Effects of environmental factors and metals on Selenastrum capricornutum lipids

Studies of the effects of illumination, temperature and heavy metal exposure (Cu2+, Zn2+, Cd2+) on Selenastrum capricornutum have shown that these factors alter both the total fatty acid and free sterol composition 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 sterol 24-ethyl-5 alpha-cholest-7-en-3 beta-ol (Delta(7)-chondrillastenol) and a decrease in 24-ethyl-5 alpha-cholesta-7,22-dien-3 beta-ol (chondrillasterol). A shift in temperature from 25 degrees to 10 degrees led to an increase in the relative proportion of oleate and a decrease in linoleate and parinate (18:4), together with a significant increase 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 increase in oleate (with all three metals) and altered the relative proportions of linoleate and parinate (changes being metal specific). Metal (ion) treatment also significantly increase Delta(22) desaturation of the 24-ethyl sterol-components. The changes in the composition of many of the individual lipid components in response to heavy metal ion exposure occurred at concentrations which did not significantly affect the organism's specific growth sate. For example, the relative proportion of oleate was affected with only I mu M Cu2+ in solution (P < 0.10). (C) 1998 Elsevier Science Ltd. All rights reserved.