Biology subjects

Young, E. D.

Publications and source records attributed to Young, E. D..

5 recordsLinked to original sources

bioRxiv2024

The clumped isotope signatures of multiple methanogenesis metabolisms

Methane is a potent greenhouse gas, an important energy source, and a potential biosignature on extraterrestrial planetary bodies. The relative abundances of doubly substituted ("clumped") methane isotopologues (13CH3D and 12CH2D2) offer important information on the sources and sinks of methane. However, the clumped isotope signatures of microbially produced methane from different methanogenic pathways lack a systematic investigation. In this study, we provide a dataset encompassing the relative isotopologue abundances produced by hydrogenotrophic, methylotrophic, acetoclastic, and methoxydotrophic methanogenesis. We find that a statistical "combinatorial effect" generates significant differences in 12CH2D2 compositions between hydrogenotrophic methanogenesis and other pathways. The thermodynamic drive of methanogenic reactions and phylogenetic affiliation may also influence the isotope compositions of methane. Our study provides new experimental constraints on the isotope signatures of different microbial methanogenic pathways, and evidence of the mechanisms responsible for the observed differences. TeaserA novel stable isotope tool to track and differentiate sources of biological methane.

microbiology↗

bioRxiv2023

The evolution of multiply substituted isotopologues of methane during microbial aerobic oxidation

Aerobic methane oxidation (AeOM) is an important biological sink of methane on Earth. Stable isotopes are critical tools in tracking the sources and sinks of Earths surface methane budget. However, the major factors that influence the two multiply-substituted (clumped) isotope signatures of AeOM, {Delta}13CH3D and {Delta}12CH2D2, are not well known. Here we quantify the influence of kinetics as a function of temperature, and different methane monooxygenase (MMO) enzymes as a function of copper, on the isotopologue concentrations of residual methane by the obligate aerobic methanotroph, Methylococcus capsulatus (Bath). We observe deviations from traditional closed-system distillation (Rayleigh) fractionation during exponential growth at high oxidation rates. We model this as a reservoir effect controlled by the ratio of oxidation rate in the cells to transport rate of methane into the cells, where environmental temperature affects both rates. We also test whether clumped isotope fractionation values vary for the particulate versus soluble MMOs, but the results show minimal differences. We further determine that the back reaction (re-equilibration) of methane with medium water is unlikely. Together, the observations and model demonstrate that at low oxidation-to-transport ratios, the clumped isotope signatures follow canonical Rayleigh fractionation, whereas at high ratios, more positive {Delta}12CH2D2 values result, deviating from simple Rayleigh-like trajectories. This study shows that the methane oxidation-to-transport ratio is a critical influence on clumped isotope signatures of AeOM that should be considered when interpreting the isotopic data of natural methane samples in both open and closed systems.

microbiology↗

bioRxiv2023

Auditory Hair Cells and Spiral Ganglion Neurons Regenerate Synapses with Refined Release Properties In Vitro

Ribbon synapses between inner hair cells (IHCs) and type I spiral ganglion neurons (SGNs) in the inner ear are damaged by noise trauma and with aging, causing synaptopathy and hearing loss. Co-cultures of neonatal denervated organs of Corti and newly introduced SGNs have been developed to find strategies for improving IHC synapse regeneration, but evidence of the physiological normality of regenerated synapses is missing. This study utilizes IHC optogenetic stimulation and SGN recordings, showing that newly formed IHC synapses are indeed functional, exhibiting glutamatergic excitatory postsynaptic currents. When older organs of Corti were plated, synaptic activity probed by deconvolution, showed more mature release properties, closer to the highly specialized mode of IHC synaptic transmission that is crucial for coding the sound signal. This newly developed functional assessment of regenerated IHC synapses provides a powerful tool for testing approaches to improve synapse regeneration.

neuroscience↗

bioRxiv2020

Resolution of subcomponents of synaptic release from post-synaptic currents in rat hair-cell/auditory-nerve fiber dendrites

The synapse between inner hair cells and auditory nerve fiber dendrites shows large EPSCs, which are either monophasic or multiphasic. Multiquantal or uniquantal flickering release have been proposed to underlie the unusual multiphasic waveforms. Here the nature of multiphasic waveforms is analyzed using EPSCs recorded in vitro in rat afferent dendrites. Spontaneous EPSCs were deconvolved into a sum of presumed release events with monophasic EPSC waveforms. Results include: first, the charge of EPSCs is about the same for multiphasic versus monophasic EPSCs. Second, EPSC amplitudes decline with the number of release events per EPSC. Third, there is no evidence of a mini-EPSC. Most results can be accounted for by versions of either uniquantal or multiquantal release. However, serial neurotransmitter release in multiphasic EPSCs shows properties that are not fully explained by either model, especially that the amplitudes of individual release events is established at the beginning of a multiphasic EPSC, constraining possible models of vesicle release.

neuroscience↗

bioRxiv2018

Exchange catalysis during anaerobic methanotrophy revealed by 12CH2D2 & 13CH3D in methane

The anaerobic oxidation of methane (AOM) is a crucial component of the methane cycle, but its enzymatic versatility under environmental conditions remains poorly understood. We use sediment samples collected during IODP Expedition 347 to the Baltic Sea to show that relative abundances of 12CH2D2 and 13CH3D molecules in methane gas trace the reversibility of methyl-coenzyme M reductase during AOM by driving methane towards internal, thermodynamic isotopic equilibrium. These data suggest that 12CH2D2 and 13CH3D together can identify the influence of methanotrophy in environments where conventional bulk isotope ratios are ambiguous, and these findings may lead to new insights regarding the global significance of enzymatic back-flux in the methane cycle.

biochemistry↗