Non-Invasive Quantification of Plasmid Dynamics:Biofilm Formation Effect on Plasmid conjugational plasmid transfer

摘要

Both the age of biofilms and the available nutrient concentrations play important roles in conjugational plasmid transfer in biofilms. At the early stage of pre-mature biofilms, nutrient concentration affects the formation of biofilms by varying the cell growth and biomass accumulation. Efficiencies of plasmid transfer appear to be independent of the variation in nutrient concentration in these early stages. In contrast, for mature biofilms with heterogeneous architecture (tulip-shaped clusters and water-filled channels and voids), the spatial structure of the biofilm has an impact on gene transfer. The availability of nutrients does not directly affect conjugational plasmid transfer within biofilms through metabolic effects on individual populations, but rather by indirectly affecting biofilm structure. Low nutrient concentrations resulted in porous biofilm clusters with open channels that enabled easier cell access and deeper penetration of donor cells throughout the biofilms, leading to faster spread of genes by conjugative plasmid transfer. Donors were found deep inside biofilms formed in flow cells. More donor cells in deeper biofilms were observed with longer incubation time between recipient biofilms and donor cells. In contrast, thick uniform and densely packed biofilm clusters were formed under the condition of high nutrient concentrations, where lower plasmid transfer rates and efficiencies were observed. Thus, penetration of donor cells within the biofilm is architecture dependent.