Award: OCE-1232982

Overview. Over 90% of ocean's volume is too deep for the sunlight to penetrate and support photosynthesis. The dark realm of the ocean is one of the largest environments inhabited by life on our planet. Dark ocean's microorganisms play a major role in the global cycling of carbon and other elements, both by remineralizing the organic compounds produced at ocean's surface and by synthesizing new biomass from inorganic constituents through chemoautotrophy. The specific biochemical reactions, energy sources and microbial groups involved in the chemoautotrophic carbon fixation in the dark ocean remained poorly understood, to a large degree due to difficulties in laboratory cultivation of relevant representatives. This project aimed at addressing some of the key knowledge gaps about the chemoautotrophy in the dark ocean, primarily by utilizing single cell genomics and other cutting-edge, cultivation-independent research tools. Intellectual merit. During the course of this project, we analyzed dark ocean samples from locations around the globe and down to the greatest depths, including the Challenger Deep at the bottom of the Marianna Trench. A large group of collaborating scientists were engaged in the analysis of the genetic information encoded in over 3,000 individual cells of microorganisms from these samples. This resulted in a major advance in our understanding of the taxonomic composition, geographic distribution, genomic content and metabolic potential of chemoautotrophs in the dark ocean, with a synergistic impact on other fields of microbial oceanography. Examples of research findings include: a) identification of chemoautotrophy pathways in diverse groups of archaea and bacteria; b) confirmation of ammonium and reduced sulfur oxidation as common sources of energy for chemoautotrophs in oxygenated dark ocean; c) estimates of the contribution of nitrite oxidizing bacteria to the marine dark carbon fixation; d) indications of the importance of extensive metabolic interdependencies among chemoautotrophs; e) improved models for the early evolution of bacteria and archaea; f) systematic differences between cultured and uncultured marine microorganisms; and g) strong latitudinal and vertical divergence of marine bacterioplankton composition. Project's findings were reported in 24 peer-reviewed publications (of them, four in Science, Nature and PNAS), 49 presentations, and 14 additional manuscripts that are in review or in preparation. Project's data can be accessed here: http://www.bco-dmo.org/project/471826. Broader impacts. This project supported training of four postdoctoral researchers and eight other professionals (computational and laboratory scientists) who were involved in various aspects of laboratory work, computational analyses, result presentations and manuscript preparation, thus obtaining hands-on experience in new research areas and technologies, as well as project management and mentorship skills. Two undergraduate students were engaged in this project in the framework of the Bigelow Research Experiences for Undergraduates (REU) program, a nationally ranked and competitive program that provides research experience in oceanography for college undergraduates across the United States. Both students excelled in their work, incorporated project results in their theses and presented findings at international science conferences. More than 50 additional students and postdoctoral scientists at collaborating institutions also received training from this project. Improvements in the single cell genomics technology, in part supported by this project, were incorporated into Bigelow Laboratory Single Cell Genomics Center's services. The SCGC serves a wide range of research projects in over 100 organizations around the globe. The ultimate goals of these projects range from basic science to applications such as environmental monitoring (e.g. oil spills) and technology (e.g. wastewater treatment plants), energy production and bioprospecting (e.g. mining industry), human health (e.g. cancer, microbiome), and law enforcement and national security (forensics). Last Modified: 12/04/2016 Submitted by: Ramunas Stepanauskas