Diminished Long and Short Term Range of Diffusive Transport into Candida Albicans Biofilms
Authors:Alina Mitina, Aaron Neumann
Mentor:Aaron Neumann , Assistant Professor , University of New Mexico
Invasive Candidiasis is often associated with fungal biofilms, surface associated microbial communities surrounded by an extracellular matrix, growing on tissues and medical devices. Diffusion is the major mode of transport of solutes throughout the biofilm, and barriers to diffusion within biofilms may influence drug permeation and local intercellular communication in biofilms. We have measured bulk diffusive transport of fluorescent probes into biofilms and predicted that bulk diffusion into biofilm region would be retarded in comparison to non-biofilm regions due to the presence of cells and ECM. At 50% maximal levels permeation of biofilms by fluorescein was significantly retarded in biofilm regions compared to low-biofilm regions (p=0.033). However, dye reached equivalent concentrations inside and outside the biofilm on a time scale too short to explain drug resistance. We would predict that local diffusion is reduced within biofilms, and this would limit the speed with which a cell can communicate at a distance. By directly measuring steady state diffusion in the biofilm via FRAP (fluorescent recovery after photobleaching) at 37ºC we observed that half-time recovery in biofilms was not significantly different in biofilm and low-biofilm regions (p=0.089). However, through FCS (fluorescent correlation spectroscopy) at 22ºC we found that the diffusion coefficients between both regions were significantly different (p=0.044). This signifies that there maybe error in FRAP measurements due to the diffusion being too quick for the lasers scanning speed. These data demonstrate that diffusion of small molecules within biofilms is significantly slowed from their expected rate of free diffusion at 37ºC and at 22ºC, and may be a significant factor in intercellular communication within biofilms. The implications for these measurements in further drug permeation studies could signify that bulk diffusion and steady state diffusion into biofilm region could potentially slow down sooner if the drug interacts with the biofilm as a substrate.