The chemolithotrophic bacterium Thiobacillus ferrooxidans

Abstract: The iron-oxidizing bacterium ThiobaciUus ferrooxidans is the most important microorganism in mineral leaching. It plays the dominant role in bioextractive processes because of its ability to oxidize both iron and reduced sulfur compounds. T. ferrooxidans is also an important microorganism in acid rock/mine drainage, a serious environmental problem. In this article, the current status of this bacterium is described with particular emphasis on the biomining industry.     

Copper and antimony extraction from tetrahedrite‐containing dolomite heterotrophic bacteria

Three hundred and thirty‐five strains of heterotrophic bacteria, isolated from various metal‐containing ores, were tested in submerged culture for their capacity to leach copper and antimony from tetrahedrite‐containing dolomitic ore (particle size <0.1 mm; Schwaz, Austria). Experiments showed that after 8 days of incubation, it was possible to differentiate between active and inactive strains. Maximum extraction values for copper (1.0%) and antimony (1.6%) were achieved with Pseudomonas spp. after 8 days. Final pH values were 6.8 in sterile controls and slightly alkaline (up to pH 8.3) in inoculated flasks. Starch and glutamine (C/N ratio of 50:1) proved to be the best carbon and nitrogen sources for growth. Variation of the C/N source resulted in only a very slight increase in the rates of extraction for copper and antimony. Not even 24 h preliminary incubation of a culture before the ore was added improved metal extraction.     

Transformation and Transport of Nitrogen Forms in a Sandy Entisol Following a Heavy Loading of Ammonium Nitrate Solution: Field Measurements and Model Simulations

Understanding the factors influencing water and nutrient transport through soil profile is important for the efficient management of nutrient and irrigation to minimize nutrient leaching below the rootzone. Transport of NO₃-N and NH₄-N was studied in a Candler fine sand following a heavy loading of a liquid fertilizer containing ammonium nitrate. Both NO₃-N and NH₄-N transported quite rapidly (within 3?d) and accumulated above the clay layer at about depth of 2.7?m. The concentrations of NH₄-N and NO₃-N approached background levels throughout the soil profile by 184?d. More than 50% of ammonium and nitrate contained in the spilled solution leached from the entire depth of soil profile sampled during the first 95?d. The cumulative amount of rainfall during this period was 329?mm, which accounted for 65% of the total rainfall for the entire study period. The concentrations of NH₄-N and NO₃-N at various depths within the entire soil profile reasonably predicted by the Leaching Estimation and Chemistry Model (LEACHM) and compared favorably with the measured concentrations, however, there are few places with high concentrations. The cumulative amount of leachate at the bottom of the soil profile predicted by LEACHM represented 90% of total rainfall that occurred during the study period. This demonstrated a substantial potential for leaching of soluble nutrients through the sandy soil profile.     

Tree species shape the elemental composition in the lichen Hypogymnia physodes transplanted to pairs of spruce and beech trunks

The lichen Hypogymnia physodes was sampled from spruce trunks and we used to assess natural elements in the throughfall from pairs of neighbouring beech (Fagus sylvatica) and spruce (Picea abies) canopies in an unmanaged forest reserve. The beech bark (pH = 4.36 ± 0.13) was less acidic than spruce bark (3.71 ± 0.06). After a 1 yr transplantation onto trunks, lichens on beech had significantly higher concentrations of Ca, K, Mg and P than on spruce, and lower Mn, Zn and C, but had similar Al, B, Fe, N, Na, S and Si concentrations. Base cations (Ca, Mg, K) in lichens highly significantly increased with bark pH, with no overlap between tree species neither for base cations, nor for pH. The results are consistent with the view that trees modify the elemental composition of lichens in their dripzone, and that trees at least to some extent can modify the elemental chemistry of their local surroundings and thus influence ecosystem processes. We discuss lichen transplantation as a method to estimate long-term effects of tree species on local chemical environments.     

Long‐term biochar application promotes rice productivity by regulating root dynamic development and reducing nitrogen leaching

Biochar is beneficial for improving soil quality and crop productivity. However, the long‐term effects of biochar addition on temporal dynamics of plant shoot and root growth, and the changes in soil properties and nitrogen (N) leaching are still obscure. Here, based on a long‐term (7 years) biochar field experiment with rice in northwest China, we investigated the effects of two biochar rates (0 and 9 t ha^?1 year^?1) and two N fertilizer rates (0 and 300 kg N ha^?1 year^?1) on shoot and root growth, root morphology, N leaching, and soil physicochemical properties. The results showed that both biochar and N fertilizer significantly promoted rice growth, with their interaction significant only in some cases. Both fertilizers enhanced rice shoot biomass and N accumulation in various growth stages as well as increased grain yield. Nitrogen fertilizer significantly promoted root growth regardless of biochar application. However, biochar application without N fertilizer increased root biomass and length during the whole growth period, except in the booting stage; biochar with N application promoted root growth at tillering, reduced root biomass but maintained root length with low root diameter and high specific root length during the jointing and booting stages, and then delayed root senescence in the grain filling stage. Long‐term applications of biochar and N fertilizer reduced 10%–12% bulk density of topsoil compared to the control treatment with no N fertilizer and no biochar. Long‐term biochar application also improved soil total organic carbon and concentrations of available N, phosphorus, and potassium. In addition, biochar and N fertilizer applied together significantly reduced nitrate and ammonium concentration in leachate at different soil depths. In conclusion, biochar could regulate root growth, root morphology, soil properties, and N leaching to increase rice N fertilizer‐use efficiency.     

