Characterization Of CO₂ Uptake Activity Of Green Alga Chlamydomonas reinhardtii With An Open Gas Exchange System

Abstract

A green alga Chlamydomonas reinhardtii acclimates to low CO₂ condition by induction of carbon concentrating mechanism (CCM). The mechanisms of CO₂ sensing and regulation of CCM are poorly understood. To understand the regulation mechanism of response against CO₂ condition, we employed an open gas exchange system as a method of rapid characterization of CO₂ uptake of cells. Light dependent CO₂ uptake was observed, which was consistent with previous studies analyzed by silicone oil filtering centrifugation method. In wild type, low and high CO₂-adapted cells showed CO₂ uptake activities of 53.4 and 8.8 μmol CO₂/mg Chl h, respectively. A Ccm1 deficient mutant showed 8.8 μmol CO₂/mg Chl h of activity in both low and high CO₂-adapted cells. We will report about the nature of CO₂ uptake in regulatory mutants of CCM and also characterize effects of photosynthetic inhibitors on CO₂ uptake of Chlamydomonas cells with this system.