Complete Genome Sequence of the Ammonia-Oxidizing Bacterium Nitrosospira sp. Strain NRS527, Isolated from the Rhizoplane of Paddy Rice

This work reports the complete genome sequence of the chemoautotrophic ammonia-oxidizing bacterium Nitrosospira sp. strain NRS527. The assembled genome is composed of a circular chromosome and two plasmids (80,750 bp and 41,389 bp, respectively).

Ammonia oxidation at pH 2.5 by a new gammaproteobacterial ammonia-oxidizing bacterium

Ammonia oxidation was considered impossible under highly acidic conditions, as the protonation of ammonia leads to decreased substrate availability and formation of toxic nitrogenous compounds. Recently, some studies described archaeal and bacterial ammonia oxidizers growing at pH as low as 4, while environmental studies observed nitrification at even lower pH values. In this work, we report on the discovery, cultivation, and physiological, genomic, and transcriptomic characterization of a novel gammaproteobacterial ammonia-oxidizing bacterium enriched via continuous bioreactor cultivation from an acidic air biofilter that was able to grow and oxidize ammonia at pH 2.5. This microorganism has a chemolithoautotrophic lifestyle, using ammonia as energy source. The observed growth rate on ammonia was 0.196 day−1, with a doubling time of 3.5 days. The strain also displayed ureolytic activity and cultivation with urea as ammonia source resulted in a growth rate of 0.104 day−1 and a doubling time of 6.7 days. A high ammonia affinity (Km(app) = 147 ± 14 nM) and high tolerance to toxic nitric oxide could represent an adaptation to acidic environments. Electron microscopic analysis showed coccoid cell morphology with a large amount of intracytoplasmic membrane stacks, typical of gammaproteobacterial ammonia oxidizers. Furthermore, genome and transcriptome analysis showed the presence and expression of diagnostic genes for nitrifiers (amoCAB, hao, nor, ure, cbbLS), but no nirK was identified. Phylogenetic analysis revealed that this strain belonged to a novel bacterial genus, for which we propose the name “Candidatus Nitrosacidococcus tergens” sp. RJ19.

Whole-Genome Sequence of the Ammonia-Oxidizing Bacterium Nitrosomonas stercoris Type Strain KYUHI-S, Isolated from Composted Cattle Manure

This work reports the complete genome sequence of a chemoautotrophic ammonia-oxidizing bacterium, Nitrosomonas stercoris strain KYUHI-ST (= ATCC BAA-2718T and NBRC 110753T). The assembled genome is composed of a circular chromosome and a large plasmid.

Draft Genome Sequence of Nitrosomonas sp. Strain APG5, a Betaproteobacterial Ammonia-Oxidizing Bacterium Isolated from Beach Sand

Nitrosomonas sp. strain APG5 (=NCIMB 14870 = ATCC TSA-116) was isolated from dry beach sand collected from a supralittoral zone of the northwest coast of the United States. The draft genome sequence revealed that it represents a new species of the cluster 6 Nitrosomonas spp. that is closely related to Nitrosomonas ureae and Nitrosomonas oligotropha.

Genome-Scale, Constraint-Based Modeling of Nitrogen Oxide Fluxes during Coculture ofNitrosomonas europaeaandNitrobacter winogradskyi

ABSTRACTNitrification, the aerobic oxidation of ammonia to nitrate via nitrite, emits nitrogen (N) oxide gases (NO, NO2, and N2O), which are potentially hazardous compounds that contribute to global warming. To better understand the dynamics of nitrification-derived N oxide production, we conducted culturing experiments and used an integrative genome-scale, constraint-based approach to model N oxide gas sources and sinks during complete nitrification in an aerobic coculture of two model nitrifying bacteria, the ammonia-oxidizing bacteriumNitrosomonas europaeaand the nitrite-oxidizing bacteriumNitrobacter winogradskyi. The model includes biotic genome-scale metabolic models (iFC578 and iFC579) for each nitrifier and abiotic N oxide reactions. Modeling suggested both biotic and abiotic reactions are important sources and sinks of N oxides, particularly under microaerobic conditions predicted to occur in coculture. In particular, integrative modeling suggested that previous models might have underestimated gross NO production during nitrification due to not taking into account its rapid oxidation in both aqueous and gas phases. The integrative model may be found at https://github.com/chaplenf/microBiome-v2.1.IMPORTANCEModern agriculture is sustained by application of inorganic nitrogen (N) fertilizer in the form of ammonium (NH4+). Up to 60% of NH4+-based fertilizer can be lost through leaching of nitrifier-derived nitrate (NO3−), and through the emission of N oxide gases (i.e., nitric oxide [NO], N dioxide [NO2], and nitrous oxide [N2O] gases), the latter being a potent greenhouse gas. Our approach to modeling of nitrification suggests that both biotic and abiotic mechanisms function as important sources and sinks of N oxides during microaerobic conditions and that previous models might have underestimated gross NO production during nitrification.