Spatial distribution of ammonia-oxidizing bacteria and archaea across a 44-hectare farm related to ecosystem functioning

Characterization of spatial patterns of functional microbial communities could facilitate the understanding of the relationships between the ecology of microbial communities, the biogeochemical processes they perform and the corresponding ecosystem functions. Because of the important role the ammonia-oxidizing bacteria (AOB) and archaea (AOA) have in nitrogen cycling and nitrate leaching, we explored the spatial distribution of their activity, abundance and community composition across a 44-ha large farm divided into an organic and an integrated farming system. The spatial patterns were mapped by geostatistical modeling and correlations to soil properties and ecosystem functioning in terms of nitrate leaching were determined. All measured community components for both AOB and AOA exhibited spatial patterns at the hectare scale. The patchy patterns of community structures did not reflect the farming systems, but the AOB community was weakly related to differences in soil pH and moisture, whereas the AOA community to differences in soil pH and clay content. Soil properties related differently to the size of the communities, with soil organic carbon and total nitrogen correlating positively to AOB abundance, while clay content and pH showed a negative correlation to AOA abundance. Contrasting spatial patterns were observed for the abundance distributions of the two groups indicating that the AOB and AOA may occupy different niches in agro-ecosystems. In addition, the two communities correlated differently to community and ecosystem functions. Our results suggest that the AOA, not the AOB, were contributing to nitrate leaching at the site by providing substrate for the nitrite oxidizers.     

The dynamic viscoelasticity and plasticizer leachability of tissue conditioners

doi: 10.1111/j.1741‐2358.2012.00639.x
The dynamic viscoelasticity and plasticizer leachability of tissue conditioners Objectives: Dynamic viscoelasticity is one of the most important characteristics of tissue conditioners. Leaching of plasticizer from tissue conditioners may cause changes in the dynamic viscoelasticity of these materials. The purpose of this study was to determine the dynamic viscoelasticity and plasticizer leachability of commercial tissue conditioners. Materials and methods: Five commercial tissue conditioners were used in this study: COE Comfort (CC), Fit Softer (FS), Hydro‐Cast (HC), Soft Conditioner (SC) and Visco‐Gel (VG). Five specimens of each material were stored in 37°C distilled water. The dynamic viscoelasticity and plasticizer leaching of each specimen were measured at 0, 1, 3, 7 and 14 days after immersion using a dynamic mechanical analyzer and high performance liquid chromatography. Data were analyzed using one‐way anova and Student–Newman–Keuls test (α = 0.05). Results: Significant differences in dynamic viscoelasticity and plasticizer leaching were found among the materials. The dynamic viscoelasticity of all materials increased or decreased significantly with time. Rapid changes in dynamic viscoelasticity were evident on day 1 after water immersion. The material CC recorded the highest level of plasticizer leaching. Conclusion: These results suggest that the dynamic viscoelasticity of commercial tissue conditioners is affected by plasticizer leaching. However, these effects are limited.     

Bioleaching of a Complex Co-Ni-Cu Sulfide Flotation Concentrate by Bacillus megaterium QM B1551 at Neutral pH

Bioleaching of sulfide minerals at neutral pH has been rarely reported. In this study, a bacterium, Bacillus megaterium QM B1551, was isolated from Jinchuan sulfide tailings and used to leach a complex sulfide flotation concentrate for the extraction of Co²⁺, Ni²⁺ and Cu²⁺ at near neutral pH. A total of 38.2% Co, 44.7% Ni and 3.6% Cu were extracted from the sulfide concentrate in 5 days with an initial pH of 6. An enhanced Co²⁺, Ni²⁺ and Cu²⁺ extraction extent was achieved by first bioleaching the concentrate with Bacillus megaterium QM B1551 at 35°C and then followed by chemical leaching with 4 M sulfuric acid at 90°C. As a result, a total of 60.7% Co²⁺, 76.3% Ni²⁺ and 39.8% Cu²⁺ were extracted. On an industrial scale, the profits from the metal recovery by such a combined leaching procedure are optimum if considering the cost-benefit ratio.     

Metal Leaching and Reductive Dissolution of Iron from Contaminated Soil and Sediment Samples by Indigenous Bacteria and Bacillus Isolates

The purpose of this study was to leach Cu, Zn, As, and Fe from contaminated soil and sediment samples with indigenous heterotrophic bacteria isolated from the study sites. The sediment contained Fe in the form of goethite and low concentrations of other metals. The soil contained hematite and high concentrations of other metals. The environmental conditions affected the bacterial activity in the metals dissolution. As and Fe were the major metals leached from the sediment sample while a minor fraction of Cu was solubilized. Cu and Zn were the major metals leached from the soil sample while only a minor fraction of Fe was dissolved. As a control, a disinfectant was used for partial inactivation of indigenous bacteria. This treatment had a negative effect on the leaching of Fe, Zn and As from soil and sediment samples, but it increased Cu dissolution from the sediment. Bacterial different dissolution of Fe during soil and sediment bioleaching was also investigated with ferrihydrite. The iron concentration was much higher during ferrihydrite dissolution when indigenous bacteria from sediment were used compared to indigenous bacteria isolated from soil. The indigenous bacterial inoculum provided more biological and metabolic diversity which may account for the difference in reductive iron reduction from ferrihydrite. The Bacillus cultures isolated from soil and sediment samples showed similar efficiencies in reductive dissolution of ferrihydrite. The synergetic bacterial inhibition effect created by the environmental conditions can influence bioremediation effect.