Recherche scientifique et enquête policière, une analogie didactique

En vue d’attirer les élèves vers des carrières scientifiques, les auteurs proposent de leur faire lire des romans policiers dans le cadre des cours de français et de littérature. L’article comprend deux parties. Dans la première, les parentés entre la démarche scientifique et l’enquête policière sont mises en évidence. Dans la deuxième partie, on propose d’initier les adolescents aux critiques littéraires qui se sont donné pour mission de vérifier si les coupables identifiés par les détectives de romans policiers célèbres sont les vrais coupables. Cet exercice permet de développer un esprit critique et un sain scepticisme face aux théories auxquelles ils seront initiés tout au long de leur curriculum scolaire.To attract students to scientific careers, the authors suggest detective novels be read in Language Arts classes. The article has two parts. First, the similarities between the scientific process and the police investigation are illustrated. Second, a proposal is made to introduce adolescents to literary criticism in the goal of verifying if the guilty parties identified by the detectives in famous detective novel are indeed guilty. This exercise develops critical thinking and a healthy scepticism toward the theories they will be presented with throughout their academic career

Impact of Groundwater Flow on Permafrost Degradation and Transportation Infrastructure Stability

INE/AUTC 13.0

Cyclic Di-GMP Riboswitch-Regulated Type IV Pili Contribute to Aggregation of Clostridium difficile

Clostridium difficile is an anaerobic Gram-positive bacterium that causes intestinal infections with symptoms ranging from mild diarrhea to fulminant colitis. Cyclic diguanosine monophosphate (c-di-GMP) is a bacterial second messenger that typically regulates the switch from motile, free-living to sessile and multicellular behaviors in Gram-negative bacteria. Increased intracel- lular c-di-GMP concentration in C. difficile was recently shown to reduce flagellar motility and to increase cell aggregation. In this work, we investigated the role of the primary type IV pilus (T4P) locus in c-di-GMP-dependent cell aggregation. Inactivation of two T4P genes, pilA1 (CD3513) and pilB1 (CD3512), abolished pilus formation and significantly reduced cell aggregation un- der high c-di-GMP conditions. pilA1 is preceded by a putative c-di-GMP riboswitch, predicted to be transcriptionally active upon c-di-GMP binding. Consistent with our prediction, high intracellular c-di-GMP concentration increased transcript levels of T4P genes. In addition, single-round in vitro transcription assays confirmed that transcription downstream of the predicted transcription terminator was dose dependent and specific to c-di-GMP binding to the riboswitch aptamer. These results support a model in which T4P gene transcription is upregulated by c-di-GMP as a result of its binding to an upstream transcriptionally activating riboswitch, promoting cell aggregation in C. difficile.Clostridium difficile is an anaerobic Gram-positive bacterium that causes intestinal infections with symptoms ranging from mild diarrhea to fulminant colitis. Cyclic diguanosine monophosphate (c-di-GMP) is a bacterial second messenger that typically regulates the switch from motile, free-living to sessile and multicellular behaviors in Gram-negative bacteria. Increased intracellular c-di-GMP concentration in C. difficile was recently shown to reduce flagellar motility and to increase cell aggregation. In this work, we investigated the role of the primary type IV pilus (T4P) locus in c-di-GMP-dependent cell aggregation. Inactivation of two T4P genes, pilA1 (CD3513) and pilB1 (CD3512), abolished pilus formation and significantly reduced cell aggregation un- der high c-di-GMP conditions. pilA1 is preceded by a putative c-di-GMP riboswitch, predicted to be transcriptionally active upon c-di-GMP binding. Consistent with our prediction, high intracellular c-di-GMP concentration increased transcript levels of T4P genes. In addition, single-round in vitro transcription assays confirmed that transcription downstream of the predicted transcription terminator was dose dependent and specific to c-di-GMP binding to the riboswitch aptamer. These results support a model in which T4P gene transcription is upregulated by c-di-GMP as a result of its binding to an upstream transcriptionally activating riboswitch, promoting cell aggregation in C. difficile

Efficient avian pollination of Strelitzia reginae outside of South Africa

AbstractIn its native South Africa, endemic birds pollinate the complex flowers of Strelitzia reginae (bird of paradise) through a highly complex method of pollination. The plant is cultivated worldwide in warm-temperated regions but systematic pollination of the ornithophilous species by local birds has not been reported, and, consequently, seed production is rare outside of South Africa. We found that a member of the New World warblers, Geothlypis trichas, efficiently carried out pollination of S. reginae in southern California, thereby supplementing its typical diet of insects with the energy-rich nectar of S. reginae. Only occasionally, seeds were found in plantings not visited by these birds. The pollinator service provided by the warbler increases seed production in an area outside of South Africa. This could lead to adaptive changes in the exotic species, advance species establishment and persistence and possibly promote invasive behavior in a non-native environment

New insights on Prestosuchus chiniquensis Huene, 1942 (Pseudosuchia, Loricata) based on new specimens from the “Tree Sanga” Outcrop, Chiniqua´ Region, Rio Grande do Sul, Brazil

The 'rauisuchians' are a group of Triassic pseudosuchian archosaurs that displayed a near global distribution. Their problematic taxonomic resolution comes from the fact that most taxa are represented only by a few and/or mostly incomplete specimens. In the last few decades, renewed interest in early archosaur evolution has helped to clarify some of these problems, but further studies on the taxonomic and paleobiological aspects are still needed. In the present work, we describe new material attributed to the 'rauisuchian' taxon Prestosuchus chiniquensis, of the Dinodontosaurus Assemblage Zone, Middle Triassic (Ladinian) of the Santa Maria Supersequence of southern Brazil, based on a comparative osteologic analysis. Additionally, we present well supported evidence that these represent juvenile forms, due to differences in osteological features (i.e., a subnarial fenestra) that when compared to previously described specimens can be attributed to ontogeny and indicate variation within a single taxon of a problematic but important osteological structure in the study of 'rauisuchians.'

