scholarly journals Quantifying Potential N Turnover Rates in Hypersaline Microbial Mats by Using 15N Tracer Techniques

2021 ◽  
Vol 87 (8) ◽  
Author(s):  
Oksana Coban ◽  
Olivia Rasigraf ◽  
Anniek E. E. de Jong ◽  
Oliver Spott ◽  
Brad M. Bebout
Keyword(s):  
Nitrogen Cycling ◽  
Microbial Mats ◽  
Ammonium Assimilation ◽  
15N Tracer ◽  
Turnover Rates ◽  
Overlying Water ◽  
N Cycle ◽  
Elkhorn Slough ◽  
Tracer Techniques ◽  
Morphological Differences

ABSTRACT Microbial mats, due to stratification of the redox zones, have the potential to include a complete N cycle; however, an attempt to evaluate a complete N cycle in these ecosystems has not been yet made. In this study, the occurrence and rates of major N cycle processes were evaluated in intact microbial mats from Elkhorn Slough, Monterey Bay, CA, USA, and Baja California Sur, Mexico, under oxic and anoxic conditions using 15N-labeling techniques. All the major N transformation pathways, with the exception of anammox, were detected in both microbial mats. Nitrification rates were found to be low at both sites for both seasons investigated. The highest rates of ammonium assimilation were measured in Elkhorn Slough mats in April and corresponded to high in situ ammonium concentrations in the overlying water. Baja mats featured higher ammonification than ammonium assimilation rates, and this, along with their higher affinity for nitrate compared to ammonium and low dissimilatory nitrate reduction to ammonium rates, characterized their differences from Elkhorn Slough mats. Nitrogen fixation rates in Elkhorn Slough microbial mats were found to be low, implying that other processes, such as recycling and assimilation from water, are the main sources of N for these mats at the times sampled. Denitrification in all the mats was incomplete, with nitrous oxide as the end product and not dinitrogen. Our findings highlight N cycling features not previously quantified in microbial mats and indicate a need for further investigations of these microbial ecosystems. IMPORTANCE Nitrogen is essential for life. The nitrogen cycle on Earth is mediated by microbial activity and has had a profound impact on both the atmosphere and the biosphere throughout geologic time. Microbial mats, present in many modern environments, have been regarded as living records of the organisms, genes, and phylogenies of microbes, as they are one of the most ancient ecosystems on Earth. While rates of major nitrogen metabolic pathways have been evaluated in a number of ecosystems, they remain elusive in microbial mats. In particular, it is unclear what factors affect nitrogen cycling in these ecosystems and how morphological differences between mats impact nitrogen transformations. In this study, we investigate nitrogen cycling in two microbial mats having morphological differences. Our findings provide insight for further understanding of biogeochemistry and microbial ecology of microbial mats.

An in situ mesocosm method for quantifying nitrogen cycling rates in oligotrophic wetlands using 15N tracer techniques

Wetlands ◽  
2008 ◽  
Vol 28 (2) ◽  
pp. 502-512 ◽  
Author(s):  
Jeffrey R. Wozniak ◽  
Daniel L. Childers ◽  
William T. Anderson ◽  
David T. Rudnick ◽  
Christopher J. Madden
Keyword(s):  
Nitrogen Cycling ◽  
15N Tracer ◽  
Tracer Techniques

scholarly journals Metagenomics reveals niche partitioning within the phototrophic zone of a microbial mat

2017 ◽  
Author(s):  
Jackson Z Lee ◽  
R Craig Everroad ◽  
Ulas Karaoz ◽  
Angela M Detweiler ◽  
Jennifer Pett-Ridge ◽  
...  
Keyword(s):  
Microbial Mats ◽  
Environmental Gradients ◽  
Gene Annotation ◽  
Niche Partitioning ◽  
Metabolic Diversity ◽  
Sequence Coverage ◽  
Carbohydrate Utilization ◽  
Strong Light ◽  
Elkhorn Slough ◽  
Conserved Gene

