Modeling and analysis of layered stationary anaerobic granular biofilms

A model that portrays substrate profiles in a steady-state multispecies granular biofilm is developed and coupled with a biofilm detachment model. The model accounts for glucose, propionate, hydrogen, and acetate transformations performed by three bacterial trophic groups: acidogens, syntrophic bacterial consortia, and methanogens. This model adequately describes the phenomenon of propionate degradation under thermodynamically unfavorable bulk hydrogen concentrations. Also suggested is the superiority of the layered biofilm structure over homogeneous distribution of the trophic groups for anaerobic degradation of organic compounds. Furthermore, model analysis suggests that with increasing bulk glucose concentration biofilm thickness reaches a maximum that is then followed by biofilm disintegration. These results may have an important impact on the design and control of upflow anaerobic sludge bed reactors. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 122-130, 1997.     

Performances of a full-scale novel multiplate anaerobic reactor treating cheese whey effluent

A 450-m(3) multiplate anaerobic reactor (MPAR) has been started-up in April 1992 for treating wastewater (whey permeate and domestic wastewater) at the Nutrinor (Lactel) cheese factory in Chambord (Québec, Canada). The MPAR consists of four superimposed sections. The liquid flows upwards from one section to the next, while the gas is collected below each plate and evacuated through side-outlets. The wastewater is concurrently distributed at the bottom of the first, second, and third sections, as 50%, 33%, and 17% of the total influent stream, respectively. Granular anaerobic sludge at an initial concentration of 30 kg of volatile suspended solids (VSS) per cubic meter of reactor liquid volume was used to inoculate the reactor. Under normal operation of the factory, the chemical oxygen demand (COD) concentration of the influent ranged from 20 to 37 kg COD m(-3). The reactor organic loading rate (OLR) fluctuated between 9 and 14.7 kg COD m(-3) d(-1) for hydraulic retention times (HRT) maintained between 55 and 68 h. At the highest OLR, the MPAR showed an efficiency of 98% and 92% for soluble and total COD removal, respectively, and a methane production rate averaging around 4 m(3) m(-3) d(-1).Biomass-specific activities ranged between 7 and 51, 1.3 and 8.5, 5.3 and 12.2, 60 and 119, and 119 and 211 mmol g(-1) VSS d(-1) for glucose, propionate, acetate, formate, and hydrogen, respectively. Average equivalent-diameter of the granules was around 0.65 mm. The MPAR reactor generally showed a large capacity for solid retention with a biomass content between 32 and 37 kg VSS m(-3). (c) 1995 John Wiley & Sons, Inc.     

Ecotoxicological Evaluation of a Bench-Scale Bioslurry Treating Explosives-Spiked Soil

The ecotoxicological effects of four bioslurry reactors treating 2,4,6-trinitotoluene (TNT)- and 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX)-spiked soil were evaluated. A control bioslurry reactor was used to assess the endogenous toxicity of the bioslurry operation conditions. A battery of ecotoxicity tests was used: Microtox, green algae growth inhibition, bacterial genotoxicity and mutagenicity, and earthworm mortality and growth inhibition. Bioslurry soluble and solid phases were separated by centrifugation in order to identify toxicity and possible toxicants associated with each phase. Microtox toxicity values were initially very high in both bioslurry reactors spiked with TNT, in relation with TNT concentration. Initial toxicity was also detected by algal growth inhibition, earthworm lethality, genotoxicity and mutagenicity tests. An endogenous toxicity was detected in the control bioreactor using the Microtox and the SOS Chromotest. The soluble phase of the control bioslurry was genotoxic, suggesting that some potentially genotoxic agents were induced in the bioslurry samples. At the end of the bioremediation treatment, data showed that toxicity was reduced using all of the bioassays, except for earthworm lethality and growth inhibition tests in both RDX-spiked bioslurries. This study demonstrates the usefulness of a battery of toxicity tests to monitor bioremediation processes.     

