Exploration du potentiel bioindustriel des cultures pures ou mixtes de bactéries pourpres non sulfureuse en conditions photohétérotrophiques

Purple non-sulfur bacteria are well known for their metabolic versatility as they can grow under both auto-and heterotrophic conditions, phototrophically or not. Moreover, they are able to assimilate a broad range of carbon sources notably volatile fatty acids (VFAs, C1-C5) but also sugars. The PROTMIC lab (UMONS) developed a tremendous expertise in the understanding of metabolic pathways used by PNSB, and more precisely Rhodospirillum rubrum, to assimilate VFAs either pure (one source of carbon) or in mix (several source of carbon). This expertise allowed us to decipher the photoheterotrophic assimilation of different VFAs such as acetic acid, butyric acid or valeric acid. In that context, our lab investigated the production of polyhydroxyalkanoate by pure culture of Rhodospirillum rubrum cultivated under photoheterotrophic conditions using acetic acid or valeric acid as source of carbon. More precisely we studied the photoheterotrophic metabolism of Rs. rubrum in the here above-mentioned conditions in order to find some tracks for PHA production optimization. More recently, our lab started analysing the production of protein-rich purple bacteria biomass using bioindustrial co-products as source of carbon. We investigate, currently, at the fundamental (e.g. metabolic pathway, interaction,…) and applied (e.g. protein content, protein quality, productivity,…) point of view the assimilation of molasses by either pure or mix culture of purple bacteria and the impact of different consortia on productivity. Since more than ten years, PNSB are extensively studied for their bioindustrial applications (e.g. Pigment, PHAs, hydrogen, protein-rich edible biomass, wastewater treatment, …). However, in order for the different bioprocesses to be economically feasible, major optimization are still needed. In that context, two schools of thought are commonly found in the literature, the first one stating that the use of pure culture allows higher process optimization thanks to a better understanding whiled the second one arguing that the use of mix culture brings synergic effects that are a key parameter in process improvement. Here, we present examples of the application of these two different strategies to increase bioindustrial productivity of PNSB based bioprocesses. First, using pure culture of Rs. rubrum, we succeeded in increasing PHA production in the presence of acetic and valeric acid thanks to a fundamental knowledge-based approach (e.g. literature reviewing, proteomic analyses, growth under different conditions; Figures 1 and 2). Secondly, we observed recently an increased productivity and substrate assimilation efficiency by switching from pure (e.g. Rs rubrum) to mix (Rs.rubrum and Rh. capsulatus) culture (Figure 3)

Are both autonomy-support and structure really important for engagement and learning?

According to the self-determination theory, autonomy-support and structure are two fostering-engagement and learning practices. However, few studies, mostly correlational, simultaneously tested the effects of both practices on engagement. Regarding learning, studies focused only on autonomy-support and produced inconsistent findings. Some authors found higher learning in autonomy-supportive contexts (Vansteenkiste et al., 2004) while others found higher learning in less autonomy supportive contexts (Furtak and Kunter, 2012). In some cases, the conditions may also have manipulated structure, which would explain contradictory findings. Clearly differentiate the effects of structure and autonomy-support is therefore needed. The current study aimed at testing the main effects and interaction of both dimensions on engagement and learning. Eighty-four students in psychology performed a learning task on computer. They were randomly assigned to one of the four conditions determined by the manipulation of autonomy-support (low vs. high) and structure (moderated vs. high). After the task, participants filled in questionnaires about their engagement and learning. The results showed that they were significantly more engaged and learned more in highly structured conditions. No effects of autonomy-support were found. These results stress the importance of structure for engagement and learning. Contradictory to previous findings, no effects of autonomy-support were found. Given the study design, these results cannot be generalized to all situations. In classroom settings, other variables as teacher support could also be influential for students’ outcomes (Furrer & Skinner, 2003). However, this study is a step forward in the understanding of respective effects of autonomy-support and structure

