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排序方式: 共有162条查询结果,搜索用时 15 毫秒
1.
Changes in northern Gulf of Mexico sediment bacterial and archaeal communities exposed to hypoxia 下载免费PDF全文
R. Devereux J. J. Mosher T. A. Vishnivetskaya S. D. Brown D. L. Beddick Jr. D. F. Yates A. V. Palumbo 《Geobiology》2015,13(5):478-493
Biogeochemical changes in marine sediments during coastal water hypoxia are well described, but less is known about underlying changes in microbial communities. Bacterial and archaeal communities in Louisiana continental shelf (LCS) hypoxic zone sediments were characterized by pyrosequencing 16S rRNA V4‐region gene fragments obtained by PCR amplification of community genomic DNA with bacterial‐ or archaeal‐specific primers. Duplicate LCS sediment cores collected during hypoxia had higher concentrations of Fe(II), and dissolved inorganic carbon, phosphate, and ammonium than cores collected when overlying water oxygen concentrations were normal. Pyrosequencing yielded 158 686 bacterial and 225 591 archaeal sequences from 20 sediment samples, representing five 2‐cm depth intervals in the duplicate cores. Bacterial communities grouped by sampling date and sediment depth in a neighbor‐joining analysis using Chao–Jaccard shared species values. Redundancy analysis indicated that variance in bacterial communities was mainly associated with differences in sediment chemistry between oxic and hypoxic water column conditions. Gammaproteobacteria (26.5%) were most prominent among bacterial sequences, followed by Firmicutes (9.6%), and Alphaproteobacteria (5.6%). Crenarchaeotal, thaumarchaeotal, and euryarchaeotal lineages accounted for 57%, 27%, and 16% of archaeal sequences, respectively. In Thaumarchaeota Marine Group I, sequences were 96–99% identical to the Nitrosopumilus maritimus SCM1 sequence, were highest in surficial sediments, and accounted for 31% of archaeal sequences when waters were normoxic vs. 13% of archaeal sequences when waters were hypoxic. Redundancy analysis showed Nitrosopumilus‐related sequence abundance was correlated with high solid‐phase Fe(III) concentrations, whereas most of the remaining archaeal clusters were not. In contrast, crenarchaeotal sequences were from phylogenetically diverse lineages, differed little in relative abundance between sampling times, and increased to high relative abundance with sediment depth. These results provide further evidence that marine sediment microbial community composition can be structured according to sediment chemistry and suggest the expansion of hypoxia in coastal waters may alter sediment microbial communities involved in carbon and nitrogen cycling. 相似文献
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Combination of 16S rRNA-targeted oligonucleotide probes with flow cytometry for analyzing mixed microbial populations. 总被引:100,自引:49,他引:51 下载免费PDF全文
R I Amann B J Binder R J Olson S W Chisholm R Devereux D A Stahl 《Applied microbiology》1990,56(6):1919-1925
Fluorescent oligonucleotide hybridization probes were used to label bacterial cells for analysis by flow cytometry. The probes, complementary to short sequence elements within the 16S rRNA common to phylogenetically coherent assemblages of microorganisms, were labeled with tetramethylrhodamine and hybridized to suspensions of fixed cells. Flow cytometry was used to resolve individual target and nontarget bacteria (1 to 5 microns) via probe-conferred fluorescence. Target cells were quantified in an excess of nontarget cells. The intensity of fluorescence was increased additively by the combined use of two or three fluorescent probes complementary to different regions of the same 16S rRNA. 相似文献
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PEPPLOT, a protein secondary structure analysis program for the UWGCG sequence analysis software package. 总被引:12,自引:4,他引:8 下载免费PDF全文
We describe a program for the analysis of protein secondary structure that operates with the Sequence Analysis Software Package of the University of Wisconsin Genetics Computer Group (UWGCG). The program produces both graphic and printed output. Structure prediction using the Chou and Fasman and Robson et al methods, and hydropathy analysis by the method of Kyte and Doolittle are included along with a simplified method of hydrophobic moment analysis. The power of the program is the coordinated presentation of many different kinds of structural information on the same plot. 相似文献
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Lisa L. Kohring David B. Ringelberg Richard Devereux David A. Stahl Marc W. Mittelman David C. White 《FEMS microbiology letters》1994,119(3):303-308
