Potential for managing pool levels in a flood-control reservoir to increase nitrate-nitrogen load reductions

Few strategies are available to reduce nitrate-nitrogen (NO3-N) loads at larger landscape scales, but flood control reservoirs are known to reduce riverine loads. In this study, we evaluated the potential to increase nitrogen (N) loss at Lake Red Rock, a large reservoir located in central Iowa, by evaluating the inundation of sediments deposited at the reservoir inflow. Sediment samples were collected at 51 locations in the lower delta region and analyzed for particle size and nutrient content. Nitrogen loss rates in delta sediments were determined from laboratory assays, and satellite imagery was used to develop a rating curve to quantify land area inundated within the delta. The daily mass of NO3-N reduced with delta inundation was estimated by applying the mean N 24-h loss rate (0.66 g N m2 day−1) by the area of inundation (m2). Results indicated that raising pool elevations to inundate more of the delta would result in greater N losses, ranging from 2 to 377 Mg per year. Potential N loss of 102 Mg achieved by increasing pool stage by 0.5 m would be equivalent to installing nearly 650 edge-of-field practices in the watershed. Although more work is needed to integrate with an existing environmental pool management plan, study results indicate that reservoir management could achieve N reductions at a novel landscape scale.This article is published as Schilling, K. E., Streeter, M. T., Anderson, E., Merryman, J., Isenhart, T., Arenas-Amado, A., & Theiling, C. (2024). Potential for managing pool levels in a flood-control reservoir to increase nitrate-nitrogen load reductions. Journal of Environmental Quality, 1–11. https://doi.org/10.1002/jeq2.20539. © 2024 The Authors.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited

Cloning whole bacterial genomes in yeast

Most microbes have not been cultured, and many of those that are cultivatable are difficult, dangerous or expensive to propagate or are genetically intractable. Routine cloning of large genome fractions or whole genomes from these organisms would significantly enhance their discovery and genetic and functional characterization. Here we report the cloning of whole bacterial genomes in the yeast Saccharomyces cerevisiae as single-DNA molecules. We cloned the genomes of Mycoplasma genitalium (0.6 Mb), M. pneumoniae (0.8 Mb) and M. mycoides subspecies capri (1.1 Mb) as yeast circular centromeric plasmids. These genomes appear to be stably maintained in a host that has efficient, well-established methods for DNA manipulation

A Bifunctional tRNA for In Vitro Selection

AbstractIn vitro selection is a powerful approach for generating novel aptamers and catalysts. Currently, several methods are being developed to extend this technique to proteins. In principle, selection methods could be applied to any library whose members can be replicated. Here, we describe a bifunctional tRNA that fuses translation products to their mRNAs. The utility of peptide-tRNA-mRNA fusions for in vitro selection was illustrated by the selective enrichment of tagged peptides—together with their mRNAs—by affinity chromatography. Our system can generate libraries larger than 1011. Because library members can be copied and amplified, they provide a means for applying in vitro selection procedures to peptides and proteins. Furthermore, because the system is amenable to translation with misacylated tRNAs, a wide range of unusual monomers could be used to make libraries of nonstandard polymers for selection experiments

A Type III restriction-modification system in Mycoplasma mycoides subsp. capri.

The sequenced genome of Mycoplasma mycoides subsp. capri revealed the presence of a Type III restriction-modification system (MmyCI). The methyltransferase (modification) subunit of MmyCI (M. MmyCI) was shown to recognize the sequence 5'-TGAG-3' and methylate the adenine. The coding region of the methyltransferase gene contains 12 consecutive AG dinucleotide repeats that result in a translational termination at a TAA codon immediately beyond the repeat region. This strain does not have MmyCI activity. A clone was found with 10 AG repeats such that the gene is in frame, and this strain has MmyCI activity, suggesting that the expression of the MmyCI methyltransferase may be phase variable

New Selectable Marker for Manipulating the Simple Genomes of Mycoplasma Species ▿

Over the past several years, significant advances have been made in the molecular genetics of the Mollicutes (the simplest cells that can be grown in axenic culture). Nevertheless, a number of basic molecular tools are still required before genetic manipulations become routine. Here we describe the development of a new dominant selectable marker based on the enzyme puromycin-N-acetyltransferase from Streptomyces alboniger. Puromycin is an antibiotic that mimics the 3′-terminal end of aminoacylated tRNAs and attaches to the carboxyl terminus of growing protein chains. This stops protein synthesis. Because puromycin conscripts rRNA recognition elements that are used by all of the various tRNAs in a cell, it is unlikely that spontaneous antibiotic resistance can be acquired via a simple point mutation—an annoying issue with existing mycoplasma markers. Our codon-optimized cassette confers pronounced puromycin resistance on all five of the mycoplasma species we have tested so far. The resistance cassette was also designed to function in Escherichia coli, which simplifies the construction of shuttle vectors and makes it trivial to produce the large quantities of DNA generally necessary for mycoplasma transformation. Due to these and other features, we expect the puromycin marker to be a widely applicable tool for studying these simple cells and pathogens