Formation of Ni- and Zn-Sulfides in Cultures of Sulfate-Reducing Bacteria

The purpose of this study was to characterize Ni- and Zn-sulfides precipitated in sulfate-reducing bacterial cultures. Fe-free media containing 58 mM SO ₄ ^2? were amended with Ni and Zn chloride followed by inoculation. Precipitates were sampled from cultures after two weeks of incubation at 22, 45, and 60 ^° C. Abiotic controls were prepared by reacting bacteria-free liquid media with Na ₂ S solutions under otherwise identical conditions. Precipitates were collected anaerobically, freeze-dried and analyzed by x-ray diffraction (XRD), scanning electron microscopy, and for total Ni, Zn, and S. In Ni-containing media, biogenic sulfide precipitates were mostly heazelwoodite (Ni ₃ S ₂ ), whereas abiotic precipitates were mixed heazelwoodite and vaesite (NiS ₂ ). The biogenic Ni-precipitates were better crystalline than the corresponding abiotic samples. Sphalerite (ZnS) was identified by XRD in precipitates sampled from Zn-containing media. Scanning electron microscopy revealed disordered morphological features for the sulfides, which occurred mostly as aggregates of fine particles in biogenic samples, whereas abiotic precipitates contained more plate- and needle-like structures.     

Ammonia Formation By The Reduction Of Nitrite/Nitrate By Fes: Ammonia Formation Under Acidic Conditions

One issue for the origin of life under a non-reducing atmosphere is the availability of the reduced nitrogen necessary for amino acids, nucleic acids, etc. One possible source of this nitrogen is the formation of ammonia from the reduction of nitrates and nitrites produced by the shock heating of the atmosphere and subsequent chemistry. Ferrous ions will reduce these species to ammonium, but not under acidic conditions. We wish to report results on the reduction of nitrite and nitrate by another source of iron (II), ferrous sulfide, FeS. FeS reduces nitrite to ammonia at lower pHs than the corresponding reduction by aqueous Fe^{+ 2}. The reduction follows a first order decay, in nitrite concentration, with a half-life of about 150 min (room temperature, CO₂, pH 6.25). The highest product yield of ammonia measured was 53%. Under CO₂, the product yield decreases from pH 5.0 to pH 6.9. The increasing concentration of bicarbonate, at higher pH, interferes with the reaction. Comparing experiments under N₂ CO₂ shows the interference of bicarbonate. The reaction proceeds well in the presence of such species as chloride, sulfate, and phosphate, though the yield drops significantly with phosphate. FeS also reduces nitrate and, unlike with Fe^{+ 2}, the reduction shows more reproducibility. Again, the product yield decreases with increasing pH, from 7% at pH 4.7 to 0% at pH 6.9. It appears that nitrate is much more sensitive to the presence of added species, perhaps not competing as well for binding sites on the FeS surface. This may be the cause of the lack of reproducibility of nitrate reduction by Fe^{+ 2} (which also can be sensitive to binding by certain species)     

Formation of large carbonate concretions in black cherts in the Gufeng Formation (Guadalupian) at Enshi,South China

The formation of carbonate concretions is a cementation process which passively infills the pore spaces within sediments. They record the original environments of deposition and diagenetic conditions of the host rocks. Little is known about the precise mechanisms responsible for the precipitation of carbonate concretions. The most common host rocks are mudstones/shales, sandstones, and limestones. This study presents an example of large carbonate concretions from an unusual host rock, the black bedded cherts of the Gufeng Formation (Guadalupian) at Enshi on the northern Yangtze Platform, South China. Petrographic observations (X‐ray diffraction, optical microscopy, scanning electron microscopy) and multiple geochemical analyses (pyrite‐ and carbonate‐associated‐sulfate (CAS)‐sulfur isotopes, carbon isotopes) indicate that (a) the studied carbonate concretion are mainly composed of micritic calcite with subordinate dolomite; (b) the concretions may have been mainly formed in the bacterial sulfate reduction (BSR) zone during very early diagenesis near the sediment–water surface; (c) the paleo‐bottom water overlying the sediments during formation of the concretions was mainly euxinic; and (d) the growth of the studied concretions proceeded via a pervasive model, where later cementation phase initiated in the lower part of the concretions and progressed upward.     

