Movement of acetate across the cytoplasmic membrane of the unicellular cyanobacteriaSynechococcusandAphanocapsa

✍ Scribed by Jane Gibson

• Publisher: Springer
• Year: 1981
• Tongue: English
• Weight: 579 KB
• Volume: 130
• Category: Article
• ISSN: 0302-8933
• DOI: 10.1007/bf00411073

✦ Synopsis

Mutants of Synechococcus and of Aphanocapsa which were unable to activate acetate have been used to demonstrate that acetate entered the cells rapidly in darkness, and to a greater extent in light. Total internal concentrations under different conditions can be explained if acetic acid equilibrates rapidly across the cell membrane while acetate ion is strongly hindered. Acetate as well as other weak acids such as 5,5-dimethyl-2,4-oxazolidenedione can therefore be used as a probe of internal pH in these mutants. The intracellular pH was maintained at about 7.1 in darkness and 7.6 in light when external pH was varied from 6.8-8.0. No carrier involved in acetic acid equilibration could be demonstrated. Of other organic acids investigated, only propionate distributed in accordance with pH differences.between the cells and surrounding fluid. The low uptake rates of glycolate, pyruvate and leucine appeared limited by slow movement of molecules into the cells.