Methane production in an UASB reactor operated under periodic mesophilic-thermophilic conditions

Methane production was studied in a laboratory-scale 10 L anaerobic upflow sludge bed (UASB) reactor with periodic variations of the reactor temperature. On a daily basis the temperature was varied between 35 and 45 degrees C or 35 and 55 degrees C with a heating period of 6 h. Each temperature increase was accompanied by an increase in methane production and a decrease in the concentration of soluble organic matter in the effluent. In comparison to a reactor operated at 35 degrees C, a net increase in methane production of up to 22% was observed. Batch activity tests demonstrated a tolerance of mesophilic methanogenic populations to short-term, 2-6 h, temperature increases, although activity of acetoclastic methanogens decreased after 6 h exposure to a temperature of 55 degrees C. 16S sequencing of DGGE bands revealed proliferation of temperature-tolerant Methanospirillum hungatii sp. in the reactor.     

Biome reconstruction from pollen and plant macrofossil data for Africa and the Arabian peninsula at 0 and 6000 years

Biome reconstruction from pollen and plant macrofossil data provides an objective method to reconstruct past vegetation. Biomes for Africa and the Arabian peninsula have been mapped for 6000 years bp and provide a new standard for the evaluation of simulated palaeovegetation distributions. A test using modern pollen data shows the robustness of the biomization method, which is able to predict the major vegetation types with a high confidence level. The application of the procedure to the 6000 years data set (pollen and plant macrofossil analyses) shows systematic differences from the present that are consistent with the numerous previous regional and continental interpretations, while providing a more extensive and more objective basis for such interpretations. Madagascar, eastern, southern and central Africa show only minor changes in terms of biomes, compared to present. Major changes in biome distributions occur north of 15°N, with steppe in many low-elevation sites that are now desert, and temperate xerophytic woods/scrub and warm mixed forest in the Saharan mountains. These shifts in biome distributions imply significant changes in climate, especially precipitation, between 6000 years and present, reflecting a change in monsoon extent combined with a southward expansion of Mediterranean influence.     

Liming impact on granules activity of the multiplate anaerobic reactor (MPAR) treating whey permeate

A 19.2 l multiplate anaerobic reactor (MPAR) was used to assess the impact of lime (Ca(OH)₂) on the anaerobic treatment of whey permeate effluents. The amount of Ca(OH)₂ required to maintain the pH of the whey permeate around 5 ranged between 3.0 and 4.5 kg/m³, which corresponded to concentration varying between 1.62 and 2.43 kg/m³. Soluble chemical oxygen demand (COD) removal efficiency exceeded 92% with a methane production rate of 6.7 m³/m³.d. at an organic loading rate (OLR) as high as 20 kg COD/m³.d. Extended operation of the MPAR resulted in the accumulation of significant amounts of calcium precipitates in the sludge bed which reached after three months of operation 0.19, 0.25 and 0.33 kg Ca²⁺ per kg of suspended solid (SS) in the lower, the middle and the upper compartment of the MPAR, respectively. The volatile suspended solids to suspended solids ratio (VSS/SS) decreased from 0.83 in inoculum to 0.37, 0.22 and 0.08 in the lower, the middle and the upper compartment of the MPAR, respectively. As a result, the soluble COD reduction and the methane production rate decreased to 31% and to 2.3 m³/m³.d. respectively, at OLR of 20 kg COD/m³.d.The authors thank Saputo Cheese Ltd. for providing the whey permeate effluents, Alain Corriveau for expert analytical assistance and Hervé Macarie for revising the article. NRC Paper No. 33907     

The Fungal Exopolysaccharide Galactosaminogalactan Mediates Virulence by Enhancing Resistance to Neutrophil Extracellular Traps

