Rhizobial Populations in Soils from Natural Acacia senegal and Acacia nilotica Forests in Mauritania and the Senegal River Valley

Eighty-two strains of rhizobia were isolated from soils taken from several sites in Mauritania and Senegal. These soil samples were collected from natural stands of Acacia nilotica and Acacia senegal. The soils from Mauritania were less rich in native rhizobia than the soils from Senegal. The strains were characterized using polymerase chain reaction–restriction fragment length polymorphism and by sequencing the rDNA 16S–23S intergenic spacer region (IGS). They were sorted into seven IGS groups. These groups were not associated with the geographical origin of the strains or with the host-plant species at the site where the soils were collected. Most of the strains were in three of the IGS groups (I, IV, and V). One representative strain from each IGS group was sequenced and showed that the strains were from the genus Mesorhizobium. IGS groups I, IV, and VI were close to the species M. plurifarium (AF34563), IGS groups IIand III were close to the species Mesorhizobium sp. (AF510360), IGS group V was close to the species Mesorhizobium sp. (AF510366), and IGS group VII was close to Mesorhizobium sp. (AF510346).     

Cytoskeletal modulation of sodium current in human jejunal circular smooth muscle cells

ANa⁺ current is present in human jejunal circular smoothmuscle cells. The aim of the present study was to determine the role ofthe cytoskeleton in the regulation of the Na⁺ current.Whole cell currents were recorded by using standard patch-clamptechniques with Cs⁺ in the pipette to block K⁺currents. Cytochalasin D and gelsolin were used to disrupt the actincytoskeleton and phalloidin to stabilize it. Colchicine was used todisassemble the microtubule cytoskeleton (and intermediate filaments)and paclitaxel to stabilize it. Acrylamide was used to disrupt theintermediate filament cytoskeleton. Perfusion of the recording chamberat 10 ml/min increased peak Na⁺ current recorded fromjejunal smooth muscle cells by 27 ± 3%. Cytochalasin D andgelsolin abolished the perfusion-induced increase in Na⁺current, whereas incubation with phalloidin, colchicine, paclitaxel, oracrylamide had no effect. In conclusion, the Na⁺ currentexpressed in human jejunal circular smooth muscle cells appears to beregulated by the cytoskeleton. An intact actin cytoskeleton is requiredfor perfusion-induced activation of the Na⁺ current.

     

Evidence of Sundaland’s subsidence requires revisiting its biogeography

It is widely accepted that sea level changes intermittently inundated the Sunda Shelf throughout the Pleistocene, separating Java, Sumatra and Borneo from the Malay Peninsula and from each other. On this basis, the dynamics of the biodiversity hotspot of Sundaland is consistently regarded as solely contingent on glacial sea level oscillations, with interglacial highstands creating intermittent dispersal barriers between disjunct landmasses. However, recent findings on the geomorphology of the currently submerged Sunda shelf suggest that it subsided during the Pleistocene and that, over the Late Pliocene and Quaternary, is was never submerged prior to Marine Isotope Stage 11 (MIS 11, 400 ka). This would have enabled the dispersal of terrestrial organisms regardless of sea level variations until 400 ka and hampered movements thereafter, at least during interglacial periods. Existing phylogeographic data for terrestrial organisms conform to this scenario: available divergence time estimates reveal an 8- to 9-fold increase in the rate of vicariance between landmasses of Sundaland after 400 ka, corresponding to the onset of episodic flooding of the Sunda shelf. These results highlight how reconsidering the paleogeographic setting of Sundaland challenges understanding the mechanisms generating Southeast Asian biodiversity.     

Optimisation of the operational conditions of trichloroethylene degradation using Trametes versicolor under quinone redox cycling conditions using central composite design methodology

Extracellular radicals produced by Trametes versicolor under quinone redox cycling conditions can degrade a large variety of pollutant compounds, including trichloroethylene (TCE). This study investigated the effect of the agitation speed and the gas–liquid phase volume ratio on TCE degradation using central composite design (CCD) methodology for a future scale-up to a reactor system. The agitation speed ranged from 90 to 200 rpm, and the volume ratio ranged from 0.5 to 4.4. The results demonstrated the important and positive effect of the agitation speed and an interaction between the two factors on TCE degradation. Although the volume ratio did not have a significant effect if the agitation speed value was between 160 and 200 rpm, at lower speed values, the specific pollutant degradation was clearly more extensive at low volume ratios than at high volume ratios. The fitted response surface was validated by performing an experiment using the parameter combination in the model that maximised TCE degradation. The results of the experiments carried out using different biomass concentrations demonstrated that the biomass concentration had a positive effect on pollutant degradation if the amount of biomass present was lower than 1.6 g dry weight l⁻¹. The results show that the maximum TCE degradation was obtained at the highest speed (200 rpm), gas–liquid phase volume ratio (4.4), and a biomass concentration of 1.6 g dry weight l⁻¹.     

