The uptake of organic compounds by Dunaliella parva CCAP 19/9

Abstract

The feasibility of growing the unicellular green microalga Dunaliella parva heterotrophically was investigated. D. parva cells were shown to take up [¹⁴C]glycerol and [¹⁴C]glucose; the rate of uptake was fastest under illuminated conditions (photon flux density of 5–10 µmol m^-2s^-1), but a significant rate of uptake was maintained in the dark for at least 6 h. The uptake of both compounds was stopped when photosynthesis and respiration were inhibited by adding carbonylcyanide m-chlorophenyl hydrazone (CCCP) or Gram's iodine to the cells. Subjecting the cells to increasing salinity, which reduces the rate of photosynthesis and respiration, also reduced the rate of [¹⁴C]glycerol uptake. These results suggested that the uptake of glycerol and glucose was due to active transport. Both transport systems were saturable and they were shown to be independent systems, since there was no effect on [¹⁴C]glycerol uptake when excess cold glucose was added or vice versa. D. parva cells could also take up [¹⁴C]acetate, but it was not determined whether this was by active transport. Despite the presence of active transport systems for glycerol and glucose and evidence of acetate uptake, D. parva was not able to grow heterotrophically on any of these three potential substrates.

Key words :

• acetate
• Dunaliella
• glucose
• glycerol
• heterotrophic growth