Award: OCE-1046144

This research project investigated the ecological and evolutionary relationships that occur between and among microbial life forms, initially within the backdrop of the deep-ocean. The focus was on bacteria, archaea and their viruses, and the environment was sediment with low-oxygen and abundant methane. Several key discoveries emerged from this work. Foremost amongst them was the finding of self-guided protein diversification within an archaeal virus endemic to this sort of environment. This finding opened a door to identify retroelement-based diversity generation as an active and commonplace mode of adaptation among ultra-small bacteria and archaea belonging to recently-discovered candidate phyla. The analysis of diversity generation among the candidate phyla suggests a role in binding dynamics that benefits the cell for adhesion, regulation, or other processes. By crystallizing the diversified proteins, patterns emerged that suggest biochemical unity in protein binding functions that link the candidate phyla to better established bacterial and archaeal phyla. Other outcomes of this research include an improved understanding of the processes that act on oil in the deep ocean, both allowing deposition to the sea floor, but also controlling the rate at which microbes access and consume the hydrocarbons; the discovery of expansive microbial mats conditionally lining the sea floor of the deep ocean; finding of carbon flow from methane to sulfur bacteria in microbial mats; and new insights to the dynamics of archaeal lipid membranes and metabolisms. This work also provided a range of broader impacts that include training of graduate students and postdoctoral scholars as well as providing at-sea oceanographic experience for undergraduate students. Last Modified: 04/07/2017 Submitted by: David L Valentine