Candida albicans and Staphylococcus aureus are opportunistic pathogens which can be found in and on an estimated 30% of healthy humans worldwide. While they are typically commensal members of the human microflora, they can become pathogenic, especially in immunocompromised individuals. C. albicans is a dimorphic fungus and transition from yeast to hyphal growth is one of its many virulence factors. Yeast-to-hyphae transitions occur in response to environmental changes, including shifts in temperature, pH, and CO2 concentration and hyphal morphology, branching frequency, and cell wall composition can vary depending on the environmental cues provoking the transition. Hyphae form biofilms on organs and implanted medical devices and can penetrate tissues. S. aureus can bind to C. albicans hyphal tips and take advantage of C. albicans-induced epithelial damage to be carried through the epithelium into the bloodstream. However, how C. albicans hyphal density and branching frequency affect S. aureus growth and its ability to traverse a biofilm and access hyphal tips is not well understood.
Results/Conclusions
We hypothesized that while low density or highly branched C. albicans hyphal growth would increase the ability of S. aureus to disperse through liquid media by providing a solid substrate on which S. aureus could employ its sliding motility, high density or infrequently branched hyphal growth would impede S. aureus dispersal by packing too tightly to permit bacterial passage. Here, we established C. albicans biofilms, used changes in abiotic growth conditions to manipulate hyphal morphology, density, and branching frequency, and measured the effects of those changes on S. aureus population size and travel time across the biofilm. We found that spatial patterns in C. albicans hyphal growth can impact S. aureus growth and dispersal as we predicted.