Dissolution of Fluorapatite by Pseudomonas fluorescens P35 Resulting in Fluorine Release

Chemical weathering of fluorine-bearing minerals is widely accepted as the main mechanism for the release of fluorine (F) to groundwater. Here, we propose a potential mechanism of F release via microbial dissolution of fluorapatite (Ca₅(PO₄)₃F), which has been neglected previously. Batch culture experiments were conducted at 30°C with a phosphate-solubilizing bacteria strain, Pseudomonas fluorescens P35, and rock phosphates as the sole source of phosphate for microbial growth in parallel with abiotic controls. Rock phosphates consisted of 55–91% of fluorapatite and 5–10% of dolomite before microbial dissolution as indicated by X-ray diffraction (XRD). Mineral composition and morphology changed after microbial dissolution characterized by the disappearance of dolomite and the development of etched cavities on rock phosphate surfaces. The pH of media used was approximately 7.4 at the beginning and increased gradually to 7.7 in abiotic controls; with the inoculum, the pH decreased to acidic values of 3.7–3.8 after 27 h. Phosphate, calcium, and fluoride were released from the rock phosphate to the acidified medium. At 42 h, the concentration of F reached 8.1–10.3 mg L^?1. The elevated F concentration was two times higher than the F levels in groundwater in regions diagnosed with fluorosis, and was toxic to the bacteria, as demonstrated by a precipitous decrease in live cells. Geochemical modeling demonstrated that the oxidation of glucose (the carbon source for microbial growth in the medium) to gluconic acid could decrease the pH to 3.7–3.8 and result in the dissolution of fluorapatite and dolomite. Dolomite and fluorapatite remained unsaturated, while concentrations of dissolved phosphorus (P), calcium (Ca), and F increased throughout the time course Fluorite reached saturation [saturation index (SI) 0.22–0.42] after 42 h in rock phosphate–amended biotic systems. However, fluorite was not detected in XRD patterns of the final residue from microcosms. Given that phosphate-solubilizing bacteria are ubiquitous in soil and groundwater ecosystems, they could play an important role in fluorapatite dissolution and the release of F to groundwater.     

Reliable computational design of biological-inorganic materials to the large nanometer scale using Interface-FF

Abstract

The function of nanomaterials and biomaterials greatly depends on understanding nanoscale recognition mechanisms, crystal growth and surface reactions. The Interface Force Field (IFF) and surface model database are the first collection of transferable parameters for inorganic and organic compounds that can be universally applied to all materials. IFF uses common energy expressions and achieves best accuracy among classical force fields due to rigorous validation of structural and energetic properties of all compounds in comparison to perpetually valid experimental data. This paper summarises key aspects of parameterisation, including atomic charges and transferability of parameters and current coverage. Examples of biomolecular recognition at metal and mineral interfaces, surface reactions of alloys, as well as new models for graphitic materials and pi-conjugated molecules are described. For several metal–organic interfaces, a match in accuracy of computed binding energies between of IFF and DFT results is demonstrated at ten million times lower computational cost. Predictive simulations of biomolecular recognition of peptides on phosphate and silicate surfaces are described as a function of pH. The use of IFF for reactive molecular dynamics is illustrated for the oxidation of Mo₃Si alloys at high temperature, showing the development of specific porous silica protective layers. The introduction of virtual pi electrons in graphite and pi-conjugated molecules enables improvements in property predictions by orders of magnitude. The inclusion of such molecule-internal polarity in IFF can reproduce cation–pi interactions, pi-stacking in graphite, DNA bases, organic semiconductors and the dynamics of aqueous and biological interfaces for the first time.     

