The RcnRA (YohLM) system of <Emphasis Type="Italic">Escherichia coli</Emphasis>: A connection between nickel,cobalt and iron homeostasis

The transporter RcnA has previously been implicated in Ni(II) and Co(II) detoxification in E. coli probably through efflux. Here we demonstrate that the divergently described rcnA and rcnR gene products constitute a link between nickel, cobalt and iron homeostasis. Deletion of the rcnA gene resulted in increased cellular nickel, cobalt and iron concentrations. Expression of rcnA was induced by Ni(II) or Co(II). Overproduction of rcnR inhibited induction of rcnA by metal cations but RcnR did not bind to the rcnA promoter in vitro. When rcnR or fur, the gene of the global repressor of iron homeostasis, was deleted, expression of rcnA was also induced by iron. The promoter region of rcnA was positive in a Fur titration (FURTA) in vivo assay indicative of Fur binding. Thus, rcnA is part of the Fur regulon of E.␣coli. The implications of a connection between the homoeostasis of closely related transition metals are discussed.     

Comparative genomic analyses of nickel, cobalt and vitamin B12 utilization

Background

Nickel (Ni) and cobalt (Co) are trace elements required for a variety of biological processes. Ni is directly coordinated by proteins, whereas Co is mainly used as a component of vitamin B₁₂. Although a number of Ni and Co-dependent enzymes have been characterized, systematic evolutionary analyses of utilization of these metals are limited.

Results

We carried out comparative genomic analyses to examine occurrence and evolutionary dynamics of the use of Ni and Co at the level of (i) transport systems, and (ii) metalloproteomes. Our data show that both metals are widely used in bacteria and archaea. Cbi/NikMNQO is the most common prokaryotic Ni/Co transporter, while Ni-dependent urease and Ni-Fe hydrogenase, and B₁₂-dependent methionine synthase (MetH), ribonucleotide reductase and methylmalonyl-CoA mutase are the most widespread metalloproteins for Ni and Co, respectively. Occurrence of other metalloenzymes showed a mosaic distribution and a new B₁₂-dependent protein family was predicted. Deltaproteobacteria and Methanosarcina generally have larger Ni- and Co-dependent proteomes. On the other hand, utilization of these two metals is limited in eukaryotes, and very few of these organisms utilize both of them. The Ni-utilizing eukaryotes are mostly fungi (except saccharomycotina) and plants, whereas most B₁₂-utilizing organisms are animals. The NiCoT transporter family is the most widespread eukaryotic Ni transporter, and eukaryotic urease and MetH are the most common Ni- and B₁₂-dependent enzymes, respectively. Finally, investigation of environmental and other conditions and identity of organisms that show dependence on Ni or Co revealed that host-associated organisms (particularly obligate intracellular parasites and endosymbionts) have a tendency for loss of Ni/Co utilization.

Conclusion

Our data provide information on the evolutionary dynamics of Ni and Co utilization and highlight widespread use of these metals in the three domains of life, yet only a limited number of user proteins.     

Effects of Soil Trace Elements on Longevity Population in China

Based on background concentrations of elements in soils and the sixth population census data of China, this study discussed the distribution characteristics of soil elements and longevity population at province level in China. Percentages of the aging population are high in Southwest China and the eastern coastal region but low in western and northwestern regions. Provinces in South and Southwest China gain a high level of longevity, while the northern part of China has a low level of longevity. The background concentration of Se in soil has a significant positive correlation with longevity index, while Ba and Ni have a significant negative correlation with longevity indexes. By regression analysis, longevity index C/100,000 can be expressed as C/100,000?=?1.679?0.205 Ni?+?0.413 Co?+?0.006 Se (with R ²?=?0.402 and p?<?0.01), C/65+ can be expressed as C/65+=3.425?0.262 Ni?+?0.435 Co?+?0.006 Se (with R ²?=?0.369 and p?<?0.01).     