A comparative life cycle assessment of two treatment technologies for the Grey Lanaset G textile dye: biodegradation by Trametes versicolor and granular activated carbon adsorption

Purpose

The aim of this study is to use life cycle assessment (LCA) to compare the relative environmental performance of the treatment using Trametes versicolor with a common method such as activated carbon adsorption. This comparison will evaluate potential environmental impacts of the two processes. This work compiles life cycle inventory data for a biological process that may be useful for other emergent biotechnological processes in water and waste management. LCA was performed to evaluate the use of a new technology for the removal of a model metal-complex dye, Grey Lanaset G, from textile wastewater by means of the fungus T. versicolor. This biological treatment was compared with a conventional coal-based activated carbon adsorption treatment to determine which alternative is preferable from an environmental point of view.

Materials and methods

The study is based on experimental research that has tested the novel process at the pilot scale. The analysis of the biological system ranges from the production of the electricity and ingredients required for the growth of the fungus and ends with the composting of the residual biomass from the process. The analysis of the activated carbon system includes the production of the adsorbent material and the electricity needed for the treatment and regeneration of the spent activated carbon. Seven indicators that measure the environmental performance of these technologies are included in the LCA. The indicators used are climate change, ozone depletion, human toxicity, photochemical oxidant formation, terrestial acidification, freshwater eutrophication, marine eutrophication, terrestrial ecotoxicity, freshwater ecotoxicity, marine ecotoxicity, metal depletion and fossil depletion.

Results

The results show that the energy use throughout the biological process, mainly for sterilisation and aeration, accounts for the major environmental impacts with the inoculum sterilisation being the most critical determinant. Nevertheless, the biological treatment has lower impacts than the physicochemical system in six of these indicators when steam is generated directly on site. A low-grade carbon source as an alternative to glucose might contribute to reduce the eutrophication impact of this process.

Conclusions

The LCA shows that the biological treatment process using the fungus T. versicolor to remove Grey Lanaset G offers important environmental advantages in comparison with the traditional activated carbon adsorption method. This study also provides environmental data and an indication of the potential impacts of characteristic processes that may be of interest for other applications in the field of biological waste treatment and wastewater treatment involving white-rot fungi.     

Phylogenetics and phylogeography of the monocot genus Baldellia (Alismataceae): Mediterranean refugia, suture zones and implications for conservation

Aquatic plants, and especially the emblematic genus Baldellia (Alismataceae), are among the most threatened organisms, due to unprecedented human-driven habitat destructions. Therefore protection plans are crucially needed and call for thoroughly documenting the genetic diversity and clarifying the taxonomy of this endangered genus. Our sampling included 282 individuals from 42 natural populations and covered the whole geographical range of the genus, across Europe and the Mediterranean. We combined sequencing of nuclear internal transcribed spacer (ITS) and chloroplastic trnL-ndhF regions with amplified fragment length polymorphism (AFLP) genotyping to investigate the Alismataceae phylogeny, and produce a phylogeography of Baldellia. Our phylogeny strongly supported the monophyly of Baldellia and placed it as the sister clade to Luronium and Alisma, therefore excluding, as previously supposed, a close genetic relatedness to the predominantly neotropical genus Echinodorus. The phylogeography of Baldellia outlined patterns consistent with a hypothesis considering glacial refugia located in the Iberian Peninsula and the Italy/Balkan region from which two distinct genetic lineages re-colonized Europe. These two lineages corresponded respectively to Baldellia ranunculoides (Italy/Balkan derived populations) and Baldellia repens (populations recovered from the Iberian Peninsula refuge), therefore supporting differences outlined between the two taxa in previous ecological and morphological studies. These results allowed clarifying taxonomic uncertainties by confirming the genetic distinctness of B. repens according to B. ranunculoides. A third lineage, Baldellia alpestris, originated and remained endemic to the mountainous regions of the Iberian Peninsula. Unexpectedly, B. repens populations collected in northern Africa, appeared to be genetically distinct from their European counterparts, this calls for further investigation to fully address their genetic and conservation status. Finally, we detected a large hybridization zone in northwestern Europe between B. repens and B. ranunculoides. These results were discussed in light of conservation approaches for Baldellia populations.     

