Effect of naphthalene and aqueous crude-oil extracts on the green flagellate Chlamydomonas angulosa. VII. Nitrate and methylamine uptake and retention

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Chlamydomonas angulosa grows equally well on nitrate and ammonium as sources of nitrogen. The presence of ammonium decreases nitrate uptake by less than 10% in short-term experiments. The presence of nitrate has no significant effect on short-term uptake of the ammonium analogue methylamine. Cells grown in nitrate media possess considerable methylamine uptake capacity during early exponential growth. This uptake capacity falls rapidly as the cells enter the declining growth phase. When cells are transferred to nitrogen-deficient media, the uptake capacity for methylamine increases threefold to fourfold in 24 h. The half-saturation constants (Km) for nitrate and methylamine uptake of this alga are 0.4 mM and 90 μM, respectively. When C. angulosa cells are transferred from control Bolds basal medium (BBM) to 50% naphthalene saturated or aqueous crude oil saturated media, the initial uptake rate for nitrate increases by a factor of two or decreases by a factor of one-third, respectively, as compared with that of cells transferred to control BBM. However, cells incubated in closed incubation systems with naphthalene or aqueous crude oil saturated media for 3 days lose nitrate when resuspended in control media. Cells transferred to media containing naphthalene up to 20% saturation show no immediate decrease in methylamine transport, while higher naphthalene concentrations cause an immediate decrease in transport activity. However, cells incubated in 50% naphthalene saturated media in a closed system for 2–4 h actually show increased methylamine transport activity when the incubation system is opened to allow escape of the hydrocarbon. Prolonged exposure to 50% naphthalene saturated media, however, causes progressive loss of transport activity.