Bioremediation of Pb-contaminated soil based on microbially induced calcite precipitation

To remediate lead (Pb)-contaminated soils, it is proposed that microbially induced calcite precipitation (MICP) would provide the best alternative to other remediation technologies. In this study, Pb bioremediation in soils was investigated using the calcite-precipitating bacterium Kocuria flava. Results indicate that the Pb is primarily associated with the carbonate fraction in bioremediated soil samples. The bioavailability of Pb in contaminated soil was reduced so that the potential stress of Pb was alleviated. This research provides insight into the geochemistry occurring in the MICP-based Pb-remediated soils, which will help in remediation decisions.     

Improved strength and durability of fly ash-amended concrete by microbial calcite precipitation

Fly ash acts as a partial replacement material for both Portland cement and fine aggregate. An innovative approach of microbial calcite precipitation in fly ash-amended concrete has been investigated. This is the first report to discuss the role of microbial calcite precipitation in enhancing the durability of fly ash-amended concrete. The present study investigated the effects of Bacillus megaterium ATCC 14581 on compressive strength, water absorption and water impermeability of fly ash-amended mortar and concrete. Mortar specimens were used for compressive strength and water absorption tests, while concrete specimens were used for water impermeability tests. At the fly ash concentrations of 10%, 20% and 40% in mortars, bacterial cell enhanced mortar compressive strength by 19%, 14% and 10%, respectively, compared to control specimens. Treated mortar cubes absorbed more than three times less water than control cubes as a result of microbial calcite deposition. Microbial deposition of a layer of calcite on the surface of the concrete specimens resulted in substantial decrease of water uptake and permeability compared to control specimens without bacteria. Microbial cells also prevented ingress of water effectively in different concentrations of fly ash-amended concrete. Scanning Electron Micrography (SEM) analyses evidenced the direct involvement of bacteria in calcite precipitation. The approach of the present study gives us dual environment friendly advantages. First, use of fly ash-a recovered resource reduces depletion of natural resources and also reduces the energy-intensive manufacturing of other concrete ingredients, leading to savings in both energy usage and emissions of greenhouse gases. And second, use of bacterial cells to improve strength and durability of fly ash-amended concrete further provides greener and economic options.     

Construction of two ureolytic model organisms for the study of microbially induced calcium carbonate precipitation

Two bacterial strains, Pseudomonas aeruginosa MJK1 and Escherichia coli MJK2, were constructed that both express green fluorescent protein (GFP) and carry out ureolysis. These two novel model organisms are useful for studying bacterial carbonate mineral precipitation processes and specifically ureolysis-driven microbially induced calcium carbonate precipitation (MICP). The strains were constructed by adding plasmid-borne urease genes (ureABC, ureD and ureFG) to the strains P. aeruginosa AH298 and E. coli AF504gfp, both of which already carried unstable GFP derivatives. The ureolytic activities of the two new strains were compared to the common, non-GFP expressing, model organism Sporosarcina pasteurii in planktonic culture under standard laboratory growth conditions. It was found that the engineered strains exhibited a lower ureolysis rate per cell but were able to grow faster and to a higher population density under the conditions of this study. Both engineered strains were successfully grown as biofilms in capillary flow cell reactors and ureolysis-induced calcium carbonate mineral precipitation was observed microscopically. The undisturbed spatiotemporal distribution of biomass and calcium carbonate minerals were successfully resolved in 3D using confocal laser scanning microscopy. Observations of this nature were not possible previously because no obligate urease producer that expresses GFP had been available. Future observations using these organisms will allow researchers to further improve engineered application of MICP as well as study natural mineralization processes in model systems.     

