Improved use of organic phosphate by Skeletonema costatum through regulation of Zn^{2 +} concentrations

Abstract

The maximum growth rate (1.4–2 × 10⁵ cells ml⁻¹ d⁻¹), cell final yields (2.6–5.2 × 10⁵ cells ml⁻¹) and extracellular alkaline phosphatase activity (2.4–10.6 μg phosphate released ml⁻¹ h⁻¹) of the red tide alga, Skeletonema costatum, increased when Zn²⁺ was increased from 0 to 24 pm, but decreased with 66 pm Zn²⁺ in growth medium with glycerophosphate as the sole phosphorus source. Extracellular carbonic anhydrase activity and the affinity for HCO₃ ⁻ and CO₂ uptake increased when Zn²⁺ was increased from 0 to 12 pm, but then decreased at higher concentrations. The results suggested that utilization of organic phosphate required more Zn²⁺ than the uptake of inorganic carbon did, while utilization of dissolved inorganic carbon by Skeletonema costatum was very sensitive to Zn²⁺ concentration variations.