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The Pacific Northwest National Laboratory (PNNL) is evaluating the performance of adsorption materials to extract uranium from natural seawater. Testing consists of measurements of the adsorption of uranium and other elements from seawater as a function of time using flow-through columns and a recirculating flume to determine adsorbent capacity and adsorption kinetics. The amidoxime-based polymer adsorbent AF1, produced by Oak Ridge National Laboratory (ORNL), had a 56-day adsorption capacity of 3.9 ± 0.2 g U/kg adsorbent material, a saturation capacity of 5.4 ± 0.2 g U/kg adsorbent material, and a half-saturation time of 23 ± 2 days. The ORNL AF1 adsorbent has a very high affinity for uranium, as evidenced by a 56-day distribution coefficient between adsorbent and solution of log KD,56day = 6.08. Calcium and magnesium account for a majority of the cations adsorbed by the ORNL amidoxime-based adsorbents (61% by mass and 74% by molar percent), uranium is the fourth most abundant element adsorbed by mass an...

A variety of adsorbent materials have been developed to extract uranium from seawater as an alternative traditional terrestrial mining. A large-scale deployment of these adsorbents would be necessary to recover useful quantities of uranium, and this raises a number of concerns regarding potential impacts on the surrounding marine environment. Two concerns are whether or not the adsorbent materials are toxic and any potentially harmful effects that may result from depleting uranium or vanadium (also highly concentrated by the adsorbents) from the local environment. To test the potential toxicity of the adsorbent with or without bound metals, Microtox assays were used to test both direct contact toxicity and the toxicity of any leachate in the seawater. The Microtox assay was chosen because it detected nonspecific mechanisms of toxicity. Toxicity was not observed with leachates from any of the 68 adsorbent materials that were tested, but direct contact with some adsorbents at very high adsorbent concentrati...

The Marine Science Laboratory at the Pacific Northwest National Laboratory evaluated the impact of biofouling on the performance or uranium adsorbents. A surface-modified polyethylene adsorbent fiber provided by Oak Ridge National Laboratory, AF adsorbent, was tested in either the presence or absence of light to simulate deployment in shallow or deep marine environments. Samples of the adsorbent fiber were exposed to seawater as loose fibers packed with glass beads in columns and as >10-cm-long braids of fiber placed in a flume that provided a continuous flow representative of natural ocean currents. Exposure tests (42 days) in column and flume settings showed that biofouling resulted in decreased uranium uptake by the adsorbent fiber. Uranium uptake was reduced by up to 30%, in the presence of simulated sunlight, which also increased biomass accumulation and altered the microbial community composition on the fibers. These results suggest that deployment below the photic zone would mitigate the effects of...

The accumulation of bacteria in surface-attached biofilms can be detrimental to human health, dental hygiene, and many industrial processes. Natural biofilms are soft and often transparent, and they have heterogeneous biological composition and structure over micro- and macroscales. As a result, it is challenging to quantify the spatial distribution and overall intensity of biofilms. In this work, a new method was developed to enhance the visibility and quantification of bacterial biofilms. First, broad-spectrum biomolecular staining was used to enhance the visibility of the cells, nucleic acids, and proteins that make up biofilms. Then, an image analysis algorithm was developed to objectively and quantitatively measure biofilm accumulation from digital photographs and results were compared to independent measurements of cell density. This new method was used to quantify the growth intensity of Pseudomonas putida biofilms as they grew over time. This method is simple and fast, and can quantify biofilm growth over a large area with approximately the same precision as the more laborious cell counting method. Stained and processed images facilitate assessment of spatial heterogeneity of a biofilm across a surface. This new approach to biofilm analysis could be applied in studies of natural, industrial, and environmental biofilms. Graphical abstract A novel photographic method was developed to quantify bacterial biofilms. Broad spectrum biomolecular staining enhanced the visibility of the biofilms. Image analysis objectively and quantitatively measured biofilm accumulation from digital photographs. When compared to independent measurements of cell density the new method accurately quantified growth of Pseudomonas putida biofilms as they grew over time. The graph shows a comparison of biofilm quantification from cell density and image analysis. Error bars show standard deviation from three independent samples. Inset photographs show effect of staining Electronic supplementary material The online version of this article (doi:10.1007/s00216-015-9195-z) contains supplementary material, which is available to authorized users.