Of the over 250 Aspergillus species, Aspergillus fumigatus accounts for up to 80% of invasive human infections. A. fumigatus produces galactosaminogalactan (GAG), an exopolysaccharide composed of galactose and N-acetyl-galactosamine (GalNAc) that mediates adherence and is required for full virulence. Less pathogenic Aspergillus species were found to produce GAG with a lower GalNAc content than A. fumigatus and expressed minimal amounts of cell wall-bound GAG. Increasing the GalNAc content of GAG of the minimally pathogenic A. nidulans, either through overexpression of the A. nidulans epimerase UgeB or by heterologous expression of the A. fumigatus epimerase Uge3 increased the amount of cell wall bound GAG, augmented adherence in vitro and enhanced virulence in corticosteroid-treated mice to levels similar to A. fumigatus. The enhanced virulence of the overexpression strain of A. nidulans was associated with increased resistance to NADPH oxidase-dependent neutrophil extracellular traps (NETs) in vitro, and was not observed in neutropenic mice or mice deficient in NADPH-oxidase that are unable to form NETs. Collectively, these data suggest that cell wall-bound GAG enhances virulence through mediating resistance to NETs.     

2H,3H-Decafluoropentane-Based Nanodroplets: New Perspectives for Oxygen Delivery to Hypoxic Cutaneous Tissues

Perfluoropentane (PFP)-based oxygen-loaded nanobubbles (OLNBs) were previously proposed as adjuvant therapeutic tools for pathologies of different etiology sharing hypoxia as a common feature, including cancer, infection, and autoimmunity. Here we introduce a new platform of oxygen nanocarriers, based on 2H,3H-decafluoropentane (DFP) as core fluorocarbon. These new nanocarriers have been named oxygen-loaded nanodroplets (OLNDs) since DFP is liquid at body temperature, unlike gaseous PFP. Dextran-shelled OLNDs, available either in liquid or gel formulations, display spherical morphology, ~600 nm diameters, anionic charge, good oxygen carrying capacity, and no toxic effects on human keratinocytes after cell internalization. In vitro OLNDs result more effective in releasing oxygen to hypoxic environments than former OLNBs, as demonstrated by analysis through oxymetry. In vivo, OLNDs effectively enhance oxy-hemoglobin levels, as emerged from investigation by photoacoustic imaging. Interestingly, ultrasound (US) treatment further improves transdermal oxygen release from OLNDs. Taken together, these data suggest that US-activated, DFP-based OLNDs might be innovative, suitable and cost-effective devices to topically treat hypoxia-associated pathologies of the cutaneous tissues.     

Advantages and disadvantages of phytolith analysis for the reconstruction of Mediterranean vegetation: an assessment based on modern phytolith, pollen and botanical data (Luberon, France)

We present here the results of a first study comparing modern soil phytolith assemblages with pollen and botanical data at a North Mediterranean site. This work has shown the following limitations and advantages of phytolith analysis for the reconstruction of Mediterranean vegetation:(1) Phytoliths are produced in sufficient quantities for analysis and are well preserved in limestone environments, widespread in the Mediterranean area. (2) Young stands of Quercus ilex and Quercus coccifera, widely distributed in the Mediterranean area do not produce characteristic phytolith types in sufficient quantities to allow the calculation of a reliable index of tree cover density. (3) Pine forests, dominated by Pinus halepensis and Pinus sylvestris, are not recorded in the studied phytolith assemblages. (4) Grassland and shrubland assemblages can be distinguished through their associated phytolith assemblages, in particular by the proportion of crenate phytoliths produced in the short cells of the grass epidermis. (5) The different vegetation groups on the massif cannot be distinguished by pollen analysis. Further studies, comparing modern phytolith assemblages and quantitative vegetation data, should be carried out on forest plots that have been established for several centuries to further assess the role of phytolith analysis in vegetation reconstructions in the Mediterranean region.     

Common molecular pathways involved in human CD133+/CD34+ progenitor cell expansion and cancer

Background  

Uncovering the molecular mechanism underlying expansion of hematopoietic stem and progenitor cells is critical to extend current therapeutic applications and to understand how its deregulation relates to leukemia. The characterization of genes commonly relevant to stem/progenitor cell expansion and tumor development should facilitate the identification of novel therapeutic targets in cancer.