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.