Variations in external and internal lipids associated with inhibition of the resistant biopolymer from the a race of Botryococcus braunii

Abstract Culture of the A race of Botryococcus braunii in the presence of SC 1058, a cinnolinyl acid derivative (1- N -benzyl-3-carboxy-4-ketocinnoline), was recently shown to result in marked inhibition of the resistant biopolymer (PRB A ) in its outer walls and of the external pool of lipids, whereas the internal pool is strongly increased. These large effects were achieved with a SC 1058 concentration (5 x 10 −3 M) which does not affect the primary metabolism of B. braunii . Examination of the influence of SC 1058 on various groups of external lipids indicated that (i) all the very long chain compounds identified in this pool are markedly inhibited (decrease of 50–80% relative to SC 1058-free controls), (ii) free fatty acids, comprising chiefly oleic acid, are sharply inhibited ( ca 95%), and (iii) triacylglycerols (TAG) show a pronounced stimulation (+ 87%). However, the decrease observed for external free fatty acids cannot be entirely accounted for by the higher production of TAG.Study of the internal lipids revealed, in control cultures, large differences in distribution relative to external lipids; free fatty acids are still dominated by oleic acid but highly polar compounds are far more abundant. Culture with SC 1058 resulted in a pronounced increase in both internal TAG ( ca × 7) and free fatty acids ( ca × 4). Together these observations on internal and external lipids revealed that de novo synthesis of fatty acids is not affected by 5 x 10 −1 M SC 1058, whereas transport of oleic acid from the internal to the external pool is markedly decreased. The parallel inhibition of external very long chain lipids and of PRB A confirms the occurrence of tight biosynthetic relationships between these compounds and the major role of oleic acid in their formation. In addition to oleic acid transport, SC 1058 would also inhibit the condensation step leading to high M r lipids implicated as important intermediates in PRB A formation. Finally, as shown by FT IR spectra and pyrolysis product distributions, the very strong inhibition in PRB A formation obtained with SC 1058 is not associated with major changes in the bulk chemical features of the resistant biopolymer.