Late Pleistocene yedoma in south-western Yukon (Canada): a remnant of Eastern Beringia?

Yedoma deposits developed from the syngenetic accumulation and freezing of organic-rich and ice-rich sediments during the Late Pleistocene over vast portions of Siberia, Alaska and Yukon Territory. Cryostratigraphic investigations revealed the presence of a yedoma deposit in the Beaver Creek area of south-western Yukon. The Beaver Creek area was not glaciated during the last glacial advance and the cryostratigraphic record comprises Middle Wisconsinian up to Holocene deposits covering the Mirror Creek disintegration moraine. Reworking of glacial deposits by alluvial and solifluction processes and peat accumulation in the depression of the hummocky moraine likely occurred during the Middle Wisconsinian period and was followed during the Late Wisconsinian by the yedoma build-up. A major thaw event interrupted the syngenetic permafrost aggradation which eventually resumed as attested by the upward growth of ice wedges

The palate and choanae structure of the Susisuchus anatoceps (Crocodyliformes, Eusuchia): phylogenetic implications

Crocodyliformes is a group with a broad fossil record, in which several morphological changes have been documented. Among known transformations the most iconic is perhaps the series of changes seen in the structural evolution of the choanae. The change in the position of the choanae was important during the evolutionary history of the Crocodyliformes. This structure is relevant in the phylogenetic position of many crocodyliforms. The new skull of Susisuchus anatoceps from the Crato Formation of the Santana Group (Lower Cretaceous) is described and the preservation in the ventral view allows character encoding not yet observed for the species. The new specimen shows a typical eusuchian palate for Susisuchus anatoceps, in which the choana is fully enclosed by the pterygoid. The Susisuchidae clade has been placed in different phylogenetic positions: as a sister group of Eusuchia, advanced Neosuchia and in Eusuchia. In Isisfordia there are reports that the choana of this taxon is or is not fully enclosed by the pterygoid. The encoding of the ventral characters of S. anatoceps places Susisuchidae in Eusuchia. However, this position must be further studied, since the matrices showed fragility in the reconstitution of the Neosuchia–Eusuchia transition

Primeiro registro de Caiman (Crocodilya, Alligatoridae) para o Pleistoceno do Estado do Rio Grande do Sul, Brasil

A first record of Alligatoridae reptiles is made to the coastal plain deposits from Rio Grande do Sul State, in southern Brazil. The fossil bone represents a part of a left premaxilla and is probably related to the lagoon sediments of the Barrier-Lagoon System III, considered to be formed at 120 ka and exposed at Hermenegildo Beach, Santa Vitória do Palmar city. In spite of its incomplete preservation, the comparison with modern specimens and other elements of the family from South America suggests its relation with the modern genus Caiman. Key-words: Alligatoridae, Caiman, Pleistocene, Coastal Plain, Rio Grande do Sul, Brazil.A presença de répteis da família Alligatoridae é registrada pela primeira vez em depósitos da Planície Costeira do Rio Grande do Sul. O fóssil, representado por um fragmento incompleto de pré-maxila esquerda, foi identificado entre o material depositado na praia do Balneário Hermenegildo, em Santa Vitória do Palmar, com provável origem a partir dos níveis lagunares do Sistema Laguna-Barreira III, datados como correspondendo a 120 ka. Apesar de seu caráter incompleto, a comparação com formas recentes e com outros elementos da família para a América do Sul permite associá-lo ao gênero Caiman. Palavras chaves: Alligatoridae, Caiman, Pleistoceno, Planície Costeira, Rio Grande do Sul, Brasil

Primeiro registro de Caiman (Crocodilya, Alligatoridae) para o Pleistoceno do Estado do Rio Grande do Sul, Brasil

A first record of Alligatoridae reptiles is made to the coastal plain deposits from Rio Grande do Sul State, in southern Brazil. The fossil bone represents a part of a left premaxilla and is probably related to the lagoon sediments of the Barrier-Lagoon System III, considered to be formed at 120 ka and exposed at Hermenegildo Beach, Santa Vitória do Palmar city. In spite of its incomplete preservation, the comparison with modern specimens and other elements of the family from South America suggests its relation with the modern genus Caiman. Key-words: Alligatoridae, Caiman, Pleistocene, Coastal Plain, Rio Grande do Sul, Brazil.A presença de répteis da família Alligatoridae é registrada pela primeira vez em depósitos da Planície Costeira do Rio Grande do Sul. O fóssil, representado por um fragmento incompleto de pré-maxila esquerda, foi identificado entre o material depositado na praia do Balneário Hermenegildo, em Santa Vitória do Palmar, com provável origem a partir dos níveis lagunares do Sistema Laguna-Barreira III, datados como correspondendo a 120 ka. Apesar de seu caráter incompleto, a comparação com formas recentes e com outros elementos da família para a América do Sul permite associá-lo ao gênero Caiman. Palavras chaves: Alligatoridae, Caiman, Pleistoceno, Planície Costeira, Rio Grande do Sul, Brasil