Precipitation of minerals by 22 species of moderately halophilic bacteria in artificial marine salts media: Influence of salt concentration

Precipitation of minerals was shown by 22 species of moderately halophilic bacteria in both solid and liquid artificial marine salts media at different concentration and different Mg2+-to-Ca2+ ratio. Precipitation of minerals was observed for all the bacteria used. When salt concentration increased, the quantity and the size of bioliths decreased, the time required for precipitation being increased. The precipitated minerals were calcite, magnesian calcite, aragonite, dolomite, monohydrocalcite, hydromagnesite and struvite in variable proportions, depending on the bacterial species, the salinity and the physical state of the medium; the Mg content of the magnesian calcite also varied according to the same parameters. The precipitated minerals do not correspond exactly to those which could be precipitated inorganically according to the saturation indices. Scanning electron microscopy showed that the formation of the bioliths is initiated by grouping of calcified cells and that the dominant final morphologies were spherulitic with fibrous radiated interiors. It was demonstrated that moderately halophilic bacteria play an active role in the precipitation of carbonates and we hypothesize about this process of biomineralization.     

Biotransformation of struvite by Aspergillus niger: phosphate release and magnesium biomineralization as glushinskite

Struvite (magnesium ammonium phosphate-MgNH₄PO₄·6H₂O), which can extensively crystallize in wastewater treatments, is a potential source of N and P as fertilizer, as well as a means of P conservation. However, little is known of microbial interactions with struvite which would result in element release. In this work, the geoactive fungus Aspergillus niger was investigated for struvite transformation on solid and in liquid media. Aspergillus niger was capable of solubilizing natural (fragments and powder) and synthetic struvite when incorporated into solid medium, with accompanying acidification of the media, and extensive precipitation of magnesium oxalate dihydrate (glushinskite, Mg(C₂O₄).2H₂O) occurring under growing colonies. In liquid media, A. niger was able to solubilize natural and synthetic struvite releasing mobile phosphate (PO₄³⁻) and magnesium (Mg²⁺), the latter reacting with excreted oxalate resulting in precipitation of magnesium oxalate dihydrate which also accumulated within the mycelial pellets. Struvite was also found to influence the morphology of A. niger mycelial pellets. These findings contribute further understanding of struvite solubilization, element release and secondary oxalate formation, relevant to the biogeochemical cycling of phosphate minerals, and further directions utilizing these mechanisms in environmental biotechnologies such as element biorecovery and biofertilizer applications.     

Carbonate Precipitation of Bacterial Strains Isolated from Sediments and Seawater: Formation Mechanisms

This article presents a research study on carbonate formation in solid and liquid media by Thalassospira sp., Halomonas sp., Bacillus pumilus, and Pseudomonas grimontii, four bacterial strains isolated from sediments and deep seawater. As part of this study, we analyzed carbonic anhydrase activity, pH, adsorption of calcium and magnesium ions, and total organic and inorganic carbon. The geochemical program PHREEQC was also used to calculate the mineral saturation indexes in all the cultures. The minerals formed were studied with X-ray diffraction, X-ray dispersive energy microanalysis, and scanning electron microscopy. In addition, all four bacterial strains were found to induce carbonate precipitation and to have carbonic anhydrase activity. Sterile control experiments did not precipitate carbonate. In solid M1 and B4 media, all of the strains precipitated magnesium calcite, whereas in the liquid media, they precipitated different percentages of magnesium calcite, aragonite, and monohydrocalcite. In both cases, small amounts of amorphous precipitates were also produced. This article discusses carbonate formation and the possible role played by metabolic activity, bacterial surfaces and carbonic anhydrase in this process. Finally, the results obtained lead to a hypothesis regarding the importance of carbonate precipitation for the survival of bacteria populations in certain habitats.     

