Pressure reduction affects growth and morphology of Chlamydomonas reinhardtii Pressure reduction affects growth and morphology of Chlamydomonas reinhardtii

Cellular perception of pressure is a largely unknown field in microalgae research although it should be addressed for optimization of a photobioreactor design regarding typically occurring pressure cycles. Also for the purpose of using microalgae as basicmodules for material cycles in controlled ecological life support systems, the absence of pressure in outer space or the low absolute pressures on other planets is an abiotic factor that needs to be considered for design of integrated microalgaebased modules. The aim of this work is to study the effects of lowered pressure and pressure changes on photosynthesis as well as morphology. Two Chlamydomonas reinhardtii wild-type strains were exposed to controlled pressure patterns during batch cultivations. Sudden pressure changes should test for existing threshold values for cell survival to mimic such events during space missions. Algae were grown inside a 2 L photobioreactor with an integrated vacuum pump ensuring constant pressures down to 700 mbar. Cultivation samples were analyzed for OD750, cell dry weight, and morphology via light microscope. Chlamydomonas reinhardtii CC-1690 cells showed decreased growth rates, higher carbon dioxide uptake rates, and unchanged oxygen production rates at lower pressures. For sudden pressures changes in the range of 300 mbar no fatal threshold was determined. This study shows that pressure reduction affects growth, gas exchange rates, and morphology. Within the tested pressure range no fatal threshold value was reached.