Effects of pH on cell morphology and carbonic anhydrase activity and localization in bloom-forming <i>Mougeotia</i> (Chlorophyta, Charophyceae)

Abstract

A species of Mougeotia (C.A. Agardh) that was the dominant component of a metaphytic bloom-forming filamentous algal assemblage in an experimentally acidified lake (Little Rock Lake, Vilas County, Wisconsin, U.S.A.) was isolated into unialgal culture for analysis of pH effects on cell morphology and carbonic anhydrase activity and localization. External and total carbonic anhydrase activities at pH 8 were significantly greater than those at pH 5, but internal carbonic anhydrase activities were not significantly different at the two pH levels, as determined by use of a potentiometric technique. Ultrastructural immunogold labeling with a polyclonal antibody to Chlamydomonas periplasmic carbonic anhydrase suggested that an antigenically similar protein was located in the periplasmic space, inflated end walls, chloroplast, and peripheral cytoplasm of Mougeotia grown at both pH 8 and 5. Activity measurements and localization data were consistent with the hypothesis that a carbon concentration mechanism operate...