Effects of Four Heavy Metals on Cell Morphology and Survival Rate of the Ciliate Bresslauides sp.

Abstract

Heavy metals are highly toxic chemicals often contaminating several ecosystems and causing detrimental effects on organisms living in such polluted environments. To evaluate the toxicity of heavy metals on eukaryotic microbes, a ciliate Bresslauides sp. was isolated from a canal located in Chulalongkorn University. A clonal culture of this ciliate was established and subsequently used to examine detailed morphological features of the isolated organism using light and scanning electron microscopy. The ciliate culture in exponential phase was then tested with several chosen concentrations of soluble compounds of copper, lead, zinc, and cadmium under laboratory conditions. The survival rate was documented after 24 hr incubation. Based on the median lethal concentration (LC50), the result indicated that cadmium was the most toxic metal with an LC50 of 0.09 mg/l, followed by copper (1.91 mg/l), zinc (3.66 mg/l), and lead (10.03 mg/l), respectively. Bresslauides sp. showed its highest sensitivity to Cd but considerable tolerance to Pb. Microscopic examination of cells treated with heavy metals at the LC50 concentration revealed cytological alterations, displaying intracellular vacuolarization, morphological deformities, and cellular lysis. This investigation not only reports for the first time the acute toxicity of the four metals to this ciliate genus, but also reveals the potential utilization of this isolate as a biological indicator for Cd-polluted environments.