Fragmented aqueous habitats affect bacterial plasmid transfer in porous environments
- Conference Poster
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Horizontal transfer of plasmids among bacterial populations is critical to genetic exchange and adaptation to environmental stresses. Studies have examined how bacterial cell density, donor-recipient ratio and nutrient availability affect plasmid transfer rates in homogeneous cultures. The insights are useful, however, they often neglect the ubiquitous physical heterogeneity of natural microbial habitats such as soil environments. Our hypothesis is that unsaturated and dynamic water conditions prevailing in most soils lead to fragmentation of the aquatic bacterial habitat, which could enhance plasmid spread through local (microscale) higher cell densities with reduced competition. However, the biophysical processes at play eschew quantitative observations at the cell level owing to soil complexity and opacity. We report and new microfluidic chip comprised of connected microhabitats that permit external control of aqueous fragmentation and observations at the single-cell level. These elements were used to quantify conjugation events in the microchip at various scales as function of fragmentation dynamics. We used the soil bacterium Pseudomonas putida as donor and recipient of a conjugative plasmid carrying a tetracycline resistance gene, while a tagging system with autofluorescent proteins allowed us to distinguish donors and transconjugants with epifluorescence microscopy. We successfully generated various patterns of aqueous fragmentation in the microchips, hence resulting in disconnected aqueous habitats for the bacteria. Plasmid transfer rate in individual microhabitats was linked to local cell densities as well as aqueous and gas phase distribution. This study highlights the importance of microhydrological processes that affect the ecology and evolution of bacteria in natural soil habitats. Show more
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Organisational unit03812 - Or, Dani / Or, Dani
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