AbstractHypersaline photosynthetic microbial mats are stratified microbial communities known for their taxonomic and metabolic diversity and strong light-driven day-night environmental gradients. In this study of the upper photosynthetic zone of hypersaline microbial mats of Elkhorn Slough, California (USA), we show how reference-based and reference-free methods can be used to meaningfully assess microbial ecology and genetic partitioning in these complex microbial systems. Mapping of metagenome reads to the dominantCyanobacteriaobserved in the system,Coleofasciculus (Microcoleus) chthonoplastes, was used to examine strain variants within these metagenomes. Highly conserved gene subsystems indicate a core genome for the species, and a number of variant genes and subsystems suggest strain level differentiation, especially for carbohydrate utilization. Metagenome sequence coverage binning was used to assess ecosystem partitioning of remaining microbes. Functional gene annotation of these bins (primarily ofProteobacteria, Bacteroidetes,andCyanobacteria) recapitulated the known biogeochemical functions in microbial mats using a genetic basis, and also revealed evidence of novel functional diversity within theGemmatimonadetesandGammaproteobacteria. Combined, these two approaches show how genetic partitioning can inform biogeochemical partitioning of the metabolic diversity within microbial ecosystems.

scholarly journals Mesophilic microorganisms build terrestrial mats analogous to Precambrian microbial jungles

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
N. Finke ◽  
R. L. Simister ◽  
A. H. O’Neil ◽  
S. Nomosatryo ◽  
C. Henny ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Microbial Mats ◽  
Biogeochemical Cycles ◽  
Land Plants ◽  
Rock Weathering ◽  
Precambrian Rock ◽  
Turnover Rates ◽  
Early Proterozoic ◽  
Ambient Temperatures ◽  
The Past

Abstract Development of Archean paleosols and patterns of Precambrian rock weathering suggest colonization of continents by subaerial microbial mats long before evolution of land plants in the Phanerozoic Eon. Modern analogues for such mats, however, have not been reported, and possible biogeochemical roles of these mats in the past remain largely conceptual. We show that photosynthetic, subaerial microbial mats from Indonesia grow on mafic bedrocks at ambient temperatures and form distinct layers with features similar to Precambrian mats and paleosols. Such subaerial mats could have supported a substantial aerobic biosphere, including nitrification and methanotrophy, and promoted methane emissions and oxidative weathering under ostensibly anoxic Precambrian atmospheres. High C-turnover rates and cell abundances would have made these mats prime locations for early microbial diversification. Growth of landmass in the late Archean to early Proterozoic Eons could have reorganized biogeochemical cycles between land and sea impacting atmospheric chemistry and climate.

Removal of nitrogen in different wetland filter materials: use of stable nitrogen isotopes to determine factors controlling denitrification and DNRA

2005 ◽  
Vol 51 (9) ◽  
pp. 63-71 ◽  
Author(s):  
P.T. Mørkved ◽  
A.K. Søvik ◽  
B. Kløve ◽  
L.R. Bakken
Keyword(s):  
Nitrogen Isotopes ◽  
Raw Materials ◽  
15N Tracer ◽  
Relative Role ◽  
Filter Materials ◽  
Tracer Techniques ◽  
Initial Oxygen ◽  
Materials Used ◽  
The One

Laboratory incubations with varying O2 and NO3 concentrations were performed with a range of filter materials used in constructed wetlands (CWs). The study included material sampled from functioning CWs as well as raw materials subjected to laboratory pre-incubation. 15N-tracer techniques were used to assess the rates of denitrification versus dissimilatory nitrate reduction to ammonium (DNRA), and the relative role of nitrification versus denitrification in producing N2O. The N2O/(N2+N2O) product ratio was assessed for the different materials. Sand, shell sand, and peat sustained high rates of denitrification. Raw light-weight aggregates (LWA) had a very low rate, while in LWA sampled from a functioning CW, the rate was similar to the one found in the other materials. The N2O/(N2+N2O) ratio was very low for sand, shell sand and LWA from functioning CWs, but very high for raw LWA. The ratio was intermediate but variable for peat. The N2O produced by nitrification accounted for a significant percentage of the N2O accumulated during the incubation, but was dependent on the initial oxygen concentration. DNRA was significant only for shell sand taken from a functioning CW, suggesting that the establishment of active DNRA is a slower process than the establishment of a denitrifying flora.