HNPCC家系血清中游离氨基酸及矿物质测定

目的 :探讨HNPCC家族血清游离的氨基酸与矿物质的变化 ,为HNPCC家族的监测提供论据 ;方法 :用HPLC及原子吸收分光光度法检测正常人与HNPCC家族成员血清中游离氨基酸及Cu、Ca、Fe、Zn的含量 ;结果 :HNPCC组血清中Glu、Cys、Val高于正常对照组 ;而His、Pro、Leu、Phe低于正常对照组 ,血清Fe比正常人高 ,血清Ca低于正常人。结论 :血清中的部分游离氨基酸及Fe、Ca可作为HNPCC家族监测的间接指标。     

Mineral Resource Availability and Consumption by Colobus in Kibale National Park,Uganda

Very little information exists on mineral nutrition of tropical, forest-dwelling species, yet minerals are critical to growth, reproduction, and survival. We examined the mineral resources available to and consumed by colobus in Kibale National Park, Uganda. We combined behavioral data on black-and-white (Colobus guereza) and red colobus (Piliocolobus tephrosceles) in a section of unlogged forest, a heavily logged area, and a forest fragment with mineral analysis of their foods to estimate the proportion of the diet containing specific minerals (mineral content). We compared mineral content of colobus foods (natural and crops) across plant parts and among plant species. Additionally, we estimated mineral intake of frugivorous primates in Kibale from published dietary data and our estimates of mineral content of foods. Dietary mineral content for all colobus groups and frugivorous species is similar despite significant differences in the mineral content of foods. Ripe and unripe fruits are lower in mineral content than most foods. Foods rarely consumed, such as bark, petioles, and caterpillars have high levels of some minerals. The mineral content of crops is low in comparison to that ofnatural foods. For all colobus groups of both species, sodium content of foods was extremely low and iron content was generally low, suggesting that intake isbelow suggested requirements, though current suggested iron requirements may overestimate physiological needs. Copper content was marginal and deficient seasonally for most colobus groups. Despite a sodium-limiting environment, only one of 8 colobus groups appeared to select sodium; however, this may be due to a lack of variation in sodium content among plant species and a positive correlation between high plant sodium content and secondary compounds. Despite the lack of selection for sodium by colobines, some behaviors point to a potential sodium deficiency, including urine drinking, consumption of high-sodium swamp plants, and use of mud-puddles.     

Cations as Mediators of the Adsorption of Nucleic Acids on Clay Surfaces in Prebiotic Environments

Monovalent ([Na⁺] > 10 mM) and divalent ([Ca²⁺], [Mg²⁺] > 1.0 mM) cations induced the precipitationof nucleic acid molecules. In the presence of clay minerals (montmorillonite and kaolinite), there was adsorption instead of precipitation. The cation concentration needed for adsorption depended on both the valence of the cations and the chemical nature of the nucleic acid molecules. Double-stranded nucleic acids needed higher cation concentrations than single-stranded ones to be adsorbed to the same extent on clay. Divalent cations were more efficient than monovalent ones in mediating adsorption. Adsorption to the clay occurred only when both nucleic acids and cations were present. However, once the complexes were formed, the cations could not be removed from the system by washing, indicating that they are directly involved in the association between nucleic acids and mineral surfaces.These observations indicate that cations take part directly in the formation of nucleic acid-clay complexes, acting as a `bridge' between the negative charges on the mineral surface and those of the phosphate groups of the genetic polymer. The relatively low cation concentrations needed for adsorption and the ubiquitous presence of clay minerals in the environment suggest that the adsorption of nucleic acids on mineral surfaces could have taken place in prebiotic habitats. This may have played an important role in the formation and preservation of nucleic acids and/or their precursor polymers.     

地球熔岩管道微生物研究对天体生物学的启示

天体生物学作为与深空探测相结合的交叉学科,旨在从地球极端环境类比、古代生命载体信息发掘和模拟等方面揭示地外行星体是否适合生命生存和繁衍,其中适宜的环境条件是评价所有天体是否宜居的重要条件。近年来在月球和火星等行星表面发现了大量由火山熔岩流形成的熔岩管道,这些巨型管状地下空间具有稳定的温度和防辐射等环境条件,为生物在地外星体上的生存提供了潜在的庇护场所。基于地球熔岩管道的天体生物学的类比研究可以为探索地外生命痕迹提供重要线索,本文综述了现阶段地球熔岩管道内微生物的研究进展、微生物痕量气体代谢在天体生物学研究中的潜力及天体生物学的研究进展,旨在为后续开展地球及地外熔岩管道的天体生物学研究提供思路。     

