Growth and ATP levels in Porphyridium purpureum (Rhodophyceae, Bangiales) cultured in the presence of surfactants

Abstract

Growth and ATP levels were studied in the unicellular red alga Porphyridium purpureum cultured on a synthetic agar medium in the presence of seven different commonly used synthetic surfactants. The surfactants were used in concentrations of 0–50 ppm; the alga did not tolerate higher concentrations of the surfactants. Of the surfactants tested, three “mild” compounds (sodium desoxycholate, Synperonic NP9 (a nonyl phenol ethoxylate) and Triton X-100) did not change the normal ATP levels found in control algae (30–45 μg ATP gdw^-1). In contrast, the surfactants Ufasan 65 (a linear alkylbenzene sulphonate, LAS) and Genapol ZRO (a polyglycol ether sulphate) increased the ATP levels markedly at concentrations of 30–40 ppm. A similar large increase was observed at 10 ppm of TEGO-Betain L7 (an amphoteric betaine derivative) and Ungerol N2-70 (an ethoxylated fatty alcohol sulphate). The effects of the three “mild” surfactants on the growth of P. purpureum were not linear: at 50 ppm all were growth-inhibitory, and also some lower concentrations could be harmful. The mild surfactants could also increase growth to some extent. The other four (“hard”) surfactants were growth-inhibitory. The inhibition proceeded linearly with increasing surfactant concentration, and no cells survived at 50 ppm. In spite of this, none of the tested surfactants decreased the ATP levels. Thus, no uncoupling effect could be observed with the surfactants.