Project description:Ammonia-oxidizing archaeal (AOA) amoA diversity and relative abundance in Gulf of Mexico sediments (0-2 cm) were investigated using a functional gene microarray; a two color array with a universal internal standard
Project description:The abundance of bacterial (AOB) and archaeal (AOA) ammonia oxidisers, assessed using quantitative PCR measurements of their respective a-subunit of the ammonia monooxygenase (amoA) genes, and ammonia oxidation rates were measured in four contrasting coastal sediments in the Western English Channel. Sediment was sampled bimonthly from July 2008 to May 2011, and measurements of ammonia oxidiser abundance and activity compared to a range of environmental variables including salinity, temperature, water column nutrients and sediment carbon and nitrogen content. Despite a higher abundance of AOA amoA genes within all sediments, and at all time-points, rates of ammonia oxidation correlated with AOB and not AOA amoA gene abundance. Other than ammonia oxidation rate, sediment particle size was the only variable that correlated with the spatial and temporal patterns of AOB amoA gene abundance, implying a preference of the AOB for larger sediment particles. This is possibly due to deeper oxygen penetration into the sandier sediments, increasing the area available for ammonia oxidation to occur, higher concentrations of inhibitory sulphide with pore waters of muddier sediments or a combination of both oxygen and sulphide concentrations. Similar to many other temporal studies of nitrification within estuarine and coastal sediments, decreases in AOB amoA gene abundance were evident during summer and autumn, with maximum abundance and ammonia oxidation rates occurring in winter and early spring. The lack of correlation between AOA amoA gene abundance and ammonium oxidation rate suggests an alternative role for amoA-carrying AOA within these sediments.
Project description:This study evaluated the ammonium oxidizing communities (COA) associated with a potato crop (Solanum phureja) rhizosphere soil in the savannah of Bogotá (Colombia) by examining the presence and abundance of amoA enzyme genes and transcripts by qPCR and next-generation sequence analysis. amoA gene abundance could not be quantified by qPCR due to problems inherent in the primers; however, the melting curve analysis detected increased fluorescence for Bacterial communities but not for Archaeal communities. Transcriptome analysis by next-generation sequencing revealed that the majority of reads mapped to ammonium-oxidizing Archaea, suggesting that this activity is primarily governed by the microbial group of the Crenarchaeota phylum. In contrast,a lower number of reads mapped to ammonia-oxidizing bacteria.
Project description:Oxygen minimum zones (OMZs) are expanding due to increased sea surface temperatures, subsequent increased oxygen demand through respiration, reduced oxygen solubility, and thermal stratification driven in part by anthropogenic climate change. Devil's Hole, Bermuda is a model ecosystem to study OMZ microbial biogeochemistry because the formation and subsequent overturn of the suboxic zone occur annually. During thermally driven stratification, suboxic conditions develop, with organic matter and nutrients accumulating at depth. In this study, the bioavailability of the accumulated dissolved organic carbon (DOC) and the microbial community response to reoxygenation of suboxic waters was assessed using a simulated overturn experiment. The surface inoculated prokaryotic community responded to the deep (formerly suboxic) 0.2 μm filtrate with cell densities increasing 2.5-fold over 6 days while removing 5 μmol L<sup>-1</sup> of DOC. After 12 days, the surface community began to shift, and DOC quality became less diagenetically altered along with an increase in SAR202, a Chloroflexi that can degrade recalcitrant dissolved organic matter (DOM). Labile DOC production after 12 days coincided with an increase of <i>Nitrosopumilales,</i> a chemoautotrophic ammonia oxidizing archaea (AOA) that converts ammonia to nitrite based on the ammonia monooxygenase (<i>amoA</i>) gene copy number and nutrient data. In comparison, the inoculation of the deep anaerobic prokaryotic community into surface 0.2 μm filtrate demonstrated a die-off of 25.5% of the initial inoculum community followed by a 1.5-fold increase in cell densities over 6 days. Within 2 days, the prokaryotic community shifted from a <i>Chlorobiales</i> dominated assemblage to a surface-like heterotrophic community devoid of <i>Chlorobiales</i>. The DOM quality changed to less diagenetically altered material and coincided with an increase in the ribulose-1,5-bisphosphate carboxylase/oxygenase form I (<i>cbbL</i>) gene number followed by an influx of labile DOM. Upon reoxygenation, the deep DOM that accumulated under suboxic conditions is bioavailable to surface prokaryotes that utilize the accumulated DOC initially before switching to a community that can both produce labile DOM via chemoautotrophy and degrade the more recalcitrant DOM.
