Microbial Oxidation of Methane in Aquatic Systems Illuminated by Functional Metagenomics

Freshwater and marine environments are hotspots of methane cycling. Vast amounts of methane, a potent greenhouse gas, are produced predominantly in the sediments of these environments but very little eventually escapes to the atmosphere due to the activity of methane-oxidizing microorganisms. These microorganisms are pivotal in regulating methane emissions from the oceans and freshwater systems and their study therefore transcends scientific curiosity and is of global relevance to society as a whole. Despite their importance, the knowledge about these microorganisms is restricted to cultured isolates and little is known about the physiology of environmentally-relevant uncultured species. Using culture-independent functional metagenomics in combination with physiological experiments, this thesis aims to improve our understanding of the individual metabolic potential and activity that underlie the ecophysiology and environmental relevance of several uncultured methane-oxidizing microorganisms.