The uptake and excretion of partially oxidized sulfur expands the repertoire of energy resources metabolized by hydrothermal vent symbioses

Symbiotic associations between animals and chemoautotrophic bacteria crowd around hydrothermal vents. In these associations, symbiotic bacteria use chemical reductants from venting fluid for the energy to support autotrophy, providing primary nutrition for the host. At vents along the Eastern Lau Spreading Center, the partially oxidized sulfur compounds (POSCs) thiosulfate and polysulfide have been detected in and around animal communities but away from venting fluid. The use of POSCs for autotrophy, as an alternative to the chemical substrates in venting fluid, could mitigate competition in these communities. To determine whether ESLC symbioses could use thiosulfate to support carbon fixation or produce POSCs during sulfide oxidation, we used high-pressure, flow-through incubations to assess the productivity of three symbiotic mollusc genera—the snails Alviniconcha spp. and Ifremeria nautilei, and the mussel Bathymodiolus brevior—when oxidizing sulfide and thiosulfate. Via the incorporation of isotopically labelled inorganic carbon, we found that the symbionts of all three genera supported autotrophy while oxidizing both sulfide and thiosulfate, though at different rates. Additionally, by concurrently measuring their effect on sulfur compounds in the aquaria with voltammetric microelectrodes, we showed that these symbioses excreted POSCs under highly sulfidic conditions, illustrating that these symbioses could represent a source for POSCs in their habitat. Furthermore, we revealed spatial disparity in the rates of carbon fixation among the animals in our incubations, which might have implications for the variability of productivity in situ. Together, these results re-shape our thinking about sulfur cycling and productivity by vent symbioses, demonstrating that thiosulfate may be an ecologically important energy source for vent symbioses and that they also likely impact the local geochemical regime through the excretion of POSCs.     

5-Oxo-prolinase activity in tobacco suspension cultures: Regulation by sulfate nutrition

In heterotrophic and photoheterotrophic tobacco ( Nicotiana tabacum L., var. Samsun) suspensions cultured with growth-limiting amounts of sulfate, 5-oxo-prolinase activity declines at the same time as the growth rate of the cells decreases. However, 5-oxo-prolinase activity is reduced to a greater extent than growth. As a result, the specific activity of 5-oxo-prolinase also declines when sulfur is scarce. The decrease in both growth and 5-oxo-prolinase activity can be prevented by adding sulfate to the suspensions during exponential growth. Addition of sulfate after the exponential growth phase restored neither growth nor 5-oxo-prolinase activity. These observations show that 5-oxo-prolinase activity in tobacco cells is regulated by the sulfate supply in the medium. Such a regulation is an essential prerequisite, but not a proof, for a role of 5-oxo-prolinase as the rate-limiting factor in glutathione degradation.
During exponential growth the average specific activity of 5-oxo-prolinase in heterotrophic tobacco cells is twice as high as in photoheterotrophic cells. This difference is consistent with the idea that green cells are equipped for glutathione synthesis and export, and chloroplast-free cells for uptake and degradation of this peptide.     

微生物硫循环网络的研究进展

硫元素是所有生物的基本组成成分,是生物体必需的营养元素之一.硫氧化还原微生物的数量多、分布广、代谢途径多样化,硫化合物之间的平衡依赖于微生物代谢网络中的各种硫转化反应与代谢过程.此外,硫循环与碳、氮循环紧密相关,对地球生态循环起到了至关重要的作用.本文综述了近期微生物硫循环网络的研究进展,包括所涉及的主要微生物、硫循环...     

The "rhodanese" fold and catalytic mechanism of 3-mercaptopyruvate sulfurtransferases: crystal structure of SseA from Escherichia coli

3-Mercaptopyruvate sulfurtransferases (MSTs) catalyze, in vitro, the transfer of a sulfur atom from substrate to cyanide, yielding pyruvate and thiocyanate as products. They display clear structural homology with the protein fold observed in the rhodanese sulfurtransferase family, composed of two structurally related domains. The role of MSTs in vivo, as well as their detailed molecular mechanisms of action have been little investigated. Here, we report the crystal structure of SseA, a MST from Escherichia coli, which is the first MST three-dimensional structure disclosed to date. SseA displays specific structural differences relative to eukaryotic and prokaryotic rhodaneses. In particular, conformational variation of the rhodanese active site loop, hosting the family invariant catalytic Cys residue, may support a new sulfur transfer mechanism involving Cys237 as the nucleophilic species and His66, Arg102 and Asp262 as residues assisting catalysis.     

