic framework that has long been used to identify the sources of methane.
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Archaeal lipid membrane cyclization: bioenergetic considerations for proxy applications
The modification of membrane composition in response to changing environments is crucial for cell survival and growth. The degree of cyclization, or ring index (RI), in archaeal lipids has been shown to reflect changes in various environmental and physiological factors. Here we show that: 1) shifts in carbon and energy metabolism alone can result in significant changes in RI, and 2) the patterns in RI do not always align with thermodynamic predictions. We discuss factors that could affect the kinetics of metabolic reactions and explain experimental observations. These findings suggest that bioenergetic (in addition to environmental) considerations are crucial for proxy applications for climate reconstruction using lipid biomarkers.
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Archaeal lipid hydrogen isotope composition: potential (paleo)hydrological proxy applications
The hydrogen isotope composition (𝛿2H) of lipids (eukaryotic lipids, in particular) has been widely explored as a biomarker for reconstructing past hydrologic cycles which, in turn, improve our understanding of future climate projections. Despite their diverse habitats and long preservation potential, archaeal lipids remain understudied. Here we show that, in general, large fractions of archaeal lipid H directly reflect water 𝛿2H, resulting in relatively constant isotope fractionation. We developed a biochemically informed isotope flux-balance model that identify specific biochemical mechanisms that explain observed isotopic patterns. These findings support the potential application of archaeal lipid 𝛿2H as an environmental proxy.
