© 2004 Oxford University Press
Effects of Chloramphenicol on Photosynthesis, Protein Profiles and Transketolase Activity under Extremely High CO2 Concentration in an Extremely-high-CO2-tolerant Green Microalga, Chlorococcum littorale
Marine Biotechnology Institute, 3-75-1Heita, Kamaishi, Iwate, 026-0001 Japan
An extremely-high-CO2-tolerant alga, Chlorococcum littorale, showed high quantum efficiency of PSII (
II) in the light at 40% CO2, as well as at 5% CO2. However, II decreased greatly when chloramphenicol (CAP) was added at 40% CO2, while no such decrease was observed at 5% CO2. Cycloheximide showed no effect on II at either 5% or 40% CO2. The amount of a 76 kDa polypeptide (p76) on SDS–PAGE decreased markedly in the presence of CAP at 40% CO2 but not at 5% CO2. A partial amino acid sequence of p76 was 71–100% identical (10–14 identical residues out of 14 amino acids determined) to those of transketolases (TKLs) reported in higher plants and a cyanobacterium. In agreement with these observations, the TKL activity in C. littorale was decreased by CAP at 40% CO2, but not at 5% CO2. The transient decrease in TKL activity caused by CAP under 40% CO2 was well correlated with that in II. These results indicate that the addition of CAP directly or indirectly influences the stability of TKL in C. littorale at 40% CO2, but not at 5% CO2, and that photosynthetic activity was reduced by a decrease in TKL activity.
1 Corresponding author: E-mail, akira.satoh{at}mbio.jp; Fax, +81-193-26-6592.
2 Present address: National Institute of Technology and Evaluation, 2-5-8 Kazusakamatari, Kisarazu, Chiba, 292-0818 Japan.