The influence of cadmium and zinc on the cell size distribution of the alga Chlorella vulgaris

Abstract

The mean cell size and the size distribution of a population of microbial cells are known to be influenced by the growth phase of the culture and the environment in which the cells are growing. Various studies have suggested that the presence of trace metals may seriously affect cellular functions (such as cell division and volume regulation). The work reported here is an investigation of the effect of cadmium and zinc ions (both singly and together), at various concentrations, on the mean cell size and the size distribution of the alga Chlorella vulgaris. It was found that algal cultures exposed to low levels of cadmium and zinc singly (from 1 × 10-5 to 8 × 10-5 M) generally showed the same response as the control, except that slightly larger cells resulted at the higher end of this range of concentration. While the presence of the metal ions singly at 2 × 10-5 M did not significantly affect the mean cell size and the size distribution of the culture, equimolar concentrations of cadmium and zinc at this concentration resulted in size distribution profiles that were markedly different from the control. However, the giant aberrant cells reported by some authors to have arisen from high metal toxicity were clearly absent. A probit analysis of the size distribution of the cultures also showed that the size data from all the experiments could best be described as a log-normal distribution rather than as a normal distribution. © 1991.