Search for: All records

Ocean microbial communities are made up of thousands of diverse taxa whose metabolic demands set the rates of both biomass production and degradation. Thus, these microscopic organisms play a critical role in ecosystem dynamics, global carbon cycling, and climate. While we have frameworks for relating phytoplankton diversity to rates of carbon fixation, our knowledge of how variations in heterotrophic microbial populations drive changes in carbon cycling is in its infancy. Here, we leverage global metagenomic datasets and metabolic models to identify a set of metabolic niches with distinct growth strategies. These groupings provide a simplifying framework for describing microbial communities in different oceanographic regions and for understanding how heterotrophic microbial populations function. This framework, predicated directly on metabolic capability rather than taxonomy, enables us to tractably link heterotrophic diversity directly to biogeochemical rates in large scale ecosystem models. 

Adsorption of organics on surfaces is important in both outdoor and indoor environments. Surfaces can serve as sinks for gas-phase species, act as reservoirs by emitting previously partitioned organics back into the gas phase, and can facilitate heterogeneous chemistry. We report here studies of the uptake and desorption energetics of gas-phase limonene, a volatile and widely-distributed monoterpene, on solid silica nanoparticles using a unique apparatus that allows for temperature programmed desorption (TPD) measurements of surface binding energies as well as Knudsen cell gas uptake measurements. A multiphase kinetic model was applied to these data to provide additional molecular-level understanding of the processes involved. TPD experiments yielded an average desorption energy of 47.5 ± 8.2 kJ mol-1 (±1s, sample standard deviation), the first direct experimental measurement of this parameter over a broad temperature range (150–320 K). Initial net uptake coefficients (0,net) range from (1.7 ± 0.3) ×10-3 (±1s) at 210 K to (2.3 ± 0.4) ×10-4 (±1s) at 250 K, reflecting increased rates of desorption with an increase in temperature combined with increased rates of diffusion and re-adsorption within the pores between adjacent silica nanoparticles. Effective Langmuir constants, which also reflect the effects of pore diffusion and re-adsorption, were determined from the uptake data and vary from (1.8–0.3)×10-13 cm3 molecule-1 over the same temperature range. These results are in excellent agreement with previous studies around room temperature and with theoretical calculations of the energetics of the limonene-silica interaction. The strong attraction between limonene and the polar silica surface shows the importance of including such interactions in models of the atmospheric fates of terpenes both indoors and outdoors. 

Abstract Gyrochronology is the empirical relation between rotation and age. NASA's Transiting Exoplanet Survey Satellite (TESS), Kepler, and K2 missions have observed thousands of wide main sequence binaries. Since components of a binary are coeval, their rotation periods should be consistent with gyrochronology models. However, the usefulness of gyrochronology depends upon reliable rotation periods. We explore the reliability of rotation period determinations for a sample of wide binary components from the TESS cycle 3. Wide binaries with the most reliable rotation period determinations provide a strong basis for testing whether the gyrochronology empirical relation derived from open clusters is also valid for field stars.