Fig. 2. (A) Transmitted light image of Chlamydomonas sp. isolated from the Rio Tinto. (B) Pseudocolored images of BCECF fluorescence in Chlamydomonas sp. The color bar to the right indicates relative pixel intensity. Imaging parameters were adjusted to eliminate low-level autofluorescence and to reduce exciting light intensity. The distribution of dye in the 488 nm (H⁺-sensitive) is similar to the distribution of dye in the 440 nm (H⁺-insensitive). Also the distribution of the dye is relatively homogenous. The ratio pairs show homogenous intensity except near the edges where the signal to noise ratio of the ratioed pixel intensity will decrease due to lower signals in the raw images. Scale bar, 10 µm.