Consequences of lysine auxotrophy for Candida albicans adherence and biofilm formation

A number of factors are known to be involved in Candida albicans virulence, although biofilm development on the surfaces of indwelling medical devices is considered to promote superficial or systemic disease. Based on previously reported up-regulation of saccharopine and acetyllysine in biofilm cells and activation of the lysine biosynthesis/degradation pathway, we investigated the consequences of Candida albicans lysine auxotrophy on adhesion to host tissues and biofilm formation. Our data indicate that mutant strains lysΔ21/lysΔ22, defective in homocitrate synthase, and lysΔ4, defective in homoaconitase activity (the first two α-aminoadipate pathway enzymes), are able to adhere to mouse embryonic fibroblast cells (cell line NIH/3T3) to the same extent as a control strain SC5314. On the other hand, the auxotrophic mutant strains' development on mouse fibroblast monolayers was significantly reduced up to 5 h post infection. Although invasion into human-derived oral epithelial cells was unaltered, both mutant strains formed a significantly different biofilm architecture and demonstrated diminished viability during long term biofilm propagation.