Iron reduction and sulfate reduction are two of the major biogeochemical processes that occur in anoxic sediments. Microbes that catalyze these reactions are therefore some of the most abundant organisms in the subsurface, and some of the... more
Iron reduction and sulfate reduction are two of the major biogeochemical processes that occur in anoxic sediments. Microbes that catalyze these reactions are therefore some of the most abundant organisms in the subsurface, and some of the most important. Due to the variety of mechanisms that microbes employ to derive energy from these reactions, including the use of soluble electron shuttles, the dynamics between iron- and sulfate-reducing populations under changing biogeochemical conditions still elude complete characterization. Here, we amended experimental bioreactors comprised of freshwater aquifer sediment with ferric iron, sulfate, acetate, and the model electron shuttle AQDS (9,10-anthraquinone-2,6-disulfonate) and monitored both the changing redox conditions as well as changes in the microbial community over time. The addition of the electron shuttle AQDS did increase the initial rate of FeIIIreduction; however, it had little effect on the composition of the microbial commun...
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Methane is a microbially derived greenhouse gas whose emissions are highly variable throughout wetland ecosystems. Differences in plant community composition account for some of this variability, suggesting an influence of plant species... more
Methane is a microbially derived greenhouse gas whose emissions are highly variable throughout wetland ecosystems. Differences in plant community composition account for some of this variability, suggesting an influence of plant species on microbial community structure and function in these ecosystems. Given that closely related plant species have similar morphological and biochemical features, we hypothesize that plant evolutionary history is related to differences in microbial community composition. To examine species-specific patterns in microbiomes, we selected five monoculture-forming wetland plant species based on the evolutionary distances among them. We detected significant differences in microbial communities between sample types (unvegetated soil, bulk soil, rhizosphere soil, internal root tissues, and internal leaf tissues) associated with these plant species based on 16S relative abundances. We additionally found that differences in plant evolutionary history were correl...
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Here, we report the draft genome sequence of Arthrobacter sp. strain ATCC 49987, consisting of three contigs with a total length of 4.4 Mbp. Based on the genome sequence, we suggest reclassification of Arthrobacter sp. strain ATCC 49987... more
Here, we report the draft genome sequence of Arthrobacter sp. strain ATCC 49987, consisting of three contigs with a total length of 4.4 Mbp. Based on the genome sequence, we suggest reclassification of Arthrobacter sp. strain ATCC 49987 as Pseudarthrobacter sp. strain ATCC 49987.
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Here, we report the features and draft genome sequence of Pseudarthrobacter sp. strain AG30, isolated from the Zijin gold and copper mine in China.
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Two closely related enzymes with more than 50% sequence identity have been identified that catalyze the esterification of cholesterol using acyl-CoA substrates, namely acyl-CoA:cholesterol acyltransferase 1 (ACAT1) and ACAT2. Both are... more
Two closely related enzymes with more than 50% sequence identity have been identified that catalyze the esterification of cholesterol using acyl-CoA substrates, namely acyl-CoA:cholesterol acyltransferase 1 (ACAT1) and ACAT2. Both are membrane-spanning proteins believed to reside in the endoplasmic reticulum of cells. ACAT2 has been hypothesized to be associated with lipoprotein particle secretion whereas ACAT1 is ubiquitous and may serve a more general role in cellular cholesterol homeostasis. We have prepared and affinity purified rabbit polyclonal antibodies unique to either ACAT enzyme to identify their cellular localization in liver and intestine, the two main lipoprotein-secreting tissues of the body, and for comparison, kidney and adrenal. In the liver, ACAT2 was identified in the rough endoplasmic reticulum of essentially all hepatocytes whereas ACAT1 was confined to cells lining the intercellular spaces among hepatocytes in a pattern typical of Kupffer cells. In the intesti...