scholarly journals Decadal fates and impacts of nitrogen additions on temperate forest carbon storage: a data–model comparison

2019 ◽  
Vol 16 (13) ◽  
pp. 2771-2793 ◽  
Author(s):  
Susan J. Cheng ◽  
Peter G. Hess ◽  
William R. Wieder ◽  
R. Quinn Thomas ◽  
Knute J. Nadelhoffer ◽  
...  
Keyword(s):  
Temperate Forest ◽  
15N Tracer ◽  
N Recovery ◽  
Soil N ◽  
Short Term ◽  
Tracer Studies ◽  
N Cycle ◽  
C Stocks ◽  
N Additions

Abstract. To accurately capture the impacts of nitrogen (N) on the land carbon (C) sink in Earth system models, model responses to both N limitation and ecosystem N additions (e.g., from atmospheric N deposition and fertilizer) need to be evaluated. The response of the land C sink to N additions depends on the fate of these additions: that is, how much of the added N is lost from the ecosystem through N loss pathways or recovered and used to increase C storage in plants and soils. Here, we evaluate the C–N dynamics of the latest version of a global land model, the Community Land Model version 5 (CLM5), and how they vary when ecosystems have large N inputs and losses (i.e., an open N cycle) or small N inputs and losses (i.e., a closed N cycle). This comparison allows us to identify potential improvements to CLM5 that would apply to simulated N cycles along the open-to-closed spectrum. We also compare the short- (< 3 years) and longer-term (5–17 years) N fates in CLM5 against observations from 13 long-term 15N tracer addition experiments at eight temperate forest sites. Simulations using both open and closed N cycles overestimated plant N recovery following N additions. In particular, the model configuration with a closed N cycle simulated that plants acquired more than twice the amount of added N recovered in 15N tracer studies on short timescales (CLM5: 46±12 %; observations: 18±12 %; mean across sites ±1 standard deviation) and almost twice as much on longer timescales (CLM5: 23±6 %; observations: 13±5 %). Soil N recoveries in simulations with closed N cycles were closer to observations in the short term (CLM5: 40±10 %; observations: 54±22 %) but smaller than observations in the long term (CLM5: 59±15 %; observations: 69±18 %). Simulations with open N cycles estimated similar patterns in plant and soil N recovery, except that soil N recovery was also smaller than observations in the short term. In both open and closed sets of simulations, soil N recoveries in CLM5 occurred from the cycling of N through plants rather than through direct immobilization in the soil, as is often indicated by tracer studies. Although CLM5 greatly overestimated plant N recovery, the simulated increase in C stocks to recovered N was not much larger than estimated by observations, largely because the model's assumed C:N ratio for wood was nearly half that suggested by measurements at the field sites. Overall, results suggest that simulating accurate ecosystem responses to changes in N additions requires increasing soil competition for N relative to plants and examining model assumptions of C:N stoichiometry, which should also improve model estimates of other terrestrial C–N processes and interactions.

