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Symbiotic N2-fixing microorganisms have a crucial role in the assimilation of nitrogen by eukaryotes in nitrogen-limited environments1–3. Particularly among land plants, N2-fixing symbionts occur in a variety of distantly related plant lineages and often involve an intimate association between host and symbiont2,4. Descriptions of such intimate symbioses are lacking for seagrasses, which evolved around 100 million years ago from terrestrial flowering plants that migrated back to the sea5. Here we describe an N2-fixing symbiont, ‘Candidatus Celerinatantimonas neptuna’, that lives inside seagrass root tissue, where it provides ammonia and amino acids to its host in exchange for sugars. As such, this symbiosis is reminiscent of terrestrial N2-fixing plant symbioses. The symbiosis between Ca. C. neptuna and its host Posidonia oceanica enables highly productive seagrass meadows to thrive in the nitrogen-limited Mediterranean Sea. Relatives of Ca. C. neptuna occur worldwide in coastal ecosystems, in which they may form similar symbioses with other seagrasses and saltmarsh plants. Just like N2-fixing microorganisms might have aided the colonization of nitrogen-poor soils by early land plants6, the ancestors of Ca. C. neptuna and its relatives probably enabled flowering plants to invade nitrogen-poor marine habitats, where they formed extremely efficient blue carbon ecosystems7.The N2-fixing symbiont ‘Candidatus Celerinatantimonas neptuna’ lives inside the root tissue of the seagrass Posidonia oceanica, providing ammonia and amino acids to its host in exchange for sugars and enabling highly productive seagrass meadows to thrive in the nitrogen-limited Mediterranean Sea. [ABSTRACT FROM AUTHOR]

The authors discuss a biosynthetic gene cluster (MIBiG) data standard. They comment that adoption of the MIBiG standard will allow collation of all annotations and experimental data on each biosynthetic gene cluster (BGC). They mention that the data standard, MIBiG repository and online databases will enable researchers to connect genes to chemistry, to better understand secondary metabolite biosynthesis and to effectively use synthetic biology to engineer BGC.

Publicly available sequence databases of the small subunit ribosomal RNA gene, also known as 16S rRNA in bacteria and archaea, are growing rapidly, and the number of entries currently exceeds 4 million. However, a unified classification and nomenclature framework for all bacteria and archaea does not yet exist. In this Analysis article, we propose rational taxonomic boundaries for high taxa of bacteria and archaea on the basis of 16S rRNA gene sequence identities and suggest a rationale for the circumscription of uncultured taxa that is compatible with the taxonomy of cultured bacteria and archaea. Our analyses show that only nearly complete 16S rRNA sequences give accurate measures of taxonomic diversity. In addition, our analyses suggest that most of the 16S rRNA sequences of the high taxa will be discovered in environmental surveys by the end of the current decade. [ABSTRACT FROM AUTHOR]

Here we present a standard developed by the Genomic Standards Consortium (GSC) for reporting marker gene sequences-the minimum information about a marker gene sequence (MIMARKS). We also introduce a system for describing the environment from which a biological sample originates. The 'environmental packages' apply to any genome sequence of known origin and can be used in combination with MIMARKS and other GSC checklists. Finally, to establish a unified standard for describing sequence data and to provide a single point of entry for the scientific community to access and learn about GSC checklists, we present the minimum information about any (x) sequence (MIxS). Adoption of MIxS will enhance our ability to analyze natural genetic diversity documented by massive DNA sequencing efforts from myriad ecosystems in our ever-changing biosphere. [ABSTRACT FROM AUTHOR]