Research Interests: Immunohistochemistry, Cercopithecus aethiops, Cell line, Kidney, Liver, and 15 moreAnimals, Male, Endoplasmic Reticulum, Apolipoprotein B, Enzyme, Intestines, Isoenzymes, Lipid, Lipoprotein a, Biochemistry and cell biology, Differential expression, Adrenal glands, CHO cells, Cricetinae, and Medical biochemistry and metabolomics
The iron chelator deferoxamine has been reported to inhibit both xanthine oxidase (XO) and xanthine dehydrogenase activity, but the relationship of this effect to the availability of iron in the cellular and tissue environment remains... more
The iron chelator deferoxamine has been reported to inhibit both xanthine oxidase (XO) and xanthine dehydrogenase activity, but the relationship of this effect to the availability of iron in the cellular and tissue environment remains unexplored. XO and total xanthine oxidoreductase activity in cultured V79 cells was increased with exposure to ferric ammonium sulfate and inhibited by deferoxamine. Lung XO and total xanthine oxidoreductase activities were reduced in rats fed an iron-depleted diet and increased in rats supplemented with iron, without change in the ratio of XO to total oxidoreductase. Intratracheal injection of an iron salt or silica-iron, but not aluminum salts or silica-zinc, significantly increased rat lung XO and total xanthine oxidoreductase activities, immunoreactive xanthine oxidoreductase, and the concentration of urate in bronchoalveolar fluid. These results suggest the possibility that the production of uric acid, a major chelator of iron in extracellular flu...
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... New Reviews. Standard Article. Uric Acid Metabolism. Kelly A Skinner 1 ,; Sidhartha Tan 2 ,; Dale A Parks 3. Published Online: 25 APR 2001. DOI: 10.1038/npg.els.0001400. ... Additional Information. How to Cite. Skinner, KA, Tan, S.... more
... New Reviews. Standard Article. Uric Acid Metabolism. Kelly A Skinner 1 ,; Sidhartha Tan 2 ,; Dale A Parks 3. Published Online: 25 APR 2001. DOI: 10.1038/npg.els.0001400. ... Additional Information. How to Cite. Skinner, KA, Tan, S. and Parks, DA 2001. Uric Acid Metabolism. ...
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In general, the simple concepts first proposed over a decade ago for the role of xanthine oxidase (XO) in pathophysiolgy are no longer sufficient. This review summarizes evidence that has led to a resurgence in interest of XO physiology... more
In general, the simple concepts first proposed over a decade ago for the role of xanthine oxidase (XO) in pathophysiolgy are no longer sufficient. This review summarizes evidence that has led to a resurgence in interest of XO physiology and pathology and in particular, data that implicates XO and nitric oxide (⋅NO) in the development of multiple organ dysfunction (MODS)
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Page 1. Chapter 15 Xanthine Oxidase in Biology and Medicine Dale A. Parks, Kelly A. Skinner, Sidhartha Tan, and Henry B. Skinner 1. INTRODUCTION Xanthine oxidoreductase (xanthine: oxidoreductase, EC 1.1.1.204) is an ...
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A second form of the enzyme acyl-CoA:cholesterol acyltransferase, ACAT2, has been identified. To explore the hypothesis that the two ACAT enzymes have separate functions, the membrane topologies of ACAT1 and ACAT2 were examined. A... more
A second form of the enzyme acyl-CoA:cholesterol acyltransferase, ACAT2, has been identified. To explore the hypothesis that the two ACAT enzymes have separate functions, the membrane topologies of ACAT1 and ACAT2 were examined. A glycosylation reporter and FLAG epitope tag sequence was appended to a series of ACAT cDNAs truncated after each predicted transmembrane domain. Fusion constructs were assembled into microsomal membranes, in vitro, and topologies were determined based on glycosylation site use and accessibility to exogenous protease. The accessibility of the C-terminal FLAG epitope in constructs was determined by immunofluorescence microscopy of permeabilized transfected cells. Both ACAT1 and ACAT2 span the membrane five times with their N termini in the cytosol and C termini in the ER lumen. The fourth transmembrane domain is located in a different region for each protein, placing the putative active site ACAT1 serine (Ser269) in the cytosol and the analogous residue in A...