15N Tracer Techniques for the Differential Diagnosis of Dwarfism and Prediction of Growth Hormone Action in Children

1987 ◽  
Vol 65 (1) ◽  
pp. 74-77 ◽  
Author(s):  
INGO RICHTER ◽  
WILLI HEINE ◽  
CHRISTIAN PLATH ◽  
MONIKA MIX ◽  
KLAUS D. WUTZKE ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Differential Diagnosis ◽  
15N Tracer ◽  
Hormone Action ◽  
Tracer Techniques ◽  
Growth Hormone Action

scholarly journals Massive developments of microbial mats following phytoplankton blooms in a naturally eutrophic bay: Implications for nitrogen cycling

2001 ◽  
Vol 46 (4) ◽  
pp. 821-832 ◽  
Author(s):  
Michelle Graco ◽  
Laura Farías ◽  
Verónica Molina ◽  
Dimitri Gutiérrez ◽  
Lars Peter Nielsen
Keyword(s):  
Nitrogen Cycling ◽  
Microbial Mats ◽  
Phytoplankton Blooms

Identification and quantification of nitrogen removal in a rotating biological contactor by 15N tracer techniques

2003 ◽  
Vol 37 (6) ◽  
pp. 1252-1259 ◽  
Author(s):  
Stijn Wyffels ◽  
Kris Pynaert ◽  
Pascal Boeckx ◽  
Willy Verstraete ◽  
Oswald Van Cleemput
Keyword(s):  
Nitrogen Removal ◽  
15N Tracer ◽  
Rotating Biological Contactor ◽  
Tracer Techniques ◽  
Identification And Quantification

Nitrogen cycling in a dryland stream ecosystem as determined by a 15N tracer experiment (LINX)

2000 ◽  
Vol 27 (1) ◽  
pp. 601-601
Author(s):  
Nancy B. Grimm ◽  
Eugenia Martí ◽  
Jennifer L. Tank
Keyword(s):  
Nitrogen Cycling ◽  
Tracer Experiment ◽  
15N Tracer ◽  
Stream Ecosystem

scholarly journals Millimeter-scale vertical partitioning of nitrogen cycling in hypersaline mats reveals prominence of genes encoding multi-heme and prismane proteins

2021 ◽  
Author(s):  
P. Maza-Márquez ◽  
M. D. Lee ◽  
A. M. Detweiler ◽  
B. M. Bebout
Keyword(s):  
Nitrogen Cycling ◽  
Nitrogen Metabolism ◽  
Microbial Mats ◽  
Ammonia Oxidizing Bacteria ◽  
Free Oxygen ◽  
Metagenome Analysis ◽  
Oxygen Gradient ◽  
The Earth ◽  
Genes Encoding ◽  
Metagenome Sequencing

AbstractMicrobial mats are modern analogues of the first ecosystems on the Earth. As extant representatives of microbial communities where free oxygen may have first been available on a changing planet, they offer an ecosystem within which to study the evolution of biogeochemical cycles requiring and inhibited by oxygen. Here, we report the distribution of genes involved in nitrogen metabolism across a vertical oxygen gradient at 1 mm resolution in a microbial mat using quantitative PCR (qPCR), retro-transcribed qPCR (RT-qPCR) and metagenome sequencing. Vertical patterns in the presence and expression of nitrogen cycling genes, corresponding to oxygen requiring and non-oxygen requiring nitrogen metabolism, could be seen across gradients of dissolved oxygen and ammonium. Metagenome analysis revealed that genes annotated as hydroxylamine dehydrogenase (proper enzyme designation EC 1.7.2.6, hao) and hydroxylamine reductase (hcp) were the most abundant nitrogen metabolism genes in the mat. The recovered hao genes encode hydroxylamine dehydrogenase EC 1.7.2.6 (HAO) proteins lacking the tyrosine residue present in aerobic ammonia oxidizing bacteria (AOB). Phylogenetic analysis confirmed that those proteins were more closely related to ɛHao protein present in Campylobacterota lineages (previously known as Epsilonproteobacteria) rather than oxidative HAO of AOB. BLAST analysis of some transcribed proteins indicated that they likely functioned as a nitrate reductase. The presence of hao sequences related with ɛHao protein, as well as numerous hcp genes encoding a prismane protein, suggest the presence of a nitrogen cycling pathway previously described in Nautilia profundicola as ancestral to the most commonly studied present day nitrogen cycling pathways.

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