microbial mechanisms in biomineralization

<p>Activities of microorganisms can lead to formation of biominerals. This biomineralization has been described to be either 'microbially controlled' or 'microbially induced'. The control over crystalization can work intracellularly, e.g. with magnetosomes, or extracellularly like in mammals. With increasing evidence for intermediate processes with specific proteins inducing different crystalloid (macro)morphology even at a distance to a colony, and processes involving both bioweathering and formation of new minerals, the concept of biomineralization should be re-visited and a more detailed classification of biomineralization processes is needed including formation of a stable backbone determining the macromorphology of biominerals even at distance from cell surfaces.</p><p>Here, the supply of mineral components (e.g. phosphate, reduced nitrogen compounds, etc.) through microbial exudation and matrix provided by bacteria or fungi are discussed. Especially with respect to metal resistance mechanisms, this is an active process, costly to the cells. Examples are given for microbial biomineralization processes in metal rich environments on  a former heap site. The formation of manganese hydroxides, like birnessite, leading to massive hardpan formation, is one of the examples derived from the former uranium mining site in Thuringia, Germany. Other examples with different macromorphologies include carbonates, (magnesium) calcite or vaterite, formed under laboratory conditions with strains of streptomycetes in dependence of excreted amphipathic surface proteins of the bacteria. And as a third example, the formation of (nickel) struvite, switzerite and nickel phosphate formation on soil from the former mining site under laboratory conditions will be discussed.</p><p>From the original research, a new concept for microbially aided, extracellular biomineral formation is developed. The concept thus extends the previous distinction of biomineralization on the part of the 'microbially induced' formation in a process oriented way, including microbial physiology and secondary metabolism into a unified concept of biomineralization.</p>

BACKGROUND PHYSICAL AND CHEMICAL CHARACTERISTICS OF THE SOIL COVER OF THE NORTHERN PART OF THE STATE RESERVE «VERKHNE-TAZOVSKY»

Analytical studies of background soils on the territory of the Yamal-Nenets Autonomous Okrug were Carried out using generally accepted methods in soil science. Low availability of tested soils with organic matter and basic exchange cations is shown. Indicators of heavy metal concentrations, silt and humus content, and sorbents (iron and manganese hydroxides) were obtained.

HEAVY METAL SPECIATION IN BOTTOM SEDIMENTS OF THE VYSHNEVOLOTSKY RESERVOIR

The study of heavy metal speciation in bottom sediments of the Vyshnevolotsky water reservoir is presented in this paper. Sequential selective procedure was used to determine the heavy metal speciation in bottom sediments and thermodynamic calculation — to determine ones in interstitial water. It has been shown that Mn are mainly presented in exchangeable and carbonate forms; for Fe, Zn, Pb и Co the forms are related to iron and manganese hydroxides is played an important role; and Cu and Ni are mainly associated with organic matter. In interstitial waters the main forms of heavy metal speciation are free ions for Zn, Ni, Co and Cd, carbonate complexes for Pb, fulvate complexes for Cu. Effects of particle size and organic matter content in sediments on distribution of mobile and potentially mobile forms of toxic elements have been revealed.

Phosphorus and arsenic distributions in a seasonally stratified, iron- and manganese-rich lake: microbiological and geochemical controls

Environmental context Despite being present at trace concentrations, arsenic and phosphorus are among the most important of freshwater contaminants. This research highlights the biogeochemical coupling of both elements in a New Zealand lake. We find that the mineralisation of organic residues coupled to the dissolution of colloidal iron and manganese hydroxides may be an important driver of the bioavailability of phosphorus and arsenic. Abstract Seasonal stratification in temperate lakes greater than a few metres deep provides conditions amenable to pronounced vertical zonation of redox chemistry. Such changes are particularly evident in eutrophic systems where high phytoplankton biomass often leads to seasonally established anaerobic hypolimnia and profound changes in geochemical conditions. In this study, we investigated the behaviour of trace elements in the water column of a seasonally stratified, eutrophic lake. Two consecutive years of data from Lake Ngapouri, North Island, New Zealand, demonstrate the occurrence of highly correlated profiles of phosphorus, arsenic, iron and manganese, all of which increased in concentration by 1–2 orders of magnitude within the anaerobic hypolimnion. Stoichiometric and mass-balance considerations demonstrate that increases in alkalinity in hypolimnetic waters were consistent with observed changes in sulfate, Fe and Mn concentrations with depth, corresponding to dissimilatory reduction of sulfate, FeIII and MnIV hydroxides. Thermodynamic constraints on Fe, Mn and Al solubility indicate that amorphous FeIII, MnIV hydroxides most probably controlled Fe and Mn in the surface mixed layer (~0 to 8m) whereas AlIII hydroxides were supersaturated throughout the entire system. Surface complexation modelling indicated that iron hydroxides (HFO) potentially dominated As speciation in the lake. It is likely that other colloidal phases such as allophanic clays also limited HPO42– activity, reducing competition for HAsO42– adsorption to iron hydroxides. This research highlights the coupling of P, As, Fe and Mn in Lake Ngapouri, and the apparent role of multiple colloidal phases in affecting P and As activity within overarching microbiological and geochemical processes.

Clogging of water supply wells in alluvial aquifers by mineral incrustations, central Serbia

The formation of incrustations on public water supply well screens reduces their performance considerably. The incrustations increase hydraulic losses, reduce the capacity of the well and screen, affect the quality of the pumped water and increase maintenance costs. In alluvial environments, the most common deposits are iron and manganese hydroxides. However, the rates of formation, compositions and levels of crystallization vary, depending on the geochemical characteristics of the alluvial environment, the microbiological characteristics of the groundwater and the abstraction method. Samples of 15 incrustations were collected from wells that tap shallow alluvial aquifers and were found to be dominated by iron. XRD analyses detected low-crystalline ferrihydrite and manganese hydroxide in the samples collected from the water supply source at Trnovce (Velika Morava alluvial). The incrustations from the Belgrade Groundwater Source revealed the presence of ferrihydrite and a substantial amount of goethite ?-FeOOH. Apart from goethite, greigite (Fe3S4) was detected in three samples, while one sample additionally contained bernalite Fe(OH)3 and monoclinic sulfur S8. Among carbonates, only siderite was detected. Iron oxidizing bacteria generally catalyze deposition processes in wells, while sulfate reducing bacteria (SRB) play a role in the biogenic formation of greigite. Determining the nature of the deposited material allows better selection of rehabilitation chemicals and procedure.