scholarly journals Autotrophic Ammonia Oxidation at Low pH through Urea Hydrolysis

2001 ◽  
Vol 67 (7) ◽  
pp. 2952-2957 ◽  
Author(s):  
Simon A. Q. Burton ◽  
Jim I. Prosser
Keyword(s):  
Ammonia Oxidation ◽  
Acid Soils ◽  
Urea Hydrolysis ◽  
Extracellular Ph ◽  
Ammonia Oxidizer ◽  
Ammonium Transport ◽  
Ammonia Oxidizers ◽  
Batch Cultures ◽  
Ph Values ◽  
Nitrite Production

ABSTRACT Ammonia oxidation in laboratory liquid batch cultures of autotrophic ammonia oxidizers rarely occurs at pH values less than 7, due to ionization of ammonia and the requirement for ammonium transport rather than diffusion of ammonia. Nevertheless, there is strong evidence for autotrophic nitrification in acid soils, which may be carried out by ammonia oxidizers capable of using urea as a source of ammonia. To determine the mechanism of urea-linked ammonia oxidation, a ureolytic autotrophic ammonia oxidizer, Nitrosospira sp. strain NPAV, was grown in liquid batch culture at a range of pH values with either ammonium or urea as the sole nitrogen source. Growth and nitrite production from ammonium did not occur at pH values below 7. Growth on urea occurred at pH values in the range 4 to 7.5 but ceased when urea hydrolysis was complete, even though ammonia, released during urea hydrolysis, remained in the medium. The results support a mechanism whereby urea enters the cells by diffusion and intracellular urea hydrolysis and ammonia oxidation occur independently of extracellular pH in the range 4 to 7.5. A proportion of the ammonia produced during this process diffuses from the cell and is not subsequently available for growth if the extracellular pH is less than 7. Ureolysis therefore provides a mechanism for nitrification in acid soils, but a proportion of the ammonium produced is likely to be released from the cell and may be used by other soil organisms.

Competition of Ammonia-Oxidizing Archaea and Bacteria from Freshwater Environments

2021 ◽  
Author(s):  
Elizabeth French ◽  
Jessica A. Kozlowski ◽  
Annette Bollmann
Keyword(s):  
Ammonia Oxidation ◽  
Heterotrophic Bacteria ◽  
Ammonia Oxidizer ◽  
Ammonium Concentration ◽  
Natural Environments ◽  
Ammonia Oxidizing Bacteria ◽  
Ammonia Oxidizers ◽  
Batch Cultures ◽  
Freshwater Systems ◽  
Ammonia Oxidizing Archaea

In the environment, nutrients are rarely available in constant supply. Therefore, microorganisms require strategies to compete for limiting nutrients. In freshwater systems, ammonia-oxidizing archaea (AOA) and bacteria (AOB) compete with heterotrophic bacteria, photosynthetic microorganisms, and each other for ammonium, which AOA and AOB utilize as their sole source of energy and nitrogen. We investigated the competition between highly enriched cultures of an AOA (AOA-AC1) and an AOB (AOB-G5-7) for ammonium. Based on the amoA gene, the newly enriched archaeal ammonia oxidizer in AOA-AC1 was closely related to Nitrosotenuis spp. and the bacterial ammonia oxidizer in AOB-G5-7, Nitrosomonas sp. Is79, belonged to the Nitrosomonas oligotropha group ( Nitrosomonas cluster 6a). Growth experiments in batch cultures showed that AOB-G5-7 had higher growth rates than AOA-AC1 at higher ammonium concentrations. During chemostat competition experiments under ammonium-limiting conditions, AOA-AC1 dominated the cultures, while AOB-G5-7 decreased in abundance. In batch cultures, the outcome of the competition between AOA and AOB was determined by the initial ammonium concentrations. AOA-AC1 was the dominant ammonia oxidizer at an initial ammonium concentration of 50 μM and AOB-G5-7 at 500 μM. These findings indicate that, during direct competition, AOA-AC1 was able to use ammonium that was unavailable to AOB-G5-7, while AOB-G5-7 dominated at higher ammonium concentrations. The results are in strong accordance with environmental survey data suggesting that AOA are mainly responsible for ammonia oxidation under more oligotrophic conditions, whereas AOB dominate under eutrophic conditions. Importance Nitrification is an important process in the global nitrogen cycle. The first step - ammonia oxidation to nitrite – can be carried out by Ammonia-oxidizing Archaea (AOA) and Ammonia-oxidizing Bacteria (AOB). In many natural environments, these ammonia oxidizers coexist. Therefore, it is important to understand the population dynamics in response to increasing ammonium concentrations. Here, we study the competition between AOA and AOB enriched from freshwater systems. The results demonstrate that AOA are more abundant in systems with low ammonium availabilities and AOB when the ammonium availability increases. These results will help to predict potential shifts in community composition of ammonia oxidizers in the environment due to changes in ammonium availability.