Phylogenetic reassessment of Hyaloscyphaceae sensu lato (Helotiales, Leotiomycetes) based on multigene analyses

Hyaloscyphaceae is the largest family in Helotiales, Leotiomycetes. It is mainly characterized by minute apothecia with well-differentiated hairs, but its taxonomic delimitation and infrafamilial classification remain ambiguous. This study performed molecular phylogenetic analyses using multiple genes including the ITS-5.8S rDNA, the D1–D2 region of large subunit of rDNA, RNA polymerase II subunit 2, and the mitochondrial small subunit. The primary objective was to evaluate the phylogenetic utility of morphological characters traditionally used in the taxonomy of Hyaloscyphaceae through reassessment of the monophyly of this family and its genera. The phylogenetic analyses inferred Hyaloscyphaceae as being a heterogeneous assemblage of a diverse group of fungi and not supported as monophyletic. Among the three tribes of Hyaloscyphaceae only Lachneae formed a monophyletic lineage. The presence of hairs is rejected as a synapomorphy, since morphologically diversified hairs have originated independently during the evolution of Helotiales. The true- and false-subiculum in Arachnopezizeae are hypothesized to have evolved through different evolutionary processes; the true-subiculum is likely the product of a single evolutionary origin, while the false-subiculum is hypothesized to have originated multiple times. Since Hyaloscyphaceae sensu lato was not resolved as monophyletic, Hyaloscyphaceae sensu stricto is redefined and only applied to the genus Hyaloscypha.     

Characterization of a copper-resistant symbiotic bacterium isolated from Medicago lupulina growing in mine tailings

A root nodule bacterium, Sinorhizobium meliloti CCNWSX0020, resistant to 1.4 mM Cu²⁺ was isolated from Medicago lupulina growing in mine tailings. In medium supplied with copper, this bacterium showed cell deformation and aggregation due to precipitation of copper on the cell surface. Genes similar to the copper-resistant genes, pcoR and pcoA from Escherichia coli, were amplified by PCR from a 1.4-Mb megaplasmid. Inoculation with S. meliloti CCNWSX0020 increased the biomass of M. lupulina grown in medium added 0 and 100 mg Cu²⁺ kg⁻¹ by 45.8% and 78.2%, respectively, and increased the copper concentration inside the plant tissues grown in medium supplied with 100 μM Cu²⁺ by 39.3%, demonstrating that it is a prospective symbiotic system for bioremediation purposes.     

Effect of biosurfactant and fertilizer on biodegradation of crude oil by marine isolates of Bacillus megaterium, Corynebacterium kutscheri and Pseudomonas aeruginosa

This study was conducted to investigate the effects of fertilizers and biosurfactants on biodegradation of crude oil by three marine bacterial isolates; Bacillus megaterium, Corynebacterium kutscheri and Pseudomonas aeruginosa. Five sets of experiments were carried out in shake flask and microcosm conditions with crude oil as follows: Set 1-only bacterial cells added (no fertilizer and biosurfactant), Set 2-with additional fertilizer only, Set 3-with additional biosurfactant only, Set 4-with added biosurfactant + fertilizer, Set 5-with no bacterial cells added (control), all the above experimental sets were incubated for 168 h. The biosurfactant + fertilizer added Set 4, resulted in maximum crude oil degradation within shake flask and microcosm conditions. Among the three bacterial isolates, P. aeruginosa and biosurfactant produced by this strain resulted in maximum crude oil degradation compared to the other two bacterial strains investigated. Interestingly, when biosurfactant and bacterial cells were used (Set 3), significant oil biodegradation activity occurred and the difference between this treatment and that in Set 4 with added fertilizer + biosurfactant were only 4-5% higher degradation level in shake flask and 3.2-7% in microcosm experiments for all three bacterial strains used. It is concluded that, biosurfactants alone capable of promoting biodegradation to a large extent without added fertilizers, which will reduce the cost of bioremediation process and minimizes the dilution or wash away problems encountered when water soluble fertilizers used during bioremediation of aquatic environments.     

Immobilization of cadmium in soil by microbially induced carbonate precipitation with Exiguobacterium undae at low temperature

Microbially induced carbonate precipitation (MICP) is an advanced biological treatment technology to immobilize heavy metals in form of carbonate salts. In this MICP study, ureolytic Exiguobacterium undae was employed for immobilization of cadmium in contaminated soil at low temperature (10 °C). The sequential extraction test revealed conversion of more than 90% of cadmium in the tested soil from the soluble-exchangeable fraction to carbonate-bound fraction in 14 days of treatment. The cadmium may be precipitated in a separate CdCO₃ phase or be co-precipitated in calcite crystals. Activities of urease and dehydrogenase were enhanced during MICP, which were not affected by the testing temperatures. MICP with E. undae is a biological approach that may be worth investigating further to immobilize cadmium in soils of cold regimes.     

