EFFECTS OF ENVIRONMENTAL-FACTORS AND METALS ON SELENASTRUM-CAPRICORNUTUM LIPIDS

Studies of the effects of illumination, temperature and heavy metal ex posure (Cu2+, Zn2+, Cd2+) on Selenastrum capricornutum have shown that these factors alter both the total fatty acid and free sterol composi tion of cells in batch culture. Dark treatment resulted in a decrease in the relative proportions of oleate (18:1) and an increase linoleate (18:2), together with an increase in the relative proportion of the s terol 24-ethyl-5 alpha-cholest-7-en-3 beta-ol (Delta(7)-chondrillasten ol) and a decrease in 24-ethyl-5 alpha-cholesta-7,22-dien-3 beta-ol (c hondrillasterol). A shift in temperature from 25 degrees to 10 degrees led to an increase in the relative proportion of oleate and a decreas e in linoleate and parinate (18:4), together with a significant increa se in the relative proportion of 24-methyl-5 alpha-cholest-7-en-3 beta -ol (ergostenol). Generally, exposure to heavy metal ions led to an in crease in oleate (with all three metals) and altered the relative prop ortions of linoleate and parinate (changes being metal specific). Meta l (ion) treatment also significantly increase Delta(22) desaturation o f the 24-ethyl sterol-components. The changes in the composition of ma ny of the individual lipid components in response to heavy metal ion e xposure occurred at concentrations which did not significantly affect the organism's specific growth sate. For example, the relative proport ion of oleate was affected with only I mu M Cu2+ in solution (P < 0.10 ). (C) 1998 Elsevier Science Ltd. All rights reserved.