Evaluation of the taproot elongation rates of soybean cultivars

Soybean Glycine max (L.) Merr. genotypes with rapidly elongating taproots may attain greater rooting depths and may be more drought avoidant than soybean genotypes with taproots that elongate more slowly. The objectives of this study were to improve and standardize a glasshouse procedure for measuring soybean taproot elongation rates, and to determine whether soybean cultivars with widely differing taproot elongation rates have different patterns of root growth and water extraction in the field;Taproot elongation rates of 105 soybean cultivars were measured by growing individual plants in a glasshouse in acrylic plastic tubes filled with vermiculite and slanted at 15(DEGREES) from the vertical. There were significant differences in taproot elongation rate among cultivars. In general, the procedure developed for measuring taproot elongation rates yielded reasonably consistent and reproducible rankings of cultivars;Seed weight, seed source and quality, planting depth, and seedling damage affected taproot elongation rate. Plants grown from heavier seed had faster taproot elongation rates than those grown from lighter seed, at least within cultivars. Cultivar differences, however, were not related to seed weight. Older or poorer quality seed produced plants with slower taproot elongation rates. Deeper planting slowed rate of taproot elongation. Lastly, seedling damage treatments, consisting of removal of various plant parts, decreased taproot elongation rates;Eight soybean cultivars, four with relatively fast rate of elongation and four with relatively slow rates, were grown in field plots at Castana, Iowa. Rooting depth and relative root length density with depth were determined from 10 cm diameter cores using the core-break method. Soil-water-use with depth was determined using a neutron soil moisture probe. Generally, cultivars with relatively fast taproot elongation had deeper maximum rooting depths and greater relative root length densities at 100, 150 and 200 cm depths than did those in the slow elongating group. Additionally, cultivars with faster elongation rates obtained a larger percentage of their water from below 120 cm

The use of monoclonal and polyclonal antibodies to identify Escherichia coli

Coagglutination tests with polyclonal antibodies were developed for the detection of Escherichia coli [beta]-galactosidase (GAL), [beta]-glucuronidase (GUD), and glutamate decarboxylase (GAD) in cell lysates. All three enzymes were detected in 93% of the E. coli tested; two of the three enzymes were detected in the remaining 7%. Among 42 non-E. coli, two (5%) were agglutinated by all three anti-enzyme conjugates, two (5%) were agglutinated by two conjugates, six (14%) were agglutinated by a single conjugate, and 32 (76%) were not agglutinated by any of the conjugates;Enzyme-capture assays with polyclonal antibodies detected the presence of GAL in seven of eight and GUD in all eight E. coli tested. Some GAL-positive Citrobacter freundii and Enterobacter cloacae also were positive by the enzyme-capture assay, indicating that the antibodies were not specific for E. coli GAL. Five other GAL-positive non-E. coli were negative by the enzyme-capture assay;The coagglutination tests and the enzyme-capture assay were rapid methods for the detection of GAL, GUD, and GAD in cell lysates;Polyclonal antibodies to heat-treated E. coli differed in the numbers of E. coli and non-E. coli detected by enzyme immunoassay. Antiserum to one E. coli strain reacted with all of the bacteria tested while antiserum to a second strain was positive for just two of five E. coli tested, Enterobacter agglomerans and Klebsiella ozanae. Attempts to remove the cross-reacting antibodies by adsorption were unsuccessful;Monoclonal antibodies to heat-treated E. coli varied in specificity. Antibodies from hybridoma 6H2 reacted with 35 of 68 (51%) E. coli; of the 13 non-E. coli tested, Enterobacter agglomerans was weakly positive and the others were negative. Antibodies from hybridoma 9B12 reacted with all six E. coli tested and with Enterobacter cloacae; however, 9B12 stopped producing E. coli-specific antibody. The antibodies from five hybridomas produced antibodies which reacted with a majority of the bacteria tested. Additional monoclonal antibodies that can supplement antibodies from 6H2 are needed

Coagglutination and Enzyme Capture Tests for Detection of \u3ci\u3eEscherichia coli\u3c/i\u3e β-Galactosidase, β-Glucuronidase, and Glutamate Decarboxylase