scholarly journals Thaumarchaeal Ammonia Oxidation in an Acidic Forest Peat Soil Is Not Influenced by Ammonium Amendment

2010 ◽  
Vol 76 (22) ◽  
pp. 7626-7634 ◽  
Author(s):  
Nejc Stopnišek ◽  
Cécile Gubry-Rangin ◽  
Špela Höfferle ◽  
Graeme W. Nicol ◽  
Ines Mandič-Mulec ◽  
...  
Keyword(s):  
Ammonia Oxidation ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Inorganic Nitrogen ◽  
Peat Soil ◽  
Selective Advantage ◽  
Ammonia Oxidizer ◽  
Ammonium Concentration ◽  
Rrna Gene ◽  
Ammonia Oxidizers ◽  
Ammonia Release

ABSTRACT Both bacteria and thaumarchaea contribute to ammonia oxidation, the first step in nitrification. The abundance of putative ammonia oxidizers is estimated by quantification of the functional gene amoA, which encodes ammonia monooxygenase subunit A. In soil, thaumarchaeal amoA genes often outnumber the equivalent bacterial genes. Ecophysiological studies indicate that thaumarchaeal ammonia oxidizers may have a selective advantage at low ammonia concentrations, with potential adaptation to soils in which mineralization is the major source of ammonia. To test this hypothesis, thaumarchaeal and bacterial ammonia oxidizers were investigated during nitrification in microcosms containing an organic, acidic forest peat soil (pH 4.1) with a low ammonium concentration but high potential for ammonia release during mineralization. Net nitrification rates were high but were not influenced by addition of ammonium. Bacterial amoA genes could not be detected, presumably because of low abundance of bacterial ammonia oxidizers. Phylogenetic analysis of thaumarchaeal 16S rRNA gene sequences indicated that dominant populations belonged to group 1.1c, 1.3, and “deep peat” lineages, while known amo-containing lineages (groups 1.1a and 1.1b) comprised only a small proportion of the total community. Growth of thaumarchaeal ammonia oxidizers was indicated by increased abundance of amoA genes during nitrification but was unaffected by addition of ammonium. Similarly, denaturing gradient gel electrophoresis analysis of amoA gene transcripts demonstrated small temporal changes in thaumarchaeal ammonia oxidizer communities but no effect of ammonium amendment. Thaumarchaea therefore appeared to dominate ammonia oxidation in this soil and oxidized ammonia arising from mineralization of organic matter rather than added inorganic nitrogen.

scholarly journals Identifying Potential Mechanisms Enabling Acidophily in the Ammonia-Oxidizing Archaeon “Candidatus Nitrosotalea devanaterra”

2016 ◽  
Vol 82 (9) ◽  
pp. 2608-2619 ◽  
Author(s):  
Laura E. Lehtovirta-Morley ◽  
Luis A. Sayavedra-Soto ◽  
Nicolas Gallois ◽  
Stefan Schouten ◽  
Lisa Y. Stein ◽  
...  
Keyword(s):  
Biochemical Characterization ◽  
Ammonia Oxidation ◽  
Membrane Lipids ◽  
Acid Soils ◽  
Low Ph ◽  
Ammonia Oxidizer ◽  
Ammonia Oxidizing Bacteria ◽  
Ph Homeostasis ◽  
A Genome ◽  
Genes Encoding

