Cellular dynamics in liquid static cultures of Aureobasidiumpullulans

Aureobasidium pullulans is used as a bio-protectant of crops and wood and can stimulate plant growth. This fungus forms different cell types including blastoconidia, swollen cells, and hyphae. The role of these cells in bio-protectant performance of A. pullulans is not yet described. Here, dynamics in formation and differentiation of blastoconidia, swollen cells, and hyphae were quantitatively assessed in liquid static cultures of four isolates. During 16 h of culturing, blastoconidia were formed by cell division of swollen cells, hyphae, and existing blastoconidia, while blastoconidia differentiated into swollen cells and swollen cells differentiated into hyphae. As a result, blastoconidia were no longer the most dominant cell type after 10 h of culturing, although they represented more than 75 % of the cells at the moment of inoculation. A mathematical model was developed based on Ordinary Differential Equations to describe the time-dependent cellular dynamics of the neotype strain A. pullulans CBS 584.75 under fixed culture conditions. The quantitative data of its 16 h static liquid cultures was used as input with the incubation time as input variable. The model predicted that blastoconidia would again be the most prominent cell type from 18 h of incubation onwards with relative abundances of the blastoconidia, swollen cells and hyphae of 57 %, 32 %, and 11 %, respectively, after 72 h of growth. The quantitative assessment of cell division and differentiation and its mathematical model can be used in future studies to optimize performance of A. pullulans as a bio-protectant and to stimulate plant growth.