Short-term physiologic response of the green microalga Picochlorum sp. (BPE23) to supra-optimal temperature

Abstract

Photobioreactors heat up significantly during the day due to irradiation by sunlight. High temperatures affect cell physiology negatively, causing reduced growth and productivity. To elucidate the microalgal response to stressful supra-optimal temperature, we studied the physiology of Picochlorum sp. (BPE23) after increasing the growth temperature from 30 °C to 42 °C, whereas 38 °C is its optimal growth temperature. Cell growth, cell composition and mRNA expression patterns were regularly analyzed for 120 h after increasing the temperature. The supra-optimal temperature caused cell cycle arrest for 8 h, with concomitant changes in metabolic activity. Accumulation of fatty acids was observed during this period to store unspent energy which was otherwise used for growth. In addition, the microalgae changed their pigment and fatty acid composition. For example, palmitic acid (C16:0) content in the polar fatty acid fraction increased by 30%, hypothetically to reduce membrane fluidity to counteract the effect of increased temperature. After the relief of cell cycle arrest, the metabolic activity of Picochlorum sp. (BPE23) reduced significantly over time. A strong response in gene expression was observed directly after the increase in temperature, which was dampened in the remainder of the experiment. mRNA expression levels associated with pathways associated with genes acting in photosynthesis, carbon fixation, ribosome, citrate cycle, and biosynthesis of metabolites and amino acids were downregulated, whereas the proteasome, autophagy and endocytosis were upregulated.

Multi-omics analysis reveals the molecular response to heat stress in a “red tide” dinoflagellate

“…Multi-omics data integration showed functions essential for energy production (photosynthetic electron transport chain) and energy consumption (fixation of carbon dioxide, protein synthesis) to be impaired, consequently resulting in reduced central metabolism and protein synthesis. Our findings extend those from previous studies [40][51][52][53][54] and represent the first comprehensive analysis of heat-shock response in a bloom forming dinoflagellate under strictly phototrophic conditions, thus providing a basis for understanding dinoflagellate ecology.…”

Influence of Carbon Sources on Biomass and Biomolecule Accumulation in Picochlorum sp. Cultured under the Mixotrophic Condition

“…Furthermore, Cano et al [ 30 ] also reported that the Picochlorum celeri contains β-carotene, chlorophyll and canthaxanthin in an 80% methanol and 20% acetone extract mix. Similarly, Barten et al [ 31 ] also reported the presence of carotenoids and chlorophyll in Picochlorum sp. They studied the short-term physiological responses in Picochlorum sp.…”

“…Only very limited studies have reported on the presence of astaxanthin from the Picochlorum sp. biomass [ 30 , 31 , 32 ]. These reported findings strongly supported the results obtained in this study, which contained different carotenoids in Picochlorum sp.…”

Thermotolerant microalgae : bioprospecting followed by adaptive laboratory evolution for strain selection and improvement

“…The quantum yield, cell size, cell number, and biomass concentration were measured as described in [117]. Biomass harvest and biomass lyophilization, determination of pigments through HPLC, and determination of fatty acids through GC was performed as described in [150]. The photosynthesis irradiance curve and the maximal specific growth rate were measured as described in [157].…”

“…The initial rapid adaptation was hypothesized to be caused by pleiotropy [28]. Temperature as a stress factor impacts nearly every cellular process as it affects the protein configuration and membrane fluidity [150]. In addition to the general cellular metabolism, microalgae grow autotrophically through photosynthesis which is considered a thermosensitive process [6].…”