Elevated pCO2 Level Affects the Extracellular Polymer Metabolism of Phaeodactylum tricornutum

Abstract

Extracellular polymeric substances (EPS) play an important role in diatom physiology and carbon biogeochemical cycling in marine ecosystems. Both the composition and yield of EPS in diatom cells can vary with environmental changes. However, information on intracellular pathways and controls of both biochemical and genetic of EPS is limited. Further, how such changes would affect their critical ecological roles in marine systems is also unclear. Here, we evaluated the physiological characteristics, EPS yields, EPS compositions, and gene expression levels of Phaeodactylum tricornutum under elevated pCO 2 levels. Genes and pathways related to EPS metabolism in P. tricornutum were identified. Carbohydrate yields in different EPS fractions increased with elevated pCO 2 exposure. Although the proportions of monosaccharide sugars among total sugars did not change, higher abundances of uronic acid were observed under high pCO 2 conditions, suggesting the alterations of EPS composition. Elevated pCO 2 increased PSII light energy conversion efficiency and carbon sequestration efficiency. The upregulation of most genes involved in carbon fixation pathways led to increased growth and EPS release. RNA-Seq analysis revealed a number of genes and divergent alleles related to EPS production that were up-regulated by elevated pCO 2 levels. Nucleotide diphosphate (NDP)-sugar activation and accelerated glycosylation could be responsible for more EPS responding to environmental signals. Further, NDP-sugar transporters exhibited increased expression levels, suggesting roles in EPS over-production. Overall, these results provide critical data for understanding the mechanisms of EPS production in diatoms and evaluating the metabolic plasticity of these organisms in response to environmental changes.

Golgi fucosyltransferase 1 reveals its important role in α-1,4-fucose modification of N-glycan in CRISPR/Cas9 diatom Phaeodactylum tricornutum

“…The algal cells (2 mL) were cultured in the dark for 15 min to achieve completely oxidative PSII reaction centers before the measurement [ 29 ]. Chlorophyll a content was analyzed by 80% methanol and quantified by UV–VIS spectrophotometer at 652, 665 and 750 nm [ 32 ]. The soluble polysaccharides were analyzed by Micro Plant Soluble Sugar Content Assay Kit (NanJing JianCheng Bioengineering Institute).…”

Shaping the phycosphere: Analysis of the EPS in diatom‐bacterial co‐cultures

“…In our analysis of the EPS produced by the diatom and the bacterium cultures, we identified a total of 13 different monosaccharide moieties (Figure 1; nine sugars, two uronic acids, and two amino sugars). Notably, the diatom EPS was composed of a relatively high number of monosaccharide units (Figure 1), indicating its heteropolysaccharide nature (Zhang et al, 2020). The EPS production consistently followed the growth curves (refer to Appendix S1 for detailed description of growth curves, Figure S1, and rates, Tables S1 and S2).…”

Golgi fucosyltransferase 1 reveals its role in α-1,4-fucose modification of N-glycan in Diatom Phaeodactylum tricornutum

“…The algal cells (2 mL) were cultured in the dark for 15 min to achieve completely oxidative PSII reaction centers before the measurement (27). Chlorophyll a content was analyzed by 80% methanol and quanti ed by UV-VIS spectrophotometer at 652, 665 and 750 nm (30). The soluble polysaccharides were analyzed by Micro Plant Soluble Sugar Content Assay Kit (NanJing JianCheng Bioengineering Institute).…”