Effects of Silicon Deficiency on Lipid Composition and Metabolism in the Diatom Cyclotella Cryptica

Abstract

The effects of silicon deficiency on the metabolism and composition of lipids i n Cyclotella cryptica T 1 3 L Reimann, Lewin, and Guillard were examined. Silicon-deficient cells had higher levels of neutral lipids (primarily triacylglycerols) and higher proportions of saturated and monounsaturated fatty acids than silicon-replete cells. After 4 h of silicon deficiency, the percentage of newly assimilated NaH14C0, partitioned into lipids increased from 27.6% to 54.1 %, whereas the percentage partitioned into chrysolaminarin decreased from 21.6% to 10.6%. I n addition, pulse-chase experiments with NaHI4C0, indicated that the amount of 14C in the total cellular lipid fraction increased by 32% after 1 2 h of silicon dejciency despite the absence of additional photoassimilable 14C. Therefore, the accumulation of lipids in response to silicon dejciency appears to be due to two distinct processes: (1) an increase i n the proportion of newly assimilated carbon partitioned into lipids, and (2) a slow conversion of previously assimilated carbon from non-lipid compounds into lipids.

Exploring Valuable Lipids in Diatoms

“…P. tricorntum had a 2-fold increase in fatty acid content but reduced in a half in biomass production under phosphorus starvation environment (Wurch et al, 2011). In most diatom species, silicon is one key component of cell wall structure and therefore a limiting micro-nutrient for diatom biomass production (Roessler, 1988). The acetyl-CoA carboxylase activity was enhanced by 2-fold and 4-fold respectively after 4 and15 h growth without silicate in Cyclotella cryptica (Roessler, 1988).…”

The place of diatoms in the biofuels industry

“…Factoring this into DCW measurements, this suggests that lipid content in diatoms on a per cell carbon basis is substantially higher than usually reported. Illustrating this point is a comparison of Si-induced lipid accumulation in C. cryptica, in which total lipid based on DCW was 42% [97] compared with 54.1% when calculated on an AFDW basis [109]. The data suggest that diatoms are at least on par with, if not superior to, other classes of algae in terms of their ability to accumulate lipids.…”

“…Published literature has shown that TAG accumulates under either Si or N limitation [98,109], and in Figure 4 we present a comparison of these conditions with a treatment where the cells were exposed to the microtubule-based cell cycle inhibitor nocodazole. There are several important points to consider from this.…”

Purification and Characterization of Acetyl-CoA Carboxylase from the Diatom Cyclotella cryptica

“…Cells were cultured in 2 L polycarbonate bottles as described previously (18). Cultures were bubbled with 0.5% CO2 in air (500 mL/min) and maintained at 25°C under constant illumination from fluorescent lamps (photon flux density at the vessel surface averaged over 3600 = 85 ,umol quanta-m-2.…”