Disentangling the effects of autonomy-support and structure on engagement and learning

According to the self-determination theory, autonomy-support (opportunities given to students to determine their behaviors and creation of congruence between students’ inner motives and classroom activities) and structure (amount and clarity of information given about the way to achieve desired outcomes; Jang et al., 2010) are two fostering-engagement and learning practices. However, few studies, mostly correlational, simultaneously tested the effects of both practices on engagement. Regarding learning, studies focused only on autonomy-support and produced inconsistent results. Vansteenkiste and colleagues (2004) found higher learning in autonomy-supportive contexts. Furtak and Kunter (2012) found higher learning in the least (e.g. teacher showed how to do) than in the most autonomy-supportive context (e.g. students encouraged to find their own solutions). These conditions may also have manipulated structure, which would explain contradictory findings. Thus, differentiate the effects of structure and autonomysupport is needed. This study aimed at testing the main effects and interaction of both dimensions on engagement and learning. 84 students in psychology performed a learning task on computer. They were randomly assigned to one of the four conditions based on a 2 (moderated vs. high structure) X 2 (low vs. high autonomy-support) between-participants design. Structure was manipulated through the communication of expectations and guidance during the task; autonomy-support, through the opportunity of choice, autonomy-supportive vocabulary, and relevance of examples given (Reeve, 2006; Jang et al., 2010). After the task, participants filled in questionnaires about their engagement and learning. When structure was high, they reported significantly more engagement and learned more, controlling for gender and previous knowledge. No effects of autonomy-support or interaction were found. These results stress the importance of structure for engagement and learning. Contradictory to previous findings, no effects of autonomy-support were found. Given the study design, these results cannot be generalized to all situations. In classroom settings, other variables as teacher support could also be influential for students’ outcomes (Furrer & Skinner, 2003). However, this study is a step forward in the understanding of respective effects of autonomy-support and structure

Démêler les effets du support à l'autonomie et de la structure sur l'engagement et l'apprentissage

Selon la théorie de l’autodétermination, le support à l’autonomie et la structure favorisent l’engagement et l’apprentissage des étudiants. Toutefois, la plupart des études se sont focalisées sur le support à l’autonomie. Peu d’éléments sont dès lors connus sur l’importance relative des deux types de pratiques et sur l’intérêt de les combiner. Cette étude visait à approfondir cette question en testant les effets principaux et interaction du support à l’autonomie et de la structure sur l’engagement et l’apprentissage. 84 étudiants en psychologie, répartis aléatoirement dans 4 conditions (structure - modérée vs. élevée - x support à l’autonomie - faible vs. élevé), ont réalisé une tâche sur ordinateur. Ils ont ensuite rempli des questionnaires mesurant leur engagement et apprentissage. Les étudiants étaient plus engagés et apprenaient davantage dans les conditions plus structurées. Aucun effet du support à l’autonomie n’a été mis en évidence. Ces résultats soulignent l’importance de la structure. Ils ne sont toutefois pas généralisables à l’ensemble des situations d’apprentissage. D’autres variables, comme la relation entre l’enseignant et l’élève, influencent également les étudiants

Behavioural responses to a photovoltaic subretinal prosthesis implanted in non-human primates

International audienceRetinal dystrophies and age-related macular degeneration related to photoreceptor degeneration can cause blindness. In blind patients, although the electrical activation of the residual retinal circuit can provide useful artificial visual perception, the resolutions of current retinal prostheses have been limited either by large electrodes or small numbers of pixels. Here we report the evaluation, in three awake non-human primates, of a previously reported near-infrared-light-sensitive photovoltaic subretinal prosthesis. We show that multipixel stimulation of the prosthesis within radiation safety limits enabled eye tracking in the animals, that they responded to stimulations directed at the implant with repeated saccades and that the implant-induced responses were present two years after device implantation. Our findings pave the way for the clinical evaluation of the prosthesis in patients affected by dry atrophic age-related macular degeneration