Aims: To examine the relationship between the growth and pH gradients of Debaryomyces hansenii at a single-cell level.

Methods and Results: Using bioimaging techniques, the cell areas and early pH gradients (¿pH₁₀), i.e. the pH gradients determined 10 min after initiation of experiments, were determined for single cells of two D. hansenii strains in fluid and on solid (agar) substrate with and without 8% (w/v) NaCl. The combination of NaCl and solid substrate prolonged the growth initiation of both D. hansenii strains additively. In all our experiments, primarily two groups of cells existed; a vital group consisting of growing single cells with intact early pH gradients, and a group of dead cells without early pH gradients.

Conclusions: Our results show that growth initiation of the D. hansenii cells is severely affected by NaCl and to a lesser extent by the type of substrate in an additive and strain dependent way. Moreover, the early pH gradient of a vital D. hansenii cell cannot be correlated with the rate of its subsequent growth.

Significance and Impact of the Study: Our study reveals new knowledge on the growth and pH gradients of D. hansenii on solid surfaces in the presence of NaCl.