ABSTRACTAmmonia oxidation is the first and rate-limiting step in nitrification and is dominated by two distinct groups of microorganisms in soil: ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). AOA are often more abundant than AOB and dominate activity in acid soils. The mechanism of ammonia oxidation under acidic conditions has been a long-standing paradox. While high rates of ammonia oxidation are frequently measured in acid soils, cultivated ammonia oxidizers grew only at near-neutral pH when grown in standard laboratory culture. Although a number of mechanisms have been demonstrated to enable neutrophilic AOB growth at low pH in the laboratory, these have not been demonstrated in soil, and the recent cultivation of the obligately acidophilic ammonia oxidizer “CandidatusNitrosotalea devanaterra” provides a more parsimonious explanation for the observed high rates of activity. Analysis of the sequenced genome, transcriptional activity, and lipid content of “Ca. Nitrosotalea devanaterra” reveals that previously proposed mechanisms used by AOB for growth at low pH are not essential for archaeal ammonia oxidation in acidic environments. Instead, the genome indicates that “Ca. Nitrosotalea devanaterra” contains genes encoding both a predicted high-affinity substrate acquisition system and potential pH homeostasis mechanisms absent in neutrophilic AOA. Analysis of mRNA revealed that candidate genes encoding the proposed homeostasis mechanisms were all expressed during acidophilic growth, and lipid profiling by high-performance liquid chromatography–mass spectrometry (HPLC-MS) demonstrated that the membrane lipids of “Ca. Nitrosotalea devanaterra” were not dominated by crenarchaeol, as found in neutrophilic AOA. This study for the first time describes a genome of an obligately acidophilic ammonia oxidizer and identifies potential mechanisms enabling this unique phenotype for future biochemical characterization.

Numbers, activities, and diversity of autotrophic ammonia-oxidizing bacteria in a freshwater, eutrophic lake sediment

1991 ◽  
Vol 37 (11) ◽  
pp. 828-833 ◽  
Author(s):  
W. T. Smorczewski ◽  
E. L. Schmidt
Keyword(s):  
Lake Sediment ◽  
Environmental Changes ◽  
Ammonia Oxidation ◽  
Eutrophic Lake ◽  
Ammonia Oxidizer ◽  
Most Probable Number ◽  
Ammonia Oxidizing Bacteria ◽  
Ammonia Oxidizers ◽  
Probable Number ◽  
Nitrite Oxidizers

The microbiological and chemical potential for ammonia oxidation in a freshwater, eutrophic lake sediment was examined in relation to environmental changes caused by seasonal, dimictic circulation. Poulations of both ammonia and nitrite oxidizers as estimated by most probable number (MPN) were sustained throughout extended anaerobic summer intervals, with nitrite oxidizers outnumbering ammonia oxidizers by a factor ranging from 3.0 to 8.1. Ammonia oxidation potential on a per cell basis was affected by seasonal changes and was seen to decrease as oxygen was removed from the sediments. Pure-culture isolations from a positive MPN tube inoculated with oxygenated sediment and representing a single point in a seasonal cycle produced ammonia-oxidizing strains belonging to the genus Nitrosospira. These strains did not react with known ammonia-oxidizer serotypes and, therefore, extend the serological diversity of this group of bacteria. An immunofluorescence analysis of MPN tubes from sediment collected during a period of lake stratification revealed progressive changes in the diversity of the ammonia-oxidizer population. The genera Nitrosomonas, Nitrosolobus, and Nitrosospira, including the novel serotype of Nitrosospira isolated from the sediment a year earlier, were found to coexist in well-oxygenated sediment. This diversity was seen to disappear, with Nistrosomonas surviving, as anaerobic conditions persisted. Key words: ammonia oxidizers, lake sediments, nitrifiers, nitrification.

scholarly journals Ammonia-oxidizing archaea possess a wide range of cellular ammonia affinities