Biomineralization of carbonate and phosphate by moderately halophilic bacteria

We investigated the precipitation of carbonate and phosphate minerals by 19 species of moderately halophilic bacteria using media with variable Mg(2+)/Ca(2+) ratios. The precipitated minerals were calcite, magnesium (Mg) calcite, and struvite (MgNH(4)PO(4) x 6H(2)O) in variable proportions depending on the Mg(2+)/Ca(2+) ratio of the medium. The Mg content of the Mg-calcite decreased with increasing Ca(2+) concentration in the medium. According to the saturation indices, other minerals could also have precipitated. We observed important differences between the morphology of carbonate and phosphate, which may help us to recognize these minerals in natural systems. We studied the growth and pH curves of four bacteria in media specific for carbonate and struvite precipitation. We consider the biomineralization processes that produce carbonate and phosphate minerals, and propose a hypothesis for the lack of struvite in natural environments and ancient rocks.     

Production of syngenetic minerals with struvite by myxococcus coralloides D

The formation under laboratory conditions of newberyite, schertelite, and taylorite in conjunction with struvite by the bacterium Myxococcus coralloides D is reported for the first time. The presence of these syngenetic minerals with struvite was only detected in static liquid cultures.     

Precipitation of calcium carbonate byDeleya halophila in media containing NaCl as sole salt

The precipitation of calcium carbonate by 27 strains ofDeleya halophila using solid and liquid media containing different NaCl concentrations (2.5, 7.5, or 20%, wt/vol) as sole salt, and two incubation temperatures (22° and 32°C) have been studied. All the strains tested were able to precipitate calcium carbonate under the different environmental conditions assayed. Crystals formed were calcite and vaterite; the ratio of calcite to vaterite was dependent on total salts and on the type of medium.     

Bacterial formation of struvite

We studied the formation of exocellular precipitates of struvite (Mg NH₄PO4.6H₂O) by 96 kinds of calcite‐pro‐ducing bacterial strains isolated from soil. We also studied the influence of calcium ions on struvite precipitation. The number of strains producing struvite was 20. Only four consistently formed large amounts. These results seem to indicate that the bacterial precipitation of struvite is not a general phenomenon. The strains studied were taxonomically identified, and no relationship was found between the production of struvite and the taxonomic identity of such strains. Calcium, supplied as Ca acetate in the culture medium, appeared to inhibit the biological precipitation of struvite.     

Effects of pH and phosphate on the production of struvite by Myxococcus xanthus

We studied the influence of pH and the phosphate content of the culture medium on the precipitation of struvite by Myxococcus xanthus, a bacterium that undergoes autolysis at the end of its exponential growth phase in liquid cultures. The best results were obtained with pH values between 7.2 and 8.0 and with a phosphate concentration of 10 mM. Our studies reveal for the first time that the precipitation of struvite always begins at the onset of autolysis and that culture conditions favoring the early occurrence of autolysis also enhance struvite production.     

Struvite Precipitation Induced by a Novel Sulfate-Reducing Bacterium Acinetobacter calcoaceticus SRB4 Isolated from River Sediment

This article presents a study of struvite formation in liquid medium induced by the sulfate-reducing bacterium Acinetobacter calcoaceticus SRB4, a strain isolated from river sediment. We identified the bacterial strain A. calcoaceticus SRB4 and analyzed its micromorphology. The minerals formed were studied with an electroprobe microanalyzer, Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, selected-area electron diffraction, X-ray diffraction, thermogravimetry, differential thermogravimetry, and differential scanning calorimetry. Acinetobacter calcoaceticus SRB4 was found to induce struvite precipitation, whereas sterile control cultures did not. Many transparent stick-shaped struvite precipitates were distributed at the bottom of the conical flasks in the experimental group. Most bacteria were spherical and a large quantity of spherical struvite particles (less than 200 nm in diameter) adhered to the bacterial surface. An electron probe microanalysis showed that the precipitates contained C, O, P, Mg, and other elements. Fourier transformation infrared spectra showed that the precipitates contained crystalline water, NH₄⁺, and PO₄^3? groups. X-ray diffraction spectra showed that the precipitates were struvite crystals, with preferential orientation and lattice distortion. Thermogravimetry showed that the weight loss was caused by the evaporation of crystalline water at temperatures lower than 136°C and the release of ammonia from struvite at temperatures of 136–228.5°C. In this article, we discuss the possible mechanism of struvite formation and the possible role played by A. calcoaceticus SRB4. Our study extends our understanding of the phosphate biomineralization mechanism and should prove useful in recycling phosphorus in wastewater.     