Polyclonal antibodies to Escherichia coli β-galactosidase, β-glucuronidase, and glutamate decarboxylase were used in coagglutination tests for identification of these three enzymes in cell lysates. Enzyme capture assays were also developed for the detection of E. coli β-galactosidase and β-glucuronidase. The enzymes were released by using a gentle lysis procedure that did not interfere with antibody-enzyme interactions. All three enzymes were detected in 93% (51 of 55) of the E. coli strains tested by coagglutination; two of the three enzymes were identified in the remaining 7%. Of 42 non-E. coli tested by coagglutination, only four nonspecifically agglutinated either two or three of the anti-enzyme conjugates. Thirty-two (76%) non-E. coli isolates were negative by coagglutination for all three enzymes. The enzyme capture assay detected the presence of β-galactosidase in seven of eight and β-glucuronidase in all eight strains of E. coli tested. Some strains of β-galactosidase-positive Citrobacterfreundii and Enterobacter cloacae were also positive by the enzyme capture assay, indicating that the antibodies were not entirely specific for E. coli β-galactosidase; however, five other gas-positive non-E. coli isolates were negative by the enzyme capture assay. The coagglutination tests and enzyme capture assays were rapid and sensitive methods for the detection of E. coli ,β-galactosidase, β-glucuronidase, and glutamate decarboxylase

Coagglutination and Enzyme Capture Tests for Detection of \u3ci\u3eEscherichia coli\u3c/i\u3e β-Galactosidase, β-Glucuronidase, and Glutamate Decarboxylase

Polyclonal antibodies to Escherichia coli β-galactosidase, β-glucuronidase, and glutamate decarboxylase were used in coagglutination tests for identification of these three enzymes in cell lysates. Enzyme capture assays were also developed for the detection of E. coli β-galactosidase and β-glucuronidase. The enzymes were released by using a gentle lysis procedure that did not interfere with antibody-enzyme interactions. All three enzymes were detected in 93% (51 of 55) of the E. coli strains tested by coagglutination; two of the three enzymes were identified in the remaining 7%. Of 42 non-E. coli tested by coagglutination, only four nonspecifically agglutinated either two or three of the anti-enzyme conjugates. Thirty-two (76%) non-E. coli isolates were negative by coagglutination for all three enzymes. The enzyme capture assay detected the presence of β-galactosidase in seven of eight and β-glucuronidase in all eight strains of E. coli tested. Some strains of β-galactosidase-positive Citrobacterfreundii and Enterobacter cloacae were also positive by the enzyme capture assay, indicating that the antibodies were not entirely specific for E. coli β-galactosidase; however, five other gas-positive non-E. coli isolates were negative by the enzyme capture assay. The coagglutination tests and enzyme capture assays were rapid and sensitive methods for the detection of E. coli ,β-galactosidase, β-glucuronidase, and glutamate decarboxylase

Activities of methionine-γ-lyase in the acidophilic archaeon “Ferroplasma acidarmanus” strain fer1

Biogeochemical processes on exposed pyrite ores result in extremely high levels of sulfuric acid at these locations. Acidophiles that thrive in these conditions must overcome significant challenges, including an environment with proton concentrations at pH 3 or below. The role of sulfur metabolism in the archaeon “Ferroplasma acidarmanus” strain fer1’s ability to thrive in this environment was investigated due to its growth-dependent production of methanethiol, a volatile organic sulfur compound. Two putative sequences for methionine- γ-lyase (EC 4.4.1.11), an enzyme known to carry out α,γ-elimination on L-methionine to produce methanethiol, were identified in fer1. Bioinformatic analyses identified a conserved pyridoxal-5′-phosphate (PLP) binding domain and a partially conserved catalytic domain in both putative sequences. Detection of PLP-dependent and L-methionine-dependent production of α-keto compounds and thiol groups in fer1 confirmed the presence of methionine-γ-lyase activity. Further, fer1 lysate was capable of processing related substrates, including D-methionine, L-cysteine, L-cystathionine, and L/D-homocysteine. When the two putative fer1 methionine-γ- lyase gene-coded proteins were expressed in Escherichia coli cells, one sequence demonstrated an ability to carry out α, γ-elimination activity, while the other exhibited γ-replacement activity. These fer1 methionine-γ-lyases also exhibited optimum pH, substrate specificity, and catalytic preferences that are different from methionine-γ-lyases from other organisms. These differences are discussed in the context of molecular phylogeny constructed using a maximum likelihood algorithm based on methionine-γ-lyase sequences from a diverse selection of organisms

Activities of methionine-γ-lyase in the acidophilic archaeon “Ferroplasma acidarmanus” strain fer1

