EFFECTS OF ULTRAVIOLET RADIATION ON PHOTOSYNTHESIS IN THE SUBTROPICAL MARINE DIATOM, CHAETOCEROS GRACILIS (BACILLARIOPHYCEAE)1

Previous studies have shown that reduced levels of solar UV radiation (280–400 nm) can enhance photosynthetic carbon fixation of marine phytoplankton, but the mechanisms are not known. The supply of CO2 for photosynthesis is facilitated by extracellular (periplasmic) carbonic anhydrase (CAe) in most marine phytoplankton species. The present study showed that the CAe activity of Skeletonema costatum (Greville) Cleve was stimulated when treated with UV-A (320–395 nm) or UV-A + UV-B (295–320 nm) in addition to visible radiation. The presence of UV-A and UV-B enhanced the activity by 28% and 24%, respectively, at a low irradiance (PAR 161, UV-A 28, UV-B 0.9 W m−2) and by 21% and 19%, respectively, at a high irradiance (PAR 328, UV-A 58, UV-B 1.9 W m−2) level after exposure for 1 h. Ultraviolet radiation stimulated CAe activity contributed up to 6% of the photosynthetic carbon fixation as a result of the enhanced supply of CO2, as revealed using the CAe inhibitor (acetazolamide). As a result, there was less inhibition of photosynthetic carbon fixation compared with the apparent quantum yield of PSII. The UV radiation stimulated CAe activity coincided with the enhanced redox activity at the plasma membrane in the presence of UV-A and/or UV-B. The present study showed that UV radiation can enhance CAe activity, which plays an important role in counteracting UV inhibition of photosynthesis.

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Increase in Rubisco activity and gene expression due to elevated temperature partially counteracts ultraviolet radiation-induced photoinhibition in the marine diatom Thalassiosira weissflogii

Limnology and Oceanography ◽

10.4319/lo.2011.56.4.1330 ◽

2011 ◽

Vol 56 (4) ◽

pp. 1330-1342 ◽

Cited By ~ 29

Author(s):

E. Walter Helbling ◽

Anita G. J. Buma ◽

Peter Boelen ◽

Han J. van der Strate ◽

M. Valeria Fiorda Giordanino ◽

...

Keyword(s):

Gene Expression ◽

Elevated Temperature ◽

Ultraviolet Radiation ◽

Marine Diatom ◽

Thalassiosira Weissflogii ◽

Rubisco Activity ◽

Radiation Induced

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High Productivity of Eicosapentaenoic Acid and Fucoxanthin by a Marine Diatom Chaetoceros gracilis in a Semi-Continuous Culture

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2020.602721 ◽

2020 ◽

Vol 8 ◽

Author(s):

Saki Tachihana ◽

Norio Nagao ◽

Tomoyo Katayama ◽

Minamo Hirahara ◽

Fatimah Md. Yusoff ◽

...

Keyword(s):

Eicosapentaenoic Acid ◽

Continuous Culture ◽

Dilution Rate ◽

Cell Size ◽

Light Condition ◽

Dry Weight ◽

Marine Diatom ◽

High Productivity ◽

Chaetoceros Gracilis ◽

High Production Rate

Significantly high eicosapentaenoic acid (EPA) and fucoxanthin contents with high production rate were achieved in semi continuous culture of marine diatom. Effects of dilution rate on the production of biomass and high value biocompounds such as EPA and fucoxanthin were evaluated in semi-continuous cultures of Chaetoceros gracilis under high light condition. Cellular dry weight increased at lower dilution rate and higher light intensity conditions, and cell size strongly affected EPA and fucoxanthin contents. The smaller microalgae cells showed significantly higher (p < 0.05) value of 17.1 mg g-dw–1 fucoxanthin and 41.5% EPA content per total fatty acid compared to those observed in the larger cells. Chaetoceros gracilis can accumulate relatively higher EPA and fucoxanthin than those reported previously. In addition, maintenance of small cell size by supplying sufficient nutrients and light energy can be the key for the increase production of valuable biocompounds in C. gracilis.

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