Establishment of endosymbiosis: the case of cnidarians and <i>Symbiodinium</i>

The symbiosis between cnidarians and Symbiodinium algae (dinoflagellates) is the keystone responsible for the formation of the huge and important structures that are coral reefs. Today many environmental and/or anthropogenic threats compromise this tight relationship and lead to more frequent events of drastic loss of Symbiodinium pigments and eventually of algae themselves from cnidarians, better known as cnidarian bleaching. While the mechanisms underlying the collapse of the algae–coral symbiosis are progressively getting unraveled, the understanding of the mechanisms involved in the de novo infection of bleached cnidarians by Symbiodinium remains elusive. In this review, we describe the various steps needed to establish a stable symbiotic relationship between Symbiodinium and cnidarians. We review the mechanisms implicated in host–symbiont recognition and in symbiosome formation and persistence, with a special emphasis on the role played by lectins and Rab proteins. A better understanding of these molecular mechanisms may contribute to the development of strategies to promote post-bleaching recovery of corals

Détermination du régime hydrodynamique dans une colonne à bulles par tomographie électrique résistive

peer reviewe

A possible new mineral species, "ferrogatehouseite" (Fe,Mn)5(PO4)2(OH)4 from Conţu Pegmatite, Romania.

peer reviewe

A structural, magnetic, and Mossbauer spectral study of several Na-Mn-Fe-bearing alluaudites

The synthesis and the chemical, structural, magnetic, and Mossbauer spectral characterization of three synthetic alluaudites, Na2Mn2Fe(PO4)(3), NaMn Fe-2(PO4)(3) and (Na2MnFeFeIII)-Fe-II(PO4)(3), and a natural sample with the nominal composition of NaMn Fe-2(PO4)(3), collected in the Buranga pegmatite, Rwanda, are reported. All four compounds have the expected alluaudite monoclinic C2/c structure with the general formula [A(2)A(2)'][A(1)A(1)'A(1)(2)'']M(1)M(2)(2)(PO4)(3) in which manganese(II) is on the M(1) site and manganese(II), iron(III) and, in some cases, iron(II) on the M(2) site. The X-ray structure of Na2Mn2Fe(PO4)(3) also indicates a partially disordered distribution of Na-I and Mn-II on the M(1) and A(1) crystallographic sites. All four compounds are paramagnetic above 40 K and antiferromagnetically ordered below. Above 40 K the effective magnetic moments of NaMnFe2(PO4)(3) and Na2MnFeII Fe-III(PO4)(3) are those expected of high-spin manganese(II) and iron(III) with the (6)A(1g) electronic ground state and high-spin iron(II) with the T-5(2g) electronic ground state. In contrast, the effective magnetic moment of Na2Mn2Fe(PO4)(3) is lower than expected as a result of enhanced antiferromagnetic exchange coupling by the manganese(II) on the M(2) site. The Mossbauer spectra of all four compounds have been measured from 4.2 to 295 K and have been found to be magnetically ordered below 40 K for Na2Mn2Fe(PO4)(3) and similar to35 K for the remaining compounds. The Mossbauer spectra of Na2Mn2Fe(PO4)(3) exhibit the two expected iron(III) quadrupole doublets and/or magnetic sextets expected for a random distribution of manganese(II) and iron(III) ions on the M(2) site. Further, the Mossbauer spectra of (Na2MnFeFeIII)-Fe-II(PO4)(3) exhibit the two iron(II) and two iron(III) quadrupole doublets and/or magnetic sextets expected for a random distribution of iron(II) and iron(III) on the M(2) site. Surprisingly, the synthetic and natural samples of NaMnFe2(PO4)(3) have 19 and 10% of iron(II) on the M(2) site; apparently the presence of some iron(II) stabilizes the alluaudite structure through the reduction of iron(III)-iron(III) repulsion. The temperature dependence of the iron(II) quadrupole splitting yields a 440 to 600 cm(-1) low-symmetry component to the octahedral crystal field splitting at the M(2) site. The iron(II) and iron(III) hyperfine fields observed at 4.2 K are consistent with the presence of antiferromagnetic ordering at low temperatures in all four compounds

An overview of electrical tomographic measurements in pharmaceutical and related application areas

Tomographic measurement techniques offer the opportunity to quantify the degree of homogeneity of particulate suspensions and other multiphase mixtures. Electrical resistance tomography is a relatively simple and inexpensive technique for measuring the distribution of electrical conductivity within multiphase systems. This can provide pertinent information about the physical form, the chemical composition, or the general status of manufacturing. In this contribution, we present recent applications of this technology to processes in pharmaceutical and related application areas. Examples include on-line measurement of solids distribution in stirred tanks and crystallizers, monitoring the performance of an industrial pressure filter, and flow profile and velocity measurements in a physical model of a catalytic reactor

Increased Cell Proliferation and Mucocyte Density in the Sea Anemone Aiptasia pallida Recovering from Bleaching

Recovery of coral after bleaching episodes is a critical period for the health of the reef ecosystem. While events such as symbiont (genus Symbiodinium) shifting/shuffling or tissue apoptosis have been demonstrated to occur following bleaching, little is known concerning tissue recovery or cell proliferation. Here, we studied the sea anemone Aiptasia pallida exposed to a transient elevation of water temperature combined with high illumination (33°C and 1900 μmolphotons.m.s for 30h). Following such treatment bleached anemones showed a significant reduction of their Symbiodinium density. Cell proliferation in the ectodermis and gastrodermis was determined by assessing the densities of cells labeled with a thymidine analogue (EdU). Cell proliferation significantly increased during the first day following stress in both tissue types. This increased cell proliferation returned to pre-stress values after one week. Although cell proliferation was higher in the ectodermis in absence of stress, it was relatively more pronounced in the gastrodermis of stressed anemones. In addition, the ratio of ectodermal mucocytes significantly increased three weeks after induced stress. These results suggest that thermal/photic stress coupled with the loss of the symbionts is able to enhance cell proliferation in both gastrodermis and ectodermis of cnidarians. While new cells formed in the gastrodermis are likely to host new Symbiodinium, the fate of new cells in the ectodermis was only partially revealed. Some new ectodermal cells may, in part, contribute to the increased number of mucocytes which could eventually help strengthen the heterotrophic state until restoration of the symbiosis