Pool sizes of fructans in roots and leaves of mycorrhizal and non-mycorrhizal barley

The effect of arbuscular mycorrhizas on fructan accumulation was studied in barley ( Hordeum vulgare ) infected with Glomus mosseae . Treatments with and without fertilizer were included in order to distinguish between mere fertilizer effects and the effects of the symbiosis, and plants were harvested at two different time points, 35 and 50 d after planting. Fructan was the major storage carboyhdrate in both leaves and roots. The amounts of fructan were markedly altered in the mycorrhizal plants. In roots of non-fertilized mycorrhizal plants, fructan pools were significantly greater than in the corresponding non-mycorrhizal plants. By contrast, fertilization caused a general decrease in amounts of fructan in roots. The increase of fructan in mycorrhizal roots was correlated with a decrease of invertase activity. In leaves, fructan pools decreased or remained unchanged upon mycorrhizal infection; fertilization had a similar effect. However, when individual leaves of a plant were compared, intriguing effects of the mycorrhizal symbiosis could be observed. Whereas in non-mycorrhizal plants, the youngest leaves had the highest fructan contents and the oldest leaves the lowest (as previously reported), this gradient was markedly altered in mycorrhizal plants, indicating systemic effects of mycorrhiza on assimilate partitioning in shoots.     

激素型肾阳虚动物肝线粒体蛋白质组与能量代谢相关性

应用凝胶内差异显示电泳技术研究肾阳虚大鼠肝线粒体蛋白质组,并从肝线粒体蛋白质组角度阐述肾阳虚与能量代谢的关系.8个分别来自于肾阳虚大鼠和正常大鼠的肝线粒体蛋白质样品(各4个)分别用荧光染料Cy3、Cy5标记,以及8个样品等量混合物用Cy2标记作为内标,每一Cy3、Cy5标记样品与Cy2标记的内标等量混合后在同一胶中进行电泳分离,经不同光激发后扫描得到不同样品的蛋白质组图谱.经DeCyder软件结合内标分析,以肾阳虚组动物与正常组动物肝线粒体蛋白质相差1.2倍以上的蛋白作为差异蛋白,实验共获得16个差异蛋白质,经质谱测定和与蛋白质文库比对,鉴定11个蛋白质.其中,肾阳虚动物热休克蛋白60和70、肌氨酸脱氢酶、氨甲酰磷酸合成酶、亚硫酸盐氧化酶、ATP合酶、醛脱氢酶和NADH脱氢酶表达量增加,而丙酮酸脱氢酶、α酮戊二酸脱氢酶、脂酰辅酶A脱氢酶和鸟氨酸氨基转移酶表达量降低.实验表明,肾阳虚动物能量代谢相关酶的变化与肾阳虚的临床虚寒症状有关.     

Metabolic integration during the evolutionary origin of mitochondria

Although mitochondria provide eukaryotic cells with certain metabolic advantages, in other ways they may be disadvantageous. For example, mitochondria produce reactive oxygen species that damage both nucleocytoplasm and mitochondria, resulting in mutations, diseases, and aging. The relationship of mito-chondria to the cytoplasm is best understood in the context of evolutionary history. Although it is clearthat mitochondria evolved from symbiotic bacteria, the exact nature of the initial symbiosis is a matter of continuing debate. The exchange of nutrients between host and symbiont may have differed from that be-tween the cytoplasm and mitochondria in modern cells. Speculations about the initial relationships includethe following. (1) The pre-mitochondrion may have been an invasive, parasitic bacterium. The host did notbenefit. (2) The relationship was a nutritional syntrophy based upon transfer of organic acids from host tosymbiont. (3) The relationship was a syntrophy based upon H2 transfer from symbiont to host, where thehost was a methanogen. (4) There was a syntrophy based upon reciprocal exchange of sulfur compounds.The last conjecture receives support from our detection in eukaryotic cells of substantial H2S-oxidizing activity in mitochondria, and sulfur-reducing activity in the cytoplasm.     

Raman microspectrometry sulfur detection and characterization in the marine ectosymbiotic nematode Eubostrichus dianae (Desmodoridae, Stilbonematidae)

Background information. Marine nematodes belonging to the Stilbonematidae (Desmodoridae) family are described as living in obligatory association with sulfur‐oxidizing chemoautotrophic ectosymbionts. The symbiotic bacteria carrying out this chemosynthesis should contain elemental sulfur in periplasmic granules as sulfur granules of chemoautotrophic endosymbionts described in various marine invertebrates. Results. Based on TEM (transmission electron microscopy) analyses, extracellular bacteria surrounding Eubostrichus dianae possess these spherical periplasmic granules. Few investigative techniques can be used to identify elemental sulfur, S₈, such as EDXS (energy dispersive X‐ray spectroscopy) and EELS (electron energy loss spectroscopy), which are associated with cryo‐fixation of the sample to avoid sulfur loss. These techniques are time consuming, expensive and require technical skills. Raman microspectrometry applied to the analysis of E. dianae allowed us to detect elemental sulfur, S₈, and confirmed the location of these sulfur clusters in the bacterial coat. In the same way, Raman spectrometry was positively applied to the endosymbiotic bivalve Codakia orbicularis, suggesting that this technique can be used to characterize sulfur in ecto‐ as well as in endo‐symbiotic sulfur‐oxidizing bacteria. Conclusions. As Raman spectrometry can be used on living organisms (without preliminary fixation) without sample damage and preserving the molecular structure of the sulfur (denatured during chemical fixation), it represents a very well‐adapted investigative tool for biologists. This technique therefore permits us to detect quickly and easily (in a few seconds and on entire living animals) the presence of sulfur compounds in the symbiotic nematode.     