Abstract Twenty-five isolates of dissimilatory sulfate-reducing bacteria were clustered based on similarity analysis of their phospholipid ester-linked fatty acids (PLFA). Of these, 22 showed that phylogenetic relationships based on the sequence similarity of their 16S rRNA directly paralleled the PLFA relationships. Desulfobacter latus and Desulfobacter curvatus grouped with the other Desulfobacter spp. by 16S rRNA comparison but not with the PLFA analysis as they contained significantly more monoenoic PLFA than the others. Similarly, Desulfovibrio africanus clustered with the Desulfovibrio spp. by 16S rRNA but not with them when analyzed by PLFA patterns because of higher monoenoic PLFA content. Otherwise, clustering obtained with either analysis was essentially congruent. The relationships defined by PLFA patterns appeared robust to shifts in nutrients and terminal electron acceptors. Additional analyses utilizing the lipopolysaccharide-lipid A hydroxy fatty acid patterns appeared not to shift the relationships based on PLFA significantly except when completely absent, as in Gram-positive bacteria. Phylogenetic relationships between isolates defined by 16S rRNA sequence divergence represent a selection clearly different from the multi-enzyme activities responsible for the PLFA patterns. Determination of bacterial relationships based on different selective pressures for various cellular components provides more clues to evolutionary history leading to a more rational nomenclature. 相似文献
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S Devereux T G Selassie G Vaughan Hudson B Vaughan Hudson D C Linch 《BMJ (Clinical research ed.)》1990,301(6760):1077-1080
OBJECTIVE--To determine the incidence of and risk factors for the development of secondary acute leukaemia and myelodysplasia in patients treated in British National Lymphoma Investigation''s studies of Hodgkin''s disease since 1970. PATIENTS--2676 Patients entered into Hodgkin''s disease studies between February 1970 and November 1986. Data accrued up to November 1988 were analysed, ensuring a minimum follow up period of two years. DESIGN--Retrospective analysis of multicentre trial data by case-control and life table methods. RESULTS--17 Cases of secondary leukaemia were recorded in this group of 2676 patients, giving an overall risk at 15 years of 1.7%. The risks of leukaemia after chemotherapy alone and chemotherapy with radiotherapy were not significantly different. The risk of leukaemia increased sharply with the amount of treatment given as measured by the number of attempts at treatment. The 15 year risks of leukaemia were 0.2%, 2.3%, and 8.1% for patients receiving one, two, or three or more attempts at treatment. The highest risk, 22.8% at 15 years, was observed in patients treated with lomustine (CCNU), and a case-control study suggested that this was an independent risk factor. The risk of secondary leukaemia was largely related to the overall quantity of treatment, although exposure to lomustine seemed to be an important risk factor. Treatment with both drugs and radiation was not more leukaemogenic than treatment with drugs alone. The greatest risk of secondary leukaemia was seen in multiply treated patients who were unlikely to be cured of Hodgkin''s disease. CONCLUSIONS--Avoidance of secondary leukaemia should be a minor factor in the choice of treatment for Hodgkin''s disease. 相似文献
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The anabolic action of intermittent parathyroid hormone on cortical bone depends partly on its ability to induce nitric oxide‐mediated vasorelaxation in BALB/c mice 下载免费PDF全文
S Gohin A Carriero C Chenu AA Pitsillides TR Arnett M Marenzana 《Cell biochemistry and function》2016,34(2):52-62
There is strong evidence that vasodilatory nitric oxide (NO) donors have anabolic effects on bone in humans. Parathyroid hormone (PTH), the only osteoanabolic drug currently approved, is also a vasodilator. We investigated whether the NO synthase inhibitor L‐NAME might alter the effect of PTH on bone by blocking its vasodilatory effect. BALB/c mice received 28 daily injections of PTH[1–34] (80 µg/kg/day) or L‐NAME (30 mg/kg/day), alone or in combination. Hindlimb blood perfusion was measured by laser Doppler imaging. Bone architecture, turnover and mechanical properties in the femur were analysed respectively by micro‐CT, histomorphometry and three‐point bending. PTH increased hindlimb blood flow by >30% within 10 min of injection (P < 0.001). Co‐treatment with L‐NAME blocked the action of PTH on blood flow, whereas L‐NAME alone had no effect. PTH treatment increased femoral cortical bone volume and formation rate by 20% and 110%, respectively (P < 0.001). PTH had no effect on trabecular bone volume in the femoral metaphysis although trabecular thickness and number were increased and decreased by 25%, respectively. Co‐treatment with L‐NAME restricted the PTH‐stimulated increase in cortical bone formation but had no clear‐cut effects in trabecular bone. Co‐treatment with L‐NAME did not affect the mechanical strength in femurs induced by iPTH. These results suggest that NO‐mediated vasorelaxation plays partly a role in the anabolic action of PTH on cortical bone. © 2016 The Authors. Cell Biochemistry and Function published by John Wiley & Sons, Ltd. 相似文献