Biogeochemical processes on exposed pyrite ores result in extremely high levels of sulfuric acid at these locations. Acidophiles that thrive in these conditions must overcome significant challenges, including an environment with proton concentrations at pH 3 or below. The role of sulfur metabolism in the archaeon “Ferroplasma acidarmanus” strain fer1’s ability to thrive in this environment was investigated due to its growth-dependent production of methanethiol, a volatile organic sulfur compound. Two putative sequences for methionine- γ-lyase (EC 4.4.1.11), an enzyme known to carry out α,γ-elimination on L-methionine to produce methanethiol, were identified in fer1. Bioinformatic analyses identified a conserved pyridoxal-5′-phosphate (PLP) binding domain and a partially conserved catalytic domain in both putative sequences. Detection of PLP-dependent and L-methionine-dependent production of α-keto compounds and thiol groups in fer1 confirmed the presence of methionine-γ-lyase activity. Further, fer1 lysate was capable of processing related substrates, including D-methionine, L-cysteine, L-cystathionine, and L/D-homocysteine. When the two putative fer1 methionine-γ- lyase gene-coded proteins were expressed in Escherichia coli cells, one sequence demonstrated an ability to carry out α, γ-elimination activity, while the other exhibited γ-replacement activity. These fer1 methionine-γ-lyases also exhibited optimum pH, substrate specificity, and catalytic preferences that are different from methionine-γ-lyases from other organisms. These differences are discussed in the context of molecular phylogeny constructed using a maximum likelihood algorithm based on methionine-γ-lyase sequences from a diverse selection of organisms

Acid stress damage of DNA is prevented by Dps binding in Escherichia coli O157:H7

<p>Abstract</p> <p>Background</p> <p>Acid tolerance in <it>Escherichia coli </it>O157:H7 contributes to persistence in its bovine host and is thought to promote passage through the gastric barrier of humans. Dps (DNA-binding protein in starved cells) mutants of <it>E. coli </it>have reduced acid tolerance when compared to the parent strain although the role of Dps in acid tolerance is unclear. This study investigated the mechanism by which Dps contributes to acid tolerance in <it>E. coli </it>O157:H7.</p> <p>Results</p> <p>The results from this study showed that acid stress lead to damage of chromosomal DNA, which was accentuated in <it>dps </it>and <it>recA </it>mutants. The use of <it>Bal</it>31, which cleaves DNA at nicks and single-stranded regions, to analyze chromosomal DNA extracted from cells challenged at pH 2.0 provided <it>in vivo </it>evidence of acid damage to DNA. The DNA damage in a <it>recA </it>mutant further corroborated the hypothesis that acid stress leads to DNA strand breaks. Under <it>in vitro </it>assay conditions, Dps was shown to bind plasmid DNA directly and protect it from acid-induced strand breaks. Furthermore, the extraction of DNA from Dps-DNA complexes required a denaturing agent at low pH (2.2 and 3.6) but not at higher pH (>pH4.6). Low pH also restored the DNA-binding activity of heat-denatured Dps. Circular dichroism spectra revealed that at pH 3.6 and pH 2.2 Dps maintains or forms α-helices that are important for Dps-DNA complex formation.</p> <p>Conclusion</p> <p>Results from the present work showed that acid stress results in DNA damage that is more pronounced in <it>dps </it>and <it>recA </it>mutants. The contribution of RecA to acid tolerance indicated that DNA repair was important even when Dps was present. Dps protected DNA from acid damage by binding to DNA. Low pH appeared to strengthen the Dps-DNA association and the secondary structure of Dps retained or formed α-helices at low pH. Further investigation into the precise interplay between DNA protection and damage repair pathways during acid stress are underway to gain additional insight.</p

H-NS controls metabolism and stress tolerance in Escherichia coli O157:H7 that influence mouse passage