Chemical and biological mobilization of Fe(III) in marsh sediments

Iron reduction in marine sulfitic environments may occur via a mechanism involving direct bacterial reduction with the use of hydrogen as an electron donor, direct bacterial reduction involving carbon turnover, or by indirect reduction where sulfide acts to reduce iron. In the presented experiments, the relative importance of direct and indirect mechanisms of iron reduction, and the contribution of these two mechanisms to overall carbon turnover has been evaluated in two marsh environments. Sediments collected from two Northeastern US salt marshes each having different Fe (III) histories were incubated with the addition of reactive iron (as amorphous oxyhydroxide). These sediments were either incubated alone or in conjunction with sodium molybdate. Production of both inorganic and organic pore water constituents and a calculation of net carbon production were used as measures to compare the relative importance of direct bacterial reduction and indirect bacterial reduction. Results indicate that in the environments tested, the majority of the reduced iron found results from indirect reduction mediated by hydrogen sulfide, a result of dissolution and precipitation phenomena, or is a result of direct bacterial reduction using hydrogen as an electron donor. Direct iron reduction plays a minor role in carbon turnover in these environments.     

Anaerobic mineralization of pentachlorophenol (PCP) by combining PCP-dechlorinating and phenol-degrading cultures

The dechlorination and mineralization of pentachlorophenol (PCP) was investigated by simultaneously or sequentially combining two different anaerobic microbial populations, a PCP-dechlorinating culture capable of the reductive dechlorination of PCP to phenol and phenol- degrading cultures able to mineralize phenol under sulfate- or iron-reducing conditions. In the simultaneously combined mixture, PCP (about 35 microM) was mostly dechlorinated to phenol after incubation for 17 days under sulfate-reducing conditions or for 22 days under iron-reducing conditions. Thereafter, the complete removal of phenol occurred within 40 days under both conditions. In the sequentially combined mixture, most of the phenol, the end product of PCP dechlorination, was degraded within 12 days of inoculation with the phenol degrader, without a lag phase, under both sulfate- and iron-reducing conditions. In a radioactivity experiment, [14C-U]-PCP was mineralized to 14CO2 and 14CH4 by the combined anaerobic microbial activities. Analysis of electron donor and acceptor utilization and of the production and consumption of H2, CO2, and CH4 suggested that the dechlorinating and degrading microorganisms compete with other microorganisms to perform PCP dechlorination and part of the phenol degradation in complex anoxic environments in the presence of electron donors and acceptors. The presence of a small amount of autoclaved soil slurry in the medium was possibly another advantageous factor in the successful dechlorination and mineralization of PCP by the combined mixtures. This anaerobic-anaerobic combination technology holds great promise as a cost-effective strategy for complete PCP bioremediation in situ.     

The self-assembly and liquid crystal formation of d(GpGpApGpG)

d(GpGpApGpG) dissolved in water forms liquid crystalline phases of the cholesteric and hexagonal type. The building blocks of the phases are columnar four-stranded aggregates composed of G quartets. The diameter of the columnar aggregates is larger and the melting temperature is lower than for homoguanylic derivatives, indicating a distorsion and loss of stability due to the presence of adenines, which do not form a hydrogen-bonded quartet. The present study shows that, as often observed for single crystals, it is possible also in the liquid crystalline phase to construct long columnar aggregates composed of shorter segments of the blunt-end type in a “closed architecture.” © 1997 John Wiley & Sons, Inc. Biopoly 42: 561–574, 1997     

Factors Influencing Formation of Sclerotia in Grifola umbellate （Pers.） Pilaet Under Artificial Conditions