Project description:The abundance of bacterial (AOB) and archaeal (AOA) ammonia oxidisers, assessed using quantitative PCR measurements of their respective a-subunit of the ammonia monooxygenase (amoA) genes, and ammonia oxidation rates were measured in four contrasting coastal sediments in the Western English Channel. Sediment was sampled bimonthly from July 2008 to May 2011, and measurements of ammonia oxidiser abundance and activity compared to a range of environmental variables including salinity, temperature, water column nutrients and sediment carbon and nitrogen content. Despite a higher abundance of AOA amoA genes within all sediments, and at all time-points, rates of ammonia oxidation correlated with AOB and not AOA amoA gene abundance. Other than ammonia oxidation rate, sediment particle size was the only variable that correlated with the spatial and temporal patterns of AOB amoA gene abundance, implying a preference of the AOB for larger sediment particles. This is possibly due to deeper oxygen penetration into the sandier sediments, increasing the area available for ammonia oxidation to occur, higher concentrations of inhibitory sulphide with pore waters of muddier sediments or a combination of both oxygen and sulphide concentrations. Similar to many other temporal studies of nitrification within estuarine and coastal sediments, decreases in AOB amoA gene abundance were evident during summer and autumn, with maximum abundance and ammonia oxidation rates occurring in winter and early spring. The lack of correlation between AOA amoA gene abundance and ammonium oxidation rate suggests an alternative role for amoAÂ-carrying AOA within these sediments. 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:Increasing atmospheric CO2 concentrations are causing decreased pH over vast expanses of the ocean. This decreasing pH may alter biogeochemical cycling of carbon and nitrogen via the microbial process of nitrification, a key process that couples these cycles in the ocean, but which is often sensitive to acidic conditions. Recent reports indicate a decrease in oceanic nitrification rates under experimentally lowered pH. How composition and abundance of ammonia oxidizing bacteria (AOB) and archaea (AOA) assemblages respond to decreasing oceanic pH, however, is unknown. We sampled microbes from two different acidification experiments and used a combination of qPCR and functional gene microarrays for the ammonia monooxygenase gene (amoA) to assess how acidification alters the structure of ammonia oxidizer assemblages. We show that despite widely different experimental conditions, acidification consistently altered the community composition of AOB by increasing the relative abundance of taxa related to the Nitrosomonas ureae clade. In one experiment this increase was sufficient to cause an increase in the overall abundance of AOB. There were no systematic shifts in the community structure or abundance of AOA in either experiment. These different responses to acidification underscore the important role of microbial community structure in the resiliency of marine ecosystems. SUBMITTER_CITATION: Title: Acidification alters the composition of ammonia oxidizing microbial assemblages in marine mesocosms Journal: Marine Ecology Progress Series Issue: 492 Pages: 1-8 DOI: 10.3354/meps 10526 Authors: Jennifer L Bowen Patrick J Kearns Michael Holcomb Bess B Ward
Project description:Ammonia-oxidizing archaeal (AOA) amoA diversity and relative abundance in Gulf of Mexico sediments (0-2 cm) were investigated using a functional gene microarray; a two color array with a universal internal standard Two color array (cy3 and cy5): the universal standard 20 bp oligo (fluoresced with cy5) is printed to the slide with a 70-mer. Environmental DNA sequences (fluoresced with Cy3) within 15% of the 70-mer will bind to it. Signal is the cy3/cy5. Up to four arrays per sample, with two biological replicates made into two targets, each run on duplicate arrays.
Project description:Transcriptional profiling of marine ammonia oxidizing archaea Nitrosopumilus maritimus cells comparing exponential phase control cells with cells under 24 hours starvation and with cells under recovery after 24 hours starvation. Goal was to determine the effects of global transcriptional responses of N. maritimus cells under ammonia starvation and recovery conditions.