BACKGROUND: H-NS is a DNA-binding protein with central roles in gene regulation and nucleoid structuring in Escherichia coli. There are over 60 genes that are influenced by H-NS many of which are involved in metabolism. To determine the significance of H-NS-regulated genes in metabolism and stress tolerance, an hns mutant of E. coli O157:H7 was generated (hns::nptI, FRIK47001P) and its growth, metabolism, and gastrointestinal passage compared to the parent strain (43895) and strain FRIK47001P harboring pSC0061 which contains a functional hns and 90-bp upstream of the open-reading frame. RESULTS: The hns mutant grew slower and was non-motile in comparison to the parent strain. Carbon and nitrogen metabolism was significantly altered in the hns mutant, which was incapable of utilizing 42 carbon, and 19 nitrogen sources that the parent strain metabolized. Among the non-metabolized substrates were several amino acids, organic acids, and key metabolic intermediates (i.e., pyruvate) that limit carbon acquisition and energy generation. Growth studies determined that the parent strain grew in LB containing 14 to 15% bile or bile salts, while the hns mutant grew in 6.5 and 9% of these compounds, respectively. Conversely, log-phase cells of the hns mutant were significantly (p < 0.05) more acid tolerant than the parent strain and hns mutant complemented with pSC0061. In mouse passage studies, the parent strain was recovered at a higher frequency (p < 0.01) than the hns mutant regardless of whether log- or stationary-phase phase cells were orally administered. CONCLUSION: These results demonstrate that H-NS is a powerful regulator of carbon and nitrogen metabolism as well as tolerance to bile salts. It is likely that the metabolic impairments and/or the reduced bile tolerance of the E. coli O157:H7 hns mutant decreased its ability to survive passage through mice. Collectively, these results expand the influence of H-NS on carbon and nitrogen metabolism and highlight its role in the ability of O157:H7 strains to respond to changing nutrients and conditions encountered in the environment and its hosts

Stellar Parameters for HD 69830, a Nearby Star with Three Neptune Mass Planets and an Asteroid Belt

We used the CHARA Array to directly measure the angular diameter of HD 69830, home to three Neptune mass planets and an asteroid belt. Our measurement of 0.674+/-0.014 milli-arcseconds for the limb-darkened angular diameter of this star leads to a physical radius of R$_*$ = 0.9058$\pm$0.0190 R\sun and luminosity of L* = 0.622+/-0.014 Lsun when combined with a fit to the spectral energy distribution of the star. Placing these observed values on an Hertzsprung-Russel (HR) diagram along with stellar evolution isochrones produces an age of 10.6+/-4 Gyr and mass of 0.863$\pm$0.043 M\sun. We use archival optical echelle spectra of HD 69830 along with an iterative spectral fitting technique to measure the iron abundance ([Fe/H]=-0.04+/-0.03), effective temperature (5385+/-44 K) and surface gravity (log g = 4.49+/-0.06). We use these new values for the temperature and luminosity to calculate a more precise age of 7.5+/-Gyr. Applying the values of stellar luminosity and radius to recent models on the optimistic location of the habitable zone produces a range of 0.61-1.44 AU; partially outside the orbit of the furthest known planet (d) around HD 69830. Finally, we estimate the snow line at a distance of 1.95+/-0.19 AU, which is outside the orbit of all three planets and its asteroid belt.Comment: 5 pages, 3 figures, accepted to Ap

Molecular and behavioral changes associated with adult hippocampus-specific SynGAP1 knockout

The synaptic Ras/Rap-GTPase-activating protein (SynGAP1) plays a unique role in regulating specific downstream intracellular events in response to N-methyl-D-aspartate receptor (NMDAR) activation. Constitutive heterozygous loss of SynGAP1 disrupts NMDAR-mediated physiological and behavioral processes, but the disruptions might be of developmental origin. Therefore, the precise role of SynGAP1 in the adult brain, including its relative functional significance within specific brain regions, remains unexplored. The present study constitutes the first attempt in achieving adult hippocampal-specific SynGAP1 knockout using the Cre/loxP approach. Here, we report that this manipulation led to a significant numerical increase in both small and large GluA1 and NR1 immunoreactive clusters, many of which were non-opposed to presynaptic terminals. In parallel, the observed marked decline in the amplitude of spontaneous excitatory currents (sEPSCs) and inter-event intervals supported the impression that SynGAP1 loss might facilitate the accumulation of extrasynaptic glutamatergic receptors. In addition, SynGAP1-mediated signaling appears to be critical for the proper integration and survival of newborn neurons. The manipulation impaired reversal learning in the probe test of the water maze and induced a delay-dependent impairment in spatial recognition memory. It did not significantly affect anxiety or reference memory acquisition but induced a substantial elevation in spontaneous locomotor activity in the open field test. Thus, the present study demonstrates the functional significance of SynGAP1 signaling in the adult brain by capturing several changes that are dependent on NMDAR and hippocampal integrity