The effects of substrate composition and temperature on myceilal growth and sclerotium production in Grlfola umbellate （Pers.） Pilaet were Investigated In the present study. The Induction of sclerotla of G. umbellate was affected greatly by the type of medium, as well as the type of carbon source. Malt-extract agar was able to induce the production of sclerotia. The production of sclerotia was also observed when the carbon source in the GPC agar medium （glucose 20 g/L, peptone 6 g/L, corn steep liquor 10 g/L, and agar 15 g/L） was replaced with glycerol or mannitol. Altering the composition of the GPC medium with milk powder, thiamine hydrochlorlde, extract of Armlllarla mellea, active clay, dlatomite, kaolin, or arginlne did not induce the production of sclerotla. A temperature range of 18-25 ℃ was suitable for both mycellai growth and sclerotium formation. Glycerol significantly Induced slerotium formation on nutrient supplemented with sawdust substrates In bottle culture. 24S-Polyporusterone A and polyporusterone B were assayed In samples of natural and cultured sclerotla. Both natural and cultured sclerotla contained 24S- polyporusterone A and polyporusterone B.     

异化铁还原细菌LQ25还原重金属Cr (VI)的特性研究

[背景] 异化铁还原细菌能够在还原Fe （III）的同时将毒性较大的Cr （VI）还原成毒性较小的Cr （III）,解决铬污染的问题。[目的] 基于丁酸梭菌（Clostridium butyricum） LQ25异化铁还原过程制备生物磁铁矿,开展异化铁还原细菌还原Cr （VI）的特性研究。[方法] 构建以氢氧化铁为电子受体和葡萄糖为电子供体的异化铁培养体系。菌株LQ25培养结束时制备生物磁铁矿。设置不同初始Cr （VI）浓度（5、10、15、25和30 mg/L）,分别测定菌株LQ25对Cr （VI）还原效率以及生物磁铁矿对Cr （VI）的还原效率。[结果] 菌株LQ25在设置的Cr （VI）浓度范围内都能良好生长。当Cr （VI）浓度为15 mg/L时,在异化铁培养条件下,菌株LQ25对Cr （VI）的还原率为63.45%±5.13%,生物磁铁矿对Cr （VI）的还原率为87.73%±9.12%,相比菌株还原Cr （VI）的效率提高38%。pH变化能影响生物磁铁矿对Cr （VI）的还原率,当pH 2.0时,生物磁铁矿对Cr （VI）的还原率最高,几乎达到100%。电子显微镜观察发现生物磁铁矿表面有许多孔隙,X-射线衍射图谱显示生物磁铁矿中Fe （II）的存在形式是Fe （OH）₂。[结论] 基于异化铁还原细菌制备生物磁铁矿可用于还原Cr （VI）,这是一种有效去除Cr （VI）的途径。     

Formation of palladium(0) nanoparticles at microbial surfaces

The increasing demand and limited natural resources for industrially important platinum‐group metal (PGM) catalysts render the recovery from secondary sources such as industrial waste economically interesting. In the process of palladium (Pd) recovery, microorganisms have revealed a strong potential. Hitherto, bacteria with the property of dissimilatory metal reduction have been in focus, although the biochemical reactions linking enzymatic Pd(II) reduction and Pd(0) deposition have not yet been identified. In this study we investigated Pd(II) reduction with formate as the electron donor in the presence of Gram‐negative bacteria with no documented capacity for reducing metals for energy production: Cupriavidus necator, Pseudomonas putida, and Paracoccus denitrificans. Only large and close‐packed Pd(0) aggregates were formed in cell‐free buffer solutions. Pd(II) reduction in the presence of bacteria resulted in smaller, well‐suspended Pd(0) particles that were associated with the cells (called “bioPd(0)” in the following). Nanosize Pd(0) particles (3–30 nm) were only observed in the presence of bacteria, and particles in this size range were located in the periplasmic space. Pd(0) nanoparticles were still deposited on autoclaved cells of C. necator that had no hydrogenase activity, suggesting a hydrogenase‐independent formation mechanism. The catalytic properties of Pd(0) and bioPd(0) were determined by the amount of hydrogen released in a reaction with hypophosphite. Generally, bioPd(0) demonstrated a lower level of activity than the Pd(0) control, possibly due to the inaccessibility of the Pd(0) fraction embedded in the cell envelope. Our results demonstrate the suitability of bacterial cells for the recovery of Pd(0), and formation and immobilization of Pd(0) nanoparticles inside the cell envelope. However, procedures to make periplasmic Pd(0) catalytically accessible need to be developed for future nanobiotechnological applications. Biotechnol. Bioeng. 2010;107: 206–215. © 2010 Wiley Periodicals, Inc.     

