Active, Irreversible Accumulation of Extreme Levels of H₂SO₄ in the Brown Alga, Desmarestia

Abstract

The brown algae Desmarestia ligulata var. ligulata (Lightf.) Certain species of the macrophytic brown alga Desmarestia accumulate high intracellular concentrations of acid (5,11,14,22). This acid accumulation is unusual in two respects; the pH (0.4-0.8) is considerably lower than that found in any other plant cell, and the acid is H2SO4 rather than an organic acid such as malic acid (14) Ion Concentration Determination. Tissue segments were rinsed and suspended for 10 min in either 0.5 M KC1 (for the Na+ and S042 assays) or 0.28 M Na2SO4 (for the K+ and C1-assays) at 0°C. Fresh weight was then determined and the segments frozen. Ions were extracted from the frozen segments via the boiling water method of Higinbotham et al. (7). The efficiency of this extraction method was checked by digesting the insoluble material in hot, concentrated HNO3 and assaying this for K+ and Na+. The average amount of either of these two ions remaining in the insoluble fraction was less than 0.1% of their total.Ion concentrations were determined as follows: K+ and Na+ by flame emission spectrophotometry, Cl-via potentiometric titration, and SO22 by precipitation with barium (added as BaCl2). Internal ion concentrations were estimated using, as the aqueous tissue volume, the fresh weight minus the dry weight on a 1 ml/g basis.Membrane Potential Measurement. Membrane potentials were measured using standard glass microelectrode techniques. The 3M KCl microcapillary salt bridges were connected through silversilver chloride wire to a Keithley Model 610B electrometer (input resistance 1014 ohms). Tissue segments were mounted in a tissue chamber with a continuous flow-through system for the temperature-controlled (10-12°C) bathing solution (artificial seawater). Because of the small cell size (10-20 ,um

Ligulate Desmarestia (Desmarestiales, Phaeophyceae) revisited: D. japonica sp. nov. and D. dudresnayi differ from D. ligulata

“…The thalli are annual or perennial, can measure up to 8 m in length, as observed in a Northeast Pacific individual (Pease 1920), and these macroscopic forms alternate with microscopic gametophytes that are either monoecious or dioecious (Peters et al 1997). A conspicuous character of most annual taxa of Desmarestia is a high concentration of sulfuric acid in the vacuoles (Schiff 1962, McClintock et al 1982, Sasaki et al 2004, which possibly serves to deter herbivores Velimirov 1982, Pelletreau andMuller-Parker 2002). In molecular phylogenies, the Desmarestiales forms a well-supported clade within the brown algal crown radiation (Draisma et al 2003, Kawai et al 2007, Phillips et al 2008, Silberfeld et al 2010.…”

Macroalgal canopies: distribution and diversity of associated invertebrates and effects on the recruitment and growth of mussels

“…Indeed, the small urchins found on D. viridis in our study may have simply been entangled in the fronds as they swept over the bottom. Finally, the low diversity of invertebrates may be due to the sulfuric acid contained in the tissue of this alga (McClintock et al 1982), but this characteristic should not affect non-consumers, and its impact on consumers remains unclear (Himmelman & Nélélec 1990, Konar 2000.…”

Vacuolar pH regulation in Chara australis.

“…In an extreme case, the pH of the cell extract, which may reflect the vacuolar pH, was reported to be 0.6 in Desmarestia (7). In addition, the electrical potential of the vacuole is positive against the cytoplasm (2,5,9,13).…”