Application of Stereolithographic Custom Models for Studying the Impact of Biofilms and Mineral Precipitation on Fluid Flow

Here we introduce the use of transparent experimental models fabricated by stereolithography for studying the impacts of biomass accumulation, minerals precipitation, and physical configuration of flow paths on liquid flow in fracture apertures. The internal configuration of the models ranged in complexity from simple geometric shapes to those that incorporate replicated surfaces of natural fractures and computationally derived fracture surfaces. High-resolution digital time-lapse imaging was employed to qualitatively observe the migration of colloidal and soluble dyes through the flow models. In this study, a Sphingomonas sp. and Sporosarcina (Bacillus) pasteurii influenced the fluid dynamics by physically altering flow paths. Microbial colonization and calcite deposition enhanced the stagnant regions adjacent to solid boundaries. Microbial growth and calcite precipitation occurred to a greater extent in areas behind the fabricated obstacles and less in high-velocity orifices.     

Reproducing Authigenic Carbonate Precipitation in the Hypersaline Lake Acıgöl (Turkey) with Microbial Cultures

In the present study, laboratory precipitation experiments using similar water chemistry and two different bacterial cultures from Lake Ac?göl sediments, a hypersaline lake in Turkey, were performed to reproduce mineral assemblages similar to those found in the lake. Two different bacterial cultures induce various calcium/magnesium carbonates precipitation under all the experimental conditions (solid vs. liquid): Hydromagnesite, dypingite, huntite, monohydrocalcite, and aragonite. The geochemical program PHREEQC was used to calculate the mineral saturation indexes in the cultures and in lake water. Carbonate mineral assemblages identified in the experiments seem to be independent of the type of microorganisms but rather controlled by the chemical composition and physical conditions of the media. The relative amounts of monohydrocalcite, hydromagnesite, and dypingite are controlled by varying sulfate concentration from 0 to 56 mM. This demonstrates a kinetic effect that could similarly affect the mineral assemblage in the lake. Also the spherical morphology of hydromagnesite points to growth of these minerals under partial inhibition in the brine under high concentrations of ions and organic polymers produced by the microbial communities. As reproduced by the culture experiments, the authigenic carbonate mineral assemblage of Lake Ac?göl most likely results from interplay of ionic composition of the brine and microbial effects.     

Colonization and bioweathering of monazite by Aspergillus niger: solubilization and precipitation of rare earth elements

Geoactive fungi play a significant role in bioweathering of rock and mineral substrates. Monazite is a phosphate mineral containing the rare earth elements (REE) cerium, lanthanum and neodymium. Little is known about geomicrobial transformations of REE-bearing minerals which are also relevant to REE biorecovery from terrestrial and extra-terrestrial reserves. The geoactive soil fungus Aspergillus niger colonized monazite in solid and liquid growth media without any apparent growth inhibition. In a glucose-minerals salts medium, monazite enhanced growth and mycelium extensively covered rock particle surfaces, probably due to the provision of phosphate and essential trace metals. Teeth-like and pagoda-like etching patterns indicated monazite dissolution, with extensive precipitation of secondary oxalate minerals. Biomechanical forces ensued causing aggressive bioweathering effects by tunnelling, penetration and splitting of the ore particles. High amounts of oxalic acid (~46 mM) and moderate amounts of citric acid (~5 mM) were produced in liquid media containing 2% (wt./vol.) monazite, and REE and phosphate were released. Correlation analysis suggested that citric acid was more effective than oxalic acid in REE mobilization, although the higher concentration of oxalic acid also implied complexant activity, as well as the prime role in REE-oxalate precipitation.     

Isolation and metagenomic characterization of bacteria associated with calcium carbonate and struvite precipitation in a pure moving bed biofilm reactor-membrane bioreactor

A bench-scale pure moving bed bioreactor-membrane bioreactor (MBBR-MBR) used for the treatment of urban wastewater was analyzed for the identification of bacterial strains with the potential capacity for calcium carbonate and struvite biomineral formation. Isolation of mineral-forming strains on calcium carbonate and struvite media revealed six major colonies with a carbonate or struvite precipitation capacity in the biofouling on the membrane surface and showed that heterotrophic bacteria with the ability to precipitate calcium carbonate and struvite constituted ~7.5% of the total platable bacteria. These belonged to the genera Lysinibacillus, Trichococcus, Comamomas and Bacillus. Pyrosequencing analysis of the microbial communities in the suspended cells and membrane biofouling showed a high degree of similarity in all the samples collected with respect to bacterial assemblage. The study of operational taxonomic units (OTUs) identified through pyrosequencing suggested that ~21% of the total bacterial community identified in the biofouling could potentially form calcium carbonate or struvite crystals in the pure MBBR-MBR system used for the treatment of urban wastewater.     