微生物介导硝酸盐还原耦合亚铁氧化过程的动力学及其影响因素

【目的】探究不同菌浓度和亚铁浓度条件下,Acidovorax sp. strain BoFeN1介导的厌氧亚铁氧化耦合硝酸盐还原过程的动力学和次生矿物。【方法】构建包含菌BoFeN1、硝酸盐、亚铁的厌氧培养体系,测试硝酸根、亚硝酸根、乙酸根、亚铁等浓度,并收集次生矿物,采用XRD、SEM进行矿物种类和形貌表征。【结果】在微生物介导硝酸盐还原耦合亚铁氧化的体系中,高菌浓度促进硝酸盐还原,对亚铁氧化也有一定促进作用;高浓度亚铁在低菌浓度下氧化反应速率和程度降低,但是在高菌浓度下无明显影响;亚铁浓度越高次生矿物结晶度越高,但对硝酸盐还原具有一定抑制作用。在微生物介导亚硝酸盐还原耦合亚铁氧化的体系中,高的菌浓度和亚铁浓度都会促进亚硝酸盐还原,但亚铁氧化的次生矿物会对亚硝酸盐的微生物还原产生较强的抑制作用,次生矿物的种类和结晶度主要受亚铁浓度影响。【结论】硝酸盐还原主要是生物反硝化作用,亚硝酸盐还原包含生物反硝化和化学反硝化两部分,在硝酸盐体系中亚铁氧化与次生矿物生成是受生物和化学反硝化作用的共同影响,但亚硝酸盐体系中亚铁氧化与次生矿物生成主要是受化学反硝化作用影响。该研究可为深入理解厌氧微生物介导铁氮耦合反应机制提供基础数据和理论支撑。     

嗜酸氧化亚铁硫杆菌的高效培养及浸出黄铜矿初探

采用向硫化矿培养基中补加FeSO4的方式以维持Fe2+ 浓度为4～8 g/L,可使嗜酸氧化亚铁硫杆菌菌浓在培养39 h时达到6.25×108 cells/mL,并在比生长速率几乎不降低的前提下提高了转化率和生产强度.然后对低氧化还原电位下低品位黄铜矿的浸出进行初步研究,结果表明经过30 d浸出,铜的浸出率可达28.5%...     

Health benefits and nutritional properties of nori

A brief review is presented of the properties of nori relevant to health. The dried alga contains large amounts of protein, ash, vitamins and carbohydrate. The levels of taurine (/>- 1.2%) are notable as this compound aids enterohepatic circulation of bile acid, thus preventing gallstone through controlling blood-cholesterol levels. Relatively high levels of eicosapentanoic acid, choline, inositol and other B-group vitamins are regarded as beneficial to health. The occurrence of porphyosins and betaines that prevent respectively, gastric shay ulcers and lower blood-cholesterol levels are particular interest. A sulfated galactan, similar to agar, occurs in relatively large quantities; this is a water-soluble dietary fiber that has important functional activities such as an antiblood coagulant, antihypercholesterolemia and shows antitumor activity. Minerals which occur at relatively high levels in nori include Zn, Cu, Mn and Se.It is concluded that nori is a valuable health food in human diets.     

矿物作用下A.ferrooxidans中磁小体相关基因的差异表达

目的:研究氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans,A.f)中与磁小体形成相关的mpsA、magA、thy和mamB基因分别在黄铁矿、黄铜矿、磁黄铁矿和闪锌矿的作用下的表达差异,寻找有利于磁小体形成的最佳培养矿物能源。方法:测量以不同硫化矿为能源时的菌体生长特性,用实时定量PCR方法研究与磁小体形成相关基因的表达差异。结果:在以磁黄铁矿为能源时,菌的生长量及多数基因的表达量优于其它三种矿,四个基因相对表达量分别为1.15、2.35、1.32、2.68。结论:磁黄铁矿是A.f中磁小体形成的最佳矿物能源。