Nonmetabolic Reduction of Cr(VI) by Bacterial Surfaces Under Nutrient-Absent Conditions

We have measured the ability of nonmetabolizing cells of the bacterial species Bacillus subtilis, Sporosarcina ureae , and Shewanella putrefaciens to reduce aqueous Cr(VI) to Cr(III) in the absence of externally supplied electron donors. Each species can remove significant amounts of Cr(VI) from solution, and the Cr(VI) reduction rate is strongly dependent on solution pH. The fastest reduction rates occur under acidic conditions, with decreasing rates with increasing pH. XANES data demonstrate that Cr(VI) reduction to Cr(III) occurs within the experimental systems. Control experiments indicate that the Cr removal is not a purely adsorptive process. Reduction appears to occur at the cell wall, and is not coupled to the oxidation of bacterial organic exudates. Detailed kinetic data suggest that the reduction involves at least a two-stage process, involving an initial rapid removal mechanism followed by a slower process that follows first-order reaction kinetics. Due to the prevalence of nonmetabolizing cells and cell wall fragments in soils and deeper geologic environments, our results suggest that the observed nonmetabolic reduction of Cr(VI) to Cr(III) may significantly affect the environmental distribution of Cr in bacteria-bearing systems.     

Life History Traits of Two Chaetonotids (Gastrotricha) Under Different Experimental Conditions

Summary

A marine and a freshwater species of Chaetonotida (Gastrotricha) were reared under laboratory conditions. Their life tables and principal demographic parameters were determined at 2 different temperatures (20°and 25°C). At 25°C the data relative to the marine species were collected from 5 cohorts kept at 5 different salinity levels (15, 25, 35, 45, 55°/oo).

A higher temperature increases reproductive activity while shortening its duration in both species, whereas the length of the lifespan remains unaffected. Extreme salinity values (15 and 55°/oo) reduce the maximum longevity of the marine species and have opposite effects on reproductive activity, which is higher at low salinity and becomes lower at high salinity. The postparthenogenetic phase is remarkably long relative to the life cycle: this was observed in all experimental conditions and may be related to the existence of a second reproductive phase, which is hermaphroditic and follows the parthenogenetic one, as recently postulated from morphological data.     

Lacustrine Nostoc (Nostocales) and associated microbiome generate a new type of modern clotted microbialite

Microbialites are mineral formations formed by microbial communities that are often dominated by cyanobacteria. Carbonate microbialites, known from Proterozoic times through the present, are recognized for sequestering globally significant amounts of inorganic carbon. Recent ecological work has focused on microbial communities dominated by cyanobacteria that produce microbial mats and laminate microbialites (stromatolites). However, the taxonomic composition and functions of microbial communities that generate distinctive clotted microbialites (thrombolites) are less well understood. Here, microscopy and deep shotgun sequencing were used to characterize the microbiome (microbial taxa and their genomes) associated with a single cyanobacterial host linked by 16S sequences to Nostoc commune Vaucher ex Bornet & Flahault, which dominates abundant littoral clotted microbialites in shallow, subpolar, freshwater Laguna Larga in southern Chile. Microscopy and energy‐dispersive X‐ray spectroscopy suggested the hypothesis that adherent hollow carbonate spheres typical of the clotted microbialite begin development on the rigid curved outer surfaces of the Nostoc balls. A surface biofilm included >50 nonoxygenic bacterial genera (taxa other than Nostoc) that indicate diverse ecological functions. The Laguna Larga Nostoc microbiome included the sulfate reducers Desulfomicrobium and Sulfospirillum and genes encoding all known proteins specific to sulfate reduction, a process known to facilitate carbonate deposition by increasing pH. Sequences indicating presence of nostocalean and other types of nifH, nostocalean sulfide:ferredoxin oxidoreductase (indicating anoxygenic photosynthesis), and biosynthetic pathways for the secondary products scytonemin, mycosporine, and microviridin toxin were identified. These results allow comparisons with microbiota and microbiomes of other algae and illuminate biogeochemical roles of ancient microbialites.     