Palaeomicrocodium: A new view on its origin

Remains of Palaeomicrocodium from the Silurian and Devonian carbonate and clay deposits from the Timan-Northern Ural region, Salair, and Western Siberia are studied using various lithological and geochemical techniques. Characters suggesting their paleoecological and geochemical specialization are discussed. It is suggested that Palaeomicrocodium structures belong to ancient lichens or actinolichens. This hypothesis is based on a number of features of Palaeomicrocodium, including the presence of typical biologically fixed microelements of soil, such as Co, Cu, Zn, Ni, and Cd, sourced from the atmosphere; presence of kerogen carbonaceous matter in prismatic calcite monocrystals of Palaeomicrocodium; identification in their structure of probable hypha-like and rhizoid-like structures; morphological similarity to extant encrusting lichens. Like lichens, Palaeomicrocodium significantly contributed to chemical weathering of rocks by excreting various organic acids, which could effectively dissolve minerals and chelate metallic cations. As a result of the weathering induced by vital function of Palaeomicrocodium, rock-forming minerals exhibit surface corrosion.     

Metals in some dominant vascular plants, mosses, lichens, algae, and the biological soil crust in various types of terrestrial tundra, SW Spitsbergen, Norway

Arctic environments are commonly considered to be relatively pristine because of minimal local human activity. However, these areas receive air pollution from lower latitude regions. Our goal was to determine concentrations of metals (Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) in dominant species of vascular plants, mosses, lichens, algae, and in the biological soil crust (BSC), and topsoil (0–3 cm) from various types of tundra in the southwestern part of Spitsbergen, Norway. Results indicate that mosses are more efficient bioaccumulators of Cd, Co, Cr, Cu, Fe, Mn, and Zn than lichens. The highest levels of Co, Cr, Cu, Fe, Hg, Mn, Ni, and Pb were found in the BSC, and the moss species Racomitrium lanuginosum, Sanionia uncinata, and Straminergon stramineum from the polygonal tundra, initial cyanobacteria-moss wet tundra, snow bed cyanobacteria-moss tundra, and flow water moss tundra alimented by melting ice or snow. The observed higher concentrations of Cu and lower concentrations of Hg in mosses, lichens, and vascular plants compared with values observed 20 years earlier were apparently associated with changes in the atmospheric deposition of contaminants over Spitsbergen due to changes in the long-distance transport of anthropogenic emissions from industrialized areas. Prasiola crispa and Salix polaris may be useful bioindicators of Cd and Zn, and the BSC, R. lanuginosum, S. uncinata, and S. stramineum as bioindicators of Co, Cr, Cu, Fe, Hg, Mn, Ni, and Pb. These results may be extrapolated across other areas of Spitsbergen with similar climates.     

Stability studies in relation to IR data of some schiff base complexes of transition metals and their biological and pharmacological studies

Schiff bases derived from salicylaldehyde and 2-substituted anilines and their Cu(II), Ni(II) and Co(II) complexes have been synthesized and characterized by their elemental analysis, TGA, IR and electronic spectral studies, molar conductance and magnetic susceptibility measurements. The mode of bonding between Cu(II), Ni(II) and Co(Il) and Schiff bases has been studied by IR spectrophotometry. The shift in the band positions of the groups involved in coordination has been utilized to estimate the metal- nitrogen bond lengths. The results obtained are in good agreement with the values of metal-nitrogen modes and ligand-field splitting energy (10 Dq). The antimicrobial activities of the synthesized ligands and their metal complexes have been determined on Gram-positive (Staphylococcus aureus), Gram- negative (Escherichia coli) bacteria and on fungi like Aspergillus niger, Aspergillus nidulense and Candida albicans. The antimicrobial activity of the organic ligands increased several folds on chelation as compared to the ligand molecule alone. However, their anti-inflammatory activity showed a different pattern; the activity of some ligands was more than their respective metal chelates. It is interesting to note that only cobalt complexes exhibited anti-inflammatory activity.     