Protective role of Mangifera indica, Cucumis melo and Citrullus vulgaris peel extracts in chemically induced hypothyroidism

An investigation was made to evaluate the pharmacological importance of fruit peel extracts of Mangifera indica (MI), Citrullus vulgaris (CV) and Cucumis melo (CM) with respect to the possible regulation of tissue lipid peroxidation (LPO), thyroid dysfunctions, lipid and glucose metabolism. Pre-standardized doses (200 mg/kg of MI and 100 mg/kg both of CV and CM), based on the maximum inhibition in hepatic LPO, were administered to Wistar albino male rats for 10 consecutive days and the changes in tissue (heart, liver and kidney) LPO and in the concentrations of serum triiodothyronine (T₃), thyroxin (T₄), insulin, glucose, α-amylase and different lipids were examined. Administration of three test peel extracts significantly increased both the thyroid hormones (T₃ and T₄) with a concomitant decrease in tissue LPO, suggesting their thyroid stimulatory and antiperoxidative role. This thyroid stimulatory nature was also exhibited in propylthiouracil (PTU) induced hypothyroid animals. However, only minor influence was observed in serum lipid profile in which CM reduced the concentrations of total cholesterol and low-density lipoprotein-cholesterol (LDL-C), while CV decreased triglycerides and very low-density lipoprotein-cholesterol (VLDL-C). When the combined effects of either two (MI + CV) or three (MI + CV + CM) peel extracts were evaluated in euthyroid animals, serum T₃ concentration was increased in response to MI + CV and MI + CV + CM treatments, while T₄ level was elevated by the combinations of first two peels only. Interestingly, both the categories of combinations increased T₄ levels, but not T₃ in PTU treated hypothyroid animals. Moreover, a parallel increase in hepatic and renal LPO was observed in these animals, suggesting their unsafe nature in combination. In conclusion the three test peel extracts appear to be stimulatory to thyroid functions and inhibitory to tissue LPO but only when treated individually.     

Differential gene expression of the honey bees Apis mellifera and A. cerana induced by Varroa destructor infection

Varroa destructor mite is currently the most serious threat to the world bee industry. Differences in mite tolerance are reported between two honey bee species Apis mellifera and Apis cerana. Differential gene expression of two honey bee species induced by V. destructor infection was investigated by constructing two suppression subtractive hybridization (SSH) libraries, as first steps toward elucidating molecular mechanisms of Varroa tolerance. From the SSH libraries, we obtained 289 high quality sequences which clustered into 132 unique sequences grouped in 26 contigs and 106 singlets where 49 consisted in A. cerana subtracted library and 83 in A. mellifera. Using BLAST, we found that 85% sequences had counterpart known genes whereas 15% were undescribed. A Gene Ontology analysis classified 51 unique sequences into different functional categories. Eight of these differentially expressed genes, representative of different regulation patterns, were confirmed by qRT-PCR. Upon the mite induction, the differentially expressed genes from both bee species were different, except hex 110 gene, which was up-regulated in A. cerana but down-regulated in A. mellifera, and Npy-r gene, which was down-regulated in both species. In general, most of the differential expression genes were involved in metabolic processes and nerve signaling. The results provide information on the molecular response of these two bee species to Varroa infection.     

柠檬酸和EDTA对铜污染土壤环境中吊兰生长的影响

通过盆栽试验研究了在铜污染条件下,柠檬酸和EDTA作为活化剂对铜污染土壤中吊兰生长状况的影响.结果表明,柠檬酸和EDTA对吊兰富集量的影响与其对土壤中铜的活化能力呈显著性正相关.柠檬酸对土壤铜有较强的活化作用,能够有效提高吊兰对铜的吸收,且在浓度为5mmol/L时效果最为明显,而较高的铜富集量又抑制了吊兰的生长;EDTA对吊兰富集能力的影响相对较弱,对吊兰的生长也无显著影响.相比而言,柠檬酸对铜污染土壤中吊兰生长状况的影响比EDTA大.     

