Project description:Nitrification, the oxidation of ammonia via nitrite to nitrate, has always been considered to be a two-step process catalysed by chemolithoautotrophic microorganisms oxidizing either ammonia or nitrite. No known nitrifier carries out both steps, although complete nitrification should be energetically advantageous. This functional separation has puzzled microbiologists for a century. Here we report on the discovery and cultivation of a completely nitrifying bacterium from the genus Nitrospira, a globally distributed group of nitrite oxidizers. The genome of this chemolithoautotrophic organism encodes the pathways both for ammonia and nitrite oxidation, which are concomitantly activated during growth by ammonia oxidation to nitrate. Genes affiliated with the phylogenetically distinct ammonia monooxygenase and hydroxylamine dehydrogenase genes of Nitrospira are present in many environments and were retrieved on Nitrospira contigs in new metagenomes from engineered systems. These findings fundamentally change our picture of nitrification and point to completely nitrifying Nitrospira as key components of nitrogen-cycling microbial communities.
Project description:The Baltic Sea is one of the largest brackish water bodies in the world. Redoxclines that form between oxic and anoxic layers in the deepest sub-basins are a semi-permanent character of the pelagic Baltic Sea. The microbially mediated nitrogen removal processes in these redoxclines have been recognized as important ecosystem service that removes large proportion of the nitrogen load originating from the drainage basin. However, nitrification, which links mineralization of organic nitrogen and nitrogen removal processes, has remained poorly understood. To gain better understanding of the nitrogen cycling in the Baltic Sea, we analyzed the assemblage of ammonia oxidizing bacteria and archaea in the central Baltic Sea using functional gene microarrays and measured the biogeochemical properties along with potential nitrification rates. Overall, the ammonia oxidizer communities in the Baltic Sea redoxcline were very evenly distributed. However, the communities were clearly different between the eastern and western Gotland Basin and the correlations between different components of the ammonia oxidizer assemblages and environmental variables suggest ecological basis for the community composition. The more even community ammonia oxidizer composition in the eastern Gotland Basin may be related to the constantly oscillating redoxcline that does not allow domination of single archetype. The oscillating redoxcline also creates long depth range of optimal nitrification conditions. The rate measurements suggest that nitrification in the central Baltic Sea is able to produce all nitrate required by denitrification occurring below the nitrification zone.
Project description:The Baltic Sea is one of the largest brackish water bodies in the world. Redoxclines that form between oxic and anoxic layers in the deepest sub-basins are a semi-permanent character of the pelagic Baltic Sea. The microbially mediated nitrogen removal processes in these redoxclines have been recognized as important ecosystem service that removes large proportion of the nitrogen load originating from the drainage basin. However, nitrification, which links mineralization of organic nitrogen and nitrogen removal processes, has remained poorly understood. To gain better understanding of the nitrogen cycling in the Baltic Sea, we analyzed the assemblage of ammonia oxidizing bacteria and archaea in the central Baltic Sea using functional gene microarrays and measured the biogeochemical properties along with potential nitrification rates. Overall, the ammonia oxidizer communities in the Baltic Sea redoxcline were very evenly distributed. However, the communities were clearly different between the eastern and western Gotland Basin and the correlations between different components of the ammonia oxidizer assemblages and environmental variables suggest ecological basis for the community composition. The more even community ammonia oxidizer composition in the eastern Gotland Basin may be related to the constantly oscillating redoxcline that does not allow domination of single archetype. The oscillating redoxcline also creates long depth range of optimal nitrification conditions. The rate measurements suggest that nitrification in the central Baltic Sea is able to produce all nitrate required by denitrification occurring below the nitrification zone. Two color array (Cy3 and Cy5): the universal standard 20-mer oligo is printed to the slide with a 70-mer oligo (an archetype). Environmental DNA sequences (fluoresced with Cy3) within 15% of the 70-mer conjugated to a 20-mer oligo (fluoresced with Cy5) complementary to the universal standard will bind to the oligo probes on the array. Signal is the ratio of Cy3 to Cy5. Three replicate probes were printed for each archetype. Two replicate arrays were run on duplicate targets.
Project description:An Autonomous Underwater Vehicle (AUV) and large volume underwater pumps were used to collect microbial biomass from offshore waters of the Sargasso Sea, from surface waters and into the deep ocean. Seawater collection was performed along a transect in the western North Atlantic Ocean beginning near Bermuda and ending off the coast of Massachusetts, capturing metabolic signatures from oligotrophic, continental margin, and productive coastal ecosystems.