Description: From the establishment of proper cultivation conditions of phototrophic sulfur bacteria 50 years ago up to today significant improvements have been made to systematically treat the phototrophic green and purple sulfur bacteria and identify them in environmental communities. Important steps for these improvements were first of all the description of a large number of pure cultures representing a proper fraction of environmental diversity, their correct taxonomic treatment and the clear definition of the taxa. Further important steps were the establishment of a phylogenetics-based taxonomy supported by 16S rRNA gene sequences and the demonstration of congruence between phylogenies based on 16S rRNA genes and functional genes. The formation of a large database of fmoA genes of green sulfur bacteria and of pufLM genes of purple sulfur bacteria and their obvious phylogenetic congruence with the 16S rRNA gene enabled detailed studies of environmental communities of these bacteria and the recognition of species and genera in natural habitats. The comprehensive studies of selected habitats yielded promising results and demonstrated the potential of this approach for the systematic characterization of environmental communities.

Description: 17-20 May 2011 Fort de Vaise, 25 Boulevard de Saint Exupery, Lyon, France

Description: Although marine controlled source electromagnetic (CSEM) methods are effective for investigating offshore freshened groundwater (OFG) systems, interpreting the spatial extent and salinity of OFG remains challenging. Integrating CSEM resistivity models with information on sub-surface properties, such as host-rock porosity, allows for estimates of pore-water salinity. However, deterministic inversion approaches pose challenges in quantitatively analyzing these estimates as they provide only one best-fit model with no associated estimate of model parameter uncertainty. To address this limitation, we employ a trans-dimensional Markov-Chain Monte-Carlo inversion on marine CSEM data, under the assumption of horizontal stratification, collected from the Canterbury Bight, New Zealand. We integrate the resulting posterior distributions of electrical resistivity with borehole and seismic reflection data to quantify pore-water salinity with uncertainty estimates. The results reveal a low-salinity groundwater body in the center of the survey area at varying depths, hosted by consecutive silty- and fine-sand layers approximately 20 to 60 km from the coast. These observations support the previous study’s results obtained through deterministic 2-D inversion and suggest freshening of the OFG body closer to the shore within a permeable, coarse-sand layer 40 to 150 m beneath the seafloor. This implies a potential active connection between the OFG body and the terrestrial groundwater system. We demonstrate how the Bayesian approach constrains the uncertainties in resistivity models and subsequently in pore-water salinity estimates. Our findings highlight the potential of Bayesian inversions in enhancing our understanding of OFG systems, providing crucial boundary conditions for hydrogeological modeling and sustainable water resource development.

Description: Nonmammalian tooth-bearing vertebrates usually replace their teeth throughout life. Much about how a replacement pattern is generated has been learned from zebrafish. However, to understand general mechanisms of tooth replacement, advantage can be taken from studying other, “nonmodel” species. We have mapped the patterns of tooth replacement in widely divergent aquatic osteichthyans using 2D charts, in which one axis is time, the other linear spacing along the tooth row. New teeth that are generated simultaneously are considered part of the same odontogenic wave. Using this approach, it appears that a similar, general pattern underlies very distinctive dentitions in distantly related species. A simple shift in spacing of odontogenic waves, or in distance between subsequent tooth positions along a row (or both), can produce dramatically different dentitions between life stages within a species, or between closely related species. Examples will be presented from salmonids, cyprinids, and cichlids. Our observations suggest that lines linking subsequent positions may have more biological significance than replacement waves (usually linking alternate positions), often used to explain the generation of patterns. The presence of a general pattern raises questions about common control mechanisms. There is now increasing evidence, at least for the zebrafish, to support a role for stem cells in continuous tooth renewal and control of replacement patterns.