A putative serine protease,SpSsp1, from Saprolegnia parasitica is recognised by sera of rainbow trout, Oncorhynchus mykiss

Saprolegniosis, the disease caused by Saprolegnia sp., results in considerable economic losses in aquaculture. Current control methods are inadequate, as they are either largely ineffective or present environmental and fish health concerns. Vaccination of fish presents an attractive alternative to these control methods. Therefore we set out to identify suitable antigens that could help generate a fish vaccine against Saprolegnia parasitica. Unexpectedly, antibodies against S. parasitica were found in serum from healthy rainbow trout, Oncorhynchus mykiss. The antibodies detected a single band in secreted proteins that were run on a one-dimensional SDS-polyacrylamide gel, which corresponded to two protein spots on a two-dimensional gel. The proteins were analysed by liquid chromatography tandem mass spectrometry. Mascot and bioinformatic analysis resulted in the identification of a single secreted protein, SpSsp1, of 481 amino acid residues, containing a subtilisin domain. Expression analysis demonstrated that SpSsp1 is highly expressed in all tested mycelial stages of S. parasitica. Investigation of other non-infected trout from several fish farms in the United Kingdom showed similar activity in their sera towards SpSsp1. Several fish that had no visible saprolegniosis showed an antibody response towards SpSsp1 suggesting that SpSsp1 might be a useful candidate for future vaccination trial experiments.     

Biosorption of phenol and 2-chlorophenol by Funaliatrogii pellets

The removal of phenol (Ph) and 2-chlorophenol (2-CPh) from aqueous solution by native and heat inactivated fungus Funaliatrogii pellets were investigated. The effects of contact time, solid/liquid ratio, optimum pH and temperature on the phenols removal capacity by the pellets were established. The removal efficiency of phenols increased significantly with increasing biomass dose. The optimum pH was detected to be 8.0. The second-order equations are described and evaluated on the basis of a comparative estimation of the corresponding coefficients. The phenol removal equilibrium isotherm was modeled by the Langmuir equations. The enthalpy change values were obtained between −7.62 and −10.64 kJ/mol. This indicated that the uptake of phenols either on native or heat inactivated fungal pellets was based on a physical adsorption process.     

Starch grain morphology of the seagrasses Halodule wrightii, Ruppia maritima, Syringodium filiforme, and Thalassia testudinum

Starch grains are a ubiquitous component of plants that have been used in tandem with phytoliths, pollen, and macrofossils to reconstruct past floral diversity. This tool has yet to be fully explored for aquatic plants, specifically seagrasses, which lack phytoliths and are rarely preserved as macrofossils or pollen. If starch grains in seagrasses are morphologically distinct, this method has the potential to improve seagrass identification in the fossil record in such cases where its starch is preserved (e.g. scratches and occlusal surfaces of tooth enamel from seagrass consumers). The goals of this study were twofold: (1) to determine if starch is present in seagrass material and (2) to assess how starch grain morphology differs between different seagrasses.This study focused on four abundant and ecologically distinct seagrasses from the Caribbean: Halodule wrightii, Ruppia maritima, Syringodium filiforme, and Thalassia testudinum. Starch grains were observed in all species except S. filiforme. Grains from H. wrightii are typically observed in side-on orientation, are sub-round to angular, and are fairly small (3-19 μm, end-on). Grains of R. maritima are small spherical grains (4-8 μm) that have a centric hilum and a straight extinction cross with a median angle between the arms of 90°. Grains from T. testudinum are large (9-31 μm, end-on), conical in side-on and round/sub-round in end-on orientation, have a slightly eccentric hilum with an obvious particle, and prominent lamellae.Visual assessment and comparative statistics demonstrate that the morphology of starch grains from T. testudinum, R. maritima, and H. wrightii are significantly different. With more extensive research, there is potential for the positive identification of starch grains from an unknown seagrass. The ability to identify seagrass from starch grains could facilitate the identification of seagrasses in the fossil record and supply information on seagrass evolution and distribution, climate effects on seagrass distribution, and the diets of seagrass consumers.