Prion protein interaction with glycosaminoglycan occurs with the formation of oligomeric complexes stabilized by Cu(II) bridges

Several lines of evidence have shown glycosaminoglycans (GAGs) to be physiological ligands of the prion protein (PrP), but the molecular and regulatory aspects of the interaction remain unknown. Using full-length recombinant prion protein and low molecular mass heparin and heparan sulfate as glycosaminoglycans, we have found that the interaction occurs with the formation of oligomeric complexes. Within the protein-glycosaminoglycan complexes, PrP exhibited an enhanced fluorescence emission and a reduced solvent exposure. The pH and ionic strength-dependence of the interaction reveals His residues as the main binding sites at acid pH. A synthetic peptide consisting of four octarepeats is able to reproduce the His-dependent binding of the protein, thus demonstrating the role of the octarepeats in the GAG interaction. Alternatively, PrP can bind GAGs through His-bound Cu(II). These Cu(II) bridges promote a tighter interaction, as shown by the increased resistance to ionic strength, to protease action, and to pH-induced cation release. Inspection of other cations shows that Zn(II) but not Ni(II) shares the interaction trend. Taken together, our data suggest that the octarepeat region constitutes a novel GAG-binding sequence and that His-bound Cu(II) may act as a cofactor for intermolecular recognition reactions, allowing the formation of PrP-Cu(II)-glycosaminoglycan assemblies that may be crucial entities in the PrP metabolism.     

Properties of a Wolinella succinogenes mutant lacking periplasmic sulfide dehydrogenase (Sud)

A Δsud deletion mutant of Wolinella succinogenes that lacked the periplasmic sulfide dehydrogenase (Sud) was constructed using homologous recombination. The mutant grew with sulfide and fumarate, indicating that Sud was not a component of the electron transport chain that catalyzed fumarate respiration with sulfide as an electron donor. Likewise, growth with formate and either polysulfide or sulfur was not affected by the deletion. Removal of Sud from wild-type W. succinogenes by spheroplast formation did not decrease the activity of electron transport to polysulfide. The Δpsr deletion mutant that lacks polysulfide reductase (Psr) grew by fumarate respiration with sulfide as an electron donor, indicating that Psr is not required for this activity. Received: 31 August 1995 / Accepted: 25 October 1995     

Life Cycle of the Tick Haemaphysalis Leporis-palustris (Acari: Ixodidae) Under Laboratory Conditions

