Absolute Ideals of Murley Groups

For an Abelian group G, a subgroup A of G is called an absolute ideal of G if A is an ideal of any ring on G. If R is a ring and any ideal of R is an absolute ideal of the additive group of R, then R is called an AI-ring. If G is an Abelian group and there exists an AI-ring on G, then G is called an RAI-group. For RAI-groups, the description problem is formulated by L. Fuchs. Obviously, every full invariant subgroup of an Abelian group G is an absolute ideal of G. E. Fried formulated the problem of studying Abelian groups for which the converse is true; i.e., every absolute ideal is a fully invariant subgroup. Such groups are called afi-groups. In this work, we describe absolute ideals of Murley groups. This allows us to describe RAI-groups, afi-groups, and E-groups in the class of Murley groups

Copper isotope fractionation during its interaction with soil and aquatic microorganisms and metal oxy(hydr)oxides: Possible structural control

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Adsorption of metals and protons on Gloeocapsa sp. cyanobacteria: A surface speciation approach

International audienceThe purpose of the present work is to extend our knowledge of metal–cyanobacteria interactions and to contribute to the database on adsorption parameters of aquatic microorganisms with respect to metal pollutants. To this end, the surface properties of the cyanobacteria (Gloeocapsa sp. f-6gl) were studied using potentiometric acid–base titration methods and ATR-FTIR (attenuated total reflection infrared) spectroscopy. The electrophoretic mobility of viable cells was measured as a function of pH and ionic strength (0.01 and 0.1 M). Surface titrations at 0.01–1.0 M NaCl were performed using limited residence time reactors (discontinuous titration) with analysis of Ca, Mg and dissolved organic C for each titration point in order to account for alkali-earth metal–proton exchange and cell degradation, respectively. Results demonstrate that the cell-wall bound Ca and Mg from the culture media contribute to the total proton uptake via surface ion-exchange reactions. This has been explicitly taken into account for net proton balance calculations. Adsorption of Zn, Cd, Pb and Cu was studied at 25 °C in 0.01 M NaNO3 as a function of pH and metal concentration. The proportion of adsorbed metal increases as a function of culture age with cells of 44 days old having the largest adsorption capacities. A competitive Langmuir sorption isotherm in conjunction with a linear programming method (LPM) was used to fit experimental data and assess the number of surface sites and adsorption reaction constants involved in the binding of metals to the cyanobacteria surface. These observations allowed the determination of the identity and concentration of the major surface functional groups (carboxylate, amine, phosphoryl/phosphodiester and hydroxyl) responsible for the amphoteric behavior of cyanobacterial cell surfaces in aqueous solutions and for metal adsorption. Results of this work should allow better optimizing of metal bioremediation/biosequestration processes as they help to define the most efficient range of pH, cell biomass and duration of exposure necessary for controlled metal adsorption on cyanobacteria cultures. It follows from comparison of adsorption model parameters between different bacteria that technological application of cyanobacteria in wastewater bioremediation can be as efficient as other biological sorbents

Comparative study of the fatty acid composition of some groups of purple nonsulfur bacteria

The fatty acid composition (FAC) of 43 strains of purple nonsulfur bacteria belonging to six genera—Rubrivivax, Rhodopseudomonas, Rhodoplanes, Blastochloris, Rhodobium, and Rhodomicrobium—was studied by capillary gas chromatography. The cultures were grown on standard medium under standard conditions. Automatic identification of the fatty acid methyl esters and statistical processing of the results were performed by the computerized Microbial Identification System (MIS). Significant differences between the FACs of different genera, species, and, sometimes, strains were revealed. 16S rRNA genes of some of the new isolates, primarily those having a specific FAC, were sequenced. The taxonomic status of a number of the strains in question was determined using the FAC characteristics as one of the criteria. It was shown that the FAC characteristics may be used both for affiliating isolates to known species and for revealing new taxa

Phylogenetic relationships among budding purple bacteria of the genus Rhodopseudomonas

Phylogenetic relationships within a group of budding purple nonsulfur bacteria of the genus Rhodopseudomonas were studied by DNA-DNA hybridization. Most of the strains were new isolates from natural environments with a wide ränge of physicochemical conditions.A total of 32 strains were analyzed, includ- ing the type strains of Rhodopseudomonas palustris, Rps. rutila, Rps. marina, and Rps. acidophila. Nine phylo- genetically remote clusters were revealed, showing an average DNA-DNA horaology of 15%. One of the Clusters contained the type strain of Rps. marina, isolated front marine habitats, and two new isolates from hot ffeshwater springs. These new isolates tumed out to be facultative halophiles with a salinity Optimum of 1-3% and were assigned to Rps. marina on the basis of their phenotypic characteristics and DNA-DNA homology of 60% with the type strain of this species. The type strain of Rps. acidophila was not specifically related to any other strain used during this investigation. The remaining 26 isolates and the type strains of Rps. palustris and Rps. rutila were very similar phenotypically, but formed seven phylogenetically remote clusters including 13 genospecies; none of the new isolates were closely related to the type strains of Rps. palustris and Rps. rutila, which also proved to be phylogenetically distinct. Thus, the Rps. palustris-like bacteria, which are widespread in nature and comprise phenotypically a homogeneous group, appear to be phylogenetically diverse. The prospects for developing a Classification system for these budding purple nonsulfur bacteria that would be in agreement with their phylogenetic relationships are discussed. Possible correlation between the phylogenetic relationships of these bacteria and the ecological peculiarities of their natural habitats is also considered