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Bacterial contamination is an ongoing problem for commercial fuel ethanol production facilities. Both chronic and acute infections are of concern, due to the fact that bacteria compete with the ethanol-producing yeast for sugar substrates... more
Bacterial contamination is an ongoing problem for commercial fuel ethanol production facilities. Both chronic and acute infections are of concern, due to the fact that bacteria compete with the ethanol-producing yeast for sugar substrates and micronutrients. Lactic acid levels often rise during bouts of contamination, suggesting that the most common contaminants are lactic acid bacteria. However, quantitative surveys of commercial corn-based fuel ethanol facilities are lacking. For this study, samples were collected from one wet mill and two dry grind fuel ethanol facilities over a 9 month period at strategic time points and locations along the production lines, and bacterial contaminants were isolated and identified. Contamination in the wet mill facility consistently reached 10(6) bacteria/ml. Titers from dry grind facilities were more variable but often reached 10(8)/ml. Antibiotics were not used in the wet mill operation. One dry grind facility added antibiotic to the yeast propagation tank only, while the second facility dosed the fermentation with antibiotic every 4 h. Neither dosing procedure appeared to reliably reduce overall contamination, although the second facility showed less diversity among contaminants. Lactobacillus species were the most abundant isolates from all three plants, averaging 51, 38, and 77% of total isolates from the wet mill and the first and second dry grind facilities, respectively. Although populations varied over time, individual facilities tended to exhibit characteristic bacterial profiles, suggesting the occurrence of persistent endemic infections.
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Research Interests: Electrochemistry, Kinetics, Mass Spectrometry, Biological Chemistry, Biological Sciences, and 15 moreHumans, Nitric oxide, Animals, Nitrates, Spectrophotometry, CHEMICAL SCIENCES, Uric Acid, Rats, Photolysis, Imidazoles, Vasodilation, Oxidants, Isometric Contraction, Medical and Health Sciences, and In Vitro Techniques
Research Interests: Geology and Geochemistry
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ABSTRACT
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We reconstructed the complete 2.4 Mb-long genome of a previously uncultivated epsilonproteobacterium, Candidatus Sulfuricurvum sp. RIFRC-1, via assembly of short-read shotgun metagenomic data using a complexity reduction approach.... more
We reconstructed the complete 2.4 Mb-long genome of a previously uncultivated epsilonproteobacterium, Candidatus Sulfuricurvum sp. RIFRC-1, via assembly of short-read shotgun metagenomic data using a complexity reduction approach. Genome-based comparisons indicate the bacterium is a novel species within the Sulfuricurvum genus, which contains one cultivated representative, S. kujiense. Divergence between the species appears due in part to extensive genomic rearrangements, gene loss and chromosomal versus plasmid encoding of certain (respiratory) genes by RIFRC-1. Deoxyribonucleic acid for the genome was obtained from terrestrial aquifer sediment, in which RIFRC-1 comprised ∼ 47% of the bacterial community. Genomic evidence suggests RIFRC-1 is a chemolithoautotrophic diazotroph capable of deriving energy for growth by microaerobic or nitrate-/nitric oxide-dependent oxidation of S°, sulfide or sulfite or H₂oxidation. Carbon may be fixed via the reductive tricarboxylic acid cycle. Consistent with these physiological attributes, the local aquifer was microoxic with small concentrations of available nitrate, small but elevated concentrations of reduced sulfur and NH(4)(+) /NH₃-limited. Additionally, various mechanisms for heavy metal and metalloid tolerance and virulence point to a lifestyle well-adapted for metal(loid)-rich environments and a shared evolutionary past with pathogenic Epsilonproteobacteria. Results expand upon recent findings highlighting the potential importance of sulfur and hydrogen metabolism in the terrestrial subsurface.