Gnaiger 2022 Abstract Bioblast-PB

P03. Went N, Di Marcello M, Gnaiger Erich (2022) Oxygen dependence of photosynthesis and light-enhanced dark respiration studied by high-resolution PhotoRespirometry. Bioblast 2022: BEC Inaugural Conference. In: https://doi.org/10.26124/bec:2022-0001 »MitoFit Preprint«

Link: Bioblast 2022: BEC Inaugural Conference

Went Nora, Marcello M, Gnaiger Erich (2022)

Event: Bioblast 2022

Algal biotechnology has emerged as a high-potential industry for efficient and CO₂-neutral production of biomass providing biofuels, food and feed, and a variety of carbon-based chemicals and pharmaceuticals. Algal metabolism is directly involved in the regulation of growth, cell concentration, and biosynthesis of biotechnologically-relevant phytochemicals such as vitamins, antioxidants, and immune response boosters. Photoautotrophic growth rates of algae are based on light-to-chemical energy conversion and CO₂ fixation, and any optimization of biomass production requires maximizing energy-use efficiency of photosynthesis and respiration, both of which vary as a function of light intensity. As such, the bioenergetic crosstalk between mitochondria and chloroplasts plays a key role in maintaining metabolic integrity and controlling intermediary metabolite production.

In the present study, we investigated how photosynthetic O₂ production and respiratory O₂ consumption was influenced as a function of light intensity, O₂ concentration, and culture density in the unicellular model green alga Chlamydomonas reinhardtii. Cultures were grown photoautotrophically in a modified Tris-Phosphate growth medium (TRIS, N- and P-nutrient replete) at 25 °C, pH 7.0, and light intensity of 100 µmol photons·s^-1·m^-2 (16:8 h light:dark cycle). Kinetics of light-induced O₂ production and dark respiration of these microalgae was measured under culture conditions and three cell concentrations, while varying O₂ concentrations in the Oroboros NextGen-O2k equipped with the PhotoBiology-Module [1] during stepwise increases of blue actinic light from from 10 to 350 µmol∙s^-1∙m^-2, followed by darkness, again at various controlled O₂ concentrations. Maximum net photosynthesis was inhibited by 40 % at hyperoxic O₂ concentrations of 550 to 650 µM, when ROS production is known to be increased [2,3]. Transient light-enhanced dark respiration [4] peaked within 30 to 60 s after light-dark transitions and was 3.5- to 4-fold higher than steady-state dark respiration independent of O₂ concentration in the range of 200 to 650 µM.

We conclude that high-resolution photorespiratory analysis provides a new method to investigate the oxygen kinetics of O₂ production and O₂ consumption that reveal interactions of chloroplasts and mitochondria under precisely regulated experimental light and oxygen regimes.

1. Went N, Di Marcello M, Gnaiger E (2021) Oxygen dependence of photosynthesis and light-enhanced dark respiration studied by High-Resolution PhotoRespirometry. https://doi.org/10.26124/mitofit:2021-0005
2. Komlódi T, Sobotka O, Gnaiger E (2021) Facts and artefacts on the oxygen dependence of hydrogen peroxide production using Amplex UltraRed. https://doi.org/10.26124/bec:2021-0004
3. Shimakawa G, Kohara A, Miyake C (2020) Characterization of light-enhanced respiration in cyanobacteria. https://doi.org/10.3390/ijms22010342

• O2k-Network Lab: AT Innsbruck Oroboros

Affiliations and support

Went N, Di Marcello M, Gnaiger Erich

Oroboros Instruments GmbH, Innsbruck, Austria

This work was part of the Oroboros NextGen-O2k project, with funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 859770.

List of abbreviations, terms and definitions - MitoPedia

» MitoPedia: Terms and abbreviations

Labels: MiParea: Respiration, Instruments;methods, Comparative MiP;environmental MiP 

Organism: Algae 

Preparation: Intact cells 

Regulation: Oxygen kinetics  Coupling state: ROUTINE 

HRR: Oxygraph-2k, NextGen-O2k  Event: Poster  Chlamydomonas, LEDR, Photosynthesis