CRISPR-Mediated Induction of Neuron-Enriched Mitochondrial Proteins Boosts Direct Glia-to-Neuron Conversion

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Globins Scavenge Sulfur Trioxide Anion Radical

Ferrous myoglobin was oxidized by sulfur trioxide anion radical (STAR) during the free radical chain oxidation of sulfite. Oxidation was inhibited by the STAR scavenger GSH and by the heme ligand CO. Bimolecular rate constants for the reaction of STAR with several ferrous globins and biomolecules were determined by kinetic competition. Reaction rate constants for myoglobin, hemoglobin, neuroglobin, and flavohemoglobin are large at 38, 120, 2,600, and ≥ 7,500 × 10⁶ m⁻¹ s⁻¹, respectively, and correlate with redox potentials. Measured rate constants for O₂, GSH, ascorbate, and NAD(P)H are also large at ∼100, 10, 130, and 30 × 10⁶ m⁻¹ s⁻¹, respectively, but nevertheless allow for favorable competition by globins and a capacity for STAR scavenging in vivo. Saccharomyces cerevisiae lacking sulfite oxidase and deleted of flavohemoglobin showed an O₂-dependent growth impairment with nonfermentable substrates that was exacerbated by sulfide, a precursor to mitochondrial sulfite formation. Higher O₂ exposures inactivated the superoxide-sensitive mitochondrial aconitase in cells, and hypoxia elicited both aconitase and NADP⁺-isocitrate dehydrogenase activity losses. Roles for STAR-derived peroxysulfate radical, superoxide radical, and sulfo-NAD(P) in the mechanism of STAR toxicity and flavohemoglobin protection in yeast are suggested.     

基于GIS的产业生态学研究述评

产业生态学由于缺少关于空间分析的工具,使得研究结果因缺乏空间维度信息而影响对管理效率和精准度的支持。基于GIS的产业生态学相关研究已成为产业生态学研究的一个新的方向。为总结已有的研究成果并展望未来的研究方向,运用文献计量及对比分析的手段,系统分析了国内外基于GIS的产业生态学的相关研究进展,得出以下结论:当前基于GIS的产业生态研究主要集中在物质代谢、产业共生和生命周期评价3个方面,将GIS技术引入到物质代谢研究中,可以更好的展示物质代谢的时空分布格局,为物质代谢研究提供了一种新的方法;基于GIS技术,不仅可以更加高效地挖掘潜在的产业共生机会,还可应用于生态产业园的规划管理如企业的选址、空间布局等以及废弃物的回收再利用方面;将GIS与LCA耦合在一起,可以很好地补充、完善和管理传统数据,有助于探索产品、活动或工艺的环境影响的空间特性以及进行土地利用相关的环境影响评价。另外,国内外研究的侧重点也不尽相同。在物质代谢研究中,国内研究较少,仅在城市尺度上进行了基础设施的物质代谢及其存量分析,国外在国家、城市尺度上研究了铜、锌等金属的物质代谢情况;在产业共生研究中,国内侧重于生态产业园的研究,而国外侧重于城市尺度的产业共生机会识别的研究;在LCA的研究中,国内开展了基于GIS的生命周期评价数据库和产品材料信息管理系统的研究,而国外侧重于进行区域化的生命周期评价、进行土地利用影响类型的相关评价以及污染物的追踪,国内在该方面尚处于起步阶段。国内外在研究方法上存在共性,都是基于GIS的空间分析方法、缓冲区分析方法以及数据库技术等。未来将GIS作为一个平台,面向产业转型展开产业生态学综合理论方法的研究,可以为产业的可持续性管理提供有效支持。     

Evidence for thiosulfate sulfur transferase (rhodanese) trithionate reductase and tetrathionate reductase activities in Neisseria gonorrhoeae

Abstract Neisseria gonorrhoeae is unable to grow with sulfate but can use thiosulfate as sole source of sulfur.
Thiosulfate sulfur transferase (TST) (rhodanese) activity was present in the cytoplasmic soluble fraction. In the same extract, thiosulfate reductase (TSR), trithionate reductase and tetrathionate reductase activities were also detected using hydrogen as electron donor in the presence of viologen dyes and hydrogenase from Desulfovibrio gigas .
The significance of and the possible relationship between these different activities are discussed.