The survival of organisms in evolving environments is driven by their fitness. The cost-benefit ratio of traits is constantly balanced and gives rise to different populational evolutionary strategies. To succeed, organisms will have to compete, cooperate and/or specialize as a result of how fit their traits are considering their biotic and abiotic environment. Bacteria are unicellular organisms with therefore little option to specialize and give up certain traits production to limit their metabolic costs, unlike multicellular organisms that present many different forms of specialized cells in one single organism. However, auxotrophic bacteria (i.e bacteria lacking genes coding for a molecule essential for their survival) have been studied (Morris et al., 2012). Auxotroph bacteria can take advantage of the leaky functions of helper’s organisms to fulfil their needs in specific compounds (Morris et al., 2014, Estrela et al., 2016). With a reduced genetic material, the beneficiary organism fitness is improved, at the risk of being dependent on the helpers presence in their environment. The conditions in which patterns of such division of labor (DOL) arise are still obscure, but its advantages for bacterial population are clear: DOL allows to diminish the cost associated to certain functions and the possibility of cohabitation of various mutants/specialized cells within the population to respond as a whole to environmental constraints, and thrive.
The goal of the internship is to explore how the environmental pressures and nutrient availability modulate functional dependencies, within a root-colonizer bacterial species, Pseudomonas brassicacearum. The experimental set up will include a wild type strain (R401) and mutant(s) unable to produce certain molecules, grown together in an automated system. The skills developed during the project will concern microbiology, biotechnology (Millidrop AzurEvo), statistics, and possibly molecular biology depending on the outcomes of the experiments.
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