The life cycles of two separate populations (colonies A and B) of the rabbit tick, Haemaphysalis leporis-palustris, were studied under laboratory conditions. Domestic New Zealand rabbits, Oryctolagus cuniculus, and wild rabbits, Sylvilagus brasiliensis, were used as hosts for ticks from colony B and only O. cuniculus rabbits were used as hosts for ticks from colony A. Developmental periods were observed in an incubator at 27±1°C and RH 90±5%. Larvae from colonies A and B fed for 8.0±3.7 days and 8.5±1.3 days, respectively, on O. cuniculus. On S. brasiliensis larvae from colony B fed for 7.2±1.3 days. Nymphs from colony A fed for 8.1±1.4 days on O. cuniculus and nymphs from colony B fed for 8.1±1.0 days on S. brasiliensis. Only one engorged nymph from colony B was recovered from O. cuniculus. Females from colony A fed for 20.9±5.9 days on O. cuniculus and females from colony B fed for 18.6±2.4 days on O. cuniculus and 18.7±3.7 days on S. brasiliensis. Engorged larvae from colony A required 13.7±3.7 days to molt while engorged larvae from colony B required 11.8±3.0 and 11.5±1.8 days to molt, after having fed on O. cuniculus and S. brasiliensis, respectively. Engorged nymphs from colonies A and B required 16.3±1.9 days and 14.7±1.4 days to molt, respectively. Engorged females from colonies A and B required 4–7 and 3–5 days, respectively, to start oviposition. Mean egg incubation periods lasted for 33–34 days. For ticks from colony B, host species accounted for significant differences (p<0.05) in larval and nymphal feeding periods, oviposition weights and CEIs. Significant differences (p<0.05) between the two colonies when ticks fed on O. cuniculus were observed for larval and nymphal feeding and premolt periods, engorged female and oviposition weights and conversion efficiency indexes (CEI). S. brasiliensis were always a more suitable host for H. leporis-palustris than O. cuniculus. Significantly more larvae and nymphs engorged and molted when fed on S. brasiliensis (p<0.001). Females fed S. brasiliensis were more successful to lay fertile eggs and showed the highest engorged and egg mass weights, and the highest CEIs. Data of H. leporis-palustris fed on wild rabbits (one of its natural host species) are reported for the first time.     

Terbium (III) coordination polymer–copper (II) compound as fluorescent probe for time‐resolved fluorescence ‘turn‐on’ detection of hydrogen sulfide

With recognition of the biological importance of hydrogen sulfide (H₂S), we present a simple and effective fluorescent probe for H₂S using a Tb³⁺ coordination polymer–Cu²⁺ compound (DPA/Tb/G–Cu²⁺). Dipicolinic acid (DPA) and guanosine (G) can coordinate with Tb³⁺ to form a macromolecular coordination polymer (DPA/Tb/G). DPA/Tb/G specifically binds to Cu²⁺ in the presence of coexisting cations, and obvious fluorescence quenching is observed. The quenched fluorescence can be exclusively recovered upon the addition of sulfide, which is measured in the mode of time‐resolved fluorescence. The fluorescence intensities of the DPA/Tb/G–Cu²⁺ compound enhance linearly with increasing sulfide concentrations from 1 to 30 μM. The detection limit for sulfide in aqueous solution is estimated to be 0.3 μM (at 3σ). The DPA/Tb/G–Cu²⁺ compound was successfully applied to sense H₂S in human serum samples and exhibited a satisfactory result. It displays some desirable properties, such as fast detection procedure, high selectivity and excellent sensitivity. This method is very promising to be utilized for practical detection of H₂S in biological and environmental samples.     

Cellular Responses of Gelidium floridanum (Gelidiales,Rhodophyta) Tetraspores Under Heat Wave and Copper Pollution

Spore settlement and development are bottlenecks for resilience of habitat‐forming macroalgal species. These processes are directly related to temperature, a global stressor protagonist of ocean warming. The toxic effects of local pollutants such as copper may be worsened under a global warming scenario. Therefore, in this paper, we investigated the effects of increased temperature combined with elevated concentrations of copper on the viability, photosynthetic pigments, and ultrastructure of Gelidium floridanum tetraspores. Tetraspores were cultivated on slides with sterilized seawater or seawater enriched with CuCl₂, and incubated under 24°C or 30°C for 24 h. Tetraspores cultivated with copper 3.0 μM under 30°C had lower viability. Both temperature and copper had a significant effect on phycocyanin and phycoerythrin concentrations. Samples cultivated with copper under 30°C presented a heavily altered cellular structure, with vesicles throughout the cytoplasm, chloroplasts with altered structure and cells with degenerated cytoplasm and cell walls. Our findings show that temperature and copper significantly affect the viability, photosynthetic pigments, and ultrastructure of G. floridanum tetraspores, presenting an additive interaction for the physiology of this seaweed's early stages.