2021 ◽  
Author(s):  
Man-Young Jung ◽  
Christopher J. Sedlacek ◽  
K. Dimitri Kits ◽  
Anna J. Mueller ◽  
Sung-Keun Rhee ◽  
...  
Keyword(s):  
Ammonia Oxidation ◽  
Oxidation Kinetic ◽  
Ammonia Oxidizer ◽  
Substrate Affinity ◽  
Kinetic Properties ◽  
Ammonia Oxidizing Bacteria ◽  
Ammonia Oxidizers ◽  
Kinetic Measurements ◽  
Ammonia Oxidizing Archaea ◽  
Wide Range

AbstractNitrification, the oxidation of ammonia to nitrate, is an essential process in the biogeochemical nitrogen cycle. The first step of nitrification, ammonia oxidation, is performed by three, often co- occurring guilds of chemolithoautotrophs: ammonia-oxidizing bacteria (AOB), archaea (AOA), and complete ammonia oxidizers (comammox). Substrate kinetics are considered to be a major niche-differentiating factor between these guilds, but few AOA strains have been kinetically characterized. Here, the ammonia oxidation kinetic properties of 12 AOA representing all major phylogenetic lineages were determined using microrespirometry. Members of the genus Nitrosocosmicus have the lowest substrate affinity of any characterized AOA, which are similar to previously determined affinities of AOB. This contrasts previous assumptions that all AOA possess much higher substrate affinities than their comammox or AOB counterparts. The substrate affinity of ammonia oxidizers correlated with their cell surface area to volume ratios. In addition, kinetic measurements across a range of pH values strongly supports the hypothesis that – like for AOB – ammonia and not ammonium is the substrate for the ammonia monooxygenase enzyme of AOA and comammox. Together, these data will facilitate predictions and interpretation of ammonia oxidizer community structures and provide a robust basis for establishing testable hypotheses on competition between AOB, AOA, and comammox.

scholarly journals Ammonium Limitation Results in the Loss of Ammonia-Oxidizing Activity in Nitrosomonas europaea

1998 ◽  
Vol 64 (4) ◽  
pp. 1514-1521 ◽  
Author(s):  
Lisa Y. Stein ◽  
Daniel J. Arp
Keyword(s):  
Active Site ◽  
Ammonia Oxidation ◽  
Nitrosomonas Europaea ◽  
Ammonium Concentration ◽  
Ammonia Monooxygenase ◽  
Oxidation Activity ◽  
Ph Values ◽  
Nitrite Production ◽  
Steady State Levels ◽  
Logarithmic Growth

ABSTRACT The effects of limiting concentrations of ammonium on the metabolic activity of Nitrosomonas europaea, an obligate ammonia-oxidizing soil bacterium, were investigated. Cells were harvested during late logarithmic growth and were incubated for 24 h in growth medium containing 0, 15, or 50 mM ammonium. The changes in nitrite production and the rates of ammonia- and hydroxylamine-dependent oxygen consumption were monitored. In incubations without ammonium, there was little change in the ammonia oxidation activity after 24 h. With 15 mM ammonium, an amount that was completely consumed, there was an 85% loss of the ammonia oxidation activity after 24 h. In contrast, there was only a 35% loss of the ammonia oxidation activity after 24 h in the presence of 50 mM ammonium, an amount that was not consumed to completion. There was little effect on the hydroxylamine oxidation activity in any of the incubations. The loss of ammonia oxidation activity was not due to differences in steady-state levels of ammonia monooxygenase (AMO) mRNA (amoA) or to degradation of the active site-containing subunit of AMO protein. The incubations were also conducted at a range of pH values to determine whether the loss of ammonia oxidation activity was correlated to the residual ammonium concentration. The loss of ammonia oxidation activity after 24 h was less at lower pH values (where the unoxidized ammonium concentration was higher). When added in conjunction with limiting ammonium, short-chain alkanes, which are alternative substrates for AMO, prevented the loss of ammonia oxidation activity at levels corresponding to their binding affinity for AMO. These results suggest that substrates of AMO can preserve the ammonia-oxidizing activity of N. europaea in batch incubations by protecting either AMO itself or other molecules associated with ammonia oxidation.