Influence of ammonium ions on calcite and struvite formation byazotobacter in chemically defined media

The formation of calcite and struvite crystals byAzotobacter vinelandii andA.chroococcum was studied on chemically defined media. The crystals were identified microscopically and by X-ray differentiation analysis. Calcite crystal formation was inhibited specifically with 0.05 % ammonium sulfate. However, 0.2 % ammonium sulfate was required for struvite crystal formation.     

Biomineralization of Fungal Hyphae with Calcite (CaCO3) and Calcium Oxalate Mono- and Dihydrate in Carboniferous Limestone Microcosms

The formation of biogenic fabrics in limestone by two fungi, Serpula himantioides and a polymorphic fungal isolate from limestone identified as a Cephalotrichum (syn. Doratomyces) sp., was investigated. The fungal cultures were grown in laboratory microcosms consisting of Carboniferous limestone and after 21 d incubation at 25°C, biomineralization of fungal filaments was observed. Environmental electron scanning microscopy (ESEM) and X-ray micro-analysis (EDXA) of crystalline precipitates on the hyphae of S. himantioides demonstrated that the secondary crystals exhibited different crystalline forms but were similar in elemental composition to the original limestone. Powder X-ray diffraction (XRD) of crystalline precipitates showed they were composed of a mixture of calcite (CaCO ₃ ) and calcium oxalate monohydrate (CaC ₂ O ₄ · H ₂ O). Analysis of crystals precipitated on the hyphae of the limestone isolate, using ESEM and EDXA, showed that the crystals exhibited similar morphological characteristics and elemental composition to the original limestone. XRD showed that they were composed solely of calcite (CaCO ₃ ) or of calcite with some calcium oxalate dihydrate (CaC ₂ O ₄ · 2H ₂ O). These results provide direct experimental evidence for the precipitation of calcite (CaCO ₃ ) and also secondary mycogenic minerals, on fungal hyphae in low nutrient calcareous environments, and suggest that fungi may play a wider role in the biogeochemical carbon cycle than has previously been appreciated.     

Carbonate and Phosphate Precipitation by Saline Soil Bacteria in a Monitored Culture Medium

Carbonate and phosphate precipitation by bacteria isolated from a saline soil was studied in vitro in a liquid culture medium over 45 days. Physicochemical parameters of this medium were continuously monitored using both selective electrodes (continuous monitoring, CM) and individual measurements by other techniques on days 5, 10, 15, 20, 25, 35 and 45 (discontinuous monitoring, DM). In DM, the precipitated minerals were studied (XRD and SEM-EDX) and the saturation index of the mineral phases was analyzed (PHREEQC program). Using the CM and DM data it was possible to distinguish several temporary stages in which both the medium and the mineralogy changed: 1) 0 to 10 days: pH reaches 8.4; significant loss of Mg²⁺ (incorporated into the bacterial biomass) and Ca²⁺ (through mineral precipitation); formation of crystals, although not in sufficient quantity to be studied until day 10. 2) 10 to 25 days: pH decreases but remains above 8; appreciable loss of Mg²⁺ and Ca²⁺ due to formation of spherical carbonate bioliths with traces of phosphates occluded within these carbonates. 3) After 25 days: biomineralization slow down; pH returns to initial values and struvite is formed (idiomorphic prismatic crystals). These trends are in agreement with the findings of other workers, although with some peculiarities regarding stages and types of mineral precipitated. In some cases the struvite contained small quantities of K and Ca, possibly because these are intermediate mineral species between typic-struvite, K-struvite and Ca-struvite. The bacteria-mediated precipitation of carbonates of Ca and/or Mg and phosphates (struvite) by the bacteria from a saline soil is demonstrated. However, struvite was not found in the soils of origin of the bacteria, possibly because it is a metastable mineral in most soils.     

