Phosphate-uptake systems in Yarrowia lipolytica cells grown under alkalineconditions

In this study we used a newly isolated Yarrowia lipolytica strain with a un ique capacity to grow over a wide pH range (3.5-10.5), which makes it an ex cellent model system for studying phosphate transport systems in cells grow n under alkaline conditions. Phosphate uptake by Y. lipolytica yeast cells grown at pH 9.5-10 was shown to be mediated by several kinetically discrete Na+-dependent systems, One of these, a low-affinity transporter, operates at high P-i concentrations and is, to our knowledge, here kinetically chara cterized for the first time, The other two high-affinity systems are derepr essible, come into play under conditions of P-i-starvation, and appear to b e controlled by the availability of extracellular P-i, They represent the f irst examples of high-capacity, Na+-driven P-i transport systems in an orga nism belonging to neither the animal nor the bacterial kingdoms.