21 research outputs found
Scale-down of Heterogeneous Catalytic Reduction Using a Bubble Column: Controlled Mass Transfer down to 3 cm<sup>3</sup> Working Volume
Best
practice for scale-down of gas–liquid reactions requires
control of the volumetric mass transfer coefficient, <i>k</i><sub>L</sub><i>a</i>. It is demonstrated that the use of
small bubble columns can provide well-controlled <i>k</i><sub>L</sub><i>a</i> and catalyst dispersion down to a
scale of 3 cm<sup>3</sup>. This scale is several times less than has
been previously demonstrated for heterogeneously catalysed reduction
using gaseous hydrogen and is more easily reproduced than small scale
stirred vessels. Measurements have been made at a fixed total gas
flow, with the effective mass transfer rate being adjustable by dilution
of the hydrogen flow with either helium or nitrogen
Heatmap displaying the relative abundance data of 45 genes with Resistomap primers matching multiple genes in CARD.
Heatmap displaying the relative abundance data of 45 genes with Resistomap primers matching multiple genes in CARD.</p
CARD/RGI alignment results showing reads coverage of gene <i>mexB</i>.
Note that more than 95% of the gene is covered with at least one read in all samples.</p
The region of the <i>mexB</i> gene targeted by Resistomap primers.
The regions are shown as blue and red lines below the CARD sequence for mexB. In grey are conserved amino acids and mutations are represented by colors.</p
Pearson correlation breakdown by antibiotic class for single-match genes across all locations.
Pearson correlation breakdown by antibiotic class for single-match genes across all locations.</p
Genes identified by CARD/RGI but not by Resistomap.
Genes identified by CARD/RGI but not by Resistomap.</p
Fate of ISA's in microcosms treated with chloramphenicol when compared with untreated microcosm (A) ISA in presence of canal sediment and (B) reed bed sediment (n = 3).
<p>Fate of ISA's in microcosms treated with chloramphenicol when compared with untreated microcosm (A) ISA in presence of canal sediment and (B) reed bed sediment (n = 3).</p
Chemical evolution of methanogenic reactors (n = 6).
<p>Chemical evolution of methanogenic reactors (n = 6).</p
Composition of microcosm headspace gases (n = 6).
<p>Composition of microcosm headspace gases (n = 6).</p
Taxa of bacterial groups in all four samples.
Surveillance methods of circulating antibiotic resistance genes (ARGs) are of utmost importance in order to tackle what has been described as one of the greatest threats to humanity in the 21st century. In order to be effective, these methods have to be accurate, quickly deployable, and scalable. In this study, we compare metagenomic shotgun sequencing (TruSeq DNA sequencing) of wastewater samples with a state-of-the-art PCR-based method (Resistomap HT-qPCR) on four wastewater samples that were taken from hospital, industrial, urban and rural areas. ARGs that confer resistance to 11 antibiotic classes have been identified in these wastewater samples using both methods, with the most abundant observed classes of ARGs conferring resistance to aminoglycoside, multidrug-resistance (MDR), macrolide-lincosamide-streptogramin B (MLSB), tetracycline and beta-lactams. In comparing the methods, we observed a strong correlation of relative abundance of ARGs obtained by the two tested methods for the majority of antibiotic classes. Finally, we investigated the source of discrepancies in the results obtained by the two methods. This analysis revealed that false negatives were more likely to occur in qPCR due to mutated primer target sites, whereas ARGs with incomplete or low coverage were not detected by the sequencing method due to the parameters set in the bioinformatics pipeline. Indeed, despite the good correlation between the methods, each has its advantages and disadvantages which are also discussed here. By using both methods together, a more robust ARG surveillance program can be established. Overall, the work described here can aid wastewater treatment plants that plan on implementing an ARG surveillance program.</div