Award: OCE-1636045

As the primary drivers of organic carbon turnover in the ocean, natural microbial communities are essential catalysts. The ability to measure cellular function of natural and largely uncultured marine microbial communities in situ and link these functions to carbon cycling has been a research goal for decades. Since proteins carry out the majority of molecular functions and are tightly regulated within the cell, their characterization, quantification, and the timing of expression can reflect their activity and metabolic goals and were the central theme of this project. Although there have been studies that have successfully linked bacterial metaproteomic (i.e. community proteomic) responses to important biogeochemical cycles in situ, most metaproteomic analysis pipelines are adaptations of traditional single-species proteomic methods used in simple environments or for disease investigation. This leaves the complications of having multiple bacterial species analyzed in a single sample, especially the difficult assignment of an identified peptide to what may be multiple protein sequences from the community. As described in publications from this award, we have detailed the importance of capturing all the protein information to follow the role of bacteria communities as the principal catalyst of organic matter recycling despite their small mass contribution. Experiments and publications have also detailed lab and field experiments to track protein expression of natural communities together with important software tools for informatic improvements which allowed us to quantify important bacterial peptides despite the presence of large amounts of eukaryotic (algal) peptides typical of oceanic materials. This work also allowed the impact of identical peptide sequences and taxonomically indistinct peptides sequences to be evaluated to improve the detection of small amounts of proteins. Gains from this effort allowed shipboard experiments to compare natural Arctic microbial communities at different sites and their response to organic matter. The simultaneous measurement of taxonomic and functional shifts followed the comprehensive metabolic response of the native Arctic microbial community over time in the context of shifts in organic matter. At least 24 functional protein terms were shared between experimental treatments, showing that changes in organic matter directs community functionality prior to changes in taxonomy at the microbiome class level. These results need to be repeated in other systems but have important implications for how community-level functions of microbes may forecast biogeochemical gradients in oceans. Despite significant difference in community taxonomy, the process of organic degradation showed a high degree of functional consistency. At least for the Arctic Ocean, this observation argues that bacterioplankton collected from different water masses and having differing taxonomy may nevertheless have a predictable order and high degree of functional consistency in the cycling of materials. This project and the long term collaboration on which it was built acted as a conduit for interdisciplinary training of both graduate students and postdocs with research and minority serving institutions. This award supported two Ph.D.?s who received highly interdisciplinary training and several undergraduate?s students at ODU who assisted in laboratory activities. All these students received extensive experience in research and were mentored during their graduate experience. All information generated through this project and proteomic profiles generated have been submitted to publicly available databases for use by multiple communities. Software tools developed are available for full public use to encourage its dissemination and utilization. The cycling of organic material in the ocean is dependent on complex microbial communities that collectively metabolize, degrade and recycle organic material. The insights from this peptide-centric approach suggests that functional responses of microbial communities are shared across diverse taxonomic groups. It should encourage researchers to consider a broader view of protein synthesis rather than rely on select enzymes or element specific pathways. The conclusions are clear that many functional responses can cross major bacterial class levels and suggests that at least for Arctic microbial communities, bacterioplankton from different water masses and having differing taxonomy may nevertheless have a predictable order and high degree of functional consistency driving biogeochemical profiles. The sum of the information gained allow important insights into biogeochemical cycles and the functional differences of microbial communities responsible for material cycling in ocean systems. Last Modified: 10/20/2020 Submitted by: H. Rodger Harvey