Sustainable bio-bricks prepared with synthetic urine enabled by biomineralization reactions

In this study, mineralization during brick preparation was performed with ureolytic bacterium, Lysinibacillus fusiformis that use urine as a substrate, omitting the heat that is normally required. Artificial urine for reasons of standardization was used to grow the bacterium for bio-bricks made of clay and cement, but their mineralization was enabled by biological activity instead of by heat. Scanning electron microscopy and energy dispersion X-ray spectroscopy were conducted to analyse the microstructures formed by L. fusiformis that precipitated various minerals in synthetic urine. The brick specimens were tested for compressive strength that was 59% more than control ones, whereas porosity of bio-bricks was 13% compared to 22% of control specimens. The minerals formed in the bio-bricks confirmed as struvite, apatite and calcite by Fourier-transform infrared spectroscopy and X-ray diffraction spectra, were responsible for improved strength and reduced porosity. The research provided evidence in utilizing ureolytic bacteria as a mode to mineralize clay in brick production with the use of (artificial) urine as a substrate.     

Lactose mother liquor as an alternative nutrient source for microbial concrete production by <Emphasis Type="Italic">Sporosarcina pasteurii</Emphasis>

Microbiologically induced calcite precipitation by the bacterium Sporosarcina pasteurii (NCIM 2477) using the industrial effluent of the dairy industry, lactose mother liquor (LML) as growth medium was demonstrated for the first time in this study. The urease activity and the calcite precipitation by the bacterium was tested in LML and compared with the standard media like nutrient media and yeast extract media. Calcite constituted 24.0% of the total weight of the sand samples plugged by S. pasteurii and urease production was found to be 353 U/ml in LML medium. The compressive strength of cement mortar was increased by S. pasteurii in all the media used compared to control. No significant difference in the growth, urease production and compressive strength of mortar among the media suggesting LML as an alternative source for standard media. This study demonstrates that microbial calcite acts as a sealing agent for filling the gaps or cracks and fissures in constructed facilities and natural formations alike.     

Biomineralisation of carbonate and sulphate by the halophilic bacterium Halomonas maura at different manganese concentrations

The ability of Halomonas maura to bioprecipitate carbonate and sulphate crystals in solid media at different manganese concentrations has been demonstrated in this study for the first time. The precipitated minerals were studied by X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The precipitated minerals were different based on the manganese concentration present in the medium and the incubation time. In the absence of manganese, H. maura formed pseudokutnahorite crystals; in the presence of manganese, the concentration in the culture medium determined the precipitation carbonates, such as rhodochrosite and dolomites. However, in the presence of low concentrations of manganese chloride (MnCl₂) (5 g/l), kutnohorite crystals were also formed. Finally, when H. maura was grown in the presence of manganese, small amounts of sulphate crystals (such as bassanite and gypsum) were detected. Our study of the precipitated minerals showed an active role of H. maura in the biomineralisation process, but the geochemical conditions, and the manganese concentrations in particular, were clearly influential.

     

Amino acid sequence of the ribosomal protein HS23 from the halophilicHaloarcula marismortui and homology studies to other ribosomal proteins

The ribosomal protein HS23 from the 30S subunit of the extreme halophilicHaloarcula marismortui, belonging to the group of archaea, was isolated either by RP-HLPLC or two-dimensional polyacrylamide gel electrophoresis. The complete amino acid sequence was determined by automated N-terminal microsequencing. The protein consists of 123 residues with a corresponding molecular mass of 12,552 Da as determined by electrospray mass spectroscopy; the pI is 11.04. Homology studies reveal similarities to the eukaryotic ribosomal protein S8 fromHomo sapiens, Rattus norvegicus, Leishmania major, andSaccharomyces cerevisiae.Abbreviations H. marismortui Haloarcula marismortui - PVDF polyvinylidene difluoride - PTH phenylthiohydantoin - RP-HPLC reversed-phase high-performance liquid chromatography - TFA trifluoro acetic acid - TP30 total protein mixture from the 30S ribosomal subunit ofH. marismortui