Transition metal ion complexes of 2-thio-6-picoline N-oxide

Complexes of the anion 2-thio-6-picoline N-oxide (6MOS) have been isolated with the following stoichiometry: M(6MOS)₃ (M = Cr, Fe, and Co) and M(6MOS)₂ (M = Co, Ni, Cu and Zn). The spectral properties of these complexes are compared with those of 2-thiopyridine N-oxide in order to determine the stereochemical effect of the 6-methyl substituent. The nature of the Ni(I) species formed on exposure to high energy radiation, and the nature of the heterocyclic amine adducts to both the Ni(II) and Cu(II) complexes are also reported.     

Synthesis, structure and magnetic properties of a new family of chiral metal(II) citramalates

A new series of chiral carboxylate-bridged complexes of Mn(II), Co(II), and Ni(II) has been synthesized by reaction of M(II) salts with (S)-2-hydroxy-2-methyl-butanedioic acid ((S)-citramalic acid) under solvothermal conditions. The Mn(II) compound 1 is obtained as a crystalline powder, whereas the Co(II) and Ni(II) compounds (2 and 3 respectively) are obtained as single crystals. All the compounds crystallize in orthorhombic chiral space group P2₁2₁2₁. Compounds 2 and 3 are isostructural, and their structure consists in helicoïdal chains of M(II) centres linked by carboxylate bridges. The magnetic data indicate a rather weak coupling interaction between paramagnetic centres. The Mn(II) compound 1 exhibits antiferromagnetic ordering at T_N = 2.64 K. The Co(II) and Ni(II) compounds show ferromagnetic interactions within the chains. For 3, the chains couple antiferromagnetically, which leads to a metamagnetic behaviour with T_N = 1.69 K.     

Establishment of Element Fingerprint and Multielement Analysis of Fritillaria thunbergii by Inductively Coupled Plasma Optical Emission Spectrometry

Element fingerprints were deciphered for Fritillaria thunbergii from Chinese ten major fritillaria-producing regions for the purpose of examining differences in element composition with region of origin and identifying elements’ importance to F. thunbergii. Analysis by inductively coupled plasma optical emission spectrometry allowed simultaneous determination of 18 elements in F. thunbergii (Al, B, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Na, Mn, Mo, S, Ni, P, Pb, and Zn), and patterns in element concentrations were deciphered by principle component analysis (PCA) and hierarchical cluster analysis (HCA). The element fingerprint was established which well reflected the element characteristics of F. thunbergii. Meanwhile, the ten regions were discriminated with 100% accuracy using HCA and PCA based on 18 of these elements. The element Mg, Ca, K, B, P, Mo, Na, Cd, Ni, and Al were viewed as the characteristic element of F. thunbergii, and the fingerprint of these elements could be used to distinguish the authenticity of F. thunbergii Miq.     

In vitro bioaccessibility of metals from tape tea – A low-cost emerging drug

BackgroundAn in vitro physiologically relevant test based on the standard Unified Bioaccessibility Method (UBM) combined with inductively coupled plasma mass spectrometry was performed in this study to ascertain the elemental bioaccessibility pools of tape tea as emerging low-cost abuse drug under fasted conditions.MethodsElemental quantification in tape tea and body fluid extracts was performed by an inductively coupled plasma quadrupole mass spectrometer - ICP-MS, and for sample preparation of the bioaccessibility extracts prior to ICP-MS analysis, a microwave-assisted acid decomposition was applied by using a microwave oven. The Unified Bioaccessibility Method (UBM) was considered for investigation of elemental bioaccessibility in tape tea, required a full set of organic compounds, salts, and enzymes.ResultsConsidering total element evaluation through ICP-MS, Co, Ni, Mn, and Zn are found at the highest concentrations in the sample, namely 415 ± 36, 202 ± 55, 1389 ± 225 and 2397 ± 197 μg L⁻¹, respectively. Regarding the oral bioaccessibility test, after both gastric and gastrointestinal extractions Co, Ni, and Mn are fully bioaccessible while for Zn the bioaccessibility is ca. 66 %.ConclusionAccording to the first results in the literature proposed for these samples, the bioaccessibility results indicate an increment in day-to-day total element concentration and depending on the concentration of each element that an individual consumes in its usual diet, the total concentration can exceed the TDI. There are several possible toxic effects caused by the excess of Co, Ni and Mn, which might be expected by their high total concentrations.