Multi-omics Reveals the Lifestyle of the Acidophilic, Mineral-Oxidizing Model Species Leptospirillum ferriphilumT.

Leptospirillum ferriphilum plays a major role in acidic, metal-rich environments, where it represents one of the most prevalent iron oxidizers. These milieus include acid rock and mine drainage as well as biomining operations. Despite its perceived importance, no complete genome sequence of the type strain of this model species is available, limiting the possibilities to investigate the strategies and adaptations that Leptospirillum ferriphilum DSM 14647T (here referred to as Leptospirillum ferriphilum T) applies to survive and compete in its niche. This study presents a complete, circular genome of Leptospirillum ferriphilum T obtained by PacBio single-molecule real-time (SMRT) long-read sequencing for use as a high-quality reference. Analysis of the functionally annotated genome, mRNA transcripts, and protein concentrations revealed a previously undiscovered nitrogenase cluster for atmospheric nitrogen fixation and elucidated metabolic systems taking part in energy conservation, carbon fixation, pH homeostasis, heavy metal tolerance, the oxidative stress response, chemotaxis and motility, quorum sensing, and biofilm formation. Additionally, mRNA transcript counts and protein concentrations were compared between cells grown in continuous culture using ferrous iron as the substrate and those grown in bioleaching cultures containing chalcopyrite (CuFeS2). Adaptations of Leptospirillum ferriphilum T to growth on chalcopyrite included the possibly enhanced production of reducing power, reduced carbon dioxide fixation, as well as elevated levels of RNA transcripts and proteins involved in heavy metal resistance, with special emphasis on copper efflux systems. Finally, the expression and translation of genes responsible for chemotaxis and motility were enhanced.IMPORTANCE Leptospirillum ferriphilum is one of the most important iron oxidizers in the context of acidic and metal-rich environments during moderately thermophilic biomining. A high-quality circular genome of Leptospirillum ferriphilum T coupled with functional omics data provides new insights into its metabolic properties, such as the novel identification of genes for atmospheric nitrogen fixation, and represents an essential step for further accurate proteomic and transcriptomic investigation of this acidophile model species in the future. Additionally, light is shed on adaptation strategies of Leptospirillum ferriphilum T for growth on the copper mineral chalcopyrite. These data can be applied to deepen our understanding and optimization of bioleaching and biooxidation, techniques that present sustainable and environmentally friendly alternatives to many traditional methods for metal extraction

France-Québec : une comparaison de la population des sans-domicile usagers des services d’hébergement ou de distribution de repas

It is difficult to count and describe the persons with no accomodation of their own. The main difficulties relate to the lack of sampling base on this population and to the definition of the notion of “homeless.” This complex exercise has been carried out by both France and Québec. France surveyed users of accommodation and soup run services in January 2001 and Québec counted this population in 1996, then surveyed users of resources for homeless people in 1998-1999. However, before the results of the two societies could be compared, it was first necessary to examine the contexts and methods specific to each survey. Thus, the geographical and institutional fields, the reference periods, the notion of “homeless” and some other particularities were examined in order to define a common area for comparison. This was determined to be single, homeless individuals aged 25 or over who are users of assistance services in very large metropolitan areas on an average day. The results revealed that in both societies, homeless people have in common many characteristics such as age, gender, health, family and occupational history and share similar living conditions. However, they also show differences, in particular relating to the number of foreigners among the homeless in both societies.Dénombrer et caractériser la population sans domicile personnel est un exercice complexe. Les principales difficultés résident dans l’absence de base de sondage couvrant cette population et dans la définition de la notion de «sans domicile». La France et le Québec ont tous deux fait cet exercice. La France a mené une enquête auprès des personnes fréquentant les services d’hébergement ou les distributions de repas chauds en janvier 2001. Le Québec, de son côté, avait effectué un dénombrement en 1996, suivi d’une enquête auprès des usagers des ressources pour personnes itinérantes en 1998-1999. Comparer les résultats d’un pays à l’autre suppose avant tout de s’interroger sur les contextes et les méthodologies propres à chaque enquête. Ainsi, les champs géographique et institutionnel, les périodes de référence, la notion de «sans domicile» et certaines autres particularités sont examinés de manière à identifier un champ commun pour la comparaison. Celui-ci est défini comme comprenant les personnes sans domicile, isolées, âgées de 25 ans et plus, fréquentant les services d’aide des très grandes agglomérations un jour moyen. Les résultats mettent en évidence de nombreuses similitudes dans la population des sans-domicile, en termes de caractéristiques sociodémographiques, de conditions de vie, d’histoire familiale et professionnelle et en matière de santé. Ils montrent toutefois des différences, en particulier sur la part des étrangers parmi les sans-domicile dans les deux sociétés.Aliaga Christel, Brousse Cécile, Fournier Louise, Plante Nathalie. France-Québec : une comparaison de la population des sans-domicile usagers des services d’hébergement ou de distribution de repas. In: Santé, Société et Solidarité, n°1, 2003. Pauvreté et exclusion. pp. 97-113