Browsing by Author "Tigges, Michelle M."

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Dynamic processing of DOM: Insight from exometabolomics, fluorescence spectroscopy, and mass spectrometry
(2018-06) Smith, Heidi J.; Tigges, Michelle M.; D'Andrilli, Juliana; Parker, Albert E.; Bothner, Brian; Foreman, Christine M.
Dissolved organic matter (DOM) in freshwater environments is an important source of organic carbon, supporting bacterial respiration. Frozen environments cover vast expanses of our planet, with glaciers and ice-sheets storing upwards of 6 petagrams of organic carbon. It is generally believed that DOM liberated from ice stimulates downstream environments. If true, glacial DOM is an important component of global carbon cycling. However, coupling the release of DOM to microbial activity is challenging due to the molecular complexity of DOM and the metabolic connectivity within microbial communities. Using a single environmentally relevant organism, we demonstrate that processing of compositionally diverse DOM occurs, but, even though glacially derived DOM is chemically labile, it is unable to support sustained respiration. In view of projected changes in glacier DOM export, these findings imply that biogeochemical impacts on downstream environments will depend on the reactivity and heterogeneity of liberated DOM, as well as the timescale.
Untargeted Metabolomics Studies Employing NMR and LC–MS Reveal Metabolic Coupling Between Nanoarcheum Equitans and Its Archaeal Host Ignicoccus Hospitalis
(2014-11) Hamerly, Timothy; Tripet, Brian P.; Tigges, Michelle M.; Giannone, Richard J.; Wurch, Louie; Hettich, Robert L.; Podar, Mircea; Copie, Valerie; Bothner, Brian
Abstract Interspecies interactions are the basis of microbial community formation and infectious diseases. Systems biology enables the construction of complex models describing such interactions, leading to a better understanding of disease states and communities. However, before interactions between complex organisms can be understood, metabolic and energetic implications of simpler real-world host-microbe systems must be worked out. To this effect, untargeted metabolomics experiments were conducted and integrated with proteomics data to characterize key molecular-level interactions between two hyperthermophilic microbial species, both of which have reduced genomes. Metabolic changes and transfer of metabolites between the archaea Ignicoccus hospitalis and Nanoarcheum equitans were investigated using integrated LC–MS and NMR metabolomics. The study of such a system is challenging, as no genetic tools are available, growth in the laboratory is challenging, and mechanisms by which they interact are unknown. Together with informa-tion about relative enzyme levels obtained from shotgun proteomics, the metabolomics data provided useful insights into metabolic pathways and cellular networks of I. hosp-italis that are impacted by the presence of N. equitans, including arginine, isoleucine, and CTP biosynthesis. On the organismal level, the data indicate that N. equitans exploits metabolites generated by I. hospitalis to satisfy its own metabolic needs. This finding is based on N. equi-tans’s consumption of a significant fraction of the metab-olite pool in I. hospitalis that cannot solely be attributed to increased biomass production for N. equitans. Combining LC–MS and NMR metabolomics datasets improved cov-erage of the metabolome and enhanced the identification and quantitation of cellular metabolites.