Carbonic Anhydrase-Deficient Mutant of Chlamydomonas reinhardii Requires Elevated Carbon Dioxide Concentration for Photoautotrophic Growth

Abstract

A mendelian mutant of the unicellular green alp Chlamydomonas reinhardii has been isolated which is deficient in carbonic anhydrase (EC 4.2.1.1) activity. This mutant strain, designated ca-1-12-1C (gene locus ca-i), was selected on the basis of a high C02 requirement for photoautotrophic growth. Photosynthesis by the mutant at atmospheric C02 concentration was very much reduced compared to wild type and, unlike wild type, was strongly inhibited by 02. In contrast to a CO2 compensation concentration of near zero in wild type at all 02 concentrations examined, the mutant exhibited a high, 02-stimulated C02 compensation concentration. Evidence of photorespiratory activity in the mutant but not in wild type was obtained from the analysis of photosynthetic products in the presence of '4CO2. At

Isolation and Characterization of a Mutant of Chlamydomonas reinhardtii Deficient in the CO2 Concentrating Mechanism

“…In addition, these growth characteristics indicated that CIA-S may have a defect in the inorganic carbon accumulation system, as its phenotype is very similar to previously described strains (18,23,24). This hypothesis was supported …”

“…If these strains are placed on low levels of C02, they either cannot grow, or grow at slower than normal rates. Some of these strains are unable to accumulate C1 (24), while others accumulate Ci to levels higher than wild-type cells (23), but are unable to use this accumulated C1 efficiently. All of the previously characterized C. reinhardtii mutants were capable of inducing the synthesis of the periplasmic carbonic anhydrase (18,26) as indicated by enzyme assay or by detection with antibodies raised against the periplasmic carbonic anhydrase.…”

“…This protein is made only when the cells are grown in the light with low concentrations of CO2 (8, 27,29,30). The existence of other components of the CO2 concentrating system has been inferred from studies of C. reinhardtii mutants (23)(24)(25), Ci uptake measurements (21), and from 35S-labeling studies of cells that are adapting to low CO2 conditions (13).…”

“…A number of C. reinhardtii strains have been isolated that appear to be defective in some aspect of CO2 accumulation (18,(23)(24)(25)(26). These mutants are capable of photoautotrophic growth, but only ifthe CO2 concentration in the environment is elevated.…”

Dissolved inorganic carbon utilization and the development of extracellular carbonic anhydrase by the marine diatom Phaeodactylum tricornutum

“…The presence of extracellular CA located 1983). The role of CA appears to be linked to a COj-outside the plasma membrane in the periplasmic concentrating mechanism (CCM) (Badger, Kaplan space or attached to the cell wall has been reported & Berry, 1980;Spalding, Spreitzer & Ogren, 1983; for marine microalgae (Dionisio-Sese & Miyachi, 1992) iticludmg some phytoplankton species (Burns * To whom correspondence should be addressed.…”