Scaling-Up and Semi-Continuous Cultivation of Locally Isolated Marine Microalgae Tetraselmis striata in the Subtropical Island of Gran Canaria (Canary Islands, Spain)

The goal of this study was to determine the feasibility of the large-scale cultivation of locally isolated Tetraselmis striata in different open ponds in Gran Canaria. The biomass productivities were 24.66 ± 0.53 kgDW in 32 days (28.9t/ha/year) for 8000 L indoors, 42.32 ± 0.81 kgDW in 43 days (38.8 t/ha/year) for an 8000 L pond outdoors, and 54.9 ± 0.58 kgDW in 28 days (19.6 t/ha/year) for a 45,000 L pond outdoors. The photosynthetic efficiencies were 1.45 ± 0.03% for an 8000 L pond indoors, 1.95 ± 0.04% for 8000 L outdoors. and 1.10 ± 0.01% for a 45,000 L pond outdoors. The selected strain was fast-growing (µ = 0.21 day−1) and could be rapidly scaled up to 45,000 L; it formed healthy cultures that maintained high photosynthetic activity during long-term cultivation and provided stable biomass productivities, able to grow on urea, which acted as a cheap and effective grazer control. The obtained biomass is a good source of proteins and has an FA profile with a high content of some nutritionally important fatty acids: oleic, α-linolenic (ALA) and EPA. The high ash content in the biomass (>35%) can be reduced by the implementation of additional washing steps after the centrifugation of the culture.

Singlet oxygen-dependent chloroplast degradation is independent of macroautophagy in the Arabidopsis ferrochelatase two mutant

BackgroundChloroplasts respond to stress and changes in the environment by producing reactive oxygen species (ROS) that have specific signaling abilities. The ROS singlet oxygen (1O2) is unique in that it can signal to initiate selective degradation of damaged chloroplasts and then cell death. This chloroplast quality control pathway can be monitored in the Arabidopsis mutant plastid ferrochelatase two (fc2) that conditionally accumulates chloroplast 1O2 under diurnal light cycling conditions leading to rapid chloroplast degradation and eventual cell death. The cellular machinery involved in such degradation, however, remains unknown. Recently it has been demonstrated that whole damaged chloroplasts can be transported to the central vacuole via a process requiring autophagosomes and core components of the autophagy machinery. The relationship between this process, referred to as chlorophagy, and the degradation of 1O2-stressed chloroplasts and cells has remained unexplored.ResultsTo further understand 1O2-induced cellular degradation and determine what role autophagy may play, the expression of autophagy-related genes were monitored in 1O2-stressed fc2 seedlings and found to be induced. Although autophagosomes were present in fc2 cells, they did not associate with chloroplasts during 1O2 stress. Mutations blocking the core autophagy machinery (atg5, atg7, and atg10) were unable to suppress 1O2-induced chloroplast degradation or cell death in the fc2 mutant, suggesting autophagosome formation and macroautophagy are dispensable for 1O2–mediated cellular degradation. However, both atg5 and atg7 led to specific defects in chloroplast ultrastructure and photosynthetic efficiencies, suggesting macroautophagy may be involved in protecting chloroplasts from photo-oxidative damage. Finally, genes predicted to be involved in microautophagy were shown to be induced in stressed fc2 seedlings, indicating a possible role for an alternate form of autophagy in the dismantling of 1O2-damaged chloroplasts.ConclusionsOur results support the hypothesis that 1O2-dependent chloroplast degradation is independent from autophagosome formation, canonical macroautophagy, and chlorophagy. Instead, ATG-independent microautophagy may be involved in such degradation. However, canonical macroautophagy may still play a role in protecting chloroplasts from 1O2-induced photo-oxidative stress. Together, this suggests chloroplast function and degradation is a complex process that utilizes multiple autophagy and degradation machineries, possibly depending on the type of stress or damage incurred.

Symbiodinium functional diversity and clade specificity under global change stressors

ABSTRACTCoral bleaching episodes are increasing in frequency, demanding examination of the physiological and molecular responses of corals and their Symbiodinium to climate change. Here we quantify bleaching and Symbiodinium photosynthetic performance of Siderastrea siderea from two reef zones after long-term exposure to thermal and CO2-acidification stress. Molecular response of in hospite Symbiodinium to these stressors was interrogated with RNAseq. Elevated temperatures reduced photosynthetic efficiency, which was highly correlated with bleaching status. However, photosynthetic efficiencies of forereef symbionts were more negatively affected by thermal stress than nearshore symbionts, indicating greater thermal tolerance in nearshore corals. At control temperatures, CO2-acidification had little effect on symbiont physiology, although forereef symbionts exhibited greater photosynthetic efficiencies than nearshore symbionts. Transcriptome profiling revealed that S. siderea were dominated by clade C Symbiodinium, except under thermal stress, which caused shifts to thermotolerant clade D. Comparative transcriptomics of conserved genes across symbiotic partners revealed few differentially expressed Symbiodinium genes when compared to corals. Instead of responding to stress, clade C transcriptomes varied by reef zone, with forereef Symbiodinium exhibiting enrichment of genes associated with photosynthesis. Our findings suggest that functional variation in photosynthetic architecture exists between forereef and nearshore Symbiodinium populations.

Carbon Dioxide Sequestration from Biogas Production by Microalgae Chlorella sp.

In this study, the research team aimed to apply the use of biological capturing system of single cell algae, common microalgae species Chlorella sp. that have higher photosynthetic efficiencies in efficient capturing carbon dioxide. Here, , In the biological CO2 capturing process, biogas was pumped to the water recycling culturing medium, only CO2, not CH4, could dissolved efficiently with the sprayer and recycling medium system. The results showed the microorganisms could resist to methane except H2S and significantly induced at least 90-95% CO2 removal efficiency and increased in Cholerella sp. biomass production within 7 day cultivation compared the system without CO2 feeding (0.6 and 0.4 percentage (g/mL), respectively. Since the biological treatment approach was durable and could possibly further applied for treating flue carbon dioxide exhausted by power plant and fuel-types, and mitigating acid rain, heavy fuel oil, natural gas prevention.

Key differences in photosynthetic characteristics of nine species of intertidal macroalgae are related to their position on the shore

A study of the fluorescence characteristics, net photosynthetic rate, and dark respiration of nine species of intertidal macroalgae, from three divisions and from different positions on a rocky shore on the east coast of Scotland, was carried out to address the following questions: (i) Do algae at different positions along the shore respond differently to the stresses at these positions in terms of photosynthetic efficiency, net photosynthetic rate, and respiration, when fully hydrated? (ii) Do algal species at different positions respond differently, in terms of function, to desiccation, and can these responses be correlated with tolerance or intolerance to desiccation in terms of recovery? The present study demonstrated that algal species that occur higher on the shore have greater photosynthetic rates, respiration rates, maximum fluorescence / initial fluorescence ratios, and photosynthetic efficiencies while fully hydrated than do species that live lower on the shore. These findings point towards an increase in time-use efficiency in species that have less time available for productivity or nutrient uptake, since species at a greater height on the shore spend less time in a state of sufficient hydration to photosynthesize. Furthermore, algae higher up the shore, which can recover from desiccation, have significantly different fluorescence characteristics from nonrecoverers, particularly in the area above the Kautsky curve between initial fluorescence and maximum fluorescence. This is the first biophysical evidence relating to a mechanism for desiccation tolerance in macroalgae, and it is discussed within the context of other examples of increasing rates of physiological processes with decreasing time.Key words: fluorescence, zonation, function, rocky shore, Fucus.