Award: OCE-1138368

Marine microbes play a fundamental role in the cycling of carbon, nitrogen and other elements on the planet. However, most of them have never been grown in the lab and thus we know very little about the specifics of their capabilities. In this project we used metagenomics, an approach to look at all the genetic material in a water sample at once, to understand what kinds of microbes are present in the seawater and what kinds of elemental transformations they might be doing. Many approaches to analyzing metagenomic data are capable of recognizing the different types of genes that carry out different functions, but only provide a rough approximation of which organism each gene came from. Here, we developed a set of computational tools to streamline the process of more specifically identifying which organism each gene in our metagenomes came from. This software is publically available for others to use. Our samples came from two study sites, the South Atlantic Gyre, a representative of much of the open ocean, and the Eastern Tropical North Pacific, where a naturally occurring area of zero oxygen provides an environment where microbes capable of using nitrate instead of oxygen thrive. Their transformations affect the global balance of nitrogen between the ocean and the atmosphere. The transformation of nitrate in seawater to nitrogen gas that can be lost from the water to the atmosphere is a multi-step process, and there are one or more different genes responsible for each step. Our results demonstrate that there are multiple different organisms capable of carrying out each different step in this process. In many cases organisms that can do the same step of the process live in different parts of the water column. For example, they may have different distributions with depth, or they may be preferentially associated with large particles. These gene distributions give us clues about the ecology of the microbes responsible for the nitrogen transformations, and thus increase our ability to predict how the magnitude of the overall process may change in a changing ocean. We also identified the potential for arsenic based metabolisms in zero oxygen waters. The ability to transform arsenic for energy is thought to be ancient, but microbes with this ability are usually found in environments with relative high arsenic concentrations, such as polluted soils and mine drainage. Their discovery in the open ocean suggests that they may have played a large role in Pre-Cambrian oceans. Finally, we also found that some genes that enable a key nitrogen cycle transformation reside not in cells but are carried on viruses, indicating that the amount of viral infection in the ocean may influence the global nitrogen cycle. To date our work has been published in 2 papers, 3 more have been submitted and 2 more are in the final stages of preparation. A female post-doctoral researcher trained in this project has obtained a tenure-track faculty position. A female graduate student trained in this project received her PhD and was awarded a nationally competitive post-doctoral fellowship. Five undergraduate researchers, 3 of whom are members of groups underrepresented in the sciences, conducted research on this project and all went on to complete bachelors degrees in STEM. Last Modified: 03/23/2018 Submitted by: Gabrielle Rocap Metagenomic data generated by this project have been deposited in GenBank. A project page and dataset pages have been created at BCO-DMO. https://www.bco-dmo.org/project/725236 https://www.bco-dmo.org/dataset/733748 Last Modified: 06/29/2018 Submitted by: Gabrielle Rocap