scholarly journals Microbial community analysis of biofilters reveals a dominance of either comammox Nitrospira or archaea as ammonia oxidizers in freshwater aquaria

2021 ◽  
Author(s):  
Michelle M McKnight ◽  
Josh D Neufeld
Keyword(s):  
Microbial Communities ◽  
Ammonia Oxidation ◽  
16S Rrna Gene Sequencing ◽  
Community Analysis ◽  
Microbial Community Analysis ◽  
Ammonia Oxidizer ◽  
Future Research ◽  
Rrna Gene ◽  
Ammonia Oxidizing Bacteria ◽  
Ammonia Oxidizers

Nitrification by aquarium biofilters transforms toxic ammonia waste (NH3/NH4+) to less toxic nitrate (NO3-) via nitrite (NO2-). Ammonia oxidation is mediated by ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), and the recently discovered complete ammonia oxidizing (comammox) Nitrospira. Prior to the discovery of comammox Nitrospira, previous research revealed that AOA dominate among ammonia oxidizers in freshwater biofilters. Here, we characterized the composition of aquarium filter microbial communities and quantified the abundance of all three known groups of ammonia oxidizers. Aquarium biofilter and water samples were collected from representative freshwater and saltwater systems in Southwestern Ontario, Canada. Using extracted DNA, we performed 16S rRNA gene sequencing and quantitative PCR (qPCR) to assess community composition and quantify the abundance of amoA genes, respectively. Our results show that aquarium biofilter microbial communities were consistently represented by putative heterotrophs of the Proteobacteria and Bacteroides phyla, with distinct profiles associated with fresh versus saltwater biofilters. Among nitrifiers, comammox Nitrospira amoA genes were detected in all 38 freshwater aquarium biofilter samples and were the most abundant ammonia oxidizer in 30 of these samples, with the remaining biofilters dominated by AOA, based on amoA gene abundances. In saltwater biofilters, AOA or AOB were differentially abundant, with no comammox Nitrospira detected. These results demonstrate that comammox Nitrospira play an important role in biofilter nitrification that has been previously overlooked and such microcosms are useful for exploring the ecology of nitrification for future research.

Examination of an acid forest soil for ammonia- and nitrite-oxidizing autotrophic bacteria

1984 ◽  
Vol 30 (9) ◽  
pp. 1125-1132 ◽  
Author(s):  
T. R. Hankinson ◽  
E. L. Schmidt
Keyword(s):  
Forest Soil ◽  
Ammonia Oxidation ◽  
Acid Soil ◽  
Ammonia Oxidizer ◽  
Most Probable Number ◽  
Ammonia Oxidizers ◽  
Nitrite Oxidation ◽  
Probable Number ◽  
Acid Forest Soil ◽  
Nitrite Oxidizers

An acid forest soil (pH 3.9 – 4.4) from an undisturbed mixed oak stand in southern Indiana was examined for the occurrence of ammonia- and nitrite- oxidizing chemoautotrophs. Populations of both nitrifiers were detected in pH 7 most-probable-number (MPN) autotrophic media, and a Nitrosospira was isolated from highest dilution ammonia oxidizer MPN tubes. Populations of nitrite oxidizers were 10 to 1000 times higher than those of ammonia oxidizers. In pH 4.0 MPN media, ammonia oxidation was slight and unsustainable on 10% transfer to fresh medium, whereas nitrite oxidation was vigorous and sustainable. In pure culture the Nitrosospira isolate (Np IO1a) was completely inhibited by nitrapyrin at 5 μg mL−1, tolerant of 1.0 and 10.0 mM chlorate, and capable of growth only at pH 6.2 and above. Fluorescent antibodies raised against Np IO1a were used to confirm the predominance of Np IO1a in all MPN series examined. These results suggest that autotrophic ammonia oxidizers may be restricted to circumneutral microsites in this acid soil, whereas autotrophic nitrite oxidizers may not be limited to such sites.

scholarly journals Ammonia-oxidizing archaea possess a wide range of cellular ammonia affinities

