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Amy M. Becker Kathryn H. Dao Bobby Kwanghoon Han Roger Kornu Shuchi Lakhanpal Angela B. Mobley Quan-Zhen Li Yun Lian Tianfu Wu Andreas M. Reimold Nancy J. Olsen David R. Karp Fatema Z. Chowdhury J. David Farrar Anne B. Satterthwaite Chandra Mohan Peter E. Lipsky Edward K. Wakeland Laurie S. Davis 《PloS one》2013,8(6)
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Simon M Dittami Hoai TN Aas Berit Smestad Paulsen Catherine Boyen Bente Edvardsen Thierry Tonon 《Plant signaling & behavior》2011,6(8):1237-1239
Mannitol plays a central role in brown algal physiology since it represents an important pathway used to store photoassimilate. Several specific enzymes are directly involved in the synthesis and recycling of mannitol, altogether forming the mannitol cycle. The recent analysis of algal genomes has allowed tracing back the origin of this cycle in brown seaweeds to a horizontal gene transfer from bacteria, and furthermore suggested a subsequent transfer to the green micro-alga Micromonas. Interestingly, genes of the mannitol cycle were not found in any of the currently sequenced diatoms, but were recently discovered in pelagophytes and dictyochophytes. In this study, we quantified the mannitol content in a number of ochrophytes (autotrophic stramenopiles) from different classes, as well as in Micromonas. Our results show that, in accordance with recent observations from EST libraries and genome analyses, this polyol is produced by most ochrophytes, as well as the green alga tested, although it was found at a wide range of concentrations. Thus, the mannitol cycle was probably acquired by a common ancestor of most ochrophytes, possibly after the separation from diatoms, and may play different physiological roles in different classes.Key words: algae, stramenopiles, mannitol cycle, primary metabolism, osmotic stress, evolutionBrown algae produce mannitol directly from the photoassimilate fructose-6-phosphate. Its metabolism occurs through the mannitol cycle, which involves four enzymatic reactions: (1) the reduction of fructose-6-phosphate (F6P) to mannitol-1-phosphate (M1P) via the activity of an M1P dehydrogenase (M1PDH); (2) the production of mannitol from M1P via an M1P phosphatase (M1Pase); (3) the oxidation of mannitol via the activity of a mannitol-2-dehydrogenase (M2DH) yielding fructose; and (4) the phosphorylation of fructose yielding F6P and involving a hexokinase (HK).1,2 The first completed draft of a brown algal genome enabled the identification of candidate genes for each of these steps.3 As these genes were not found in the genomes of the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum, mannitol metabolism in stramenopiles was considered a trait typical for brown algae. The corresponding genes were thought to have been acquired horizontally from bacteria and subsequently transferred to some green algae.4 Recently, however, homologs of several genes of the cycle were also found in the genome of the pelagophyte Aureococcus anophagefferens5 and an EST library produced for the dictyochophyte Pseudochattonella farcimen (Dittami et al. personal communication). These observations prompted us to examine the presence of mannitol in a range of strains covering different classes of autotrophic stramenopiles (ochrophytes). In addition, because of the identification of genes encoding enzymes for the production of mannitol through the mannitol cycle in the green alga Micromonas, one strain of this genus was also included in our analysis. 相似文献
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大港孔店油田油藏特征、流体和微生物性质分析结果表明, 属于高温生态环境, 地层水矿化度较低, 氮、磷浓度低, 而且缺乏电子受体, 主要的有机物来源是油气。油田采用经过除油处理的油藏产出水回注方式开发, 油层中存在的微生物类型主要是厌氧嗜热菌, 包括发酵菌(102个/mL~105个/mL), 产甲烷菌(103个/mL); 好氧菌主要存在于注水井周围。硫酸盐还原菌(SRB)还原速率0.002 mg S2-/(L·d) ~18.9 mg S2-/(L·d), 产甲烷菌产甲烷速率0.012 mgCH4/(L·d)~16.2 mgCH4/(L·d)。好氧菌能够氧化油形成生物质, 部分氧化产物为挥发性脂肪酸和表面活性剂。产甲烷菌在油氧化菌液体培养基中产生CH4, CO2为好氧微生物和厌氧微生物的共同代谢产物。这些产物具有提高原油流动性的作用。用示踪剂研究了注入水渗流方向。通过综合分析, 油藏微生物具有较大的潜力, 基于激活油层菌的提高采收率方法在该油田是可行的。 相似文献
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Naoki?Yagishita Tetsuji?Nakabonakabo@inet.museum.kyoto-u.ac.jp" title="TN nakabo@inet.museum.kyoto-u.ac.jp" itemprop="email" data-track="click" data-track-action="Email author" data-track-label="">Email author 《Ichthyological Research》2003,50(4):358-366
