Community Composition and Abundance of Ammonia-Oxidizing Archaea in Sediments from the Changjiang Estuary and its Adjacent Area in the East China Sea

<p>Community composition and abundance of ammonia-oxidizing archaea (AOA) were investigated using ammonia monooxygenase α subunit (<i>amoA</i>) in sediments from the Changjiang estuary and its adjacent area in the East China Sea (ECS). Real-time quantitative polymerase chain reaction (qPCR), clone libraries and sequencing were performed to characterize the AOA community. Clone libraries analysis showed that the majority of <i>amoA</i> sequences fell within the <i>Nitrosopumilus</i> cluster. Correlation analysis showed that AOA diversity was closely related to the nitrite concentration, which was consistent with the canonical correspondence analysis (CCA) where a significant association between nitrite and AOA community composition was observed. The qPCR results were found to be significantly correlated with the environmental parameters. In the gravity cores, a significant positive correlation was found between ammonium concentrations and <i>amoA</i> gene copy numbers from different sediment depths at station S31. At station S33, however, ammonium concentration had a negative correlation and nitrite concentration had a positive correlation with <i>amoA</i> gene copy numbers. In the surface sediments, chlorophyll <i>a</i> concentration had a negative correlation and nitrate concentration had a positive correlation with <i>amoA</i> gene copy numbers. Compared <i>amoA</i> gene copy numbers from AOA with those from ammonia-oxidizing β-proteobacteria (β-AOB) in the same studied areas, the <i>amoA</i> gene copy ratio of β-AOB to AOA was negatively correlated with the phosphate concentration and dissolved oxygen concentration, but was not significantly correlated with either ammonium concentrations or salinity. Our data provided valuable information to achieve a better understanding of the potential role of ammonia oxidizers at the interface between terrestrial and marine environments.</p

Utilization of urea and expression profiles of related genes in the dinoflagellate <i>Prorocentrum donghaiense</i>

<div><p>Urea has been shown to contribute more than half of total nitrogen (N) required by phytoplankton in some estuaries and coastal waters and to provide a substantial portion of the N demand for many harmful algal blooms (HABs) of dinoflagellates. In this study, we investigated the physiological and transcriptional responses in <i>Prorocentrum donghaiense</i> to changes in nitrate and urea availability. We found that this species could efficiently utilize urea as sole N source and achieve comparable growth rate and photosynthesis capability as it did under nitrate. These physiological parameters were markedly lower in cultures grown under nitrate- or urea-limited conditions. <i>P</i>. <i>donghaiense</i> N content was similarly low under nitrate- or urea-limited culture condition, but was markedly higher under urea-replete condition than under nitrate-replete condition. Carbon (C) content was consistently elevated under N-limited condition. Consequently, the C:N ratio was as high as 21:1 under nitrate- or urea-limitation, but 7:1 under urea-replete condition and 9:1 to 10:1 under nitrate-replete condition. Using quantitative reverse transcription PCR, we investigated the expression pattern for four genes involved in N transport and assimilation. The results indicated that genes encoding nitrate transport, urea hydrolysis, and nickel transporter gene were sensitive to changes in general N nutrient availability whereas the urea transporter gene responded much more strongly to changes in urea concentration. Taken together, our study shows the high bioavailability of urea, its impact on C:N stoichiometry, and the sensitivity of urea transporter gene expression to urea availability.</p></div

Synergistic Combination of Graphitic Carbon Nitride and Peroxymonosulfate for Efficient Photocatalytic Destruction of Emerging Contaminants under Simulated Solar Irradiation

The prevalence of micropollutants (MPs) and antibiotic resistance in various aquatic environments has raised increasing concerns for public health and ecological security. Conventional wastewater treatment processes exhibit a relatively limited removal efficiency to these contaminants. Although photocatalytic processes are proposed as an effective solution, very few studies have investigated the simultaneous removal of chemical and biological contaminants. To develop a “one-stop” photocatalytic process, this study combined urea-based graphitic carbon nitride (g-C3N4) with peroxymonosulfate (PMS) and evaluated its performance in the simultaneous removal of multiple MPs, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs) at environmentally relevant concentrations. The system removed 87% of MPs (10 μg/L each) and achieved 6.5-log ARB reduction within a 5 min treatment. In addition, the concentrations of extracellular ARGs (e-tetA and e-blaTEM‑1) were rapidly decreased, with 4.8-log and 6.7-log reductions after a 30 min treatment, respectively. Atomic force microscopy images showed that the naked plasmid DNA was destructed. Radical quenching and electron paramagnetic resonance experiments further confirmed that both radical and nonradical pathways are involved in ARB inactivation in a g-C3N4/PMS photocatalytic system. Collectively, the g-C3N4/PMS photocatalytic system can efficiently achieve simultaneous removal of MPs and ARB as well as ARG destruction, therefore being a promising “one-stop” decontamination solution

Information of primers and thermal cycling conditions used in RT-qPCRs.

<p>Information of primers and thermal cycling conditions used in RT-qPCRs.</p

N-nutrient concentrations in the media in the first 6 days of experimental period.

<p>N-nutrient concentrations in the media in the first 6 days of experimental period.</p

Cellular nitrogen and carbon contents of <i>P</i>. <i>donghaiense</i> grown under the N-replete and N-deprived conditions.

<p>Cellular nitrogen and carbon contents of <i>P</i>. <i>donghaiense</i> grown under the N-replete and N-deprived conditions.</p

Transcriptional levels of N transporter and assimilation genes normalized to <i>calmodulin</i> (<i>Pdcalm</i>) in <i>Prorocentrum donghaiense</i> grown under nitrogen replete and deprived conditions.

<p>(A) Nitrate transporter (<i>PdNRT</i>). (B) Urea transporter (<i>PdUT</i>). (C) Urease (<i>PdURE</i>). (D) High-affinity nickel transporter (<i>PdNiT</i>). Error bars indicate ± SD of biological triplicates. Significant differences (<i>p</i> < 0.05) between experiment groups and control (nitrate-replete) are indicated by an asterisk (*).</p

The genomic structure, length and organization of <i>HIF-1α</i> from <i>T. adhaerens</i>, <i>H. magnipapillata</i>, <i>N. vectensis</i>, <i>Aurelia</i> sp.1, <i>S. purpuratus</i> and <i>H. sapiens</i>.

<p>Boxes represented the sequences of exons of the gene and thin lines indicated the sequences of introns. Values above the lines and the boxes indicated the sizes of the introns and exons, respectively. “E1 to E15” represented “Exon1 to Exon15”. The exons included bHLH domain (highlighted in green), PAS domain (highlighted in red), N-ODD domain (highlighted in yellow), C-ODD domain (highlighted in blue), and C-TAD domain (highlighted in pink).</p

The protein domain structure alignment of HIF-1α with <i>T. adhaerens</i>, <i>H. magnipapillata</i>, <i>N. vectensis</i>, <i>Aurelia</i> sp.1, <i>S. purpuratus</i> and <i>H. sapiens</i>.

<p>The protein domain structure alignment of HIF-1α with <i>T. adhaerens</i>, <i>H. magnipapillata</i>, <i>N. vectensis</i>, <i>Aurelia</i> sp.1, <i>S. purpuratus</i> and <i>H. sapiens</i>.</p

The accession numbers in GenBank for <i>HIF</i> nucleic acid sequences in alignment.

<p><b>*</b>The sequence came from DOE Joint Genome Institute.</p