Previous studies of resistance gene ecology have focused primarily on populations such as hospital patients and farm animals that are regularly exposed to antibiotics. Also, these studies have tended to focus on numerically minor populations such as enterics or enterococci. We report here a cultivation-independent approach that allowed us to assess the presence of antibiotic resistance genes in the numerically predominant populations of the vaginal microbiota of two populations of primates that are seldom or never exposed to antibiotics: baboons and mangabeys. Most of these animals were part of a captive colony in Texas that is used for scientific studies of female physiology and physical anthropology topics. Samples from some wild baboons were also tested. Vaginal swab samples, obtained in connection with a study designed to define the normal microbiota of the female vaginal canal, were tested for the presence of two types of antibiotic resistance genes: tetracycline resistance (tet) genes and erythromycin resistance (erm) genes. These genes are frequently found in human isolates of the two types of bacteria that were a substantial part of the normal microbiota of primates (Firmicutes and Bacteroidetes). Since cultivation was not feasible, polymerase chain reaction and DNA sequencing were used to detect and characterize these resistance genes. The tet(M) and tet(W) genes were found most commonly, and the tet(Q) gene was found in over a third of the samples from baboons. The ermB and ermF genes were found only in a minority of the samples. The ermG gene was not found in any of the specimens tested. Polymerase chain reaction analysis showed that at least some tet(M) and tet(Q) genes were genetically linked to DNA from known conjugative transposons (CTns), Tn916 and CTnDOT. Our results raise questions about the extent to which extensive exposure to antibiotics is the only pressure necessary to maintain resistance genes in natural settings.

The Marine Sciences Laboratory at the Pacific Northwest National Laboratory evaluated the toxicity of a diverse range of natural and synthetic materials used to extract uranium from seawater. The uranium adsorbent materials are being developed as part of the U. S. Department of Energy, Office of Nuclear Energy, Fuel Resources Program. The goal of this effort was to identify whether deployment of a farm of these materials into the marine environment would have any toxic effects on marine organisms.

Many human colonic Bacteroides spp. harbor a conjugative transposon, CTnDOT, which carries two antibiotic resistance genes, tetQ and ermF . A distinctive feature of CTnDOT is that its excision and transfer are stimulated by tetracycline. Regulation of the genes responsible for excision has been described previously. We provide here the first characterization of the regulation of CTnDOT transfer ( tra ) genes. Reverse transcription-PCR analysis of the region containing the tra genes showed that these genes are regulated at the transcriptional level. Surprisingly, increased production of tra gene mRNA in tetracycline-stimulated cells was mediated by the proteins encoded by the excision genes. Previous studies have shown that expression of the excision gene operon is controlled by the regulatory protein RteC. Accordingly, it was possible that RteC was also regulating tra gene expression and that the excision proteins were only accessory proteins. However, placing the excision gene operon under the control of a heterologous promoter showed that the excision proteins alone could activate tra gene expression and that RteC was not directly involved. We also found a second level of tra gene control. The transfer of CTnDOT was inhibited by a DNA segment that included only a portion of the 3′ end of one of the excision genes ( exc ). This segment contained a small open reading frame, rteR . By replacing the codons encoding the first two amino acids of the putative protein product of this open reading frame with stop codons, we showed that the rteR gene might encode a small regulatory RNA. RteR acted in trans to reduce the number of tra transcripts in a way that was independent of the excision proteins. The repressive effect of RteR was not the result of decreased stability of the tra mRNA. Instead, RteR appears to be modulating the level of tra gene expression in some more direct fashion. The complex regulatory system that controls and links the expression of CTnDOT excision and transfer genes may be designed to ensure stable maintenance of CTnDOT in nature by reducing the fitness toll it takes on the cell that harbors it.