Advances in high-throughput sequencing and ‘omics technologies are revolutionizing studies of naturally occurring microbial communities. Comprehensive investigations of microbial lifestyles require the ability to interactively organize and visualize genetic information and to incorporate subtle differences that enable greater resolution of complex data. Here we introduce anvi’o, an advanced analysis and visualization platform that offers automated and human-guided characterization of microbial genomes in metagenomic assemblies, with interactive interfaces that can link ‘omics data from multiple sources into a single, intuitive display. Its extensible visualization approach distills multiple dimensions of information about each contig, offering a dynamic and unified work environment for data exploration, manipulation, and reporting. Using anvi’o, we re-analyzed publicly available datasets and explored temporal genomic changes within naturally occurring microbial populations through de novo characterization of single nucleotide variations, and linked cultivar and single-cell genomes with metagenomic and metatranscriptomic data. Anvi’o is an open-source platform that empowers researchers without extensive bioinformatics skills to perform and communicate in-depth analyses on large ‘omics datasets.

Nitrogen fixation in the surface ocean impacts global marine nitrogen bioavailability and thus microbial primary productivity. Until now, cyanobacterial populations have been viewed as the main suppliers of bioavailable nitrogen in this habitat. Although PCR amplicon surveys targeting the nitrogenase reductase gene have revealed the existence of diverse non-cyanobacterial diazotrophic populations, subsequent quantitative PCR surveys suggest that they generally occur in low abundance. Here, we use state-of-the-art metagenomic assembly and binning strategies to recover nearly one thousand non-redundant microbial population genomes from the TARA Oceans metagenomes. Among these, we provide the first genomic evidence for non-cyanobacterial diazotrophs inhabiting surface waters of the open ocean, which correspond to lineages within the Proteobacteria and, most strikingly, the Planctomycetes. Members of the latter phylum are prevalent in aquatic systems, but have never been linked to nitrogen fixation previously. Moreover, using genome-wide quantitative read recruitment, we demonstrate that the discovered diazotrophs were not only widespread but also remarkably abundant (up to 0.3% of metagenomic reads for a single population) in both the Pacific Ocean and the Atlantic Ocean northwest. Our results extend decades of PCR-based gene surveys, and substantiate the importance of heterotrophic bacteria in the fixation of nitrogen in the surface ocean.

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Comprehensive analysis of shotgun metagenomic assemblies have revolutionized molecular microbial ecology, but few microbiologists command the full suite of bioinformatics skills necessary to process, interact, organize and visualize overlapping DNA sequence contigs. Here we introduce anvi’o, an advanced analysis and visualization platform for ‘omics data, and its assembly-based metagenomic workflow. Anvi’o’s interactive interface facilitates the management of contigs and associated metadata for automatic or human-guided identification of genome bins, and their curation. Its extensible visualization approach distills multiple dimensions of information about each contig into a single, intuitive display, offering a dynamic and unified work environment for data exploration, manipulation and reporting. Beyond its easy-to-use interface, the advanced modular architecture of anvi’o as a platform allows users with programming skills to implement and test novel ideas with minimal effort. To demonstrate anvi’o’s capabilities, we re-analyzed a metagenomic time-series data from an infant gut microbiome. Through the anvi’o interface we identified near-complete draft genomes, and explored temporal genomic changes within the abundant microbial populations through de novo characterization of subtle nucleotide variations. We also used anvi’o to re-analyze a collection of datasets from multiple investigators who studied microbial responses to the Deepwater Horizon oil spill. We linked metagenomic, metatranscriptomic, and single-cell genomic data from the water plume, and used the holistic perspective anvi’o provides to identify the draft genome of a previously uncharacterized, active population of Oceanospirillales. We also linked environmental isolates with metagenomes recovered from an oil-contaminated beach, and identified 56 near-complete draft genomes including abundant oil degraders whose functional features suggested an oceanic origin.

Members of the SAR11 order Pelagibacterales dominate the surface oceans. Their extensive diversity challenges emerging operational boundaries defined for microbial 'species' and complicates efforts of population genetics to study their evolution. Here, we employed single-amino acid variants (SAAVs) to investigate ecological and evolutionary forces that maintain the genomic heterogeneity within ubiquitous SAR11 populations we accessed through metagenomic read recruitment using a single isolate genome. Integrating amino acid and protein biochemistry with metagenomics revealed that systematic purifying selection against deleterious variants governs non-synonymous variation among very closely related populations of SAR11. SAAVs partitioned metagenomes into two main groups matching large-scale oceanic current temperatures, and six finer proteotypes that connect distant oceanic regions. These findings suggest that environmentally-mediated selection plays a critical role in the journey of cosmopolitan surface ocean microbial populations, and the idea ‘everything is everywhere but the environment selects’ has credence even at the finest resolutions.