Although some Girella species are herbivorous, having basically tricuspid teeth, some are omnivorous. To determine the evolutionary trends in feeding habits of Girella, the phylogenetic relationships of several species of Girella were estimated by partially sequencing the mitochondrially encoded NADH dehydrogenase subunit 2 gene, and the dentition and adductor mandibulae complex of each species were examined. The cladogram determined from the mitochondrial DNA analysis indicated that multiple tooth-rows containing incisor-like teeth existed in adults of the ancestral species of Girella, species with a single tooth-row of tricuspid teeth in the adult stage having diverged subsequently on several occasions. The tendinous connections between each section of the adductor mandibulae complex are believed to have been simple in the ancestral species, more complicated connections also having diverged later on several occasions. Multiple tooth-rows containing incisor-like teeth and the simple adductor mandibulae complex are deduced as adaptations to herbivory; on the other hand, a single tooth-row of tricuspid teeth and the complicated adductor mandibulae complex are deduced as adaptations to omnivory. Therefore, the ancestral species of Girella is suggested as having been adapted to herbivory, with species adapted to omnivory having diverged on several subsequent occasions. 相似文献
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Summary of the aims Women with epilepsy using antiepileptic drug valproic acid (VPA) often suffer from reproductive endocrine disorders, menstrual
disorders and polycystic ovaries. Valproic acid exerts anticonvulsive effects via gamma amino butyric acid (GABA) neurotransmitter
system, which also acts as a neurochemical regulator of gonadotropin-releasing hormone (GnRH) neurons and suggests possibility
of valproic acid mediated interruption in gonadotropin releasing hormone pulse generator in hypothalamus. The aim of this
study was to investigate the effects of valproic acid treatment on the expression of gonadotropin releasing hormone, gamma
amino butyric acid and polysialylated form of neural cell adhesion molecule (PSA-NCAM) a marker of neuronal plasticity in
the median preoptic area (mPOA) and median eminence-arcuate (ME-ARC) region having GnRH neuron cell bodies and axon terminals,
respectively. Methods Three-month-old virgin Wistar strain female rats received VPA (i.p.) at a dose of 300 mg/kg once a day for 12 weeks; control group received an equivalent volume of vehicle. GnRH, GABA and PSA-NCAM
expressions were studied by immunohistofluorescence technique from mPOA and ME-ARC region of hypothalamus. Ovarian histology
was also studied using Mayer’s Haematoxylin-Eosin staining method. Results GnRH and PSA-NCAM staining was much higher in mPOA and ME-ARC region from vehicle treated control proestrous rats, whereas
VPA treatment significantly enhanced GABA expression, and reduced both GnRH and PSA-NCAM expression. Mayer’s Haematoxylin-Eosin
staining of mid-ovarian sections revealed significantly higher number of ovarian follicular cysts in VPA treated rats. Conclusions Our findings of alterations in GnRH and GABA expression and GnRH neuronal plasticity marker PSA-NCAM as well as changes in
ovarian histology suggest that treatment with VPA disrupts hypothalamo-hypophyseal-gonadal axis (HPG) at the level of GnRH
pulse generator in hypothalamus. 相似文献
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Background
There is a growing interest in Jatropha curcas L. (jatropha) as a biodiesel feedstock plant. Variations in its morphology and seed productivity have been well documented. However, there is the lack of systematic comparative evaluation of distinct collections under same climate and agronomic practices. With the several reports on low genetic diversity in jatropha collections, there is uncertainty on genetic contribution to jatropha morphology. 相似文献20.
Cloning, expression, purification, and characterization of the acid alpha-mannosidase from Trypanosoma cruzi 总被引:1,自引:0,他引:1
Vandersall-Nairn AS; Merkle RK; O'Brien K; Oeltmann TN; Moremen KW 《Glycobiology》1998,8(12):1183-1194
The acid alpha-mannosidase of Trypanosoma cruzi is a broad-specificity
hydrolase involved in the catabolism of glycoconjugates, presumably in the
digestive vacuole. We have cloned the alpha-mannosidase gene from a T.cruzi
epimastigote genomic library. The alpha-mannosidase gene was determined to
be single copy by Southern analysis, and similar sequences were not
detected in genomic digests of either Trypanosoma brucei or Leishmania
donovani. The coding region was subcloned into the Pichia pastoris
expression vector pPICZ, and alpha-mannosidase activity was detected in the
medium of induced cultures. The recombinant alpha- mannosidase demonstrated
a pH optimum, inhibition by swainsonine, Km, and substrate specificity
consistent with the characteristics of the alpha-mannosidase previously
purified from T.cruzi epimastigotes. The recombinant enzyme was purified
103-fold from the culture medium of Pichia pastoris and had a native
molecular mass of 359 kDa by gel filtration. A combination of SDS-PAGE,
deglycosylation with endo H, and NH2-terminal sequencing indicates that the
enzyme is originally synthesized as a homodimeric polypeptide that is
subsequently cleaved to form a heterotetramer composed of 57 and 46 kDa
subunits. A polyclonal antibody raised to the recombinant enzyme was shown
to immunoprecipitate the alpha-mannosidase from T.cruzi cell extracts and
will be used in future immunolocalization studies.
相似文献