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:<p>While irrigation and fertilization are basic cultivation practices in poplar plantations on a global scale, the impact of these practices on the environment is not well understood. Here, we demonstrate that water-urea coupling and water-compound fertilizer coupling differentially impact soil ecosystems. We report that water-fertilizer coupling did not significantly alter taxonomic diversity indices (richness, evenness), but it did drive significant shifts in microbial community composition, reflected by changes in the relative abundance of specific taxa (e.g., core phyla) and their functional profiles. Water-urea coupling reduced Proteobacteria and Actinobacteria in non-rhizosphere soils while increasing Acidobacteria and Chloroflexi. In contrast, water-compound fertilizer coupling amplified Proteobacteria and Actinobacteria dominance in rhizosphere soils. Water-fertilizer coupling reshaped microbial composition and functional gene abundance linked to nitrogen and sulfur cycling, indicating a potential shift in microbial-mediated N and S transformation processes. Water-urea treatment enriched denitrification genes and dissimilatory nitrate reduction genes (napABC) in rhizosphere soil, while water-compound fertilizer treatment enhanced nitrification (amoABC, HAO) and denitrification gene abundance in both soils. For sulfur (S) cycling, water-urea treatment favored thiosulfate oxidation genes (SOX complex), whereas water-compound fertilizer treatment increased assimilatory sulfate reduction genes. Multi-omics integration linked these microbial dynamics to metabolic reprogramming—water-urea increased lipid and secondary metabolites in rhizosphere soils, while water-compound fertilizers elevated amino acid-associated metabolites in non-rhizosphere soils.</p>
Project description:Marine sponges represent one of the few eukaryotic groups that ubiquitously harbor symbiotic members of the Thaumarchaeota, which are important chemoautotrophic ammonia-oxidizers in many environments. However in most studies, direct demonstration of ammonia-oxidation by these archaea within sponges is lacking, and little is known about sponge-specific adaptations of archaeal ammonia oxidizers (AOA). In this study, we characterized the thaumarchaeal symbiont of the marine sponge Ianthella basta using metaproteogenomics, fluorescence in situ hybridization, qPCR and direct isotope-based functional assays. We demonstrate that the I. basta symbiont is not closely related to other genomically sequenced sponge AOA and is a member of a new genus. “Candidatus Nitrosospongia bastadiensis” is an abundant symbiont that is solely responsible for nitrite formation from ammonia in I. basta that surprisingly does not harbor nitrite-oxidizing microbes. Consistently, Ca N. bastadiensis encodes and expresses the genetic repertoire required for chemolithoautotrophic ammonia oxidation. Furthermore, we show that this AOA is equipped with an expanded set of extracellular subtilisin-like proteases, a metalloprotease unique among archaea, as well as a putative branched-chain amino acid ABC transporter. This repertoire is strongly indicative of a mixotrophic lifestyle and is (with slight variations) also found in other sponge-associated, but not in free-living AOA. We predict that this feature as well as an expanded and unique set of secreted serpins (protease inhibitors), a unique array of eukaryotic-like proteins, and a DNA-phosporothioation system likely involved in defense against foreign DNA, represent important adaptations of AOA to life within these ancient filter-feeding animals.
Project description:In the soil the stability of urea is affected by the presence of urease, a ubiquitous enzyme released in the rhizosphere by microbial population and by decomposition of organic matter. To reduce the impact on farmer economies and environmental pollution, a common agronomical practice consists of applying urease inhibitors which delays the hydrolysis of urea and, in turn, ammonia is slowly release in the soil. General aim of the present work was the description of changes in maize root transcriptome occurring in response to treatment with the urease inhibitor NBPT.
2017-02-09 | GSE76828 | GEO
Project description:ammonia oxidizers and methanotrophs in paddy soils
| PRJNA1128431 | ENA
Project description:Actitity of ammonia-oxidizers in agricultural soils