2021 ◽  
Author(s):  
Man-Young Jung ◽  
Christopher J. Sedlacek ◽  
K. Dimitri Kits ◽  
Anna J. Mueller ◽  
Sung-Keun Rhee ◽  
...  
Keyword(s):  
Ammonia Oxidation ◽  
Oxidation Kinetic ◽  
Ammonia Oxidizer ◽  
Substrate Affinity ◽  
Kinetic Properties ◽  
Ammonia Oxidizing Bacteria ◽  
Ammonia Oxidizers ◽  
Kinetic Measurements ◽  
Wide Range ◽  
Total Ammonium

AbstractNitrification, the oxidation of ammonia to nitrate, is an essential process in the biogeochemical nitrogen cycle. The first step of nitrification, ammonia oxidation, is performed by three, often co-occurring guilds of chemolithoautotrophs: ammonia-oxidizing bacteria (AOB), archaea (AOA), and complete ammonia oxidizers (comammox). Substrate kinetics are considered to be a major niche-differentiating factor between these guilds, but few AOA strains have been kinetically characterized. Here, the ammonia oxidation kinetic properties of 12 AOA representing all major cultivated phylogenetic lineages were determined using microrespirometry. Members of the genus Nitrosocosmicus have the lowest affinity for both ammonia and total ammonium of any characterized AOA, and these values are similar to previously determined ammonia and total ammonium affinities of AOB. This contrasts previous assumptions that all AOA possess much higher substrate affinities than their comammox or AOB counterparts. The substrate affinity of ammonia oxidizers correlated with their cell surface area to volume ratios. In addition, kinetic measurements across a range of pH values supports the hypothesis that—like for AOB—ammonia and not ammonium is the substrate for the ammonia monooxygenase enzyme of AOA and comammox. Together, these data will facilitate predictions and interpretation of ammonia oxidizer community structures and provide a robust basis for establishing testable hypotheses on competition between AOB, AOA, and comammox.

scholarly journals Straw mulching and nitrogen application altered ammonia oxidizers communities and improved soil quality in the alkaline purple soil of southwest China

AMB Express ◽  
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Songhe Chen ◽  
Rencai Gao ◽  
Xiaoling Xiang ◽  
Hongkun Yang ◽  
Hongliang Ma ◽  
...  
Keyword(s):  
Soil Quality ◽  
Ammonia Oxidation ◽  
Management Strategies ◽  
Rflp Analysis ◽  
Available Phosphorus ◽  
Purple Soil ◽  
Ammonia Oxidizers ◽  
Nitrogen Application ◽  
Available Nitrogen ◽  
Straw Mulching

AbstractMicrobe-mediated ammonia oxidation is a key process in soil nitrogen cycle. However, the effect of maize straw mulching on the ammonia oxidizers in the alkaline purple soil remains largely unknown. A three-year positioning experiment was designed as follows: straw mulching measures as the main-plot treatment and three kinds of nitrogen application as the sub-plot treatment. We found the contents of soil organic carbon (SOC), total nitrogen (TN), available potassium (AK), available nitrogen (AN), available phosphorus (AP), and NH4+-N were increased after straw mulching and nitrogen application in alkaline purple soil, so did the amoA genes abundance of ammonia-oxidizing archaeal (AOA) and bacterial (AOB). Terminal restriction fragment length polymorphism (T-RFLP) analysis revealed that Thaumarchaeote (448-bp T-RF) was dominated the AOA communities, whereas Nitrosospira sp (111-bp T-RF) dominated the AOB communities. The community compositions of both AOA and AOB were altered by straw mulching and nitrogen application in alkaline purple soil, however, the AOB communities was more responsive than AOA communities to the straw mulching and nitrogen application. Further analysis indicated that SOC and AP were the main factors affecting the abundance and community compositions of AOA and AOB in alkaline purple soil. The present study reported that straw mulching and nitrogen strategies differently shape the soil ammonia oxidizers community structure and abundance, which should be considered when evaluating agricultural management strategies regarding their sustainability and soil quality.

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