THE UPTAKE OF ORGANIC-COMPOUNDS BY DUNALIELLA-PARVA CCAP-19 9/

The feasibility of growing the unicellular green microalga Dunaliella parva heterotrophically was investigated. D. parva cells were shown to take up [C-14]glycerol and [C-14]glucose; the rate of uptake was fast est under illuminated conditions (photon flux density of 5-10 mu mol m (-2) s(-1)), but a significant rate of uptake was maintained in the da rk for at least 6 h. The uptake of both compounds was stopped when pho tosynthesis and respiration were inhibited by adding carbonylcyanide m -chlorophenyl hydrazone (CCCP) or Gram's iodine to the cells. Subjecti ng the cells to increasing salinity, which reduces the rate of photosy nthesis and respiration, also reduced the rate of [C-14]glycerol uptak e. These results suggested that the uptake of glycerol and glucose was due to active transport. Both transport systems were saturable and th ey were shown to be independent systems, since there was no effect on [C-14]glycerol uptake when excess cold glucose was added or vice versa . D. parva cells could also take up [C-14]acetate, but it was not dete rmined whether this was by active transport. Despite the presence of a ctive transport systems for glycerol and glucose and evidence of aceta te uptake, D. parva was not able to grow heterotrophically on any of t hese three potential substrates.