Assessment of genome organization among diploid species (2n = 2x = 14) belonging to primary and tertiary gene pools of pearl millet using fluorescent in situ hybridization with rDNA probes.

Two contrasting forms of Pennisetum belonging to the primary and tertiary gene pools were assessed for genomic organization using in situ hybridization with rDNA probes (18S-5.8S-25S and 5S) on metaphase and interphase cell nuclei. The primary gene pool is represented by diploid (2n = 2x = 14) cultivated pearl millet (Pennisetum glaucum) and its close wild relatives (Pennisetum violaceum and Pennisetum mollissimum). Pennisetum schweinfurthii (2n = 2x = 14) was taken as representative of the tertiary gene pool, owing to its diploid status and its similarity to the accessions of the primary gene pool in chromosome number. Using the 18S-5.8S-25S probe, we observed two sites of distribution in the four species but at different locations. Within the primary gene pool, signals were detected on the telomeric part of the short arm of chromosome pair VI and at the nucleolar organizing region (NOR) of the satellited chromosome pair (VII). Signals were observed at the NOR of the two satellited chromosome pairs (I and IV) of P. schweinfurthii. The 5S probe was detected at the telomeric part of the short arm of metacentric chromosome pair IV of the three species of the primary gene pool, while it occured in an intercalary position on the short arm of chromosome pair II of P. schweinfurthii. These results showed a chromosomal similarity of rDNA sequence locations within the primary gene pool and are in agreement with the high genetic identity between wild and cultivated forms of pearl millet previously revealed by allozyme studies. Implications of genomic organization for genetic resource enhancement are discussed. Key words : Pennisetum, in situ hybridization, rDNA probes, genomic organization.     

Ostracodes et incursions marines dans l’Holocène terminal du lac Retba (Cap Vert, Sénégal)

The study of marine incursions based on ostracods is carried out for the first time in the late Holocene, with core sediments of the Lac Retba edge. Twenty-four species are identified along the core; most of them are encountered in the Gulf of Guinea shelf and its adjacent lagoons. For the first time Buntonia olokundudui Reyment and Van Valen, Hermanites foveolata Omatsola and Soudanella africana Omatsola are recorded in Senegal. Four ostracods assemblages are evidenced along the core, corresponding to different stages of the lake evolution. Cyprideis nigeriensis Omatsola, Neomonoceratina iddoensis Omatsola and Aglaiocypris gambiensis Witte dominate the first assemblage; they indicate a lagoon slightly open to the sea and bordered with mangrove swamps under relatively humid climate conditions. The second association yields the most diversified ostracod fauna with C. nigeriensis, N. iddoensis and high proportion of reworked “marine species” which evidence a marine little gulf bordered by mangrove under a humid climate. The third, monospecific association (C. nigeriensis) is typical of a closed and hypersaline lagoon under dry climate conditions. An oligospecific association with C. nigeriensis, Pseudoconcha omatsolai Witte and very scarce reworked “marine species” occurs at the top of the core and characterises an open and hypersaline lagoon under arid climate conditions. Ostracods evidence two marine incursions. The first and the stronger one is dated here for the first time between 1420 and 1250 years B.P. The more recent is the weaker and is not yet dated. Evidence of the beginning of the Retba Lake closure towards 680 years B.P. appears at the top of the core, as indicated by high reduction of ostracods abundance, predominance of reticulate Cyprideis and disappearance of the “marine species”, while salts precipitated at the bottom of the lake.     

Chromosome assignments of the human TNF p55 and p75 receptor genes.

At least two different receptor molecules have been described that are capable of binding tumor necrosis factor alpha, a cytokine that plays an important role in inflammation and antitumor activity. Comparative analyses at the nucleotide sequence level suggest that these receptors are members of a newly defined protein family that also includes human and rat nerve growth factor receptors. In this study, we determine the chromosome assignments of the human TNF alpha receptor genes, one of which may have evolved as part of a conserved Hox locus-containing chromosome segment.