Heavy metals generate reactive oxygen species in terrestrial and aquatic ciliated protozoa.
Reactive oxygen species (ROS) induction by exposure to heavy metals (Cd, Cu or Zn) in diverse free-living ciliated protozoa (Tetrahymena sp. and three strains of Colpoda steinii, isolated from freshwater and soils with different level of metal pollution) has been evaluated. Using specific fluorophores, such as 2',7'-dichlorofluorescein diacetate, hydroethidine and dihydrorhodamine 123, and a fluorescence microscope with the program MetaMorph Imaging System 4.0, we have analyzed both the average fluorescence emission and the heterogeneous distribution of fluorescence in control and treated cells. This is the first time that these fluorophores are used to detect ROS production in ciliated protozoa. All metals generate ROS, mainly superoxide and peroxides, showing a remarkable inter- and intra-specific variations. Likewise, resistance against each metal was also very diverse. Cu and specially Cd, the most toxic heavy metal for these ciliates, are the best oxidative stress inducers. However, a correlation between fluorescence emission intensity and cellular metal sensitivity for each strain cannot be established. Results are discussed and compared with similar findings previously published in other unicellular and pluricellular organisms.
Rico
Daniel
D
Departamento Microbiología-III, Facultad de Biología, Universidad Complutense (UCM), Madrid, Spain.
Martín-González
Ana
A
Díaz
Silvia
S
de Lucas
Pilar
P
Gutiérrez
Juan-Carlos
JC
D000818:Animals; D019256:Cadmium Chloride / Q000633:toxicity; D019327:Copper Sulfate / Q000633:toxicity; D005456:Fluorescent Dyes; D005618:Fresh Water; D006861:Hydrogen Peroxide / Q000378:metabolism; D020128:Inhibitory Concentration 50; D019216:Metals, Heavy / Q000633:toxicity*; D008856:Microscopy, Fluorescence; D016877:Oxidants / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012815:Signal Processing, Computer-Assisted; D012989:Soil Pollutants / Q000633:toxicity*; D013481:Superoxides / Q000378:metabolism; D013768:Tetrahymena / Q000187:drug effects* / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D019287:Zinc Sulfate / Q000633:toxicity
D005456:Fluorescent Dyes; D019216:Metals, Heavy; D016877:Oxidants; D017382:Reactive Oxygen Species; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D013481:Superoxides; D019287:Zinc Sulfate; D006861:Hydrogen Peroxide; D019256:Cadmium Chloride; D019327:Copper Sulfate